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: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index c20b85e28d81c6e468f4673af1fd9d47fb5791c4..dae3be1b9c8f01078a0f6ab259b6f4640ed5534c 100644 (file)
--- 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