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

Alexandre Belloni
2015-03-09T07:55:49Z

Hi,

On 08/03/2015 at 02:12:53 +0100, Rafael J. Wysocki wrote :
> > > I think you misunderstood, that is exactly the expected behaviour. This
> > > is hardware defined. Once the watchdog is started, nobody can stop it.
> > > Trying to change the mode register will result in a reset of the
> > > SoC.
> >
> > Well, it boils down to "what is stronger". Desire to suspend the
> > system, or desire to reboot the system.
> >
> > It is "echo mem > state", not "echo reboot > state".
> >
> > > It is documented in the datasheet and any user wanting another behaviour
> > > is out of luck.
> >
> > Actaully, your platform should just refuse to enter suspend-to-RAM
> > when hw watchdog is enabled.
>
> Quite likely, depending on how exactly the suspend is implemented.
>

We've had absolutely zero complain on that. It is quite clear in the
datasheet that failing to refresh the watchdog once started will lead to
a reset and that it is impossible to stop.
It is actually quite convenient to also ensure that you can actually
wake up from suspend because that can obviously go wrong.

--
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering