Re: [PATCH 0/2] add ripple counter dt binding and driver

Arnd Bergmann
2021-03-01T09:48:13Z

On Mon, Mar 1, 2021 at 9:34 AM Rasmus Villemoes
<linux@rasmusvillemoes.dk> wrote:
> On 26/02/2021 20.53, Guenter Roeck wrote:
> >
> > Sorry, I am missing something. If the watchdog is controlled by the clock,
> > it is a consumer of that clock.
>
> But that's just it, the watchdog chip is _not_ a consumer of the clock -
> I don't think I've ever seen a gpio_wdt that is not internally clocked,
> but even if they exist, that's not the case for this board.
>
> What else does "consumer" mean ? And why
> > not just add optional clock support to the gpio_wdt driver ?
>
> Because, the consumer is a piece of electronics sitting _between_ the
> watchdog chip's reset output and the SOCs reset pin, namely the ripple
> counter that implements a 64 ms delay from the watchdog fires till the
> actual reset. (The watchdog's reset is also routed directly to an
> interrupt; so software gets a 64 ms warning that a hard reset is imminent).

I think it's a question of how you look at what the gpio_wdt device is.
While physical gpio chip is not a consumer of the clock, I agree with
Guenter that the conceptual device is: The functionality of the watchdog
in this case is provided by the combination of the external chip with the
ripple counter. I think it is therefore appropriate to have the gpio_wdt
and the driver refer to the clock as part of the watchdog.

Arnd