Patchwork [v11,1/4] dmaengine: 8250_mtk_dma: add MediaTek uart DMA support

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Submitter Long Cheng
Date March 7, 2019, 1:45 a.m.
Message ID <1551923135-32479-2-git-send-email-long.cheng@mediatek.com>
Download mbox | patch
Permalink /patch/742909/
State New
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Comments

Long Cheng - March 7, 2019, 1:45 a.m.
In DMA engine framework, add 8250 uart dma to support MediaTek uart.
If MediaTek uart enabled(SERIAL_8250_MT6577), and want to improve
the performance, can enable the function.

Signed-off-by: Long Cheng <long.cheng@mediatek.com>
---
 drivers/dma/mediatek/Kconfig          |   11 +
 drivers/dma/mediatek/Makefile         |    1 +
 drivers/dma/mediatek/mtk-uart-apdma.c |  660 +++++++++++++++++++++++++++++++++
 3 files changed, 672 insertions(+)
 create mode 100644 drivers/dma/mediatek/mtk-uart-apdma.c
Nicolas Boichat - March 10, 2019, 11:15 a.m.
On Thu, Mar 7, 2019 at 9:45 AM Long Cheng <long.cheng@mediatek.com> wrote:
>
> In DMA engine framework, add 8250 uart dma to support MediaTek uart.
> If MediaTek uart enabled(SERIAL_8250_MT6577), and want to improve
> the performance, can enable the function.
>
> Signed-off-by: Long Cheng <long.cheng@mediatek.com>
> ---
>  drivers/dma/mediatek/Kconfig          |   11 +
>  drivers/dma/mediatek/Makefile         |    1 +
>  drivers/dma/mediatek/mtk-uart-apdma.c |  660 +++++++++++++++++++++++++++++++++
>  3 files changed, 672 insertions(+)
>  create mode 100644 drivers/dma/mediatek/mtk-uart-apdma.c
>
> diff --git a/drivers/dma/mediatek/Kconfig b/drivers/dma/mediatek/Kconfig
> index 680fc05..ac49eb6 100644
> --- a/drivers/dma/mediatek/Kconfig
> +++ b/drivers/dma/mediatek/Kconfig
> @@ -24,3 +24,14 @@ config MTK_CQDMA
>
>           This controller provides the channels which is dedicated to
>           memory-to-memory transfer to offload from CPU.
> +
> +config MTK_UART_APDMA
> +       tristate "MediaTek SoCs APDMA support for UART"
> +       depends on OF && SERIAL_8250_MT6577
> +       select DMA_ENGINE
> +       select DMA_VIRTUAL_CHANNELS
> +       help
> +         Support for the UART DMA engine found on MediaTek MTK SoCs.
> +         When SERIAL_8250_MT6577 is enabled, and if you want to use DMA,
> +         you can enable the config. The DMA engine can only be used
> +         with MediaTek SoCs.
> diff --git a/drivers/dma/mediatek/Makefile b/drivers/dma/mediatek/Makefile
> index 41bb381..61a6d29 100644
> --- a/drivers/dma/mediatek/Makefile
> +++ b/drivers/dma/mediatek/Makefile
> @@ -1,2 +1,3 @@
> +obj-$(CONFIG_MTK_UART_APDMA) += mtk-uart-apdma.o
>  obj-$(CONFIG_MTK_HSDMA) += mtk-hsdma.o
>  obj-$(CONFIG_MTK_CQDMA) += mtk-cqdma.o
> diff --git a/drivers/dma/mediatek/mtk-uart-apdma.c b/drivers/dma/mediatek/mtk-uart-apdma.c
> new file mode 100644
> index 0000000..9ed7a49
> --- /dev/null
> +++ b/drivers/dma/mediatek/mtk-uart-apdma.c
> @@ -0,0 +1,660 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * MediaTek Uart APDMA driver.
> + *
> + * Copyright (c) 2018 MediaTek Inc.
> + * Author: Long Cheng <long.cheng@mediatek.com>
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/dmaengine.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/iopoll.h>
> +#include <linux/kernel.h>
> +#include <linux/list.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/of_dma.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +
> +#include "../virt-dma.h"
> +
> +/* The default number of virtual channel */
> +#define MTK_UART_APDMA_NR_VCHANS       8
> +
> +#define VFF_EN_B               BIT(0)
> +#define VFF_STOP_B             BIT(0)
> +#define VFF_FLUSH_B            BIT(0)
> +#define VFF_4G_SUPPORT_B       BIT(0)
> +#define VFF_RX_INT_EN0_B       BIT(0)  /* rx valid size >=  vff thre */
> +#define VFF_RX_INT_EN1_B       BIT(1)
> +#define VFF_TX_INT_EN_B                BIT(0)  /* tx left size >= vff thre */
> +#define VFF_WARM_RST_B         BIT(0)
> +#define VFF_RX_INT_CLR_B       (BIT(0) | BIT(1))
> +#define VFF_TX_INT_CLR_B       0
> +#define VFF_STOP_CLR_B         0
> +#define VFF_INT_EN_CLR_B       0
> +#define VFF_4G_SUPPORT_CLR_B   0
> +
> +/* interrupt trigger level for tx */
> +#define VFF_TX_THRE(n)         ((n) * 7 / 8)
> +/* interrupt trigger level for rx */
> +#define VFF_RX_THRE(n)         ((n) * 3 / 4)
> +
> +#define VFF_RING_SIZE  0xffffU

Drop the U, it's not very useful (there are a a few more below, grep
for [0-9a-f]U).

> +/* invert this bit when wrap ring head again */
> +#define VFF_RING_WRAP  0x10000U
> +
> +#define VFF_INT_FLAG           0x00
> +#define VFF_INT_EN             0x04
> +#define VFF_EN                 0x08
> +#define VFF_RST                        0x0c
> +#define VFF_STOP               0x10
> +#define VFF_FLUSH              0x14
> +#define VFF_ADDR               0x1c
> +#define VFF_LEN                        0x24
> +#define VFF_THRE               0x28
> +#define VFF_WPT                        0x2c
> +#define VFF_RPT                        0x30
> +/* TX: the buffer size HW can read. RX: the buffer size SW can read. */
> +#define VFF_VALID_SIZE         0x3c
> +/* TX: the buffer size SW can write. RX: the buffer size HW can write. */
> +#define VFF_LEFT_SIZE          0x40
> +#define VFF_DEBUG_STATUS       0x50
> +#define VFF_4G_SUPPORT         0x54
> +
> +struct mtk_uart_apdmadev {
> +       struct dma_device ddev;
> +       struct clk *clk;
> +       bool support_33bits;
> +       unsigned int dma_requests;
> +       unsigned int *dma_irq;
> +};
> +
> +struct mtk_uart_apdma_desc {
> +       struct virt_dma_desc vd;
> +
> +       unsigned int avail_len;
> +};
> +
> +struct mtk_chan {
> +       struct virt_dma_chan vc;
> +       struct dma_slave_config cfg;
> +       void __iomem *base;
> +       struct mtk_uart_apdma_desc *desc;
> +
> +       enum dma_transfer_direction dir;
> +
> +       bool requested;
> +
> +       unsigned int rx_status;
> +};
> +
> +static inline struct mtk_uart_apdmadev *
> +to_mtk_uart_apdma_dev(struct dma_device *d)
> +{
> +       return container_of(d, struct mtk_uart_apdmadev, ddev);
> +}
> +
> +static inline struct mtk_chan *to_mtk_uart_apdma_chan(struct dma_chan *c)
> +{
> +       return container_of(c, struct mtk_chan, vc.chan);
> +}
> +
> +static inline struct mtk_uart_apdma_desc *to_mtk_uart_apdma_desc
> +       (struct dma_async_tx_descriptor *t)
> +{
> +       return container_of(t, struct mtk_uart_apdma_desc, vd.tx);
> +}
> +
> +static void mtk_uart_apdma_write(struct mtk_chan *c,
> +                              unsigned int reg, unsigned int val)
> +{
> +       writel(val, c->base + reg);
> +}
> +
> +static unsigned int mtk_uart_apdma_read(struct mtk_chan *c, unsigned int reg)
> +{
> +       return readl(c->base + reg);
> +}
> +
> +static void mtk_uart_apdma_desc_free(struct virt_dma_desc *vd)
> +{
> +       struct dma_chan *chan = vd->tx.chan;
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +
> +       kfree(c->desc);
> +}
> +
> +static void mtk_uart_apdma_start_tx(struct mtk_chan *c)
> +{
> +       unsigned int len, send, left, wpt, d_wpt, tmp;
> +       int ret;
> +
> +       left = mtk_uart_apdma_read(c, VFF_LEFT_SIZE);
> +       if (!left) {
> +               mtk_uart_apdma_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
> +               return;
> +       }
> +
> +       /* Wait 1sec for flush, can't sleep */
> +       ret = readx_poll_timeout(readl, c->base + VFF_FLUSH, tmp,
> +                       tmp != VFF_FLUSH_B, 0, 1000000);
> +       if (ret)
> +               dev_warn(c->vc.chan.device->dev, "tx: fail, debug=0x%x\n",
> +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> +
> +       send = min_t(unsigned int, left, c->desc->avail_len);
> +       wpt = mtk_uart_apdma_read(c, VFF_WPT);
> +       len = c->cfg.dst_port_window_size;
> +
> +       d_wpt = wpt + send;
> +       if ((d_wpt & VFF_RING_SIZE) >= len) {
> +               d_wpt = d_wpt - len;
> +               d_wpt = d_wpt ^ VFF_RING_WRAP;
> +       }
> +       mtk_uart_apdma_write(c, VFF_WPT, d_wpt);
> +
> +       c->desc->avail_len -= send;
> +
> +       mtk_uart_apdma_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
> +       if (mtk_uart_apdma_read(c, VFF_FLUSH) == 0U)
> +               mtk_uart_apdma_write(c, VFF_FLUSH, VFF_FLUSH_B);
> +}
> +
> +static void mtk_uart_apdma_start_rx(struct mtk_chan *c)
> +{
> +       struct mtk_uart_apdma_desc *d = c->desc;
> +       unsigned int len, wg, rg;
> +       int cnt;
> +
> +       if ((mtk_uart_apdma_read(c, VFF_VALID_SIZE) == 0U) ||
> +               !d || !vchan_next_desc(&c->vc))
> +               return;
> +
> +       len = c->cfg.src_port_window_size;
> +       rg = mtk_uart_apdma_read(c, VFF_RPT);
> +       wg = mtk_uart_apdma_read(c, VFF_WPT);
> +       cnt = (wg & VFF_RING_SIZE) - (rg & VFF_RING_SIZE);
> +       /*
> +        * The buffer is ring buffer. If wrap bit different,
> +        * represents the start of the next cycle for WPT
> +        */
> +       if ((rg ^ wg) & VFF_RING_WRAP)
> +               cnt += len;
> +
> +       c->rx_status = d->avail_len - cnt;
> +       mtk_uart_apdma_write(c, VFF_RPT, wg);
> +
> +       list_del(&d->vd.node);
> +       vchan_cookie_complete(&d->vd);
> +}
> +
> +static irqreturn_t mtk_uart_apdma_irq_handler(int irq, void *dev_id)
> +{
> +       struct dma_chan *chan = (struct dma_chan *)dev_id;
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       struct mtk_uart_apdma_desc *d;
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(&c->vc.lock, flags);
> +       if (c->dir == DMA_DEV_TO_MEM) {
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> +               mtk_uart_apdma_start_rx(c);
> +       } else if (c->dir == DMA_MEM_TO_DEV) {
> +               d = c->desc;
> +
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> +
> +               if (d->avail_len != 0U) {
> +                       mtk_uart_apdma_start_tx(c);
> +               } else {
> +                       list_del(&d->vd.node);
> +                       vchan_cookie_complete(&d->vd);
> +               }
> +       }
> +       spin_unlock_irqrestore(&c->vc.lock, flags);
> +
> +       return IRQ_HANDLED;
> +}
> +
> +static int mtk_uart_apdma_alloc_chan_resources(struct dma_chan *chan)
> +{
> +       struct mtk_uart_apdmadev *mtkd = to_mtk_uart_apdma_dev(chan->device);
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       unsigned int tmp;
> +       int ret;
> +
> +       pm_runtime_get_sync(mtkd->ddev.dev);
> +
> +       mtk_uart_apdma_write(c, VFF_ADDR, 0);
> +       mtk_uart_apdma_write(c, VFF_THRE, 0);
> +       mtk_uart_apdma_write(c, VFF_LEN, 0);
> +       mtk_uart_apdma_write(c, VFF_RST, VFF_WARM_RST_B);
> +
> +       ret = readx_poll_timeout(readl, c->base + VFF_EN, tmp, !tmp, 10, 100);
> +       if (ret) {
> +               dev_err(chan->device->dev, "dma reset: fail, timeout\n");
> +               return ret;
> +       }
> +
> +       if (!c->requested) {
> +               c->requested = true;
> +               ret = request_irq(mtkd->dma_irq[chan->chan_id],
> +                                 mtk_uart_apdma_irq_handler, IRQF_TRIGGER_NONE,
> +                                 KBUILD_MODNAME, chan);
> +               if (ret < 0) {
> +                       dev_err(chan->device->dev, "Can't request dma IRQ\n");
> +                       return -EINVAL;
> +               }
> +       }
> +
> +       if (mtkd->support_33bits)
> +               mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_CLR_B);
> +
> +       return ret;
> +}
> +
> +static void mtk_uart_apdma_free_chan_resources(struct dma_chan *chan)
> +{
> +       struct mtk_uart_apdmadev *mtkd = to_mtk_uart_apdma_dev(chan->device);
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +
> +       if (c->requested) {
> +               c->requested = false;
> +               free_irq(mtkd->dma_irq[chan->chan_id], chan);
> +       }
> +
> +       tasklet_kill(&c->vc.task);
> +
> +       vchan_free_chan_resources(&c->vc);
> +
> +       pm_runtime_put_sync(mtkd->ddev.dev);
> +}
> +
> +static enum dma_status mtk_uart_apdma_tx_status(struct dma_chan *chan,
> +                                        dma_cookie_t cookie,
> +                                        struct dma_tx_state *txstate)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       enum dma_status ret;
> +
> +       ret = dma_cookie_status(chan, cookie, txstate);
> +
> +       dma_set_residue(txstate, c->rx_status);
> +
> +       return ret;
> +}
> +
> +static void mtk_uart_apdma_config_write(struct dma_chan *chan,
> +                              struct dma_slave_config *cfg,
> +                              enum dma_transfer_direction dir)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       struct mtk_uart_apdmadev *mtkd =
> +                               to_mtk_uart_apdma_dev(c->vc.chan.device);
> +       unsigned int tmp;
> +
> +       if (mtk_uart_apdma_read(c, VFF_EN) == VFF_EN_B)
> +               return;
> +
> +       c->dir = dir;
> +
> +       if (dir == DMA_DEV_TO_MEM) {
> +               tmp = cfg->src_port_window_size;
> +
> +               mtk_uart_apdma_write(c, VFF_ADDR, cfg->src_addr);
> +               mtk_uart_apdma_write(c, VFF_LEN, tmp);
> +               mtk_uart_apdma_write(c, VFF_THRE, VFF_RX_THRE(tmp));
> +               mtk_uart_apdma_write(c, VFF_INT_EN,
> +                               VFF_RX_INT_EN0_B | VFF_RX_INT_EN1_B);
> +               mtk_uart_apdma_write(c, VFF_RPT, 0);
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> +       } else if (dir == DMA_MEM_TO_DEV)       {
> +               tmp = cfg->dst_port_window_size;
> +
> +               mtk_uart_apdma_write(c, VFF_ADDR, cfg->dst_addr);
> +               mtk_uart_apdma_write(c, VFF_LEN, tmp);
> +               mtk_uart_apdma_write(c, VFF_THRE, VFF_TX_THRE(tmp));
> +               mtk_uart_apdma_write(c, VFF_WPT, 0);
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> +       }
> +
> +       mtk_uart_apdma_write(c, VFF_EN, VFF_EN_B);
> +
> +       if (mtkd->support_33bits)
> +               mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_B);
> +
> +       if (mtk_uart_apdma_read(c, VFF_EN) != VFF_EN_B)
> +               dev_err(chan->device->dev, "dir[%d] fail\n", dir);
> +}
> +
> +/*
> + * dmaengine_prep_slave_single will call the function. and sglen is 1.
> + * 8250 uart using one ring buffer, and deal with one sg.
> + */
> +static struct dma_async_tx_descriptor *mtk_uart_apdma_prep_slave_sg
> +       (struct dma_chan *chan, struct scatterlist *sgl,
> +       unsigned int sglen, enum dma_transfer_direction dir,
> +       unsigned long tx_flags, void *context)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       struct mtk_uart_apdma_desc *d;
> +
> +       if (!is_slave_direction(dir))
> +               return NULL;
> +
> +       mtk_uart_apdma_config_write(chan, &c->cfg, dir);
> +
> +       /* Now allocate and setup the descriptor */
> +       d = kzalloc(sizeof(*d), GFP_ATOMIC);
> +       if (!d)
> +               return NULL;
> +
> +       /* sglen is 1 */
> +       d->avail_len = sg_dma_len(sgl);
> +       c->rx_status = d->avail_len;
> +
> +       return vchan_tx_prep(&c->vc, &d->vd, tx_flags);
> +}
> +
> +static void mtk_uart_apdma_issue_pending(struct dma_chan *chan)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       struct virt_dma_desc *vd;
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(&c->vc.lock, flags);
> +       if (vchan_issue_pending(&c->vc)) {
> +               vd = vchan_next_desc(&c->vc);
> +               c->desc = to_mtk_uart_apdma_desc(&vd->tx);
> +       }
> +
> +       if (c->dir == DMA_DEV_TO_MEM)
> +               mtk_uart_apdma_start_rx(c);
> +       else if (c->dir == DMA_MEM_TO_DEV)
> +               mtk_uart_apdma_start_tx(c);
> +
> +       spin_unlock_irqrestore(&c->vc.lock, flags);
> +}
> +
> +static int mtk_uart_apdma_slave_config(struct dma_chan *chan,
> +                                  struct dma_slave_config *config)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +
> +       memcpy(&c->cfg, config, sizeof(*config));
> +
> +       return 0;
> +}
> +
> +static int mtk_uart_apdma_terminate_all(struct dma_chan *chan)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       unsigned long flags;
> +       unsigned int tmp;
> +       int ret;
> +
> +       spin_lock_irqsave(&c->vc.lock, flags);
> +
> +       mtk_uart_apdma_write(c, VFF_FLUSH, VFF_FLUSH_B);
> +       /* Wait 1sec for flush, can't sleep */
> +       ret = readx_poll_timeout(readl, c->base + VFF_FLUSH, tmp,
> +                       tmp != VFF_FLUSH_B, 0, 1000000);
> +       if (ret)
> +               dev_err(c->vc.chan.device->dev, "flush: fail, debug=0x%x\n",
> +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> +
> +       /* set stop as 1 -> wait until en is 0 -> set stop as 0 */
> +       mtk_uart_apdma_write(c, VFF_STOP, VFF_STOP_B);
> +       ret = readx_poll_timeout(readl, c->base + VFF_EN, tmp, !tmp, 10, 100);
> +       if (ret)
> +               dev_err(c->vc.chan.device->dev, "stop: fail, debug=0x%x\n",
> +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> +
> +       mtk_uart_apdma_write(c, VFF_STOP, VFF_STOP_CLR_B);
> +       mtk_uart_apdma_write(c, VFF_INT_EN, VFF_INT_EN_CLR_B);
> +
> +       if (c->dir == DMA_DEV_TO_MEM)
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> +       else if (c->dir == DMA_MEM_TO_DEV)
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> +
> +       spin_unlock_irqrestore(&c->vc.lock, flags);
> +
> +       return 0;
> +}
> +
> +static int mtk_uart_apdma_device_pause(struct dma_chan *chan)
> +{
> +       /* just for check caps pass */
> +       dev_err(chan->device->dev, "Pause can't support\n");
> +
> +       return 0;
> +}

I think we've said repeatedly that leaving this stub function is incorrect.

> +
> +static void mtk_uart_apdma_free(struct mtk_uart_apdmadev *mtkd)
> +{
> +       while (!list_empty(&mtkd->ddev.channels)) {
> +               struct mtk_chan *c = list_first_entry(&mtkd->ddev.channels,
> +                       struct mtk_chan, vc.chan.device_node);
> +
> +               list_del(&c->vc.chan.device_node);
> +               tasklet_kill(&c->vc.task);
> +       }
> +}
> +
> +static const struct of_device_id mtk_uart_apdma_match[] = {
> +       { .compatible = "mediatek,mt6577-uart-dma", },
> +       { /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, mtk_uart_apdma_match);
> +
> +static int mtk_uart_apdma_probe(struct platform_device *pdev)
> +{
> +       struct device_node *np = pdev->dev.of_node;
> +       struct mtk_uart_apdmadev *mtkd;
> +       struct resource *res;
> +       struct mtk_chan *c;
> +       int bit_mask = 32, rc;
> +       unsigned int i;
> +
> +       mtkd = devm_kzalloc(&pdev->dev, sizeof(*mtkd), GFP_KERNEL);
> +       if (!mtkd)
> +               return -ENOMEM;
> +
> +       mtkd->clk = devm_clk_get(&pdev->dev, NULL);
> +       if (IS_ERR(mtkd->clk)) {
> +               dev_err(&pdev->dev, "No clock specified\n");
> +               rc = PTR_ERR(mtkd->clk);
> +               return rc;
> +       }
> +
> +       if (of_property_read_bool(np, "mediatek,dma-33bits"))
> +               mtkd->support_33bits = true;
> +
> +       if (mtkd->support_33bits)
> +               bit_mask = 33;
> +
> +       rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(bit_mask));
> +       if (rc)
> +               return rc;
> +
> +       dma_cap_set(DMA_SLAVE, mtkd->ddev.cap_mask);
> +       mtkd->ddev.device_alloc_chan_resources =
> +                               mtk_uart_apdma_alloc_chan_resources;
> +       mtkd->ddev.device_free_chan_resources =
> +                               mtk_uart_apdma_free_chan_resources;
> +       mtkd->ddev.device_tx_status = mtk_uart_apdma_tx_status;
> +       mtkd->ddev.device_issue_pending = mtk_uart_apdma_issue_pending;
> +       mtkd->ddev.device_prep_slave_sg = mtk_uart_apdma_prep_slave_sg;
> +       mtkd->ddev.device_config = mtk_uart_apdma_slave_config;
> +       mtkd->ddev.device_pause = mtk_uart_apdma_device_pause;
> +       mtkd->ddev.device_terminate_all = mtk_uart_apdma_terminate_all;
> +       mtkd->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
> +       mtkd->ddev.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
> +       mtkd->ddev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
> +       mtkd->ddev.residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
> +       mtkd->ddev.dev = &pdev->dev;
> +       INIT_LIST_HEAD(&mtkd->ddev.channels);
> +
> +       mtkd->dma_requests = MTK_UART_APDMA_NR_VCHANS;
> +       if (of_property_read_u32(np, "dma-requests", &mtkd->dma_requests)) {
> +               dev_info(&pdev->dev,
> +                        "Using %u as missing dma-requests property\n",
> +                        MTK_UART_APDMA_NR_VCHANS);
> +       }
> +
> +       mtkd->dma_irq = devm_kcalloc(&pdev->dev, mtkd->dma_requests,
> +                                sizeof(*mtkd->dma_irq), GFP_KERNEL);
> +       if (!mtkd->dma_irq)
> +               return -ENOMEM;
> +
> +       for (i = 0; i < mtkd->dma_requests; i++) {
> +               c = devm_kzalloc(mtkd->ddev.dev, sizeof(*c), GFP_KERNEL);
> +               if (!c) {
> +                       rc = -ENODEV;
> +                       goto err_no_dma;
> +               }
> +
> +               res = platform_get_resource(pdev, IORESOURCE_MEM, i);
> +               if (!res) {
> +                       rc = -ENODEV;
> +                       goto err_no_dma;
> +               }
> +
> +               c->base = devm_ioremap_resource(&pdev->dev, res);
> +               if (IS_ERR(c->base)) {
> +                       rc = PTR_ERR(c->base);
> +                       goto err_no_dma;
> +               }
> +               c->requested = false;
> +               c->vc.desc_free = mtk_uart_apdma_desc_free;
> +               vchan_init(&c->vc, &mtkd->ddev);
> +
> +               mtkd->dma_irq[i] = platform_get_irq(pdev, i);
> +               if ((int)mtkd->dma_irq[i] < 0) {
> +                       dev_err(&pdev->dev, "failed to get IRQ[%d]\n", i);
> +                       rc = -EINVAL;
> +                       goto err_no_dma;
> +               }
> +       }
> +
> +       pm_runtime_enable(&pdev->dev);
> +       pm_runtime_set_active(&pdev->dev);
> +
> +       rc = dma_async_device_register(&mtkd->ddev);
> +       if (rc)
> +               goto rpm_disable;
> +
> +       platform_set_drvdata(pdev, mtkd);
> +
> +       /* Device-tree DMA controller registration */
> +       rc = of_dma_controller_register(np, of_dma_xlate_by_chan_id, mtkd);
> +       if (rc)
> +               goto dma_remove;
> +
> +       return rc;
> +
> +dma_remove:
> +       dma_async_device_unregister(&mtkd->ddev);
> +rpm_disable:
> +       pm_runtime_disable(&pdev->dev);
> +err_no_dma:
> +       mtk_uart_apdma_free(mtkd);
> +       return rc;
> +}
> +
> +static int mtk_uart_apdma_remove(struct platform_device *pdev)
> +{
> +       struct mtk_uart_apdmadev *mtkd = platform_get_drvdata(pdev);
> +
> +       if (pdev->dev.of_node)
> +               of_dma_controller_free(pdev->dev.of_node);
> +
> +       pm_runtime_disable(&pdev->dev);
> +       pm_runtime_put_noidle(&pdev->dev);
> +
> +       dma_async_device_unregister(&mtkd->ddev);
> +       mtk_uart_apdma_free(mtkd);
> +
> +       return 0;
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int mtk_uart_apdma_suspend(struct device *dev)
> +{
> +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> +
> +       if (!pm_runtime_suspended(dev))
> +               clk_disable_unprepare(mtkd->clk);
> +
> +       return 0;
> +}
> +
> +static int mtk_uart_apdma_resume(struct device *dev)
> +{
> +       int ret;
> +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> +
> +       if (!pm_runtime_suspended(dev)) {
> +               ret = clk_prepare_enable(mtkd->clk);
> +               if (ret)
> +                       return ret;
> +       }
> +
> +       return 0;
> +}
> +#endif /* CONFIG_PM_SLEEP */
> +
> +#ifdef CONFIG_PM
> +static int mtk_uart_apdma_runtime_suspend(struct device *dev)
> +{
> +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> +
> +       clk_disable_unprepare(mtkd->clk);
> +
> +       return 0;
> +}
> +
> +static int mtk_uart_apdma_runtime_resume(struct device *dev)
> +{
> +       int ret;
> +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> +
> +       ret = clk_prepare_enable(mtkd->clk);
> +       if (ret)
> +               return ret;
> +
> +       return 0;
> +}
> +#endif /* CONFIG_PM */
> +
> +static const struct dev_pm_ops mtk_uart_apdma_pm_ops = {
> +       SET_SYSTEM_SLEEP_PM_OPS(mtk_uart_apdma_suspend, mtk_uart_apdma_resume)
> +       SET_RUNTIME_PM_OPS(mtk_uart_apdma_runtime_suspend,
> +                          mtk_uart_apdma_runtime_resume, NULL)
> +};
> +
> +static struct platform_driver mtk_uart_apdma_driver = {
> +       .probe  = mtk_uart_apdma_probe,
> +       .remove = mtk_uart_apdma_remove,
> +       .driver = {
> +               .name           = KBUILD_MODNAME,
> +               .pm             = &mtk_uart_apdma_pm_ops,
> +               .of_match_table = of_match_ptr(mtk_uart_apdma_match),
> +       },
> +};
> +
> +module_platform_driver(mtk_uart_apdma_driver);
> +
> +MODULE_DESCRIPTION("MediaTek UART APDMA Controller Driver");
> +MODULE_AUTHOR("Long Cheng <long.cheng@mediatek.com>");
> +MODULE_LICENSE("GPL v2");
> +
> --
> 1.7.9.5
>
Sean Wang - March 11, 2019, 12:31 a.m.
Hi, Long

List some comments as the below and this week I will find a board to
test and then improve the driver.

         Sean

On Wed, Mar 6, 2019 at 5:45 PM Long Cheng <long.cheng@mediatek.com> wrote:
>
> In DMA engine framework, add 8250 uart dma to support MediaTek uart.
> If MediaTek uart enabled(SERIAL_8250_MT6577), and want to improve
> the performance, can enable the function.
>
> Signed-off-by: Long Cheng <long.cheng@mediatek.com>
> ---
>  drivers/dma/mediatek/Kconfig          |   11 +
>  drivers/dma/mediatek/Makefile         |    1 +
>  drivers/dma/mediatek/mtk-uart-apdma.c |  660 +++++++++++++++++++++++++++++++++
>  3 files changed, 672 insertions(+)
>  create mode 100644 drivers/dma/mediatek/mtk-uart-apdma.c
>
> diff --git a/drivers/dma/mediatek/Kconfig b/drivers/dma/mediatek/Kconfig
> index 680fc05..ac49eb6 100644
> --- a/drivers/dma/mediatek/Kconfig
> +++ b/drivers/dma/mediatek/Kconfig
> @@ -24,3 +24,14 @@ config MTK_CQDMA
>
>           This controller provides the channels which is dedicated to
>           memory-to-memory transfer to offload from CPU.
> +
> +config MTK_UART_APDMA
> +       tristate "MediaTek SoCs APDMA support for UART"
> +       depends on OF && SERIAL_8250_MT6577
> +       select DMA_ENGINE
> +       select DMA_VIRTUAL_CHANNELS
> +       help
> +         Support for the UART DMA engine found on MediaTek MTK SoCs.
> +         When SERIAL_8250_MT6577 is enabled, and if you want to use DMA,
> +         you can enable the config. The DMA engine can only be used
> +         with MediaTek SoCs.
> diff --git a/drivers/dma/mediatek/Makefile b/drivers/dma/mediatek/Makefile
> index 41bb381..61a6d29 100644
> --- a/drivers/dma/mediatek/Makefile
> +++ b/drivers/dma/mediatek/Makefile
> @@ -1,2 +1,3 @@
> +obj-$(CONFIG_MTK_UART_APDMA) += mtk-uart-apdma.o
>  obj-$(CONFIG_MTK_HSDMA) += mtk-hsdma.o
>  obj-$(CONFIG_MTK_CQDMA) += mtk-cqdma.o
> diff --git a/drivers/dma/mediatek/mtk-uart-apdma.c b/drivers/dma/mediatek/mtk-uart-apdma.c
> new file mode 100644
> index 0000000..9ed7a49
> --- /dev/null
> +++ b/drivers/dma/mediatek/mtk-uart-apdma.c
> @@ -0,0 +1,660 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * MediaTek Uart APDMA driver.
> + *
> + * Copyright (c) 2018 MediaTek Inc.
> + * Author: Long Cheng <long.cheng@mediatek.com>
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/dmaengine.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/iopoll.h>
> +#include <linux/kernel.h>
> +#include <linux/list.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/of_dma.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +
> +#include "../virt-dma.h"
> +
> +/* The default number of virtual channel */
> +#define MTK_UART_APDMA_NR_VCHANS       8
> +
> +#define VFF_EN_B               BIT(0)
> +#define VFF_STOP_B             BIT(0)
> +#define VFF_FLUSH_B            BIT(0)
> +#define VFF_4G_SUPPORT_B       BIT(0)
> +#define VFF_RX_INT_EN0_B       BIT(0)  /* rx valid size >=  vff thre */
> +#define VFF_RX_INT_EN1_B       BIT(1)
> +#define VFF_TX_INT_EN_B                BIT(0)  /* tx left size >= vff thre */
> +#define VFF_WARM_RST_B         BIT(0)
> +#define VFF_RX_INT_CLR_B       (BIT(0) | BIT(1))
> +#define VFF_TX_INT_CLR_B       0
> +#define VFF_STOP_CLR_B         0
> +#define VFF_INT_EN_CLR_B       0
> +#define VFF_4G_SUPPORT_CLR_B   0
> +
> +/* interrupt trigger level for tx */
> +#define VFF_TX_THRE(n)         ((n) * 7 / 8)
> +/* interrupt trigger level for rx */
> +#define VFF_RX_THRE(n)         ((n) * 3 / 4)
> +
> +#define VFF_RING_SIZE  0xffffU
> +/* invert this bit when wrap ring head again */
> +#define VFF_RING_WRAP  0x10000U
> +
> +#define VFF_INT_FLAG           0x00
> +#define VFF_INT_EN             0x04
> +#define VFF_EN                 0x08
> +#define VFF_RST                        0x0c
> +#define VFF_STOP               0x10
> +#define VFF_FLUSH              0x14
> +#define VFF_ADDR               0x1c
> +#define VFF_LEN                        0x24
> +#define VFF_THRE               0x28
> +#define VFF_WPT                        0x2c
> +#define VFF_RPT                        0x30
> +/* TX: the buffer size HW can read. RX: the buffer size SW can read. */
> +#define VFF_VALID_SIZE         0x3c
> +/* TX: the buffer size SW can write. RX: the buffer size HW can write. */
> +#define VFF_LEFT_SIZE          0x40
> +#define VFF_DEBUG_STATUS       0x50
> +#define VFF_4G_SUPPORT         0x54
> +
> +struct mtk_uart_apdmadev {
> +       struct dma_device ddev;
> +       struct clk *clk;
> +       bool support_33bits;
> +       unsigned int dma_requests;
> +       unsigned int *dma_irq;
> +};
> +
> +struct mtk_uart_apdma_desc {
> +       struct virt_dma_desc vd;
> +
> +       unsigned int avail_len;
> +};
> +
> +struct mtk_chan {
> +       struct virt_dma_chan vc;
> +       struct dma_slave_config cfg;
> +       void __iomem *base;
> +       struct mtk_uart_apdma_desc *desc;
> +
> +       enum dma_transfer_direction dir;
> +
> +       bool requested;
> +
> +       unsigned int rx_status;
> +};
> +
> +static inline struct mtk_uart_apdmadev *
> +to_mtk_uart_apdma_dev(struct dma_device *d)
> +{
> +       return container_of(d, struct mtk_uart_apdmadev, ddev);
> +}
> +
> +static inline struct mtk_chan *to_mtk_uart_apdma_chan(struct dma_chan *c)
> +{
> +       return container_of(c, struct mtk_chan, vc.chan);
> +}
> +
> +static inline struct mtk_uart_apdma_desc *to_mtk_uart_apdma_desc
> +       (struct dma_async_tx_descriptor *t)
> +{
> +       return container_of(t, struct mtk_uart_apdma_desc, vd.tx);
> +}
> +
> +static void mtk_uart_apdma_write(struct mtk_chan *c,
> +                              unsigned int reg, unsigned int val)
> +{
> +       writel(val, c->base + reg);
> +}
> +
> +static unsigned int mtk_uart_apdma_read(struct mtk_chan *c, unsigned int reg)
> +{
> +       return readl(c->base + reg);
> +}
> +
> +static void mtk_uart_apdma_desc_free(struct virt_dma_desc *vd)
> +{
> +       struct dma_chan *chan = vd->tx.chan;
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +
> +       kfree(c->desc);
> +}
> +
> +static void mtk_uart_apdma_start_tx(struct mtk_chan *c)
> +{
> +       unsigned int len, send, left, wpt, d_wpt, tmp;
> +       int ret;
> +
> +       left = mtk_uart_apdma_read(c, VFF_LEFT_SIZE);
> +       if (!left) {
> +               mtk_uart_apdma_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
> +               return;
> +       }
> +
> +       /* Wait 1sec for flush, can't sleep */
> +       ret = readx_poll_timeout(readl, c->base + VFF_FLUSH, tmp,
> +                       tmp != VFF_FLUSH_B, 0, 1000000);

It is really not a good idea that polling up to 1 second in an
interrupt context.

> +       if (ret)
> +               dev_warn(c->vc.chan.device->dev, "tx: fail, debug=0x%x\n",
> +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> +
> +       send = min_t(unsigned int, left, c->desc->avail_len);
> +       wpt = mtk_uart_apdma_read(c, VFF_WPT);
> +       len = c->cfg.dst_port_window_size;
> +
> +       d_wpt = wpt + send;
> +       if ((d_wpt & VFF_RING_SIZE) >= len) {

I am confused what size of VFF is.  Either VFF_RING_SIZE or
c->cfg.dst_port_window_size?

> +               d_wpt = d_wpt - len;
> +               d_wpt = d_wpt ^ VFF_RING_WRAP;
> +       }
> +       mtk_uart_apdma_write(c, VFF_WPT, d_wpt);
> +
> +       c->desc->avail_len -= send;
> +
> +       mtk_uart_apdma_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);

Why should we need to program interrupt enabled bit again?

> +       if (mtk_uart_apdma_read(c, VFF_FLUSH) == 0U)
> +               mtk_uart_apdma_write(c, VFF_FLUSH, VFF_FLUSH_B);
> +}
> +
> +static void mtk_uart_apdma_start_rx(struct mtk_chan *c)
> +{
> +       struct mtk_uart_apdma_desc *d = c->desc;
> +       unsigned int len, wg, rg;
> +       int cnt;
> +
> +       if ((mtk_uart_apdma_read(c, VFF_VALID_SIZE) == 0U) ||
> +               !d || !vchan_next_desc(&c->vc))
> +               return;

If the current descriptor is not available, the hardware should be
idle or stopped. so I think the condition can be removed or there is
somewhere your handle descriptors incorrectly.

> +
> +       len = c->cfg.src_port_window_size;
> +       rg = mtk_uart_apdma_read(c, VFF_RPT);
> +       wg = mtk_uart_apdma_read(c, VFF_WPT);
> +       cnt = (wg & VFF_RING_SIZE) - (rg & VFF_RING_SIZE);

Is it possible that rg and wg would be greater than VFF_RING_SIZE?

> +       /*
> +        * The buffer is ring buffer. If wrap bit different,
> +        * represents the start of the next cycle for WPT
> +        */
> +       if ((rg ^ wg) & VFF_RING_WRAP)
> +               cnt += len;

Again, I am confused what size of VFF is.  Either VFF_RING_SIZE or
c->cfg.dst_port_window_size?

> +
> +       c->rx_status = d->avail_len - cnt;
> +       mtk_uart_apdma_write(c, VFF_RPT, wg);
> +
> +       list_del(&d->vd.node);
> +       vchan_cookie_complete(&d->vd);
> +}
> +
> +static irqreturn_t mtk_uart_apdma_irq_handler(int irq, void *dev_id)
> +{
> +       struct dma_chan *chan = (struct dma_chan *)dev_id;
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       struct mtk_uart_apdma_desc *d;
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(&c->vc.lock, flags);
> +       if (c->dir == DMA_DEV_TO_MEM) {
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> +               mtk_uart_apdma_start_rx(c);
> +       } else if (c->dir == DMA_MEM_TO_DEV) {
> +               d = c->desc;
> +
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> +
> +               if (d->avail_len != 0U) {
> +                       mtk_uart_apdma_start_tx(c);
> +               } else {
> +                       list_del(&d->vd.node);
> +                       vchan_cookie_complete(&d->vd);
> +               }
> +       }
> +       spin_unlock_irqrestore(&c->vc.lock, flags);
> +
> +       return IRQ_HANDLED;
> +}
> +
> +static int mtk_uart_apdma_alloc_chan_resources(struct dma_chan *chan)
> +{
> +       struct mtk_uart_apdmadev *mtkd = to_mtk_uart_apdma_dev(chan->device);
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       unsigned int tmp;
> +       int ret;
> +
> +       pm_runtime_get_sync(mtkd->ddev.dev);

Add an error handling, something like

err = pm_runtime_get_sync(mtkd->ddev.dev);
if (err < 0) {
pm_runtime_put_noidle(dev);
...
}

> +
> +       mtk_uart_apdma_write(c, VFF_ADDR, 0);
> +       mtk_uart_apdma_write(c, VFF_THRE, 0);
> +       mtk_uart_apdma_write(c, VFF_LEN, 0);
> +       mtk_uart_apdma_write(c, VFF_RST, VFF_WARM_RST_B);
> +
> +       ret = readx_poll_timeout(readl, c->base + VFF_EN, tmp, !tmp, 10, 100);
> +       if (ret) {
> +               dev_err(chan->device->dev, "dma reset: fail, timeout\n");
> +               return ret;
> +       }
> +
> +       if (!c->requested) {
> +               c->requested = true;

The variable c->requested can be saved since the same channel
shouldn't be requested more one time

> +               ret = request_irq(mtkd->dma_irq[chan->chan_id],
> +                                 mtk_uart_apdma_irq_handler, IRQF_TRIGGER_NONE,
> +                                 KBUILD_MODNAME, chan);
> +               if (ret < 0) {
> +                       dev_err(chan->device->dev, "Can't request dma IRQ\n");
> +                       return -EINVAL;
> +               }
> +       }
> +
> +       if (mtkd->support_33bits)
> +               mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_CLR_B);
> +
> +       return ret;
> +}
> +
> +static void mtk_uart_apdma_free_chan_resources(struct dma_chan *chan)
> +{
> +       struct mtk_uart_apdmadev *mtkd = to_mtk_uart_apdma_dev(chan->device);
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +
> +       if (c->requested) {

ditto as the above

> +               c->requested = false;
> +               free_irq(mtkd->dma_irq[chan->chan_id], chan);
> +       }
> +
> +       tasklet_kill(&c->vc.task);
> +
> +       vchan_free_chan_resources(&c->vc);
> +
> +       pm_runtime_put_sync(mtkd->ddev.dev);
> +}
> +
> +static enum dma_status mtk_uart_apdma_tx_status(struct dma_chan *chan,
> +                                        dma_cookie_t cookie,
> +                                        struct dma_tx_state *txstate)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       enum dma_status ret;
> +
> +       ret = dma_cookie_status(chan, cookie, txstate);
> +
> +       dma_set_residue(txstate, c->rx_status);
> +

The handling is not enough. You should get the descriptor
corresponding to the cookie and then calculate and return the
->tx_status by the descriptor

> +       return ret;
> +}
> +
> +static void mtk_uart_apdma_config_write(struct dma_chan *chan,
> +                              struct dma_slave_config *cfg,
> +                              enum dma_transfer_direction dir)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       struct mtk_uart_apdmadev *mtkd =
> +                               to_mtk_uart_apdma_dev(c->vc.chan.device);
> +       unsigned int tmp;
> +
> +       if (mtk_uart_apdma_read(c, VFF_EN) == VFF_EN_B)
> +               return;
> +
> +       c->dir = dir;

The direction is fixed by the device, I don't think it is required to
keep it in a software state.

> +
> +       if (dir == DMA_DEV_TO_MEM) {
> +               tmp = cfg->src_port_window_size;
> +
> +               mtk_uart_apdma_write(c, VFF_ADDR, cfg->src_addr);

That is wrong. ->src_addr is the physical address where DMA slave data
should be read (RX),  not the memory address.

You should program the register VFF_ADDR and VFF_LEN by sg address and
length from device_prep_slave_sg.

> +               mtk_uart_apdma_write(c, VFF_LEN, tmp);
> +               mtk_uart_apdma_write(c, VFF_THRE, VFF_RX_THRE(tmp));
> +               mtk_uart_apdma_write(c, VFF_INT_EN,
> +                               VFF_RX_INT_EN0_B | VFF_RX_INT_EN1_B);
> +               mtk_uart_apdma_write(c, VFF_RPT, 0);
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> +       } else if (dir == DMA_MEM_TO_DEV)       {
> +               tmp = cfg->dst_port_window_size;
> +
> +               mtk_uart_apdma_write(c, VFF_ADDR, cfg->dst_addr);

That is also wrong. st_addr: this is the physical address where DMA
slave data should be written (TX), not the memory address similar to
the above explanation.

> +               mtk_uart_apdma_write(c, VFF_LEN, tmp);
> +               mtk_uart_apdma_write(c, VFF_THRE, VFF_TX_THRE(tmp));
> +               mtk_uart_apdma_write(c, VFF_WPT, 0);
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> +       }
> +
> +       mtk_uart_apdma_write(c, VFF_EN, VFF_EN_B);
> +
> +       if (mtkd->support_33bits)
> +               mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_B);
> +
> +       if (mtk_uart_apdma_read(c, VFF_EN) != VFF_EN_B)
> +               dev_err(chan->device->dev, "dir[%d] fail\n", dir);
> +}
> +
> +/*
> + * dmaengine_prep_slave_single will call the function. and sglen is 1.
> + * 8250 uart using one ring buffer, and deal with one sg.
> + */
> +static struct dma_async_tx_descriptor *mtk_uart_apdma_prep_slave_sg
> +       (struct dma_chan *chan, struct scatterlist *sgl,
> +       unsigned int sglen, enum dma_transfer_direction dir,
> +       unsigned long tx_flags, void *context)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       struct mtk_uart_apdma_desc *d;
> +
> +       if (!is_slave_direction(dir))
> +               return NULL;
> +
> +       mtk_uart_apdma_config_write(chan, &c->cfg, dir);
> +
> +       /* Now allocate and setup the descriptor */
> +       d = kzalloc(sizeof(*d), GFP_ATOMIC);
> +       if (!d)
> +               return NULL;
> +
> +       /* sglen is 1 */
> +       d->avail_len = sg_dma_len(sgl);
> +       c->rx_status = d->avail_len;
> +
> +       return vchan_tx_prep(&c->vc, &d->vd, tx_flags);
> +}
> +
> +static void mtk_uart_apdma_issue_pending(struct dma_chan *chan)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       struct virt_dma_desc *vd;
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(&c->vc.lock, flags);
> +       if (vchan_issue_pending(&c->vc)) {
> +               vd = vchan_next_desc(&c->vc);
> +               c->desc = to_mtk_uart_apdma_desc(&vd->tx);
> +       }
> +
> +       if (c->dir == DMA_DEV_TO_MEM)
> +               mtk_uart_apdma_start_rx(c);
> +       else if (c->dir == DMA_MEM_TO_DEV)
> +               mtk_uart_apdma_start_tx(c);
> +
> +       spin_unlock_irqrestore(&c->vc.lock, flags);
> +}
> +
> +static int mtk_uart_apdma_slave_config(struct dma_chan *chan,
> +                                  struct dma_slave_config *config)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +
> +       memcpy(&c->cfg, config, sizeof(*config));
> +
> +       return 0;
> +}
> +
> +static int mtk_uart_apdma_terminate_all(struct dma_chan *chan)
> +{
> +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> +       unsigned long flags;
> +       unsigned int tmp;
> +       int ret;
> +
> +       spin_lock_irqsave(&c->vc.lock, flags);
> +
> +       mtk_uart_apdma_write(c, VFF_FLUSH, VFF_FLUSH_B);
> +       /* Wait 1sec for flush, can't sleep */
> +       ret = readx_poll_timeout(readl, c->base + VFF_FLUSH, tmp,
> +                       tmp != VFF_FLUSH_B, 0, 1000000);

It is extremely bad pending so long is in the spin_lock_irqsave

> +       if (ret)
> +               dev_err(c->vc.chan.device->dev, "flush: fail, debug=0x%x\n",
> +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> +
> +       /* set stop as 1 -> wait until en is 0 -> set stop as 0 */
> +       mtk_uart_apdma_write(c, VFF_STOP, VFF_STOP_B);
> +       ret = readx_poll_timeout(readl, c->base + VFF_EN, tmp, !tmp, 10, 100);
> +       if (ret)
> +               dev_err(c->vc.chan.device->dev, "stop: fail, debug=0x%x\n",
> +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> +
> +       mtk_uart_apdma_write(c, VFF_STOP, VFF_STOP_CLR_B);
> +       mtk_uart_apdma_write(c, VFF_INT_EN, VFF_INT_EN_CLR_B);
> +
> +       if (c->dir == DMA_DEV_TO_MEM)
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> +       else if (c->dir == DMA_MEM_TO_DEV)
> +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> +
> +       spin_unlock_irqrestore(&c->vc.lock, flags);
> +
> +       return 0;
> +}
> +
> +static int mtk_uart_apdma_device_pause(struct dma_chan *chan)
> +{
> +       /* just for check caps pass */
> +       dev_err(chan->device->dev, "Pause can't support\n");
> +

If the device can't support hardware pause, we can do it as a software
pause in an implementation based on vdesc.

> +       return 0;
> +}
> +
> +static void mtk_uart_apdma_free(struct mtk_uart_apdmadev *mtkd)
> +{
> +       while (!list_empty(&mtkd->ddev.channels)) {
> +               struct mtk_chan *c = list_first_entry(&mtkd->ddev.channels,
> +                       struct mtk_chan, vc.chan.device_node);
> +
> +               list_del(&c->vc.chan.device_node);
> +               tasklet_kill(&c->vc.task);
> +       }
> +}
> +
> +static const struct of_device_id mtk_uart_apdma_match[] = {
> +       { .compatible = "mediatek,mt6577-uart-dma", },
> +       { /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, mtk_uart_apdma_match);
> +
> +static int mtk_uart_apdma_probe(struct platform_device *pdev)
> +{
> +       struct device_node *np = pdev->dev.of_node;
> +       struct mtk_uart_apdmadev *mtkd;
> +       struct resource *res;
> +       struct mtk_chan *c;
> +       int bit_mask = 32, rc;
> +       unsigned int i;
> +
> +       mtkd = devm_kzalloc(&pdev->dev, sizeof(*mtkd), GFP_KERNEL);
> +       if (!mtkd)
> +               return -ENOMEM;
> +
> +       mtkd->clk = devm_clk_get(&pdev->dev, NULL);
> +       if (IS_ERR(mtkd->clk)) {
> +               dev_err(&pdev->dev, "No clock specified\n");
> +               rc = PTR_ERR(mtkd->clk);
> +               return rc;
> +       }
> +
> +       if (of_property_read_bool(np, "mediatek,dma-33bits"))
> +               mtkd->support_33bits = true;
> +
> +       if (mtkd->support_33bits)
> +               bit_mask = 33;
> +
> +       rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(bit_mask));
> +       if (rc)
> +               return rc;
> +
> +       dma_cap_set(DMA_SLAVE, mtkd->ddev.cap_mask);
> +       mtkd->ddev.device_alloc_chan_resources =
> +                               mtk_uart_apdma_alloc_chan_resources;
> +       mtkd->ddev.device_free_chan_resources =
> +                               mtk_uart_apdma_free_chan_resources;
> +       mtkd->ddev.device_tx_status = mtk_uart_apdma_tx_status;
> +       mtkd->ddev.device_issue_pending = mtk_uart_apdma_issue_pending;
> +       mtkd->ddev.device_prep_slave_sg = mtk_uart_apdma_prep_slave_sg;
> +       mtkd->ddev.device_config = mtk_uart_apdma_slave_config;
> +       mtkd->ddev.device_pause = mtk_uart_apdma_device_pause;
> +       mtkd->ddev.device_terminate_all = mtk_uart_apdma_terminate_all;
> +       mtkd->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
> +       mtkd->ddev.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
> +       mtkd->ddev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
> +       mtkd->ddev.residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
> +       mtkd->ddev.dev = &pdev->dev;
> +       INIT_LIST_HEAD(&mtkd->ddev.channels);
> +
> +       mtkd->dma_requests = MTK_UART_APDMA_NR_VCHANS;
> +       if (of_property_read_u32(np, "dma-requests", &mtkd->dma_requests)) {
> +               dev_info(&pdev->dev,
> +                        "Using %u as missing dma-requests property\n",
> +                        MTK_UART_APDMA_NR_VCHANS);
> +       }
> +
> +       mtkd->dma_irq = devm_kcalloc(&pdev->dev, mtkd->dma_requests,
> +                                sizeof(*mtkd->dma_irq), GFP_KERNEL);
> +       if (!mtkd->dma_irq)
> +               return -ENOMEM;
> +
> +       for (i = 0; i < mtkd->dma_requests; i++) {
> +               c = devm_kzalloc(mtkd->ddev.dev, sizeof(*c), GFP_KERNEL);
> +               if (!c) {
> +                       rc = -ENODEV;
> +                       goto err_no_dma;
> +               }
> +
> +               res = platform_get_resource(pdev, IORESOURCE_MEM, i);
> +               if (!res) {
> +                       rc = -ENODEV;
> +                       goto err_no_dma;
> +               }
> +
> +               c->base = devm_ioremap_resource(&pdev->dev, res);
> +               if (IS_ERR(c->base)) {
> +                       rc = PTR_ERR(c->base);
> +                       goto err_no_dma;
> +               }
> +               c->requested = false;
> +               c->vc.desc_free = mtk_uart_apdma_desc_free;
> +               vchan_init(&c->vc, &mtkd->ddev);
> +
> +               mtkd->dma_irq[i] = platform_get_irq(pdev, i);
> +               if ((int)mtkd->dma_irq[i] < 0) {
> +                       dev_err(&pdev->dev, "failed to get IRQ[%d]\n", i);
> +                       rc = -EINVAL;
> +                       goto err_no_dma;
> +               }
> +       }
> +
> +       pm_runtime_enable(&pdev->dev);
> +       pm_runtime_set_active(&pdev->dev);
> +
> +       rc = dma_async_device_register(&mtkd->ddev);
> +       if (rc)
> +               goto rpm_disable;
> +
> +       platform_set_drvdata(pdev, mtkd);
> +
> +       /* Device-tree DMA controller registration */
> +       rc = of_dma_controller_register(np, of_dma_xlate_by_chan_id, mtkd);
> +       if (rc)
> +               goto dma_remove;
> +
> +       return rc;
> +
> +dma_remove:
> +       dma_async_device_unregister(&mtkd->ddev);
> +rpm_disable:
> +       pm_runtime_disable(&pdev->dev);
> +err_no_dma:
> +       mtk_uart_apdma_free(mtkd);
> +       return rc;
> +}
> +
> +static int mtk_uart_apdma_remove(struct platform_device *pdev)
> +{
> +       struct mtk_uart_apdmadev *mtkd = platform_get_drvdata(pdev);
> +
> +       if (pdev->dev.of_node)
> +               of_dma_controller_free(pdev->dev.of_node);
> +
> +       pm_runtime_disable(&pdev->dev);
> +       pm_runtime_put_noidle(&pdev->dev);

That pm_runtime_put_noidle should be removed or it causes an
inconsistency with the probe handler.

> +
> +       dma_async_device_unregister(&mtkd->ddev);
> +       mtk_uart_apdma_free(mtkd);
> +
> +       return 0;
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int mtk_uart_apdma_suspend(struct device *dev)
> +{
> +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> +
> +       if (!pm_runtime_suspended(dev))
> +               clk_disable_unprepare(mtkd->clk);
> +
> +       return 0;
> +}
> +
> +static int mtk_uart_apdma_resume(struct device *dev)
> +{
> +       int ret;
> +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> +
> +       if (!pm_runtime_suspended(dev)) {
> +               ret = clk_prepare_enable(mtkd->clk);
> +               if (ret)
> +                       return ret;
> +       }
> +
> +       return 0;
> +}
> +#endif /* CONFIG_PM_SLEEP */
> +
> +#ifdef CONFIG_PM
> +static int mtk_uart_apdma_runtime_suspend(struct device *dev)
> +{
> +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> +
> +       clk_disable_unprepare(mtkd->clk);
> +
> +       return 0;
> +}
> +
> +static int mtk_uart_apdma_runtime_resume(struct device *dev)
> +{
> +       int ret;
> +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> +
> +       ret = clk_prepare_enable(mtkd->clk);
> +       if (ret)
> +               return ret;
> +
> +       return 0;
> +}
> +#endif /* CONFIG_PM */
> +
> +static const struct dev_pm_ops mtk_uart_apdma_pm_ops = {
> +       SET_SYSTEM_SLEEP_PM_OPS(mtk_uart_apdma_suspend, mtk_uart_apdma_resume)
> +       SET_RUNTIME_PM_OPS(mtk_uart_apdma_runtime_suspend,
> +                          mtk_uart_apdma_runtime_resume, NULL)
> +};

It probably causes a build error when CONFIG_PM is not enabled.
and use a UNIVERSAL_DEV_PM_OPS because the runtime suspend/resume and
system suspend/resume for the dma are
almost the same.

> +
> +static struct platform_driver mtk_uart_apdma_driver = {
> +       .probe  = mtk_uart_apdma_probe,
> +       .remove = mtk_uart_apdma_remove,
> +       .driver = {
> +               .name           = KBUILD_MODNAME,
> +               .pm             = &mtk_uart_apdma_pm_ops,
> +               .of_match_table = of_match_ptr(mtk_uart_apdma_match),
> +       },
> +};
> +
> +module_platform_driver(mtk_uart_apdma_driver);
> +
> +MODULE_DESCRIPTION("MediaTek UART APDMA Controller Driver");
> +MODULE_AUTHOR("Long Cheng <long.cheng@mediatek.com>");
> +MODULE_LICENSE("GPL v2");
> +
> --
> 1.7.9.5
>
Long Cheng - April 9, 2019, 9:42 a.m.
On Sun, 2019-03-10 at 19:15 +0800, Nicolas Boichat wrote:
> On Thu, Mar 7, 2019 at 9:45 AM Long Cheng <long.cheng@mediatek.com> wrote:
> >
> > In DMA engine framework, add 8250 uart dma to support MediaTek uart.
> > If MediaTek uart enabled(SERIAL_8250_MT6577), and want to improve
> > the performance, can enable the function.
> >
> > Signed-off-by: Long Cheng <long.cheng@mediatek.com>
> > ---
> >  drivers/dma/mediatek/Kconfig          |   11 +
> >  drivers/dma/mediatek/Makefile         |    1 +
> >  drivers/dma/mediatek/mtk-uart-apdma.c |  660 +++++++++++++++++++++++++++++++++
> >  3 files changed, 672 insertions(+)
> >  create mode 100644 drivers/dma/mediatek/mtk-uart-apdma.c
> >
> > diff --git a/drivers/dma/mediatek/Kconfig b/drivers/dma/mediatek/Kconfig
> > index 680fc05..ac49eb6 100644
> > --- a/drivers/dma/mediatek/Kconfig
> > +++ b/drivers/dma/mediatek/Kconfig
> > @@ -24,3 +24,14 @@ config MTK_CQDMA
> >
> >           This controller provides the channels which is dedicated to
> >           memory-to-memory transfer to offload from CPU.
> > +
> > +config MTK_UART_APDMA
> > +       tristate "MediaTek SoCs APDMA support for UART"
> > +       depends on OF && SERIAL_8250_MT6577
> > +       select DMA_ENGINE
> > +       select DMA_VIRTUAL_CHANNELS
> > +       help
> > +         Support for the UART DMA engine found on MediaTek MTK SoCs.
> > +         When SERIAL_8250_MT6577 is enabled, and if you want to use DMA,
> > +         you can enable the config. The DMA engine can only be used
> > +         with MediaTek SoCs.
> > diff --git a/drivers/dma/mediatek/Makefile b/drivers/dma/mediatek/Makefile
> > index 41bb381..61a6d29 100644
> > --- a/drivers/dma/mediatek/Makefile
> > +++ b/drivers/dma/mediatek/Makefile
> > @@ -1,2 +1,3 @@
> > +obj-$(CONFIG_MTK_UART_APDMA) += mtk-uart-apdma.o
> >  obj-$(CONFIG_MTK_HSDMA) += mtk-hsdma.o
> >  obj-$(CONFIG_MTK_CQDMA) += mtk-cqdma.o
> > diff --git a/drivers/dma/mediatek/mtk-uart-apdma.c b/drivers/dma/mediatek/mtk-uart-apdma.c
> > new file mode 100644
> > index 0000000..9ed7a49
> > --- /dev/null
> > +++ b/drivers/dma/mediatek/mtk-uart-apdma.c
> > @@ -0,0 +1,660 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * MediaTek Uart APDMA driver.
> > + *
> > + * Copyright (c) 2018 MediaTek Inc.
> > + * Author: Long Cheng <long.cheng@mediatek.com>
> > + */
> > +
> > +#include <linux/clk.h>
> > +#include <linux/dmaengine.h>
> > +#include <linux/dma-mapping.h>
> > +#include <linux/err.h>
> > +#include <linux/init.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/iopoll.h>
> > +#include <linux/kernel.h>
> > +#include <linux/list.h>
> > +#include <linux/module.h>
> > +#include <linux/of_device.h>
> > +#include <linux/of_dma.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/pm_runtime.h>
> > +#include <linux/slab.h>
> > +#include <linux/spinlock.h>
> > +
> > +#include "../virt-dma.h"
> > +
> > +/* The default number of virtual channel */
> > +#define MTK_UART_APDMA_NR_VCHANS       8
> > +
> > +#define VFF_EN_B               BIT(0)
> > +#define VFF_STOP_B             BIT(0)
> > +#define VFF_FLUSH_B            BIT(0)
> > +#define VFF_4G_SUPPORT_B       BIT(0)
> > +#define VFF_RX_INT_EN0_B       BIT(0)  /* rx valid size >=  vff thre */
> > +#define VFF_RX_INT_EN1_B       BIT(1)
> > +#define VFF_TX_INT_EN_B                BIT(0)  /* tx left size >= vff thre */
> > +#define VFF_WARM_RST_B         BIT(0)
> > +#define VFF_RX_INT_CLR_B       (BIT(0) | BIT(1))
> > +#define VFF_TX_INT_CLR_B       0
> > +#define VFF_STOP_CLR_B         0
> > +#define VFF_INT_EN_CLR_B       0
> > +#define VFF_4G_SUPPORT_CLR_B   0
> > +
> > +/* interrupt trigger level for tx */
> > +#define VFF_TX_THRE(n)         ((n) * 7 / 8)
> > +/* interrupt trigger level for rx */
> > +#define VFF_RX_THRE(n)         ((n) * 3 / 4)
> > +
> > +#define VFF_RING_SIZE  0xffffU
> 
> Drop the U, it's not very useful (there are a a few more below, grep
> for [0-9a-f]U).
> 

OK, i will fix these.

> > +/* invert this bit when wrap ring head again */
> > +#define VFF_RING_WRAP  0x10000U
> > +
> > +#define VFF_INT_FLAG           0x00
> > +#define VFF_INT_EN             0x04
> > +#define VFF_EN                 0x08
> > +#define VFF_RST                        0x0c
> > +#define VFF_STOP               0x10
> > +#define VFF_FLUSH              0x14
> > +#define VFF_ADDR               0x1c
> > +#define VFF_LEN                        0x24
> > +#define VFF_THRE               0x28
> > +#define VFF_WPT                        0x2c
> > +#define VFF_RPT                        0x30
> > +/* TX: the buffer size HW can read. RX: the buffer size SW can read. */
> > +#define VFF_VALID_SIZE         0x3c
> > +/* TX: the buffer size SW can write. RX: the buffer size HW can write. */
> > +#define VFF_LEFT_SIZE          0x40
> > +#define VFF_DEBUG_STATUS       0x50
> > +#define VFF_4G_SUPPORT         0x54
> > +
> > +struct mtk_uart_apdmadev {
> > +       struct dma_device ddev;
> > +       struct clk *clk;
> > +       bool support_33bits;
> > +       unsigned int dma_requests;
> > +       unsigned int *dma_irq;
> > +};
> > +
> > +struct mtk_uart_apdma_desc {
> > +       struct virt_dma_desc vd;
> > +
> > +       unsigned int avail_len;
> > +};
> > +
> > +struct mtk_chan {
> > +       struct virt_dma_chan vc;
> > +       struct dma_slave_config cfg;
> > +       void __iomem *base;
> > +       struct mtk_uart_apdma_desc *desc;
> > +
> > +       enum dma_transfer_direction dir;
> > +
> > +       bool requested;
> > +
> > +       unsigned int rx_status;
> > +};
> > +
> > +static inline struct mtk_uart_apdmadev *
> > +to_mtk_uart_apdma_dev(struct dma_device *d)
> > +{
> > +       return container_of(d, struct mtk_uart_apdmadev, ddev);
> > +}
> > +
> > +static inline struct mtk_chan *to_mtk_uart_apdma_chan(struct dma_chan *c)
> > +{
> > +       return container_of(c, struct mtk_chan, vc.chan);
> > +}
> > +
> > +static inline struct mtk_uart_apdma_desc *to_mtk_uart_apdma_desc
> > +       (struct dma_async_tx_descriptor *t)
> > +{
> > +       return container_of(t, struct mtk_uart_apdma_desc, vd.tx);
> > +}
> > +
> > +static void mtk_uart_apdma_write(struct mtk_chan *c,
> > +                              unsigned int reg, unsigned int val)
> > +{
> > +       writel(val, c->base + reg);
> > +}
> > +
> > +static unsigned int mtk_uart_apdma_read(struct mtk_chan *c, unsigned int reg)
> > +{
> > +       return readl(c->base + reg);
> > +}
> > +
> > +static void mtk_uart_apdma_desc_free(struct virt_dma_desc *vd)
> > +{
> > +       struct dma_chan *chan = vd->tx.chan;
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +
> > +       kfree(c->desc);
> > +}
> > +
> > +static void mtk_uart_apdma_start_tx(struct mtk_chan *c)
> > +{
> > +       unsigned int len, send, left, wpt, d_wpt, tmp;
> > +       int ret;
> > +
> > +       left = mtk_uart_apdma_read(c, VFF_LEFT_SIZE);
> > +       if (!left) {
> > +               mtk_uart_apdma_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
> > +               return;
> > +       }
> > +
> > +       /* Wait 1sec for flush, can't sleep */
> > +       ret = readx_poll_timeout(readl, c->base + VFF_FLUSH, tmp,
> > +                       tmp != VFF_FLUSH_B, 0, 1000000);
> > +       if (ret)
> > +               dev_warn(c->vc.chan.device->dev, "tx: fail, debug=0x%x\n",
> > +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> > +
> > +       send = min_t(unsigned int, left, c->desc->avail_len);
> > +       wpt = mtk_uart_apdma_read(c, VFF_WPT);
> > +       len = c->cfg.dst_port_window_size;
> > +
> > +       d_wpt = wpt + send;
> > +       if ((d_wpt & VFF_RING_SIZE) >= len) {
> > +               d_wpt = d_wpt - len;
> > +               d_wpt = d_wpt ^ VFF_RING_WRAP;
> > +       }
> > +       mtk_uart_apdma_write(c, VFF_WPT, d_wpt);
> > +
> > +       c->desc->avail_len -= send;
> > +
> > +       mtk_uart_apdma_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
> > +       if (mtk_uart_apdma_read(c, VFF_FLUSH) == 0U)
> > +               mtk_uart_apdma_write(c, VFF_FLUSH, VFF_FLUSH_B);
> > +}
> > +
> > +static void mtk_uart_apdma_start_rx(struct mtk_chan *c)
> > +{
> > +       struct mtk_uart_apdma_desc *d = c->desc;
> > +       unsigned int len, wg, rg;
> > +       int cnt;
> > +
> > +       if ((mtk_uart_apdma_read(c, VFF_VALID_SIZE) == 0U) ||
> > +               !d || !vchan_next_desc(&c->vc))
> > +               return;
> > +
> > +       len = c->cfg.src_port_window_size;
> > +       rg = mtk_uart_apdma_read(c, VFF_RPT);
> > +       wg = mtk_uart_apdma_read(c, VFF_WPT);
> > +       cnt = (wg & VFF_RING_SIZE) - (rg & VFF_RING_SIZE);
> > +       /*
> > +        * The buffer is ring buffer. If wrap bit different,
> > +        * represents the start of the next cycle for WPT
> > +        */
> > +       if ((rg ^ wg) & VFF_RING_WRAP)
> > +               cnt += len;
> > +
> > +       c->rx_status = d->avail_len - cnt;
> > +       mtk_uart_apdma_write(c, VFF_RPT, wg);
> > +
> > +       list_del(&d->vd.node);
> > +       vchan_cookie_complete(&d->vd);
> > +}
> > +
> > +static irqreturn_t mtk_uart_apdma_irq_handler(int irq, void *dev_id)
> > +{
> > +       struct dma_chan *chan = (struct dma_chan *)dev_id;
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       struct mtk_uart_apdma_desc *d;
> > +       unsigned long flags;
> > +
> > +       spin_lock_irqsave(&c->vc.lock, flags);
> > +       if (c->dir == DMA_DEV_TO_MEM) {
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> > +               mtk_uart_apdma_start_rx(c);
> > +       } else if (c->dir == DMA_MEM_TO_DEV) {
> > +               d = c->desc;
> > +
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> > +
> > +               if (d->avail_len != 0U) {
> > +                       mtk_uart_apdma_start_tx(c);
> > +               } else {
> > +                       list_del(&d->vd.node);
> > +                       vchan_cookie_complete(&d->vd);
> > +               }
> > +       }
> > +       spin_unlock_irqrestore(&c->vc.lock, flags);
> > +
> > +       return IRQ_HANDLED;
> > +}
> > +
> > +static int mtk_uart_apdma_alloc_chan_resources(struct dma_chan *chan)
> > +{
> > +       struct mtk_uart_apdmadev *mtkd = to_mtk_uart_apdma_dev(chan->device);
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       unsigned int tmp;
> > +       int ret;
> > +
> > +       pm_runtime_get_sync(mtkd->ddev.dev);
> > +
> > +       mtk_uart_apdma_write(c, VFF_ADDR, 0);
> > +       mtk_uart_apdma_write(c, VFF_THRE, 0);
> > +       mtk_uart_apdma_write(c, VFF_LEN, 0);
> > +       mtk_uart_apdma_write(c, VFF_RST, VFF_WARM_RST_B);
> > +
> > +       ret = readx_poll_timeout(readl, c->base + VFF_EN, tmp, !tmp, 10, 100);
> > +       if (ret) {
> > +               dev_err(chan->device->dev, "dma reset: fail, timeout\n");
> > +               return ret;
> > +       }
> > +
> > +       if (!c->requested) {
> > +               c->requested = true;
> > +               ret = request_irq(mtkd->dma_irq[chan->chan_id],
> > +                                 mtk_uart_apdma_irq_handler, IRQF_TRIGGER_NONE,
> > +                                 KBUILD_MODNAME, chan);
> > +               if (ret < 0) {
> > +                       dev_err(chan->device->dev, "Can't request dma IRQ\n");
> > +                       return -EINVAL;
> > +               }
> > +       }
> > +
> > +       if (mtkd->support_33bits)
> > +               mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_CLR_B);
> > +
> > +       return ret;
> > +}
> > +
> > +static void mtk_uart_apdma_free_chan_resources(struct dma_chan *chan)
> > +{
> > +       struct mtk_uart_apdmadev *mtkd = to_mtk_uart_apdma_dev(chan->device);
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +
> > +       if (c->requested) {
> > +               c->requested = false;
> > +               free_irq(mtkd->dma_irq[chan->chan_id], chan);
> > +       }
> > +
> > +       tasklet_kill(&c->vc.task);
> > +
> > +       vchan_free_chan_resources(&c->vc);
> > +
> > +       pm_runtime_put_sync(mtkd->ddev.dev);
> > +}
> > +
> > +static enum dma_status mtk_uart_apdma_tx_status(struct dma_chan *chan,
> > +                                        dma_cookie_t cookie,
> > +                                        struct dma_tx_state *txstate)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       enum dma_status ret;
> > +
> > +       ret = dma_cookie_status(chan, cookie, txstate);
> > +
> > +       dma_set_residue(txstate, c->rx_status);
> > +
> > +       return ret;
> > +}
> > +
> > +static void mtk_uart_apdma_config_write(struct dma_chan *chan,
> > +                              struct dma_slave_config *cfg,
> > +                              enum dma_transfer_direction dir)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       struct mtk_uart_apdmadev *mtkd =
> > +                               to_mtk_uart_apdma_dev(c->vc.chan.device);
> > +       unsigned int tmp;
> > +
> > +       if (mtk_uart_apdma_read(c, VFF_EN) == VFF_EN_B)
> > +               return;
> > +
> > +       c->dir = dir;
> > +
> > +       if (dir == DMA_DEV_TO_MEM) {
> > +               tmp = cfg->src_port_window_size;
> > +
> > +               mtk_uart_apdma_write(c, VFF_ADDR, cfg->src_addr);
> > +               mtk_uart_apdma_write(c, VFF_LEN, tmp);
> > +               mtk_uart_apdma_write(c, VFF_THRE, VFF_RX_THRE(tmp));
> > +               mtk_uart_apdma_write(c, VFF_INT_EN,
> > +                               VFF_RX_INT_EN0_B | VFF_RX_INT_EN1_B);
> > +               mtk_uart_apdma_write(c, VFF_RPT, 0);
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> > +       } else if (dir == DMA_MEM_TO_DEV)       {
> > +               tmp = cfg->dst_port_window_size;
> > +
> > +               mtk_uart_apdma_write(c, VFF_ADDR, cfg->dst_addr);
> > +               mtk_uart_apdma_write(c, VFF_LEN, tmp);
> > +               mtk_uart_apdma_write(c, VFF_THRE, VFF_TX_THRE(tmp));
> > +               mtk_uart_apdma_write(c, VFF_WPT, 0);
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> > +       }
> > +
> > +       mtk_uart_apdma_write(c, VFF_EN, VFF_EN_B);
> > +
> > +       if (mtkd->support_33bits)
> > +               mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_B);
> > +
> > +       if (mtk_uart_apdma_read(c, VFF_EN) != VFF_EN_B)
> > +               dev_err(chan->device->dev, "dir[%d] fail\n", dir);
> > +}
> > +
> > +/*
> > + * dmaengine_prep_slave_single will call the function. and sglen is 1.
> > + * 8250 uart using one ring buffer, and deal with one sg.
> > + */
> > +static struct dma_async_tx_descriptor *mtk_uart_apdma_prep_slave_sg
> > +       (struct dma_chan *chan, struct scatterlist *sgl,
> > +       unsigned int sglen, enum dma_transfer_direction dir,
> > +       unsigned long tx_flags, void *context)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       struct mtk_uart_apdma_desc *d;
> > +
> > +       if (!is_slave_direction(dir))
> > +               return NULL;
> > +
> > +       mtk_uart_apdma_config_write(chan, &c->cfg, dir);
> > +
> > +       /* Now allocate and setup the descriptor */
> > +       d = kzalloc(sizeof(*d), GFP_ATOMIC);
> > +       if (!d)
> > +               return NULL;
> > +
> > +       /* sglen is 1 */
> > +       d->avail_len = sg_dma_len(sgl);
> > +       c->rx_status = d->avail_len;
> > +
> > +       return vchan_tx_prep(&c->vc, &d->vd, tx_flags);
> > +}
> > +
> > +static void mtk_uart_apdma_issue_pending(struct dma_chan *chan)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       struct virt_dma_desc *vd;
> > +       unsigned long flags;
> > +
> > +       spin_lock_irqsave(&c->vc.lock, flags);
> > +       if (vchan_issue_pending(&c->vc)) {
> > +               vd = vchan_next_desc(&c->vc);
> > +               c->desc = to_mtk_uart_apdma_desc(&vd->tx);
> > +       }
> > +
> > +       if (c->dir == DMA_DEV_TO_MEM)
> > +               mtk_uart_apdma_start_rx(c);
> > +       else if (c->dir == DMA_MEM_TO_DEV)
> > +               mtk_uart_apdma_start_tx(c);
> > +
> > +       spin_unlock_irqrestore(&c->vc.lock, flags);
> > +}
> > +
> > +static int mtk_uart_apdma_slave_config(struct dma_chan *chan,
> > +                                  struct dma_slave_config *config)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +
> > +       memcpy(&c->cfg, config, sizeof(*config));
> > +
> > +       return 0;
> > +}
> > +
> > +static int mtk_uart_apdma_terminate_all(struct dma_chan *chan)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       unsigned long flags;
> > +       unsigned int tmp;
> > +       int ret;
> > +
> > +       spin_lock_irqsave(&c->vc.lock, flags);
> > +
> > +       mtk_uart_apdma_write(c, VFF_FLUSH, VFF_FLUSH_B);
> > +       /* Wait 1sec for flush, can't sleep */
> > +       ret = readx_poll_timeout(readl, c->base + VFF_FLUSH, tmp,
> > +                       tmp != VFF_FLUSH_B, 0, 1000000);
> > +       if (ret)
> > +               dev_err(c->vc.chan.device->dev, "flush: fail, debug=0x%x\n",
> > +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> > +
> > +       /* set stop as 1 -> wait until en is 0 -> set stop as 0 */
> > +       mtk_uart_apdma_write(c, VFF_STOP, VFF_STOP_B);
> > +       ret = readx_poll_timeout(readl, c->base + VFF_EN, tmp, !tmp, 10, 100);
> > +       if (ret)
> > +               dev_err(c->vc.chan.device->dev, "stop: fail, debug=0x%x\n",
> > +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> > +
> > +       mtk_uart_apdma_write(c, VFF_STOP, VFF_STOP_CLR_B);
> > +       mtk_uart_apdma_write(c, VFF_INT_EN, VFF_INT_EN_CLR_B);
> > +
> > +       if (c->dir == DMA_DEV_TO_MEM)
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> > +       else if (c->dir == DMA_MEM_TO_DEV)
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> > +
> > +       spin_unlock_irqrestore(&c->vc.lock, flags);
> > +
> > +       return 0;
> > +}
> > +
> > +static int mtk_uart_apdma_device_pause(struct dma_chan *chan)
> > +{
> > +       /* just for check caps pass */
> > +       dev_err(chan->device->dev, "Pause can't support\n");
> > +
> > +       return 0;
> > +}
> 
> I think we've said repeatedly that leaving this stub function is incorrect.
> 

I will try to implementation it. Thanks

> > +
> > +static void mtk_uart_apdma_free(struct mtk_uart_apdmadev *mtkd)
> > +{
> > +       while (!list_empty(&mtkd->ddev.channels)) {
> > +               struct mtk_chan *c = list_first_entry(&mtkd->ddev.channels,
> > +                       struct mtk_chan, vc.chan.device_node);
> > +
> > +               list_del(&c->vc.chan.device_node);
> > +               tasklet_kill(&c->vc.task);
> > +       }
> > +}
> > +
> > +static const struct of_device_id mtk_uart_apdma_match[] = {
> > +       { .compatible = "mediatek,mt6577-uart-dma", },
> > +       { /* sentinel */ },
> > +};
> > +MODULE_DEVICE_TABLE(of, mtk_uart_apdma_match);
> > +
> > +static int mtk_uart_apdma_probe(struct platform_device *pdev)
> > +{
> > +       struct device_node *np = pdev->dev.of_node;
> > +       struct mtk_uart_apdmadev *mtkd;
> > +       struct resource *res;
> > +       struct mtk_chan *c;
> > +       int bit_mask = 32, rc;
> > +       unsigned int i;
> > +
> > +       mtkd = devm_kzalloc(&pdev->dev, sizeof(*mtkd), GFP_KERNEL);
> > +       if (!mtkd)
> > +               return -ENOMEM;
> > +
> > +       mtkd->clk = devm_clk_get(&pdev->dev, NULL);
> > +       if (IS_ERR(mtkd->clk)) {
> > +               dev_err(&pdev->dev, "No clock specified\n");
> > +               rc = PTR_ERR(mtkd->clk);
> > +               return rc;
> > +       }
> > +
> > +       if (of_property_read_bool(np, "mediatek,dma-33bits"))
> > +               mtkd->support_33bits = true;
> > +
> > +       if (mtkd->support_33bits)
> > +               bit_mask = 33;
> > +
> > +       rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(bit_mask));
> > +       if (rc)
> > +               return rc;
> > +
> > +       dma_cap_set(DMA_SLAVE, mtkd->ddev.cap_mask);
> > +       mtkd->ddev.device_alloc_chan_resources =
> > +                               mtk_uart_apdma_alloc_chan_resources;
> > +       mtkd->ddev.device_free_chan_resources =
> > +                               mtk_uart_apdma_free_chan_resources;
> > +       mtkd->ddev.device_tx_status = mtk_uart_apdma_tx_status;
> > +       mtkd->ddev.device_issue_pending = mtk_uart_apdma_issue_pending;
> > +       mtkd->ddev.device_prep_slave_sg = mtk_uart_apdma_prep_slave_sg;
> > +       mtkd->ddev.device_config = mtk_uart_apdma_slave_config;
> > +       mtkd->ddev.device_pause = mtk_uart_apdma_device_pause;
> > +       mtkd->ddev.device_terminate_all = mtk_uart_apdma_terminate_all;
> > +       mtkd->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
> > +       mtkd->ddev.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
> > +       mtkd->ddev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
> > +       mtkd->ddev.residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
> > +       mtkd->ddev.dev = &pdev->dev;
> > +       INIT_LIST_HEAD(&mtkd->ddev.channels);
> > +
> > +       mtkd->dma_requests = MTK_UART_APDMA_NR_VCHANS;
> > +       if (of_property_read_u32(np, "dma-requests", &mtkd->dma_requests)) {
> > +               dev_info(&pdev->dev,
> > +                        "Using %u as missing dma-requests property\n",
> > +                        MTK_UART_APDMA_NR_VCHANS);
> > +       }
> > +
> > +       mtkd->dma_irq = devm_kcalloc(&pdev->dev, mtkd->dma_requests,
> > +                                sizeof(*mtkd->dma_irq), GFP_KERNEL);
> > +       if (!mtkd->dma_irq)
> > +               return -ENOMEM;
> > +
> > +       for (i = 0; i < mtkd->dma_requests; i++) {
> > +               c = devm_kzalloc(mtkd->ddev.dev, sizeof(*c), GFP_KERNEL);
> > +               if (!c) {
> > +                       rc = -ENODEV;
> > +                       goto err_no_dma;
> > +               }
> > +
> > +               res = platform_get_resource(pdev, IORESOURCE_MEM, i);
> > +               if (!res) {
> > +                       rc = -ENODEV;
> > +                       goto err_no_dma;
> > +               }
> > +
> > +               c->base = devm_ioremap_resource(&pdev->dev, res);
> > +               if (IS_ERR(c->base)) {
> > +                       rc = PTR_ERR(c->base);
> > +                       goto err_no_dma;
> > +               }
> > +               c->requested = false;
> > +               c->vc.desc_free = mtk_uart_apdma_desc_free;
> > +               vchan_init(&c->vc, &mtkd->ddev);
> > +
> > +               mtkd->dma_irq[i] = platform_get_irq(pdev, i);
> > +               if ((int)mtkd->dma_irq[i] < 0) {
> > +                       dev_err(&pdev->dev, "failed to get IRQ[%d]\n", i);
> > +                       rc = -EINVAL;
> > +                       goto err_no_dma;
> > +               }
> > +       }
> > +
> > +       pm_runtime_enable(&pdev->dev);
> > +       pm_runtime_set_active(&pdev->dev);
> > +
> > +       rc = dma_async_device_register(&mtkd->ddev);
> > +       if (rc)
> > +               goto rpm_disable;
> > +
> > +       platform_set_drvdata(pdev, mtkd);
> > +
> > +       /* Device-tree DMA controller registration */
> > +       rc = of_dma_controller_register(np, of_dma_xlate_by_chan_id, mtkd);
> > +       if (rc)
> > +               goto dma_remove;
> > +
> > +       return rc;
> > +
> > +dma_remove:
> > +       dma_async_device_unregister(&mtkd->ddev);
> > +rpm_disable:
> > +       pm_runtime_disable(&pdev->dev);
> > +err_no_dma:
> > +       mtk_uart_apdma_free(mtkd);
> > +       return rc;
> > +}
> > +
> > +static int mtk_uart_apdma_remove(struct platform_device *pdev)
> > +{
> > +       struct mtk_uart_apdmadev *mtkd = platform_get_drvdata(pdev);
> > +
> > +       if (pdev->dev.of_node)
> > +               of_dma_controller_free(pdev->dev.of_node);
> > +
> > +       pm_runtime_disable(&pdev->dev);
> > +       pm_runtime_put_noidle(&pdev->dev);
> > +
> > +       dma_async_device_unregister(&mtkd->ddev);
> > +       mtk_uart_apdma_free(mtkd);
> > +
> > +       return 0;
> > +}
> > +
> > +#ifdef CONFIG_PM_SLEEP
> > +static int mtk_uart_apdma_suspend(struct device *dev)
> > +{
> > +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> > +
> > +       if (!pm_runtime_suspended(dev))
> > +               clk_disable_unprepare(mtkd->clk);
> > +
> > +       return 0;
> > +}
> > +
> > +static int mtk_uart_apdma_resume(struct device *dev)
> > +{
> > +       int ret;
> > +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> > +
> > +       if (!pm_runtime_suspended(dev)) {
> > +               ret = clk_prepare_enable(mtkd->clk);
> > +               if (ret)
> > +                       return ret;
> > +       }
> > +
> > +       return 0;
> > +}
> > +#endif /* CONFIG_PM_SLEEP */
> > +
> > +#ifdef CONFIG_PM
> > +static int mtk_uart_apdma_runtime_suspend(struct device *dev)
> > +{
> > +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> > +
> > +       clk_disable_unprepare(mtkd->clk);
> > +
> > +       return 0;
> > +}
> > +
> > +static int mtk_uart_apdma_runtime_resume(struct device *dev)
> > +{
> > +       int ret;
> > +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> > +
> > +       ret = clk_prepare_enable(mtkd->clk);
> > +       if (ret)
> > +               return ret;
> > +
> > +       return 0;
> > +}
> > +#endif /* CONFIG_PM */
> > +
> > +static const struct dev_pm_ops mtk_uart_apdma_pm_ops = {
> > +       SET_SYSTEM_SLEEP_PM_OPS(mtk_uart_apdma_suspend, mtk_uart_apdma_resume)
> > +       SET_RUNTIME_PM_OPS(mtk_uart_apdma_runtime_suspend,
> > +                          mtk_uart_apdma_runtime_resume, NULL)
> > +};
> > +
> > +static struct platform_driver mtk_uart_apdma_driver = {
> > +       .probe  = mtk_uart_apdma_probe,
> > +       .remove = mtk_uart_apdma_remove,
> > +       .driver = {
> > +               .name           = KBUILD_MODNAME,
> > +               .pm             = &mtk_uart_apdma_pm_ops,
> > +               .of_match_table = of_match_ptr(mtk_uart_apdma_match),
> > +       },
> > +};
> > +
> > +module_platform_driver(mtk_uart_apdma_driver);
> > +
> > +MODULE_DESCRIPTION("MediaTek UART APDMA Controller Driver");
> > +MODULE_AUTHOR("Long Cheng <long.cheng@mediatek.com>");
> > +MODULE_LICENSE("GPL v2");
> > +
> > --
> > 1.7.9.5
> >
Long Cheng - April 11, 2019, 8:20 a.m.
On Sun, 2019-03-10 at 17:31 -0700, Sean Wang wrote:
> Hi, Long
> 
> List some comments as the below and this week I will find a board to
> test and then improve the driver.
> 
>          Sean
> 
> On Wed, Mar 6, 2019 at 5:45 PM Long Cheng <long.cheng@mediatek.com> wrote:
> >
> > In DMA engine framework, add 8250 uart dma to support MediaTek uart.
> > If MediaTek uart enabled(SERIAL_8250_MT6577), and want to improve
> > the performance, can enable the function.
> >
> > Signed-off-by: Long Cheng <long.cheng@mediatek.com>
> > ---
> >  drivers/dma/mediatek/Kconfig          |   11 +
> >  drivers/dma/mediatek/Makefile         |    1 +
> >  drivers/dma/mediatek/mtk-uart-apdma.c |  660 +++++++++++++++++++++++++++++++++
> >  3 files changed, 672 insertions(+)
> >  create mode 100644 drivers/dma/mediatek/mtk-uart-apdma.c
> >
> > diff --git a/drivers/dma/mediatek/Kconfig b/drivers/dma/mediatek/Kconfig
> > index 680fc05..ac49eb6 100644
> > --- a/drivers/dma/mediatek/Kconfig
> > +++ b/drivers/dma/mediatek/Kconfig
> > @@ -24,3 +24,14 @@ config MTK_CQDMA
> >
> >           This controller provides the channels which is dedicated to
> >           memory-to-memory transfer to offload from CPU.
> > +
> > +config MTK_UART_APDMA
> > +       tristate "MediaTek SoCs APDMA support for UART"
> > +       depends on OF && SERIAL_8250_MT6577
> > +       select DMA_ENGINE
> > +       select DMA_VIRTUAL_CHANNELS
> > +       help
> > +         Support for the UART DMA engine found on MediaTek MTK SoCs.
> > +         When SERIAL_8250_MT6577 is enabled, and if you want to use DMA,
> > +         you can enable the config. The DMA engine can only be used
> > +         with MediaTek SoCs.
> > diff --git a/drivers/dma/mediatek/Makefile b/drivers/dma/mediatek/Makefile
> > index 41bb381..61a6d29 100644
> > --- a/drivers/dma/mediatek/Makefile
> > +++ b/drivers/dma/mediatek/Makefile
> > @@ -1,2 +1,3 @@
> > +obj-$(CONFIG_MTK_UART_APDMA) += mtk-uart-apdma.o
> >  obj-$(CONFIG_MTK_HSDMA) += mtk-hsdma.o
> >  obj-$(CONFIG_MTK_CQDMA) += mtk-cqdma.o
> > diff --git a/drivers/dma/mediatek/mtk-uart-apdma.c b/drivers/dma/mediatek/mtk-uart-apdma.c
> > new file mode 100644
> > index 0000000..9ed7a49
> > --- /dev/null
> > +++ b/drivers/dma/mediatek/mtk-uart-apdma.c
> > @@ -0,0 +1,660 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * MediaTek Uart APDMA driver.
> > + *
> > + * Copyright (c) 2018 MediaTek Inc.
> > + * Author: Long Cheng <long.cheng@mediatek.com>
> > + */
> > +
> > +#include <linux/clk.h>
> > +#include <linux/dmaengine.h>
> > +#include <linux/dma-mapping.h>
> > +#include <linux/err.h>
> > +#include <linux/init.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/iopoll.h>
> > +#include <linux/kernel.h>
> > +#include <linux/list.h>
> > +#include <linux/module.h>
> > +#include <linux/of_device.h>
> > +#include <linux/of_dma.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/pm_runtime.h>
> > +#include <linux/slab.h>
> > +#include <linux/spinlock.h>
> > +
> > +#include "../virt-dma.h"
> > +
> > +/* The default number of virtual channel */
> > +#define MTK_UART_APDMA_NR_VCHANS       8
> > +
> > +#define VFF_EN_B               BIT(0)
> > +#define VFF_STOP_B             BIT(0)
> > +#define VFF_FLUSH_B            BIT(0)
> > +#define VFF_4G_SUPPORT_B       BIT(0)
> > +#define VFF_RX_INT_EN0_B       BIT(0)  /* rx valid size >=  vff thre */
> > +#define VFF_RX_INT_EN1_B       BIT(1)
> > +#define VFF_TX_INT_EN_B                BIT(0)  /* tx left size >= vff thre */
> > +#define VFF_WARM_RST_B         BIT(0)
> > +#define VFF_RX_INT_CLR_B       (BIT(0) | BIT(1))
> > +#define VFF_TX_INT_CLR_B       0
> > +#define VFF_STOP_CLR_B         0
> > +#define VFF_INT_EN_CLR_B       0
> > +#define VFF_4G_SUPPORT_CLR_B   0
> > +
> > +/* interrupt trigger level for tx */
> > +#define VFF_TX_THRE(n)         ((n) * 7 / 8)
> > +/* interrupt trigger level for rx */
> > +#define VFF_RX_THRE(n)         ((n) * 3 / 4)
> > +
> > +#define VFF_RING_SIZE  0xffffU
> > +/* invert this bit when wrap ring head again */
> > +#define VFF_RING_WRAP  0x10000U
> > +
> > +#define VFF_INT_FLAG           0x00
> > +#define VFF_INT_EN             0x04
> > +#define VFF_EN                 0x08
> > +#define VFF_RST                        0x0c
> > +#define VFF_STOP               0x10
> > +#define VFF_FLUSH              0x14
> > +#define VFF_ADDR               0x1c
> > +#define VFF_LEN                        0x24
> > +#define VFF_THRE               0x28
> > +#define VFF_WPT                        0x2c
> > +#define VFF_RPT                        0x30
> > +/* TX: the buffer size HW can read. RX: the buffer size SW can read. */
> > +#define VFF_VALID_SIZE         0x3c
> > +/* TX: the buffer size SW can write. RX: the buffer size HW can write. */
> > +#define VFF_LEFT_SIZE          0x40
> > +#define VFF_DEBUG_STATUS       0x50
> > +#define VFF_4G_SUPPORT         0x54
> > +
> > +struct mtk_uart_apdmadev {
> > +       struct dma_device ddev;
> > +       struct clk *clk;
> > +       bool support_33bits;
> > +       unsigned int dma_requests;
> > +       unsigned int *dma_irq;
> > +};
> > +
> > +struct mtk_uart_apdma_desc {
> > +       struct virt_dma_desc vd;
> > +
> > +       unsigned int avail_len;
> > +};
> > +
> > +struct mtk_chan {
> > +       struct virt_dma_chan vc;
> > +       struct dma_slave_config cfg;
> > +       void __iomem *base;
> > +       struct mtk_uart_apdma_desc *desc;
> > +
> > +       enum dma_transfer_direction dir;
> > +
> > +       bool requested;
> > +
> > +       unsigned int rx_status;
> > +};
> > +
> > +static inline struct mtk_uart_apdmadev *
> > +to_mtk_uart_apdma_dev(struct dma_device *d)
> > +{
> > +       return container_of(d, struct mtk_uart_apdmadev, ddev);
> > +}
> > +
> > +static inline struct mtk_chan *to_mtk_uart_apdma_chan(struct dma_chan *c)
> > +{
> > +       return container_of(c, struct mtk_chan, vc.chan);
> > +}
> > +
> > +static inline struct mtk_uart_apdma_desc *to_mtk_uart_apdma_desc
> > +       (struct dma_async_tx_descriptor *t)
> > +{
> > +       return container_of(t, struct mtk_uart_apdma_desc, vd.tx);
> > +}
> > +
> > +static void mtk_uart_apdma_write(struct mtk_chan *c,
> > +                              unsigned int reg, unsigned int val)
> > +{
> > +       writel(val, c->base + reg);
> > +}
> > +
> > +static unsigned int mtk_uart_apdma_read(struct mtk_chan *c, unsigned int reg)
> > +{
> > +       return readl(c->base + reg);
> > +}
> > +
> > +static void mtk_uart_apdma_desc_free(struct virt_dma_desc *vd)
> > +{
> > +       struct dma_chan *chan = vd->tx.chan;
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +
> > +       kfree(c->desc);
> > +}
> > +
> > +static void mtk_uart_apdma_start_tx(struct mtk_chan *c)
> > +{
> > +       unsigned int len, send, left, wpt, d_wpt, tmp;
> > +       int ret;
> > +
> > +       left = mtk_uart_apdma_read(c, VFF_LEFT_SIZE);
> > +       if (!left) {
> > +               mtk_uart_apdma_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
> > +               return;
> > +       }
> > +
> > +       /* Wait 1sec for flush, can't sleep */
> > +       ret = readx_poll_timeout(readl, c->base + VFF_FLUSH, tmp,
> > +                       tmp != VFF_FLUSH_B, 0, 1000000);
> 
> It is really not a good idea that polling up to 1 second in an
> interrupt context.
> 

I will modify it in next version.

> > +       if (ret)
> > +               dev_warn(c->vc.chan.device->dev, "tx: fail, debug=0x%x\n",
> > +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> > +
> > +       send = min_t(unsigned int, left, c->desc->avail_len);
> > +       wpt = mtk_uart_apdma_read(c, VFF_WPT);
> > +       len = c->cfg.dst_port_window_size;
> > +
> > +       d_wpt = wpt + send;
> > +       if ((d_wpt & VFF_RING_SIZE) >= len) {
> 
> I am confused what size of VFF is.  Either VFF_RING_SIZE or
> c->cfg.dst_port_window_size?
> 

VFF_RRING_SIZE is max length that HW can support.The
c->cfg.dst_port_window_size is actual length. 

> > +               d_wpt = d_wpt - len;
> > +               d_wpt = d_wpt ^ VFF_RING_WRAP;
> > +       }
> > +       mtk_uart_apdma_write(c, VFF_WPT, d_wpt);
> > +
> > +       c->desc->avail_len -= send;
> > +
> > +       mtk_uart_apdma_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
> 
> Why should we need to program interrupt enabled bit again?

HW request. the step is must.

> 
> > +       if (mtk_uart_apdma_read(c, VFF_FLUSH) == 0U)
> > +               mtk_uart_apdma_write(c, VFF_FLUSH, VFF_FLUSH_B);
> > +}
> > +
> > +static void mtk_uart_apdma_start_rx(struct mtk_chan *c)
> > +{
> > +       struct mtk_uart_apdma_desc *d = c->desc;
> > +       unsigned int len, wg, rg;
> > +       int cnt;
> > +
> > +       if ((mtk_uart_apdma_read(c, VFF_VALID_SIZE) == 0U) ||
> > +               !d || !vchan_next_desc(&c->vc))
> > +               return;
> 
> If the current descriptor is not available, the hardware should be
> idle or stopped. so I think the condition can be removed or there is
> somewhere your handle descriptors incorrectly.

I will modify it in next version.

> 
> > +
> > +       len = c->cfg.src_port_window_size;
> > +       rg = mtk_uart_apdma_read(c, VFF_RPT);
> > +       wg = mtk_uart_apdma_read(c, VFF_WPT);
> > +       cnt = (wg & VFF_RING_SIZE) - (rg & VFF_RING_SIZE);
> 
> Is it possible that rg and wg would be greater than VFF_RING_SIZE?
> 

No.

> > +       /*
> > +        * The buffer is ring buffer. If wrap bit different,
> > +        * represents the start of the next cycle for WPT
> > +        */
> > +       if ((rg ^ wg) & VFF_RING_WRAP)
> > +               cnt += len;
> 
> Again, I am confused what size of VFF is.  Either VFF_RING_SIZE or
> c->cfg.dst_port_window_size?
> 
> > +
> > +       c->rx_status = d->avail_len - cnt;
> > +       mtk_uart_apdma_write(c, VFF_RPT, wg);
> > +
> > +       list_del(&d->vd.node);
> > +       vchan_cookie_complete(&d->vd);
> > +}
> > +
> > +static irqreturn_t mtk_uart_apdma_irq_handler(int irq, void *dev_id)
> > +{
> > +       struct dma_chan *chan = (struct dma_chan *)dev_id;
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       struct mtk_uart_apdma_desc *d;
> > +       unsigned long flags;
> > +
> > +       spin_lock_irqsave(&c->vc.lock, flags);
> > +       if (c->dir == DMA_DEV_TO_MEM) {
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> > +               mtk_uart_apdma_start_rx(c);
> > +       } else if (c->dir == DMA_MEM_TO_DEV) {
> > +               d = c->desc;
> > +
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> > +
> > +               if (d->avail_len != 0U) {
> > +                       mtk_uart_apdma_start_tx(c);
> > +               } else {
> > +                       list_del(&d->vd.node);
> > +                       vchan_cookie_complete(&d->vd);
> > +               }
> > +       }
> > +       spin_unlock_irqrestore(&c->vc.lock, flags);
> > +
> > +       return IRQ_HANDLED;
> > +}
> > +
> > +static int mtk_uart_apdma_alloc_chan_resources(struct dma_chan *chan)
> > +{
> > +       struct mtk_uart_apdmadev *mtkd = to_mtk_uart_apdma_dev(chan->device);
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       unsigned int tmp;
> > +       int ret;
> > +
> > +       pm_runtime_get_sync(mtkd->ddev.dev);
> 
> Add an error handling, something like
> 
> err = pm_runtime_get_sync(mtkd->ddev.dev);
> if (err < 0) {
> pm_runtime_put_noidle(dev);
> ...
> }
> 

I will modify it in next version.

> > +
> > +       mtk_uart_apdma_write(c, VFF_ADDR, 0);
> > +       mtk_uart_apdma_write(c, VFF_THRE, 0);
> > +       mtk_uart_apdma_write(c, VFF_LEN, 0);
> > +       mtk_uart_apdma_write(c, VFF_RST, VFF_WARM_RST_B);
> > +
> > +       ret = readx_poll_timeout(readl, c->base + VFF_EN, tmp, !tmp, 10, 100);
> > +       if (ret) {
> > +               dev_err(chan->device->dev, "dma reset: fail, timeout\n");
> > +               return ret;
> > +       }
> > +
> > +       if (!c->requested) {
> > +               c->requested = true;
> 
> The variable c->requested can be saved since the same channel
> shouldn't be requested more one time
> 
I will modify it in next version.

> > +               ret = request_irq(mtkd->dma_irq[chan->chan_id],
> > +                                 mtk_uart_apdma_irq_handler, IRQF_TRIGGER_NONE,
> > +                                 KBUILD_MODNAME, chan);
> > +               if (ret < 0) {
> > +                       dev_err(chan->device->dev, "Can't request dma IRQ\n");
> > +                       return -EINVAL;
> > +               }
> > +       }
> > +
> > +       if (mtkd->support_33bits)
> > +               mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_CLR_B);
> > +
> > +       return ret;
> > +}
> > +
> > +static void mtk_uart_apdma_free_chan_resources(struct dma_chan *chan)
> > +{
> > +       struct mtk_uart_apdmadev *mtkd = to_mtk_uart_apdma_dev(chan->device);
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +
> > +       if (c->requested) {
> 
> ditto as the above

I will modify it in next version.
> 
> > +               c->requested = false;
> > +               free_irq(mtkd->dma_irq[chan->chan_id], chan);
> > +       }
> > +
> > +       tasklet_kill(&c->vc.task);
> > +
> > +       vchan_free_chan_resources(&c->vc);
> > +
> > +       pm_runtime_put_sync(mtkd->ddev.dev);
> > +}
> > +
> > +static enum dma_status mtk_uart_apdma_tx_status(struct dma_chan *chan,
> > +                                        dma_cookie_t cookie,
> > +                                        struct dma_tx_state *txstate)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       enum dma_status ret;
> > +
> > +       ret = dma_cookie_status(chan, cookie, txstate);
> > +
> > +       dma_set_residue(txstate, c->rx_status);
> > +
> 
> The handling is not enough. You should get the descriptor
> corresponding to the cookie and then calculate and return the
> ->tx_status by the descriptor
> 

Because UART can't get any interrupt except DMA interrupt. So in APDMA,
need notify UART to get data. And then descriptor will be released. So
Need keep the solution.

> > +       return ret;
> > +}
> > +
> > +static void mtk_uart_apdma_config_write(struct dma_chan *chan,
> > +                              struct dma_slave_config *cfg,
> > +                              enum dma_transfer_direction dir)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       struct mtk_uart_apdmadev *mtkd =
> > +                               to_mtk_uart_apdma_dev(c->vc.chan.device);
> > +       unsigned int tmp;
> > +
> > +       if (mtk_uart_apdma_read(c, VFF_EN) == VFF_EN_B)
> > +               return;
> > +
> > +       c->dir = dir;
> 
> The direction is fixed by the device, I don't think it is required to
> keep it in a software state.

Need save it. Because RX and TX isn't all same.

> 
> > +
> > +       if (dir == DMA_DEV_TO_MEM) {
> > +               tmp = cfg->src_port_window_size;
> > +
> > +               mtk_uart_apdma_write(c, VFF_ADDR, cfg->src_addr);
> 
> That is wrong. ->src_addr is the physical address where DMA slave data
> should be read (RX),  not the memory address.
> 
> You should program the register VFF_ADDR and VFF_LEN by sg address and
> length from device_prep_slave_sg.

I will modify it in next version.
> 
> > +               mtk_uart_apdma_write(c, VFF_LEN, tmp);
> > +               mtk_uart_apdma_write(c, VFF_THRE, VFF_RX_THRE(tmp));
> > +               mtk_uart_apdma_write(c, VFF_INT_EN,
> > +                               VFF_RX_INT_EN0_B | VFF_RX_INT_EN1_B);
> > +               mtk_uart_apdma_write(c, VFF_RPT, 0);
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> > +       } else if (dir == DMA_MEM_TO_DEV)       {
> > +               tmp = cfg->dst_port_window_size;
> > +
> > +               mtk_uart_apdma_write(c, VFF_ADDR, cfg->dst_addr);
> 
> That is also wrong. st_addr: this is the physical address where DMA
> slave data should be written (TX), not the memory address similar to
> the above explanation.

I will modify it in next version.
> 
> > +               mtk_uart_apdma_write(c, VFF_LEN, tmp);
> > +               mtk_uart_apdma_write(c, VFF_THRE, VFF_TX_THRE(tmp));
> > +               mtk_uart_apdma_write(c, VFF_WPT, 0);
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> > +       }
> > +
> > +       mtk_uart_apdma_write(c, VFF_EN, VFF_EN_B);
> > +
> > +       if (mtkd->support_33bits)
> > +               mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_B);
> > +
> > +       if (mtk_uart_apdma_read(c, VFF_EN) != VFF_EN_B)
> > +               dev_err(chan->device->dev, "dir[%d] fail\n", dir);
> > +}
> > +
> > +/*
> > + * dmaengine_prep_slave_single will call the function. and sglen is 1.
> > + * 8250 uart using one ring buffer, and deal with one sg.
> > + */
> > +static struct dma_async_tx_descriptor *mtk_uart_apdma_prep_slave_sg
> > +       (struct dma_chan *chan, struct scatterlist *sgl,
> > +       unsigned int sglen, enum dma_transfer_direction dir,
> > +       unsigned long tx_flags, void *context)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       struct mtk_uart_apdma_desc *d;
> > +
> > +       if (!is_slave_direction(dir))
> > +               return NULL;
> > +
> > +       mtk_uart_apdma_config_write(chan, &c->cfg, dir);
> > +
> > +       /* Now allocate and setup the descriptor */
> > +       d = kzalloc(sizeof(*d), GFP_ATOMIC);
> > +       if (!d)
> > +               return NULL;
> > +
> > +       /* sglen is 1 */
> > +       d->avail_len = sg_dma_len(sgl);
> > +       c->rx_status = d->avail_len;
> > +
> > +       return vchan_tx_prep(&c->vc, &d->vd, tx_flags);
> > +}
> > +
> > +static void mtk_uart_apdma_issue_pending(struct dma_chan *chan)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       struct virt_dma_desc *vd;
> > +       unsigned long flags;
> > +
> > +       spin_lock_irqsave(&c->vc.lock, flags);
> > +       if (vchan_issue_pending(&c->vc)) {
> > +               vd = vchan_next_desc(&c->vc);
> > +               c->desc = to_mtk_uart_apdma_desc(&vd->tx);
> > +       }
> > +
> > +       if (c->dir == DMA_DEV_TO_MEM)
> > +               mtk_uart_apdma_start_rx(c);
> > +       else if (c->dir == DMA_MEM_TO_DEV)
> > +               mtk_uart_apdma_start_tx(c);
> > +
> > +       spin_unlock_irqrestore(&c->vc.lock, flags);
> > +}
> > +
> > +static int mtk_uart_apdma_slave_config(struct dma_chan *chan,
> > +                                  struct dma_slave_config *config)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +
> > +       memcpy(&c->cfg, config, sizeof(*config));
> > +
> > +       return 0;
> > +}
> > +
> > +static int mtk_uart_apdma_terminate_all(struct dma_chan *chan)
> > +{
> > +       struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
> > +       unsigned long flags;
> > +       unsigned int tmp;
> > +       int ret;
> > +
> > +       spin_lock_irqsave(&c->vc.lock, flags);
> > +
> > +       mtk_uart_apdma_write(c, VFF_FLUSH, VFF_FLUSH_B);
> > +       /* Wait 1sec for flush, can't sleep */
> > +       ret = readx_poll_timeout(readl, c->base + VFF_FLUSH, tmp,
> > +                       tmp != VFF_FLUSH_B, 0, 1000000);
> 
> It is extremely bad pending so long is in the spin_lock_irqsave

I will modify it in next version.
> 
> > +       if (ret)
> > +               dev_err(c->vc.chan.device->dev, "flush: fail, debug=0x%x\n",
> > +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> > +
> > +       /* set stop as 1 -> wait until en is 0 -> set stop as 0 */
> > +       mtk_uart_apdma_write(c, VFF_STOP, VFF_STOP_B);
> > +       ret = readx_poll_timeout(readl, c->base + VFF_EN, tmp, !tmp, 10, 100);
> > +       if (ret)
> > +               dev_err(c->vc.chan.device->dev, "stop: fail, debug=0x%x\n",
> > +                       mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
> > +
> > +       mtk_uart_apdma_write(c, VFF_STOP, VFF_STOP_CLR_B);
> > +       mtk_uart_apdma_write(c, VFF_INT_EN, VFF_INT_EN_CLR_B);
> > +
> > +       if (c->dir == DMA_DEV_TO_MEM)
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
> > +       else if (c->dir == DMA_MEM_TO_DEV)
> > +               mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
> > +
> > +       spin_unlock_irqrestore(&c->vc.lock, flags);
> > +
> > +       return 0;
> > +}
> > +
> > +static int mtk_uart_apdma_device_pause(struct dma_chan *chan)
> > +{
> > +       /* just for check caps pass */
> > +       dev_err(chan->device->dev, "Pause can't support\n");
> > +
> 
> If the device can't support hardware pause, we can do it as a software
> pause in an implementation based on vdesc.
> 

ok, i will try it.

> > +       return 0;
> > +}
> > +
> > +static void mtk_uart_apdma_free(struct mtk_uart_apdmadev *mtkd)
> > +{
> > +       while (!list_empty(&mtkd->ddev.channels)) {
> > +               struct mtk_chan *c = list_first_entry(&mtkd->ddev.channels,
> > +                       struct mtk_chan, vc.chan.device_node);
> > +
> > +               list_del(&c->vc.chan.device_node);
> > +               tasklet_kill(&c->vc.task);
> > +       }
> > +}
> > +
> > +static const struct of_device_id mtk_uart_apdma_match[] = {
> > +       { .compatible = "mediatek,mt6577-uart-dma", },
> > +       { /* sentinel */ },
> > +};
> > +MODULE_DEVICE_TABLE(of, mtk_uart_apdma_match);
> > +
> > +static int mtk_uart_apdma_probe(struct platform_device *pdev)
> > +{
> > +       struct device_node *np = pdev->dev.of_node;
> > +       struct mtk_uart_apdmadev *mtkd;
> > +       struct resource *res;
> > +       struct mtk_chan *c;
> > +       int bit_mask = 32, rc;
> > +       unsigned int i;
> > +
> > +       mtkd = devm_kzalloc(&pdev->dev, sizeof(*mtkd), GFP_KERNEL);
> > +       if (!mtkd)
> > +               return -ENOMEM;
> > +
> > +       mtkd->clk = devm_clk_get(&pdev->dev, NULL);
> > +       if (IS_ERR(mtkd->clk)) {
> > +               dev_err(&pdev->dev, "No clock specified\n");
> > +               rc = PTR_ERR(mtkd->clk);
> > +               return rc;
> > +       }
> > +
> > +       if (of_property_read_bool(np, "mediatek,dma-33bits"))
> > +               mtkd->support_33bits = true;
> > +
> > +       if (mtkd->support_33bits)
> > +               bit_mask = 33;
> > +
> > +       rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(bit_mask));
> > +       if (rc)
> > +               return rc;
> > +
> > +       dma_cap_set(DMA_SLAVE, mtkd->ddev.cap_mask);
> > +       mtkd->ddev.device_alloc_chan_resources =
> > +                               mtk_uart_apdma_alloc_chan_resources;
> > +       mtkd->ddev.device_free_chan_resources =
> > +                               mtk_uart_apdma_free_chan_resources;
> > +       mtkd->ddev.device_tx_status = mtk_uart_apdma_tx_status;
> > +       mtkd->ddev.device_issue_pending = mtk_uart_apdma_issue_pending;
> > +       mtkd->ddev.device_prep_slave_sg = mtk_uart_apdma_prep_slave_sg;
> > +       mtkd->ddev.device_config = mtk_uart_apdma_slave_config;
> > +       mtkd->ddev.device_pause = mtk_uart_apdma_device_pause;
> > +       mtkd->ddev.device_terminate_all = mtk_uart_apdma_terminate_all;
> > +       mtkd->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
> > +       mtkd->ddev.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
> > +       mtkd->ddev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
> > +       mtkd->ddev.residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
> > +       mtkd->ddev.dev = &pdev->dev;
> > +       INIT_LIST_HEAD(&mtkd->ddev.channels);
> > +
> > +       mtkd->dma_requests = MTK_UART_APDMA_NR_VCHANS;
> > +       if (of_property_read_u32(np, "dma-requests", &mtkd->dma_requests)) {
> > +               dev_info(&pdev->dev,
> > +                        "Using %u as missing dma-requests property\n",
> > +                        MTK_UART_APDMA_NR_VCHANS);
> > +       }
> > +
> > +       mtkd->dma_irq = devm_kcalloc(&pdev->dev, mtkd->dma_requests,
> > +                                sizeof(*mtkd->dma_irq), GFP_KERNEL);
> > +       if (!mtkd->dma_irq)
> > +               return -ENOMEM;
> > +
> > +       for (i = 0; i < mtkd->dma_requests; i++) {
> > +               c = devm_kzalloc(mtkd->ddev.dev, sizeof(*c), GFP_KERNEL);
> > +               if (!c) {
> > +                       rc = -ENODEV;
> > +                       goto err_no_dma;
> > +               }
> > +
> > +               res = platform_get_resource(pdev, IORESOURCE_MEM, i);
> > +               if (!res) {
> > +                       rc = -ENODEV;
> > +                       goto err_no_dma;
> > +               }
> > +
> > +               c->base = devm_ioremap_resource(&pdev->dev, res);
> > +               if (IS_ERR(c->base)) {
> > +                       rc = PTR_ERR(c->base);
> > +                       goto err_no_dma;
> > +               }
> > +               c->requested = false;
> > +               c->vc.desc_free = mtk_uart_apdma_desc_free;
> > +               vchan_init(&c->vc, &mtkd->ddev);
> > +
> > +               mtkd->dma_irq[i] = platform_get_irq(pdev, i);
> > +               if ((int)mtkd->dma_irq[i] < 0) {
> > +                       dev_err(&pdev->dev, "failed to get IRQ[%d]\n", i);
> > +                       rc = -EINVAL;
> > +                       goto err_no_dma;
> > +               }
> > +       }
> > +
> > +       pm_runtime_enable(&pdev->dev);
> > +       pm_runtime_set_active(&pdev->dev);
> > +
> > +       rc = dma_async_device_register(&mtkd->ddev);
> > +       if (rc)
> > +               goto rpm_disable;
> > +
> > +       platform_set_drvdata(pdev, mtkd);
> > +
> > +       /* Device-tree DMA controller registration */
> > +       rc = of_dma_controller_register(np, of_dma_xlate_by_chan_id, mtkd);
> > +       if (rc)
> > +               goto dma_remove;
> > +
> > +       return rc;
> > +
> > +dma_remove:
> > +       dma_async_device_unregister(&mtkd->ddev);
> > +rpm_disable:
> > +       pm_runtime_disable(&pdev->dev);
> > +err_no_dma:
> > +       mtk_uart_apdma_free(mtkd);
> > +       return rc;
> > +}
> > +
> > +static int mtk_uart_apdma_remove(struct platform_device *pdev)
> > +{
> > +       struct mtk_uart_apdmadev *mtkd = platform_get_drvdata(pdev);
> > +
> > +       if (pdev->dev.of_node)
> > +               of_dma_controller_free(pdev->dev.of_node);
> > +
> > +       pm_runtime_disable(&pdev->dev);
> > +       pm_runtime_put_noidle(&pdev->dev);
> 
> That pm_runtime_put_noidle should be removed or it causes an
> inconsistency with the probe handler.
> 

Ok, I will remove it.

> > +
> > +       dma_async_device_unregister(&mtkd->ddev);
> > +       mtk_uart_apdma_free(mtkd);
> > +
> > +       return 0;
> > +}
> > +
> > +#ifdef CONFIG_PM_SLEEP
> > +static int mtk_uart_apdma_suspend(struct device *dev)
> > +{
> > +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> > +
> > +       if (!pm_runtime_suspended(dev))
> > +               clk_disable_unprepare(mtkd->clk);
> > +
> > +       return 0;
> > +}
> > +
> > +static int mtk_uart_apdma_resume(struct device *dev)
> > +{
> > +       int ret;
> > +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> > +
> > +       if (!pm_runtime_suspended(dev)) {
> > +               ret = clk_prepare_enable(mtkd->clk);
> > +               if (ret)
> > +                       return ret;
> > +       }
> > +
> > +       return 0;
> > +}
> > +#endif /* CONFIG_PM_SLEEP */
> > +
> > +#ifdef CONFIG_PM
> > +static int mtk_uart_apdma_runtime_suspend(struct device *dev)
> > +{
> > +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> > +
> > +       clk_disable_unprepare(mtkd->clk);
> > +
> > +       return 0;
> > +}
> > +
> > +static int mtk_uart_apdma_runtime_resume(struct device *dev)
> > +{
> > +       int ret;
> > +       struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
> > +
> > +       ret = clk_prepare_enable(mtkd->clk);
> > +       if (ret)
> > +               return ret;
> > +
> > +       return 0;
> > +}
> > +#endif /* CONFIG_PM */
> > +
> > +static const struct dev_pm_ops mtk_uart_apdma_pm_ops = {
> > +       SET_SYSTEM_SLEEP_PM_OPS(mtk_uart_apdma_suspend, mtk_uart_apdma_resume)
> > +       SET_RUNTIME_PM_OPS(mtk_uart_apdma_runtime_suspend,
> > +                          mtk_uart_apdma_runtime_resume, NULL)
> > +};
> 
> It probably causes a build error when CONFIG_PM is not enabled.
> and use a UNIVERSAL_DEV_PM_OPS because the runtime suspend/resume and
> system suspend/resume for the dma are
> almost the same.
> 

I remember that these had test. It's build pass.

> > +
> > +static struct platform_driver mtk_uart_apdma_driver = {
> > +       .probe  = mtk_uart_apdma_probe,
> > +       .remove = mtk_uart_apdma_remove,
> > +       .driver = {
> > +               .name           = KBUILD_MODNAME,
> > +               .pm             = &mtk_uart_apdma_pm_ops,
> > +               .of_match_table = of_match_ptr(mtk_uart_apdma_match),
> > +       },
> > +};
> > +
> > +module_platform_driver(mtk_uart_apdma_driver);
> > +
> > +MODULE_DESCRIPTION("MediaTek UART APDMA Controller Driver");
> > +MODULE_AUTHOR("Long Cheng <long.cheng@mediatek.com>");
> > +MODULE_LICENSE("GPL v2");
> > +
> > --
> > 1.7.9.5
> >

Patch

diff --git a/drivers/dma/mediatek/Kconfig b/drivers/dma/mediatek/Kconfig
index 680fc05..ac49eb6 100644
--- a/drivers/dma/mediatek/Kconfig
+++ b/drivers/dma/mediatek/Kconfig
@@ -24,3 +24,14 @@  config MTK_CQDMA
 
 	  This controller provides the channels which is dedicated to
 	  memory-to-memory transfer to offload from CPU.
+
+config MTK_UART_APDMA
+	tristate "MediaTek SoCs APDMA support for UART"
+	depends on OF && SERIAL_8250_MT6577
+	select DMA_ENGINE
+	select DMA_VIRTUAL_CHANNELS
+	help
+	  Support for the UART DMA engine found on MediaTek MTK SoCs.
+	  When SERIAL_8250_MT6577 is enabled, and if you want to use DMA,
+	  you can enable the config. The DMA engine can only be used
+	  with MediaTek SoCs.
diff --git a/drivers/dma/mediatek/Makefile b/drivers/dma/mediatek/Makefile
index 41bb381..61a6d29 100644
--- a/drivers/dma/mediatek/Makefile
+++ b/drivers/dma/mediatek/Makefile
@@ -1,2 +1,3 @@ 
+obj-$(CONFIG_MTK_UART_APDMA) += mtk-uart-apdma.o
 obj-$(CONFIG_MTK_HSDMA) += mtk-hsdma.o
 obj-$(CONFIG_MTK_CQDMA) += mtk-cqdma.o
diff --git a/drivers/dma/mediatek/mtk-uart-apdma.c b/drivers/dma/mediatek/mtk-uart-apdma.c
new file mode 100644
index 0000000..9ed7a49
--- /dev/null
+++ b/drivers/dma/mediatek/mtk-uart-apdma.c
@@ -0,0 +1,660 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * MediaTek Uart APDMA driver.
+ *
+ * Copyright (c) 2018 MediaTek Inc.
+ * Author: Long Cheng <long.cheng@mediatek.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/iopoll.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/of_dma.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include "../virt-dma.h"
+
+/* The default number of virtual channel */
+#define MTK_UART_APDMA_NR_VCHANS	8
+
+#define VFF_EN_B		BIT(0)
+#define VFF_STOP_B		BIT(0)
+#define VFF_FLUSH_B		BIT(0)
+#define VFF_4G_SUPPORT_B	BIT(0)
+#define VFF_RX_INT_EN0_B	BIT(0)	/* rx valid size >=  vff thre */
+#define VFF_RX_INT_EN1_B	BIT(1)
+#define VFF_TX_INT_EN_B		BIT(0)	/* tx left size >= vff thre */
+#define VFF_WARM_RST_B		BIT(0)
+#define VFF_RX_INT_CLR_B	(BIT(0) | BIT(1))
+#define VFF_TX_INT_CLR_B	0
+#define VFF_STOP_CLR_B		0
+#define VFF_INT_EN_CLR_B	0
+#define VFF_4G_SUPPORT_CLR_B	0
+
+/* interrupt trigger level for tx */
+#define VFF_TX_THRE(n)		((n) * 7 / 8)
+/* interrupt trigger level for rx */
+#define VFF_RX_THRE(n)		((n) * 3 / 4)
+
+#define VFF_RING_SIZE	0xffffU
+/* invert this bit when wrap ring head again */
+#define VFF_RING_WRAP	0x10000U
+
+#define VFF_INT_FLAG		0x00
+#define VFF_INT_EN		0x04
+#define VFF_EN			0x08
+#define VFF_RST			0x0c
+#define VFF_STOP		0x10
+#define VFF_FLUSH		0x14
+#define VFF_ADDR		0x1c
+#define VFF_LEN			0x24
+#define VFF_THRE		0x28
+#define VFF_WPT			0x2c
+#define VFF_RPT			0x30
+/* TX: the buffer size HW can read. RX: the buffer size SW can read. */
+#define VFF_VALID_SIZE		0x3c
+/* TX: the buffer size SW can write. RX: the buffer size HW can write. */
+#define VFF_LEFT_SIZE		0x40
+#define VFF_DEBUG_STATUS	0x50
+#define VFF_4G_SUPPORT		0x54
+
+struct mtk_uart_apdmadev {
+	struct dma_device ddev;
+	struct clk *clk;
+	bool support_33bits;
+	unsigned int dma_requests;
+	unsigned int *dma_irq;
+};
+
+struct mtk_uart_apdma_desc {
+	struct virt_dma_desc vd;
+
+	unsigned int avail_len;
+};
+
+struct mtk_chan {
+	struct virt_dma_chan vc;
+	struct dma_slave_config	cfg;
+	void __iomem *base;
+	struct mtk_uart_apdma_desc *desc;
+
+	enum dma_transfer_direction dir;
+
+	bool requested;
+
+	unsigned int rx_status;
+};
+
+static inline struct mtk_uart_apdmadev *
+to_mtk_uart_apdma_dev(struct dma_device *d)
+{
+	return container_of(d, struct mtk_uart_apdmadev, ddev);
+}
+
+static inline struct mtk_chan *to_mtk_uart_apdma_chan(struct dma_chan *c)
+{
+	return container_of(c, struct mtk_chan, vc.chan);
+}
+
+static inline struct mtk_uart_apdma_desc *to_mtk_uart_apdma_desc
+	(struct dma_async_tx_descriptor *t)
+{
+	return container_of(t, struct mtk_uart_apdma_desc, vd.tx);
+}
+
+static void mtk_uart_apdma_write(struct mtk_chan *c,
+			       unsigned int reg, unsigned int val)
+{
+	writel(val, c->base + reg);
+}
+
+static unsigned int mtk_uart_apdma_read(struct mtk_chan *c, unsigned int reg)
+{
+	return readl(c->base + reg);
+}
+
+static void mtk_uart_apdma_desc_free(struct virt_dma_desc *vd)
+{
+	struct dma_chan *chan = vd->tx.chan;
+	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
+
+	kfree(c->desc);
+}
+
+static void mtk_uart_apdma_start_tx(struct mtk_chan *c)
+{
+	unsigned int len, send, left, wpt, d_wpt, tmp;
+	int ret;
+
+	left = mtk_uart_apdma_read(c, VFF_LEFT_SIZE);
+	if (!left) {
+		mtk_uart_apdma_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
+		return;
+	}
+
+	/* Wait 1sec for flush, can't sleep */
+	ret = readx_poll_timeout(readl, c->base + VFF_FLUSH, tmp,
+			tmp != VFF_FLUSH_B, 0, 1000000);
+	if (ret)
+		dev_warn(c->vc.chan.device->dev, "tx: fail, debug=0x%x\n",
+			mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
+
+	send = min_t(unsigned int, left, c->desc->avail_len);
+	wpt = mtk_uart_apdma_read(c, VFF_WPT);
+	len = c->cfg.dst_port_window_size;
+
+	d_wpt = wpt + send;
+	if ((d_wpt & VFF_RING_SIZE) >= len) {
+		d_wpt = d_wpt - len;
+		d_wpt = d_wpt ^ VFF_RING_WRAP;
+	}
+	mtk_uart_apdma_write(c, VFF_WPT, d_wpt);
+
+	c->desc->avail_len -= send;
+
+	mtk_uart_apdma_write(c, VFF_INT_EN, VFF_TX_INT_EN_B);
+	if (mtk_uart_apdma_read(c, VFF_FLUSH) == 0U)
+		mtk_uart_apdma_write(c, VFF_FLUSH, VFF_FLUSH_B);
+}
+
+static void mtk_uart_apdma_start_rx(struct mtk_chan *c)
+{
+	struct mtk_uart_apdma_desc *d = c->desc;
+	unsigned int len, wg, rg;
+	int cnt;
+
+	if ((mtk_uart_apdma_read(c, VFF_VALID_SIZE) == 0U) ||
+		!d || !vchan_next_desc(&c->vc))
+		return;
+
+	len = c->cfg.src_port_window_size;
+	rg = mtk_uart_apdma_read(c, VFF_RPT);
+	wg = mtk_uart_apdma_read(c, VFF_WPT);
+	cnt = (wg & VFF_RING_SIZE) - (rg & VFF_RING_SIZE);
+	/*
+	 * The buffer is ring buffer. If wrap bit different,
+	 * represents the start of the next cycle for WPT
+	 */
+	if ((rg ^ wg) & VFF_RING_WRAP)
+		cnt += len;
+
+	c->rx_status = d->avail_len - cnt;
+	mtk_uart_apdma_write(c, VFF_RPT, wg);
+
+	list_del(&d->vd.node);
+	vchan_cookie_complete(&d->vd);
+}
+
+static irqreturn_t mtk_uart_apdma_irq_handler(int irq, void *dev_id)
+{
+	struct dma_chan *chan = (struct dma_chan *)dev_id;
+	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
+	struct mtk_uart_apdma_desc *d;
+	unsigned long flags;
+
+	spin_lock_irqsave(&c->vc.lock, flags);
+	if (c->dir == DMA_DEV_TO_MEM) {
+		mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
+		mtk_uart_apdma_start_rx(c);
+	} else if (c->dir == DMA_MEM_TO_DEV) {
+		d = c->desc;
+
+		mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
+
+		if (d->avail_len != 0U) {
+			mtk_uart_apdma_start_tx(c);
+		} else {
+			list_del(&d->vd.node);
+			vchan_cookie_complete(&d->vd);
+		}
+	}
+	spin_unlock_irqrestore(&c->vc.lock, flags);
+
+	return IRQ_HANDLED;
+}
+
+static int mtk_uart_apdma_alloc_chan_resources(struct dma_chan *chan)
+{
+	struct mtk_uart_apdmadev *mtkd = to_mtk_uart_apdma_dev(chan->device);
+	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
+	unsigned int tmp;
+	int ret;
+
+	pm_runtime_get_sync(mtkd->ddev.dev);
+
+	mtk_uart_apdma_write(c, VFF_ADDR, 0);
+	mtk_uart_apdma_write(c, VFF_THRE, 0);
+	mtk_uart_apdma_write(c, VFF_LEN, 0);
+	mtk_uart_apdma_write(c, VFF_RST, VFF_WARM_RST_B);
+
+	ret = readx_poll_timeout(readl, c->base + VFF_EN, tmp, !tmp, 10, 100);
+	if (ret) {
+		dev_err(chan->device->dev, "dma reset: fail, timeout\n");
+		return ret;
+	}
+
+	if (!c->requested) {
+		c->requested = true;
+		ret = request_irq(mtkd->dma_irq[chan->chan_id],
+				  mtk_uart_apdma_irq_handler, IRQF_TRIGGER_NONE,
+				  KBUILD_MODNAME, chan);
+		if (ret < 0) {
+			dev_err(chan->device->dev, "Can't request dma IRQ\n");
+			return -EINVAL;
+		}
+	}
+
+	if (mtkd->support_33bits)
+		mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_CLR_B);
+
+	return ret;
+}
+
+static void mtk_uart_apdma_free_chan_resources(struct dma_chan *chan)
+{
+	struct mtk_uart_apdmadev *mtkd = to_mtk_uart_apdma_dev(chan->device);
+	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
+
+	if (c->requested) {
+		c->requested = false;
+		free_irq(mtkd->dma_irq[chan->chan_id], chan);
+	}
+
+	tasklet_kill(&c->vc.task);
+
+	vchan_free_chan_resources(&c->vc);
+
+	pm_runtime_put_sync(mtkd->ddev.dev);
+}
+
+static enum dma_status mtk_uart_apdma_tx_status(struct dma_chan *chan,
+					 dma_cookie_t cookie,
+					 struct dma_tx_state *txstate)
+{
+	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
+	enum dma_status ret;
+
+	ret = dma_cookie_status(chan, cookie, txstate);
+
+	dma_set_residue(txstate, c->rx_status);
+
+	return ret;
+}
+
+static void mtk_uart_apdma_config_write(struct dma_chan *chan,
+			       struct dma_slave_config *cfg,
+			       enum dma_transfer_direction dir)
+{
+	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
+	struct mtk_uart_apdmadev *mtkd =
+				to_mtk_uart_apdma_dev(c->vc.chan.device);
+	unsigned int tmp;
+
+	if (mtk_uart_apdma_read(c, VFF_EN) == VFF_EN_B)
+		return;
+
+	c->dir = dir;
+
+	if (dir == DMA_DEV_TO_MEM) {
+		tmp = cfg->src_port_window_size;
+
+		mtk_uart_apdma_write(c, VFF_ADDR, cfg->src_addr);
+		mtk_uart_apdma_write(c, VFF_LEN, tmp);
+		mtk_uart_apdma_write(c, VFF_THRE, VFF_RX_THRE(tmp));
+		mtk_uart_apdma_write(c, VFF_INT_EN,
+				VFF_RX_INT_EN0_B | VFF_RX_INT_EN1_B);
+		mtk_uart_apdma_write(c, VFF_RPT, 0);
+		mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
+	} else if (dir == DMA_MEM_TO_DEV)	{
+		tmp = cfg->dst_port_window_size;
+
+		mtk_uart_apdma_write(c, VFF_ADDR, cfg->dst_addr);
+		mtk_uart_apdma_write(c, VFF_LEN, tmp);
+		mtk_uart_apdma_write(c, VFF_THRE, VFF_TX_THRE(tmp));
+		mtk_uart_apdma_write(c, VFF_WPT, 0);
+		mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
+	}
+
+	mtk_uart_apdma_write(c, VFF_EN, VFF_EN_B);
+
+	if (mtkd->support_33bits)
+		mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_B);
+
+	if (mtk_uart_apdma_read(c, VFF_EN) != VFF_EN_B)
+		dev_err(chan->device->dev, "dir[%d] fail\n", dir);
+}
+
+/*
+ * dmaengine_prep_slave_single will call the function. and sglen is 1.
+ * 8250 uart using one ring buffer, and deal with one sg.
+ */
+static struct dma_async_tx_descriptor *mtk_uart_apdma_prep_slave_sg
+	(struct dma_chan *chan, struct scatterlist *sgl,
+	unsigned int sglen, enum dma_transfer_direction dir,
+	unsigned long tx_flags, void *context)
+{
+	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
+	struct mtk_uart_apdma_desc *d;
+
+	if (!is_slave_direction(dir))
+		return NULL;
+
+	mtk_uart_apdma_config_write(chan, &c->cfg, dir);
+
+	/* Now allocate and setup the descriptor */
+	d = kzalloc(sizeof(*d), GFP_ATOMIC);
+	if (!d)
+		return NULL;
+
+	/* sglen is 1 */
+	d->avail_len = sg_dma_len(sgl);
+	c->rx_status = d->avail_len;
+
+	return vchan_tx_prep(&c->vc, &d->vd, tx_flags);
+}
+
+static void mtk_uart_apdma_issue_pending(struct dma_chan *chan)
+{
+	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
+	struct virt_dma_desc *vd;
+	unsigned long flags;
+
+	spin_lock_irqsave(&c->vc.lock, flags);
+	if (vchan_issue_pending(&c->vc)) {
+		vd = vchan_next_desc(&c->vc);
+		c->desc = to_mtk_uart_apdma_desc(&vd->tx);
+	}
+
+	if (c->dir == DMA_DEV_TO_MEM)
+		mtk_uart_apdma_start_rx(c);
+	else if (c->dir == DMA_MEM_TO_DEV)
+		mtk_uart_apdma_start_tx(c);
+
+	spin_unlock_irqrestore(&c->vc.lock, flags);
+}
+
+static int mtk_uart_apdma_slave_config(struct dma_chan *chan,
+				   struct dma_slave_config *config)
+{
+	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
+
+	memcpy(&c->cfg, config, sizeof(*config));
+
+	return 0;
+}
+
+static int mtk_uart_apdma_terminate_all(struct dma_chan *chan)
+{
+	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
+	unsigned long flags;
+	unsigned int tmp;
+	int ret;
+
+	spin_lock_irqsave(&c->vc.lock, flags);
+
+	mtk_uart_apdma_write(c, VFF_FLUSH, VFF_FLUSH_B);
+	/* Wait 1sec for flush, can't sleep */
+	ret = readx_poll_timeout(readl, c->base + VFF_FLUSH, tmp,
+			tmp != VFF_FLUSH_B, 0, 1000000);
+	if (ret)
+		dev_err(c->vc.chan.device->dev, "flush: fail, debug=0x%x\n",
+			mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
+
+	/* set stop as 1 -> wait until en is 0 -> set stop as 0 */
+	mtk_uart_apdma_write(c, VFF_STOP, VFF_STOP_B);
+	ret = readx_poll_timeout(readl, c->base + VFF_EN, tmp, !tmp, 10, 100);
+	if (ret)
+		dev_err(c->vc.chan.device->dev, "stop: fail, debug=0x%x\n",
+			mtk_uart_apdma_read(c, VFF_DEBUG_STATUS));
+
+	mtk_uart_apdma_write(c, VFF_STOP, VFF_STOP_CLR_B);
+	mtk_uart_apdma_write(c, VFF_INT_EN, VFF_INT_EN_CLR_B);
+
+	if (c->dir == DMA_DEV_TO_MEM)
+		mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_RX_INT_CLR_B);
+	else if (c->dir == DMA_MEM_TO_DEV)
+		mtk_uart_apdma_write(c, VFF_INT_FLAG, VFF_TX_INT_CLR_B);
+
+	spin_unlock_irqrestore(&c->vc.lock, flags);
+
+	return 0;
+}
+
+static int mtk_uart_apdma_device_pause(struct dma_chan *chan)
+{
+	/* just for check caps pass */
+	dev_err(chan->device->dev, "Pause can't support\n");
+
+	return 0;
+}
+
+static void mtk_uart_apdma_free(struct mtk_uart_apdmadev *mtkd)
+{
+	while (!list_empty(&mtkd->ddev.channels)) {
+		struct mtk_chan *c = list_first_entry(&mtkd->ddev.channels,
+			struct mtk_chan, vc.chan.device_node);
+
+		list_del(&c->vc.chan.device_node);
+		tasklet_kill(&c->vc.task);
+	}
+}
+
+static const struct of_device_id mtk_uart_apdma_match[] = {
+	{ .compatible = "mediatek,mt6577-uart-dma", },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, mtk_uart_apdma_match);
+
+static int mtk_uart_apdma_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct mtk_uart_apdmadev *mtkd;
+	struct resource *res;
+	struct mtk_chan *c;
+	int bit_mask = 32, rc;
+	unsigned int i;
+
+	mtkd = devm_kzalloc(&pdev->dev, sizeof(*mtkd), GFP_KERNEL);
+	if (!mtkd)
+		return -ENOMEM;
+
+	mtkd->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(mtkd->clk)) {
+		dev_err(&pdev->dev, "No clock specified\n");
+		rc = PTR_ERR(mtkd->clk);
+		return rc;
+	}
+
+	if (of_property_read_bool(np, "mediatek,dma-33bits"))
+		mtkd->support_33bits = true;
+
+	if (mtkd->support_33bits)
+		bit_mask = 33;
+
+	rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(bit_mask));
+	if (rc)
+		return rc;
+
+	dma_cap_set(DMA_SLAVE, mtkd->ddev.cap_mask);
+	mtkd->ddev.device_alloc_chan_resources =
+				mtk_uart_apdma_alloc_chan_resources;
+	mtkd->ddev.device_free_chan_resources =
+				mtk_uart_apdma_free_chan_resources;
+	mtkd->ddev.device_tx_status = mtk_uart_apdma_tx_status;
+	mtkd->ddev.device_issue_pending = mtk_uart_apdma_issue_pending;
+	mtkd->ddev.device_prep_slave_sg = mtk_uart_apdma_prep_slave_sg;
+	mtkd->ddev.device_config = mtk_uart_apdma_slave_config;
+	mtkd->ddev.device_pause = mtk_uart_apdma_device_pause;
+	mtkd->ddev.device_terminate_all = mtk_uart_apdma_terminate_all;
+	mtkd->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
+	mtkd->ddev.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
+	mtkd->ddev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
+	mtkd->ddev.residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT;
+	mtkd->ddev.dev = &pdev->dev;
+	INIT_LIST_HEAD(&mtkd->ddev.channels);
+
+	mtkd->dma_requests = MTK_UART_APDMA_NR_VCHANS;
+	if (of_property_read_u32(np, "dma-requests", &mtkd->dma_requests)) {
+		dev_info(&pdev->dev,
+			 "Using %u as missing dma-requests property\n",
+			 MTK_UART_APDMA_NR_VCHANS);
+	}
+
+	mtkd->dma_irq = devm_kcalloc(&pdev->dev, mtkd->dma_requests,
+				 sizeof(*mtkd->dma_irq), GFP_KERNEL);
+	if (!mtkd->dma_irq)
+		return -ENOMEM;
+
+	for (i = 0; i < mtkd->dma_requests; i++) {
+		c = devm_kzalloc(mtkd->ddev.dev, sizeof(*c), GFP_KERNEL);
+		if (!c) {
+			rc = -ENODEV;
+			goto err_no_dma;
+		}
+
+		res = platform_get_resource(pdev, IORESOURCE_MEM, i);
+		if (!res) {
+			rc = -ENODEV;
+			goto err_no_dma;
+		}
+
+		c->base = devm_ioremap_resource(&pdev->dev, res);
+		if (IS_ERR(c->base)) {
+			rc = PTR_ERR(c->base);
+			goto err_no_dma;
+		}
+		c->requested = false;
+		c->vc.desc_free = mtk_uart_apdma_desc_free;
+		vchan_init(&c->vc, &mtkd->ddev);
+
+		mtkd->dma_irq[i] = platform_get_irq(pdev, i);
+		if ((int)mtkd->dma_irq[i] < 0) {
+			dev_err(&pdev->dev, "failed to get IRQ[%d]\n", i);
+			rc = -EINVAL;
+			goto err_no_dma;
+		}
+	}
+
+	pm_runtime_enable(&pdev->dev);
+	pm_runtime_set_active(&pdev->dev);
+
+	rc = dma_async_device_register(&mtkd->ddev);
+	if (rc)
+		goto rpm_disable;
+
+	platform_set_drvdata(pdev, mtkd);
+
+	/* Device-tree DMA controller registration */
+	rc = of_dma_controller_register(np, of_dma_xlate_by_chan_id, mtkd);
+	if (rc)
+		goto dma_remove;
+
+	return rc;
+
+dma_remove:
+	dma_async_device_unregister(&mtkd->ddev);
+rpm_disable:
+	pm_runtime_disable(&pdev->dev);
+err_no_dma:
+	mtk_uart_apdma_free(mtkd);
+	return rc;
+}
+
+static int mtk_uart_apdma_remove(struct platform_device *pdev)
+{
+	struct mtk_uart_apdmadev *mtkd = platform_get_drvdata(pdev);
+
+	if (pdev->dev.of_node)
+		of_dma_controller_free(pdev->dev.of_node);
+
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_put_noidle(&pdev->dev);
+
+	dma_async_device_unregister(&mtkd->ddev);
+	mtk_uart_apdma_free(mtkd);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int mtk_uart_apdma_suspend(struct device *dev)
+{
+	struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
+
+	if (!pm_runtime_suspended(dev))
+		clk_disable_unprepare(mtkd->clk);
+
+	return 0;
+}
+
+static int mtk_uart_apdma_resume(struct device *dev)
+{
+	int ret;
+	struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
+
+	if (!pm_runtime_suspended(dev)) {
+		ret = clk_prepare_enable(mtkd->clk);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+#endif /* CONFIG_PM_SLEEP */
+
+#ifdef CONFIG_PM
+static int mtk_uart_apdma_runtime_suspend(struct device *dev)
+{
+	struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
+
+	clk_disable_unprepare(mtkd->clk);
+
+	return 0;
+}
+
+static int mtk_uart_apdma_runtime_resume(struct device *dev)
+{
+	int ret;
+	struct mtk_uart_apdmadev *mtkd = dev_get_drvdata(dev);
+
+	ret = clk_prepare_enable(mtkd->clk);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+#endif /* CONFIG_PM */
+
+static const struct dev_pm_ops mtk_uart_apdma_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(mtk_uart_apdma_suspend, mtk_uart_apdma_resume)
+	SET_RUNTIME_PM_OPS(mtk_uart_apdma_runtime_suspend,
+			   mtk_uart_apdma_runtime_resume, NULL)
+};
+
+static struct platform_driver mtk_uart_apdma_driver = {
+	.probe	= mtk_uart_apdma_probe,
+	.remove	= mtk_uart_apdma_remove,
+	.driver = {
+		.name		= KBUILD_MODNAME,
+		.pm		= &mtk_uart_apdma_pm_ops,
+		.of_match_table = of_match_ptr(mtk_uart_apdma_match),
+	},
+};
+
+module_platform_driver(mtk_uart_apdma_driver);
+
+MODULE_DESCRIPTION("MediaTek UART APDMA Controller Driver");
+MODULE_AUTHOR("Long Cheng <long.cheng@mediatek.com>");
+MODULE_LICENSE("GPL v2");
+