[BUG] bisected: PandaBoard smsc95xx ethernet driver error from USB timeout

Hi All,

Not quite sure quite where the problem is (USB, OMAP, smsc95xx driver, other???),
so casting the nets wide...

The PandaBoard frequently fails to boot with an eth0 error when mounting
the root file system via NFS (ethernet driver fails due to a USB timeout;
no ethernet means NFS won't work).  A typical set of error messages is:

[    3.264373] smsc95xx 1-1.1:1.0: usb_probe_interface
[    3.269500] smsc95xx 1-1.1:1.0: usb_probe_interface - got id
[    3.275543] smsc95xx v1.0.4
[    8.078674] smsc95xx 1-1.1:1.0: eth0: register 'smsc95xx' at usb-ehci-omap.0-1.1, smsc95xx USB 2.0 Ethernet, 82:b9:1d:fa:67:0d
[    8.091003] hub 1-1:1.0: state 7 ports 5 chg 0000 evt 0002
[   13.509918] usb 1-1.1: swapper/0 timed out on ep0out len=0/4
[   13.515869] smsc95xx 1-1.1:1.0: eth0: Failed to write register index 0x00000108
[   13.523559] smsc95xx 1-1.1:1.0: eth0: Failed to write ADDRL: -110
[   13.529998] IP-Config: Failed to open eth0

I have bisected this to:

  commit 18aafe64d75d0e27dae206cacf4171e4e485d285
  Author: Alan Stern [off-list ref]
  Date:   Wed Jul 11 11:23:04 2012 -0400

     USB: EHCI: use hrtimer for the I/O watchdog

Note that to compile this version of the kernel, an additional fix must
also be applied:

  commit ba5952e0711b14d8d4fe172671f8aa6091ace3ee
  Author: Ming Lei [off-list ref]
  Date:   Fri Jul 13 17:25:24 2012 +0800

     USB: ehci-omap: fix compile failure(v1)

The symptom can be worked around by retrying the USB access if a timeout
occurs.  This is clearly _not_ the fix, just a hack that I used to
investigate the problem:

  http://article.gmane.org/gmane.linux.rt.user/9773

My kernel configuration is:

  arch/arm/configs/omap2plus_defconfig

  plus to get the ethernet driver I add:

    CONFIG_USB_EHCI_HCD
    CONFIG_USB_NET_SMSC95XX

I found the problem on 3.6.11, but have not replicated it on 3.9-rcX
yet because my config fails to build on 3.9-rc1 and 3.9-rc2.  I'll try
to work on that issue tomorrow.