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

Rafael J. Wysocki
2015-03-09T14:06:35Z

On Monday, March 09, 2015 08:55:46 AM Alexandre Belloni wrote:
> 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.

I gather then that the suspend implementation is such that touching the
watchdog periodically while suspended is not a problem.

Again, can you please tell me how suspend is implemented on at91?

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.