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Commit 0472bf06 authored by Mathias Nyman's avatar Mathias Nyman Committed by Greg Kroah-Hartman
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xhci: Prevent U1/U2 link pm states if exit latency is too long 



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: default avatarMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent a7d57abc

drivers/usb/host/xhci.c

+16 −0
Original line number Diff line number Diff line
@@ -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