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: <20201204092752.GE74177@piout.net> <20201211215611.24392-1-rasmus.villemoes@prevas.dk>
 <20201211215611.24392-2-rasmus.villemoes@prevas.dk> <CAL_JsqJ-5gwycTRQCdX=ZsefEJ=F1GyTjjDW6QB1PBynibFzLg@mail.gmail.com>
 <b3c05d29-3ed6-d5f5-d1dd-0ddec1f89276@prevas.dk>
In-Reply-To: <b3c05d29-3ed6-d5f5-d1dd-0ddec1f89276@prevas.dk>
From:   Rob Herring <robh+dt@kernel.org>
Date:   Thu, 17 Dec 2020 10:51:08 -0600
Message-ID: <CAL_Jsq+HeeFUR1Yv37X4OnkEPvSiAc2B86=Nshxz7tmvpKk+zw@mail.gmail.com>
Subject: Re: [PATCH v2 1/3] dt-bindings: rtc: add reset-source property
To:     Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Cc:     "open list:REAL TIME CLOCK (RTC) SUBSYSTEM" 
        <linux-rtc@vger.kernel.org>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= 
        <u.kleine-koenig@pengutronix.de>, Qiang Zhao <qiang.zhao@nxp.com>,
        Bruno Thomsen <bruno.thomsen@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Dec 11, 2020 at 5:10 PM Rasmus Villemoes
<rasmus.villemoes@prevas.dk> wrote:
>
> On 11/12/2020 23.30, Rob Herring wrote:
> > On Fri, Dec 11, 2020 at 3:56 PM Rasmus Villemoes
> > <rasmus.villemoes@prevas.dk> 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