Re: deactivating PXA255 watchdog
From: Ian Campbell
Date: Wed Aug 10 2005 - 02:57:36 EST
On Tue, 2005-08-09 at 21:24 +0200, Wim Van Sebroeck wrote:
> Hi Ian,
> > I think you are the current "watchdog guy", although watchdog doesn't
> > have a MAINTAINERS entry so I'm looking at bk/lkml history etc and might
> > be mistaken...
> Sorry for the late response. I indeed try to maintain the watchdog drivers
> and get a uniform API for all the watchdog drivers.
> > I wrote to the the linux-arm-kernel mailing list recently with a query
> > because the sa1100_wdt code supports the writing 'V' to deactivate the
> > watchdog thing, but unfortunately once armed the hardware cannot be
> > deactivated.
> > I was going to produce a patch to remove the 'V' support and it was
> > suggested by Russell that I should ask for your opinion. Do you have a
> > preference with regards to offering a warning or error etc if a 'V' is
> > written?
> > My original message is below. I have had confirmation that the SA1100
> > has the same behaviour as PXA2xx from Nico.
> the actual problem you have is not the magic char 'V' that needs to be
> written to safely stop the watchdog. The problem is that your watchdog
> can not be stopped once started.
> What we should do (in my opinion) is to add a timer like done in
> mixcomwd.c. What this timer does is ping/tickle the watchdog internally
> when the watchdog is supposed to be not active. (So it starts pinging
> the watchdog after userspace stopped/released /dev/watchdog and it stops
> again when the userspace opens /dev/atchdog again).
> The writing of the magic char V is a failsafe mechanism for if the
> watchdog daemon would crash and close /dev/watchdog when it is supposed
> to keep working...
A patch to simply pull out the 'V' failsafe handling was already merged
into the kernel.
I can try and find time to look at adding a timer etc but it might be
some time so if you feel like doing it please feel free.
Ian Campbell, Senior Design Engineer
Arcom, Clifton Road, Direct: +44 (0)1223 403 465
Cambridge CB1 7EA, United Kingdom Phone: +44 (0)1223 411 200
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