Re: [PATCH v2 5/6] watchdog: at91sam9: request the irq with IRQF_NO_SUSPEND

Pavel Machek
2015-03-07T10:39:43Z

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
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