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SubjectRe: USB Host port inoperative after kexec on Beagleboard
On Mon, Jan 09, 2012 at 10:09:54PM +0000, Peter Chubb wrote:
>
> Hi Will,

Hi Peter [adding linux-arm-kernel],

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

Great, that's good to hear!

> 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?

> 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


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