This is a note to let you know that I've just added the patch titled

xhci: Prevent U1/U2 link pm states if exit latency is too long

to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 0472bf06c6fd33c1a18aaead4c8f91e5a03d8d7b Mon Sep 17 00:00:00 2001

From: Mathias Nyman mathias.nyman@linux.intel.com Date: Wed, 5 Dec 2018 14:22:39 +0200 Subject: 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 --- drivers/usb/host/xhci.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c index c20b85e28d81..dae3be1b9c8f 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