Subject: Re: [PATCH 6/8] [WATCHDOG] mpc8xxx_wdt: add support for MPC8xx watchdogs

From: Jochen Friedrich <[email-masked]>
Date: Fri, 16 May 2008 11:17:29 +0200

Hi Anton,

> The mpc8xxx_wdt driver is using two registers: SWSRR to push magic
> numbers, and SWCRR to control the watchdog. Both registers are available
> on the MPC8xx, and seem to have the same offsets and semantics as in
> MPC83xx/MPC86xx watchdogs. The only difference is prescale value. So this
> driver should simply work on the MPC8xx CPUs.
> 
> MPC823 seem to be the first CPU in MPC8xx line, so we use fsl,mpc823-wdt
> compatible matching.
> 
> Though, this patch was only build-tested and okay to drop from this
> series until tested or corrected to work on the actual hardware.
> 
> Signed-off-by: Anton Vorontsov <[email-masked]>

Tested-by: Jochen Friedrich <[email-masked]>

The driver works OK on MPC823.

One nit however ist the late initialisation of the wdt timer. I had to add
two hardcoded wdt resets in the board setup, one in setup_arch and one in
arch_initcall, to prevent a reset until mpc8xxx_wdt kicks in. However, IMHO
this is acceptable as it only hits the 8xx series with the small prescale.

Some time ago in http://patchwork.ozlabs.org/linuxppc/patch?person=1023&id=16189,
i tried a different aproach to the problem (mainly a port of the old ARC=ppc
stuff), but the code became very ugly and the wdt maintainers didn't like it
very much.

So the only thing left for full 8xx support is a refactoring / cleanup of
http://patchwork.ozlabs.org/linuxppc/patch?person=1023&id=16262.

Thanks,
Jochen