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From: Rostislav Lisovy <lisovy@gmail.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Wim Van Sebroeck <wim@iguana.be>,
	linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org,
	sojkam1@fel.cvut.cz, michal.vokac@comap.cz,
	Rostislav Lisovy <lisovy@merica.cz>
Subject: Re: [PATCH v2] watchdog: omap_wdt: Add 'early_disable' module parameter
Date: Tue, 23 Sep 2014 12:44:47 +0200	[thread overview]
Message-ID: <1411469087.32524.6.camel@lp-lvrv.comap.cz> (raw)
In-Reply-To: <541BAD2C.8080902@roeck-us.net>

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.


> 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.

Best regards;
Rostislav



  reply	other threads:[~2014-09-23 10:44 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-16 14:20 [PATCH v2] watchdog: omap_wdt: Add 'early_disable' module parameter Rostislav Lisovy
2014-09-16 15:49 ` Guenter Roeck
2014-09-17 15:22   ` Rostislav Lisovy
2014-09-19  4:12     ` Guenter Roeck
2014-09-23 10:44       ` Rostislav Lisovy [this message]
2014-09-23 16:14         ` Guenter Roeck
2014-09-23 16:14           ` Guenter Roeck

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