USB Host port inoperative after kexec on Beagleboard

USB Host port inoperative after kexec on Beagleboard

[Peter Chubb]

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

   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.

   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?
--
Dr Peter Chubb  http://www.gelato.unsw.edu.au  peterc AT gelato.unsw.edu.au
http://www.ertos.nicta.com.au           ERTOS within National ICT Australia

Re: USB Host port inoperative after kexec on Beagleboard

[Will Deacon]

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

Re: USB Host port inoperative after kexec on Beagleboard

[Will Deacon]

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:
> > 
> > Hi Will,
> 
> Hi Peter [adding linux-arm-kernel],

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

> 
> >    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