Re: [PATCH v2 1/3] dt-bindings: rtc: add reset-source property

[Rob Herring]

On Fri, Dec 11, 2020 at 5:10 PM Rasmus Villemoes
<rasmus.villemoes@xxxxxxxxx> wrote:
>
> On 11/12/2020 23.30, Rob Herring wrote:
> > On Fri, Dec 11, 2020 at 3:56 PM Rasmus Villemoes
> > <rasmus.villemoes@xxxxxxxxx> wrote:
> >>
> >> Some RTCs, e.g. the pcf2127, can be used as a hardware watchdog. But
> >> if the reset pin is not actually wired up, the driver exposes a
> >> watchdog device that doesn't actually work.
> >>
> >> Provide a standard binding that can be used to indicate that a given
> >> RTC can perform a reset of the machine, similar to wakeup-source.
> >
> > Why not use the watchdog 'timeout-sec' property?
>
> Wouldn't that be overloading that property? AFAIU, that is used to ask
> the kernel to program an initial timeout value into the watchdog device.
> But what if one doesn't want to start the watchdog device at kernel
> boot, but just indicate that the RTC has that capability?

Yeah, I guess you're right.

> It's quite possible that if it can act as a watchdog device (and
> has-watchdog was also suggested), one would also want timeout-sec and
> other watchdog bindings to apply. But that can be added later, by those
> who actually want that.
>
> For now, I'd really like to get my board booting again (or rather, not
> get reset by the real watchdog just because the pcf2127 driver now
> exposes something as /dev/wathdog0, pushing the real one to
> /dev/wathcdog1 which doesn't get pinged from userspace).

I'm wondering how you solve which wdog to ping when there are multiple
without relying on numbering. I guess 'reset-source' will solve that
even if that's not your current fix. So I guess I'm fine with this.

But you need to send to the DT list so checks are run.

Rob