USB Host port inoperative after kexec on Beagleboard

On Mon, Jan 09, 2012 at 10:54:03PM +0000, Will Deacon wrote:

On Mon, Jan 09, 2012 at 10:09:54PM +0000, Peter Chubb wrote:

quoted

Hi Will,

Hi Peter [adding linux-arm-kernel],

*Actually* adding linux-arm-kernel this time...

quoted

   Thanks for the fixes to kexec for ARM that went into mainline this
   week.  Mostly things work now.

Great, that's good to hear!

quoted

   One issue: the USB EHCI port on the (rev C2) beagleboard doesn't
   work after a kexec.  During boot after kexec, the host device is
   detected and initialised, but nothing plugged in works, even when
   everything was working corectly before the kexec.  Das U-boot
   must set up something that is then undone during the kexec reboot.

Ouch. Have you had a chance to look at the u-boot sources to see what it
does?

quoted

   I've traced all calls to clk_enable() and clk_disable(), and
   everything looks all right --- in particular I can't see 
   anything explicitly disabled during kexec that isn't reenabled
   during boot of the subsequent kernel.

   Voltages that I can measure look correct on the port.

   Do you have any suggestions as to what else could be wrong?

I'm afraid I'm not familiar with the Beagleboard, so I can't begin to guess.
Have you tried re-initialising the host controller in the new kernel
manually (perhaps my building the driver as a module and {un}loading it a
few times?). It could be that some hardware state persists across the kexec
and it just needs resetting.

Will