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authorSarah Sharp <sarah.a.sharp@linux.intel.com>2012-12-17 14:12:35 -0800
committerSarah Sharp <sarah.a.sharp@linux.intel.com>2013-01-03 14:09:55 -0800
commit55c1945edaac94c5338a3647bc2e85ff75d9cf36 (patch)
treeaadb22c66a5225f492d6bd3886fd765b3e087098 /drivers/usb/host/xhci-mem.c
parenta49f0d1ea3ec94fc7cf33a7c36a16343b74bd565 (diff)
xhci: Handle HS bulk/ctrl endpoints that don't NAK.
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> Cc: stable@vger.kernel.org
Diffstat (limited to 'drivers/usb/host/xhci-mem.c')
-rw-r--r--drivers/usb/host/xhci-mem.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index fb51c7085ad0..35616ffbe3ae 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);
}