Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210226141411.2517368-1-linux@rasmusvillemoes.dk>
 <CAK8P3a2=nZ3bbeguXjbFrhz0nWeUOcLM7mRudhPDrcb+jZ4VvQ@mail.gmail.com>
 <e5fd7ce3-3ba6-e5de-1cbc-fa31bd46942c@rasmusvillemoes.dk> <2208f466-e509-6bbe-0358-34effb965610@roeck-us.net>
 <285d739a-b343-c411-5461-0fe1f44177a5@rasmusvillemoes.dk>
In-Reply-To: <285d739a-b343-c411-5461-0fe1f44177a5@rasmusvillemoes.dk>
From:   Arnd Bergmann <arnd@kernel.org>
Date:   Mon, 1 Mar 2021 10:44:48 +0100
Message-ID: <CAK8P3a0tTQKZ6=55yCQx=60iBt1L6RZzzSvSJMmfKYUkgiWjrQ@mail.gmail.com>
Subject: Re: [PATCH 0/2] add ripple counter dt binding and driver
To:     Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc:     Guenter Roeck <linux@roeck-us.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Rob Herring <robh+dt@kernel.org>,
        DTML <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        linux-clk <linux-clk@vger.kernel.org>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        "linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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