From mboxrd@z Thu Jan  1 00:00:00 1970
From: pavel@ucw.cz (Pavel Machek)
Date: Sat, 7 Mar 2015 11:39:39 +0100
Subject: [PATCH v2 5/6] watchdog: at91sam9: request the irq with
 IRQF_NO_SUSPEND
In-Reply-To: <20150307102056.GA28436@gradator.net>
References: <1425287898-15093-1-git-send-email-boris.brezillon@free-electrons.com>
 <1425287898-15093-6-git-send-email-boris.brezillon@free-electrons.com>
 <20150304183809.GD22156@leverpostej>
 <20150305095306.3db98ac8@bbrezillon>
 <20150305105308.GA13617@leverpostej>
 <20150305121723.1da0d016@bbrezillon>
 <20150305115307.GA14093@leverpostej>
 <20150307091846.GN23367@worktop.ger.corp.intel.com>
 <20150307102056.GA28436@gradator.net>
Message-ID: <20150307103939.GA17964@amd>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Sat 2015-03-07 11:20:56, Sylvain Rochet wrote:
> Hello,
> 
> On Sat, Mar 07, 2015 at 10:18:46AM +0100, Peter Zijlstra wrote:
> > On Thu, Mar 05, 2015 at 11:53:08AM +0000, Mark Rutland wrote:
> > > If everyone else is happy with this using IRQF_NO_SUSPEND for now then
> > > don't let my comments above block this patch.
> > 
> > Yeah, I'm really not happy with NO_SUSPEND + enable_irq_wake().
> > 
> > I really want that combo to BUG/WARN -- esp. since there's so much cargo
> > culted crap out there.
> > 
> > We should make robust interfaces, not randomly toggle flags until it
> > mostly works by accident rather than by design -- which is what this
> > feels like.
> > 
> > And while I appreciate the watchdog use-case; I think the easiest
> > solution for now is to simply disable the wathdog over suspend until
> > we've come up with something that makes sense.
> > 
> > As it is, you need to 'suspend' the watchdog at some point anyhow; you
> > don't want that thing to wake you from whatever suspend state you're in.
> 
> The Atmel watchdog can't be stopped once it's started. This is actually 
> very useful so we can reset if suspend or resume failed, the only 
> drawback is that you have to wake up from time to time (e.g. by using 
> the RTC/RTT) to clear the watchdog and then go back to sleep ASAP.

Yeah. So you do "echo mem > /sys/power/state", and few seconds/minutes
after watchdog kills the system. But you did not ask for dead system,
you asked for suspend.

And while that behaviour is useful for you, I don't think it is
exactly useful behaviour, nor it is the behaviour user would expect.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html