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Date: Thu, 5 Mar 2015 10:53:08 +0000
From: Mark Rutland <mark.rutland@arm.com>
To: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Jason Cooper <jason@lakedaemon.net>,
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Subject: Re: [PATCH v2 5/6] watchdog: at91sam9: request the irq with
 IRQF_NO_SUSPEND
Message-ID: <20150305105308.GA13617@leverpostej>
References: <1425287898-15093-1-git-send-email-boris.brezillon@free-electrons.com>
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 <20150304183809.GD22156@leverpostej>
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Hi Boris,

I'd missed the fact that this was for SW watchdog as opposed to HW
watchdog, which may explain my confusion.

[...]

> > >  		err = request_irq(wdt->irq, wdt_interrupt,
> > > -				  IRQF_SHARED | IRQF_IRQPOLL,
> > > +				  IRQF_SHARED | IRQF_IRQPOLL |
> > > +				  IRQF_NO_SUSPEND,
> > 
> > I'm a little confused by this. What happens if the watchdog fires when
> > we're actually in the suspended state (when IRQF_NO_SUSPEND interrupts
> > aren't guaranteed to be delivered).
> 
> It reboot the system.

Is the timer we use to ping the watchdog guaranted to result in a wakeup
before an interrupt will be triggered? If so, then I think we're ok.

If not, then don't we need to clear a potentially pending watchdog irq
at resume time so at to not immediately reboot the machine? I couldn't
see any logic to that effect in the driver.

Regardless, if the only reason we care about taking the interrupt during
the suspend/resume phases is due to the timer sharing the IRQ, then
shouldn't we be using IRQF_COND_SUSPEND?

Thanks,
Mark.