xhci: Handle HS bulk/ctrl endpoints that don't NAK.

commit 55c1945edaac94c5338a3647bc2e85ff75d9cf36 upstream.

A high speed control or bulk endpoint may have bInterval set to zero,
which means it does not NAK.  If bInterval is non-zero, it means the
endpoint NAKs at a rate of 2^(bInterval - 1).

The xHCI code to compute the NAK interval does not handle the special
case of zero properly.  The current code unconditionally subtracts one
from bInterval and uses it as an exponent.  This causes a very large
bInterval to be used, and warning messages like these will be printed:

usb 1-1: ep 0x1 - rounding interval to 32768 microframes, ep desc says 0 microframes

This may cause the xHCI host hardware to reject the Configure Endpoint
command, which means the HS device will be unusable under xHCI ports.

This patch should be backported to kernels as old as 2.6.31, that contain
commit dfa49c4ad120a784ef1ff0717168aa79f55a483a "USB: xhci - fix math in
xhci_get_endpoint_interval()".

Reported-by: Vincent Pelletier <plr.vincent@gmail.com>
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 5719c4d24161f42522af125ecb832029d99cabb7..ee5ec118de59f8d25db306186847fd5c8185e551 100644 (file)
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -1152,6 +1152,8 @@ static unsigned int xhci_microframes_to_exponent(struct usb_device *udev,
 static unsigned int xhci_parse_microframe_interval(struct usb_device *udev,
                struct usb_host_endpoint *ep)
 {
+       if (ep->desc.bInterval == 0)
+               return 0;
        return xhci_microframes_to_exponent(udev, ep,
                        ep->desc.bInterval, 0, 15);
 }