linux-kernel - Re: [PATCH v2] watchdog: omap_wdt: Add 'early

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Message-ID: <20140923161440.GC20591@roeck-us.net>
Date:	Tue, 23 Sep 2014 09:14:40 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Rostislav Lisovy <lisovy@...il.com>
Cc:	Wim Van Sebroeck <wim@...ana.be>, linux-watchdog@...r.kernel.org,
	linux-kernel@...r.kernel.org, sojkam1@....cvut.cz,
	michal.vokac@...ap.cz, Rostislav Lisovy <lisovy@...ica.cz>
Subject: Re: [PATCH v2] watchdog: omap_wdt: Add 'early_disable' module
 parameter

On Tue, Sep 23, 2014 at 12:44:47PM +0200, Rostislav Lisovy wrote:
> On Čt, 2014-09-18 at 21:12 -0700, Guenter Roeck wrote:
> > How about reading the OMAP_WATCHDOG_SPR register ?
> 
> Unfortunately this would be not only extremely fragile (someone writes
> correct start sequence followed by some garbage -- WD is running and we
> are reading garbage) but according to some experiments seems not to work
> at all (I am reading "0" even for a running WD probably as a result to
> the pm_runtime_get_sync() call).
> 
> One of the TI employees on the TI forum confirmed (I know this is not a
> rock-solid information) that it is not possible to safely determine if
> the WD is running or not.
> 
Annoying, but I guess we'll have to live with that.

> 
> > Either case, you can not issue a message about the watchdog being
> > stopped or started if you don't know if it was actually stopped
> > or started. Also, if you don't really know if the watchdog was
> > stopped or started, all you can do is to either stop or start it,
> > without judgment about its previous condition.
> 
> You are right. I was blinded by our use case where the watchdog is
> always started by the bootloader.
> I will wait to see if the WATCHDOG_KEEP_ON will be integrated and then I
> will add the feature for the omap_wdt.
> 
I would predict that it will be accepted. For my part I am not happy
with the name, though, and I'll have to find the time to thoroughly review
and, if possible, test it.

Guenter
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