Re: MPC83xx reset status register (RSR, offset 0x910)

[Radu Rendec <radu.rendec@gmail.com>]

Hi Christophe,

On Thu, 2018-09-13 at 10:21 +0200, Christophe LEROY wrote:
>
> Le 11/09/2018 à 00:17, Radu Rendec a écrit :
> >
> > The MPC83xx also has a watchdog and the kernel driver (mpc8xxx_wdt.c)
> > could also be improved to support the WDIOC_GETBOOTSTATUS ioctl and
> > properly report if the system rebooted due to a watchdog.
>
> Very good idea.
>
> I just submitted a patch for that. Please look at it.
> I'm sure any driver which needs reset status information can do the same.

Thanks for submitting the patch and sorry for the late reply! I followed
the conversation between you and Guenter and it seems your patches are
almost accepted. That's a good thing.

> If we want to do something more central, maybe we should look at what
> was done on ARM:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=04fef228fb00

Thanks for pointing out that commit. It's very similar to what I wanted
to do (for MPC83xx) in the first place: read the RSR value on start-up
into a variable and export it as a symbol to make it available to other
drivers.

I would take on the work to implement something similar for PowerPC, but
I need some guidance as to what goes where. For instance, what would be
the PowerPC equivalent of arch/arm/mach-pxa/reset.c, which defines the
reset_status variable?

Another question is if the device tree should be used. We already have
separate directories for each platform in arch/powerpc/platforms and I
guess for each platform the RSR is always there and at a fixed, well
known address.

Thanks,
Radu