[SeaBIOS] USB OHCI issues when keyboard activity occurs prior to booting from thumbdrive

[Kevin O'Connor]

On Wed, Mar 07, 2012 at 03:47:58PM -0700, Dave Frodin wrote:
> All,
> 
> I'm seeing another USB issue with our platform(s). I've been following the
> other active USB mail list issue "usb ohci pipe free fix" but don't exactly
> know where that one started. I'm only guessing that this could be related.
> 
> The description of my h/w setup is ...
>   - AMD/Persimmon platform (also observed failure on IEI/Kino)
>   - USB thumbdrive with GRUB (menu options for Ubuntu,memtest86,etc)
>   - USB wireless keyboard/mouse (also observed failure with wired USB keyboard)
> 
> I using the SeaBIOS master source.
> 
> The failure occurs when the system boots up to the GRUB menu. If I
> let the menu timeout it will boot the default option which is
> Ubuntu. If I hit the <Enter> key the system will lock-up with no
> output on the debug COM port. If at the GRUB menu and I <down arrow>
> to the memtest86 option, it will sometimes work and sometimes
> lockup.

In the processes of looking through the OHCI code, I did see what
appears to be a race with USB "interrupt" pipe reading.  The code is
assuming the TD is complete when the ED acknowledges the change, but
the spec is pretty clear that the TD can be modified after the ED is
updated.  However, I'd be quite surprised that such a small race would
lead to reproducible failures.  I also don't see how it would relate
to EHCI thumbdrive usage.

-Kevin