[Oneiric][SRU][PATCH 0/2] Avoid unnecessary warnings in xHCI

[leann.ogasawara at canonical.com]

From: Leann Ogasawara <leann.ogasawara at canonical.com>

BugLink: http://bugs.launchpad.net/bugs/929656

== Oneiric SRU Justification ==

When running Oneiric on a Chief River (Ivy Bridge/Panther Point)
platform, the following messages are printed to dmesg which are harmless
but could cause user concern. It's been requested we cherry-pick two
upstream patches to eliminate these messages.

"[ 1.037314] xhci_hcd 0000:00:14.0: Failed to enable MSI-X"

"[ 1.037314] WARN: short transfer on control ep"

== Fix ==

The following upstream patches remove these warnings.  They have not
been sent to upstream stable, I plan to do so shortly.

  commit 3b9783b277e66731891ab42eeaacebbdcdd6e629
  Author: Sarah Sharp <sarah.a.sharp at linux.intel.com>
  Date: Thu Dec 22 15:02:13 2011 -0800

    xhci: Remove warnings about MSI and MSI-X capabilities.

  commit 2a9227a5eeaeb3f91e3a72ceea4fa59016ca5d20
  Author: Sarah Sharp <sarah.a.sharp at linux.intel.com>
  Date: Tue Oct 25 13:55:30 2011 +0200

    xhci: Remove scary warnings about transfer issues.

Sarah Sharp (2):
  xhci: Remove scary warnings about transfer issues.
  xhci: Remove warnings about MSI and MSI-X capabilities.

 drivers/usb/host/xhci-ring.c |    7 +++----
 drivers/usb/host/xhci.c      |    8 ++++----
 2 files changed, 7 insertions(+), 8 deletions(-)

== Impact ==

There should be minimal to no risk of regression as the patches are
merely lowering the log level from an error message to a debug message.
The debug messages will only appear if CONFIG_USB_XHCI_HCD_DEBUGGING is
enabled, which it currently is not.

== Test Case ==

Boot with an unpatched kernel on an Ivy Bridge/Panther Point platform
and confirm you see something similar to "xhci_hcd 0000:00:14.0: Failed
to enable MSI-X" on boot and possibly see the "WARN: short transfer on control ep" when conducting normal operations on a USB device.

I have test confirmation from a user with an Ivy Bridge/Panther Point
platform running Oneiric.  They can confirm the "xhci_hcd 0000:00:14.0: Failed 
to enable MSI-X" error message goes away with a patched kernel.