Patchwork [v3,3/8] drm/sun4i: dsi: Enforce boundaries on the start delay

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Submitter Maxime Ripard
Date Feb. 11, 2019, 2:41 p.m.
Message ID <c9889cf5f7a3d101ef380905900b45a182596f56.1549896081.git-series.maxime.ripard@bootlin.com>
Download mbox | patch
Permalink /patch/723007/
State New
Headers show

Comments

Maxime Ripard - Feb. 11, 2019, 2:41 p.m.
The Allwinner BSP makes sure that we don't end up with a null start delay
or with a delay larger than vtotal.

The former condition is likely to happen now with the reworked start delay,
so make sure we enforce the same boundaries.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
Paul Kocialkowski - Feb. 12, 2019, 3:30 p.m.
Hi,

On Mon, 2019-02-11 at 15:41 +0100, Maxime Ripard wrote:
> The Allwinner BSP makes sure that we don't end up with a null start delay
> or with a delay larger than vtotal.
> 
> The former condition is likely to happen now with the reworked start delay,
> so make sure we enforce the same boundaries.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>

> ---
>  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 9471fa695ec7..506f2e8cf454 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -358,8 +358,12 @@ static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi,
>  					   struct drm_display_mode *mode)
>  {
>  	u16 start = clamp(mode->vtotal - mode->vdisplay - 10, 8, 100);
> +	u16 delay = mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
>  
> -	return mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
> +	if (delay > mode->vtotal)
> +		delay = delay % mode->vtotal;

I wonder whether delay == mode->vtotal would make sense at all. If not,
then we can just apply the modulo unconditionally. But in doubt, let's
keep things this way.

Cheers,

Paul

> +
> +	return max_t(u16, delay, 1);
>  }
>  
>  static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
Maxime Ripard - Feb. 14, 2019, 9:21 a.m.
hi,

On Tue, Feb 12, 2019 at 04:30:33PM +0100, Paul Kocialkowski wrote:
> Hi,
> 
> On Mon, 2019-02-11 at 15:41 +0100, Maxime Ripard wrote:
> > The Allwinner BSP makes sure that we don't end up with a null start delay
> > or with a delay larger than vtotal.
> > 
> > The former condition is likely to happen now with the reworked start delay,
> > so make sure we enforce the same boundaries.
> > 
> > Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
> 
> Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>

Thanks!

> > ---
> >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > index 9471fa695ec7..506f2e8cf454 100644
> > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > @@ -358,8 +358,12 @@ static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi,
> >  					   struct drm_display_mode *mode)
> >  {
> >  	u16 start = clamp(mode->vtotal - mode->vdisplay - 10, 8, 100);
> > +	u16 delay = mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
> >  
> > -	return mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
> > +	if (delay > mode->vtotal)
> > +		delay = delay % mode->vtotal;
> 
> I wonder whether delay == mode->vtotal would make sense at all. If not,
> then we can just apply the modulo unconditionally. But in doubt, let's
> keep things this way.

I guess that situation can happen, especially with the start clamping.

But even without it, it can happen when mode->vtotal - mode->vsync_end
(so the backporch) is equal to 10.

Maxime

Patch

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 9471fa695ec7..506f2e8cf454 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -358,8 +358,12 @@  static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi,
 					   struct drm_display_mode *mode)
 {
 	u16 start = clamp(mode->vtotal - mode->vdisplay - 10, 8, 100);
+	u16 delay = mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
 
-	return mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
+	if (delay > mode->vtotal)
+		delay = delay % mode->vtotal;
+
+	return max_t(u16, delay, 1);
 }
 
 static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,