Re: [Patch v2 1/3] dt-bindings: rtc: pcf2127: Add bindings for nxp,pcf2127

From: Bruno Thomsen <bruno.thomsen@gmail.com>
To: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: "Qiang Zhao" <qiang.zhao@nxp.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Wim Van Sebroeck" <wim@linux-watchdog.org>,
	"Guenter Roeck" <linux@roeck-us.net>,
	"linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
	"a.zummo@towertech.it" <a.zummo@towertech.it>,
	"robh+dt@kernel.org" <robh+dt@kernel.org>,
	"linux-rtc@vger.kernel.org" <linux-rtc@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kernel@pengutronix.de" <kernel@pengutronix.de>
Subject: Re: [Patch v2 1/3] dt-bindings: rtc: pcf2127: Add bindings for nxp,pcf2127
Date: Thu, 24 Sep 2020 18:59:33 +0200	[thread overview]
Message-ID: <CAH+2xPAi+f2eKdeYiipc=W7eeeNdiXngTLkchpdoFMjJn9Og9w@mail.gmail.com> (raw)
In-Reply-To: <20200924074715.GT9675@piout.net>

Den tor. 24. sep. 2020 kl. 09.47 skrev Alexandre Belloni
<alexandre.belloni@bootlin.com>:
>
> Hi,
>
> On 24/09/2020 07:23:18+0000, Qiang Zhao wrote:
> > > > Yes, you are right, There is not a fundamental solution.
> > > > However it somewhat avoid this situation at least.
> > > >
> > > > And if without this issue,
> > > > is it correct to register a rtc device as watchdog no matter it is used as
> > > watchdog on the board?
> > > > Every time Linux are booted up, watchdog device should be configured to the
> > > right one manually.
> > > > So the patch are useful, even though it is not for the issue.
> > > >
> > > > What should we do to really resolve this issue?
> > >
> > > I still think we need a kernel solution here. I would expect that most assembled
> > > pcf2127 chips are unable to act as a watchdog (i.e. don't have the RST output
> > > connected to something that resets the machine).
> > >
> > > So my favoured solution would be a positive property like:
> > >
> > >     has-watchdog;
> > >
> > > or something similar. In my eyes this is definitely something we want to specify
> > > in the device tree because it is a relevant hardware property.
> > > I consider it a bug to give a watchdog device to userspace that isn't functional.
> > >
> > > Best regards
> > > Uwe
> >
> > I strongly agree with you! It should be positive property.
> > However, we couldn't identify which board are using pcf2127 as watchdog,
> > So we are unable to modify the boards' dts to correct (watchdog or not) in this patchset.
> >
> > I noticed that only LS series platforms and imx6 have pcf2127 node, as far as I know, the LS platforms don't use it as watchdog,
> > But I am not sure about imx6
> >
>
> I don't think there is any user upstream and it is recent engouh that we
> can probably make that a positive property.
>
> Bruno, is it ok for you? you are the only know user of the feature.

Hi

This seems like an okay solution to me.

I have a patch series on the way with a new product dts[1] that is
using the watchdog
feature in the pcf2127 chip.

I know that the watchdog feature is used by other products with
out-of-tree dts, but I
will make sure to give them a heads up.

/Bruno

[1] https://lore.kernel.org/linux-arm-kernel/20200923154024.11417-2-bruno.thomsen@gmail.com/