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 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@xxxxxxxxx> Suggested-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxx --- Hi Vincent, Will you please apply this patch to whatever stable kernel you're running and see if the device works under xHCI? Please send the dmesg output in either case. If you need directions for applying the patch and compiling your kernel, please see: http://kernelnewbies.org/KernelBuild Sarah Sharp drivers/usb/host/xhci-mem.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c index fb51c70..35616ff 100644 --- a/drivers/usb/host/xhci-mem.c +++ b/drivers/usb/host/xhci-mem.c @@ -1250,6 +1250,8 @@ 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); } -- 1.7.9 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
