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

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Message-ID: <2208f466-e509-6bbe-0358-34effb965610@roeck-us.net>
Date:   Fri, 26 Feb 2021 11:53:14 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Arnd Bergmann <arnd@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        DTML <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        linux-clk <linux-clk@...r.kernel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>
Subject: Re: [PATCH 0/2] add ripple counter dt binding and driver

On 2/26/21 8:35 AM, Rasmus Villemoes wrote:
> On 26/02/2021 15.35, Arnd Bergmann wrote:
>> On Fri, Feb 26, 2021 at 3:14 PM Rasmus Villemoes
>> <linux@...musvillemoes.dk> wrote:
>>
>>>
>>> So I'm thinking that the proper way to handle this is to be able to
>>> represent that ripple counter as a clock consumer in DT and have a
>>> driver do the clk_prepare_enable(), even if that driver doesn't and
>>> can't do anything else. But I'm certainly open to other suggestions.
>>
>> How about adding support for the optional clock to the gpio_wdt driver,
>> would that work?
> 
> I think it would _work_ (all I need is some piece of code doing the
> clock_prepare_enable(), and until now we've just stashed that in some
> otherwise unrelated out-of-tree driver, but we're trying to get rid of
> that one), but the watchdog chip isn't really the consumer of the clock
> signal, so in-so-far as DT is supposed to describe the hardware, I don't
> think it's appropriate.
> 
> OTOH, one could argue that the watchdog chip and the ripple counter
> together constitute the watchdog circuit.
> 
> Cc += watchdog maintainers. Context: I have a gpio-wdt which can
> unfortunately effectively be disabled by disabling a clock output, and
> that happens automatically unless the clock has a consumer in DT. But
> the actual consumer is not the gpio-wdt.
> Please see
> https://lore.kernel.org/lkml/20210226141411.2517368-1-linux@rasmusvillemoes.dk/
> for the original thread.
> 

Sorry, I am missing something. If the watchdog is controlled by the clock,
it is a consumer of that clock. What else does "consumer" mean ? And why
not just add optional clock support to the gpio_wdt driver ?

Guenter