Patchwork [2/2] xhci: Prevent U1/U2 link pm states if exit latency is too long

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Submitter Mathias Nyman
Date Dec. 5, 2018, 12:22 p.m.
Message ID <1544012559-20871-3-git-send-email-mathias.nyman@linux.intel.com>
Download mbox | patch
Permalink /patch/672983/
State New
Headers show

Comments

Mathias Nyman - Dec. 5, 2018, 12:22 p.m.
Don't allow USB3 U1 or U2 if the latency to wake up from the U-state
reaches the service interval for a periodic endpoint.

This is according to xhci 1.1 specification section 4.23.5.2 extra note:

"Software shall ensure that a device is prevented from entering a U-state
 where its worst case exit latency approaches the ESIT."

Allowing too long exit latencies for periodic endpoint confuses xHC
internal scheduling, and new devices may fail to enumerate with a
"Not enough bandwidth for new device state" error from the host.

Cc: <stable@vger.kernel.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/host/xhci.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

Patch

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index c20b85e..dae3be1 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4514,6 +4514,14 @@  static u16 xhci_calculate_u1_timeout(struct xhci_hcd *xhci,
 {
 	unsigned long long timeout_ns;
 
+	/* Prevent U1 if service interval is shorter than U1 exit latency */
+	if (usb_endpoint_xfer_int(desc) || usb_endpoint_xfer_isoc(desc)) {
+		if (xhci_service_interval_to_ns(desc) <= udev->u1_params.mel) {
+			dev_dbg(&udev->dev, "Disable U1, ESIT shorter than exit latency\n");
+			return USB3_LPM_DISABLED;
+		}
+	}
+
 	if (xhci->quirks & XHCI_INTEL_HOST)
 		timeout_ns = xhci_calculate_intel_u1_timeout(udev, desc);
 	else
@@ -4570,6 +4578,14 @@  static u16 xhci_calculate_u2_timeout(struct xhci_hcd *xhci,
 {
 	unsigned long long timeout_ns;
 
+	/* Prevent U2 if service interval is shorter than U2 exit latency */
+	if (usb_endpoint_xfer_int(desc) || usb_endpoint_xfer_isoc(desc)) {
+		if (xhci_service_interval_to_ns(desc) <= udev->u2_params.mel) {
+			dev_dbg(&udev->dev, "Disable U2, ESIT shorter than exit latency\n");
+			return USB3_LPM_DISABLED;
+		}
+	}
+
 	if (xhci->quirks & XHCI_INTEL_HOST)
 		timeout_ns = xhci_calculate_intel_u2_timeout(udev, desc);
 	else