Re: [PATCH 2/3] dt-bindings: power: reset: add document for renesas-reset driver

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Chris Brandt <Chris.Brandt@renesas.com>
Cc: Sebastian Reichel <sre@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Simon Horman <horms@verge.net.au>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Linux PM list <linux-pm@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>
Subject: Re: [PATCH 2/3] dt-bindings: power: reset: add document for renesas-reset driver
Date: Thu, 16 Feb 2017 14:51:40 +0100	[thread overview]
Message-ID: <CAMuHMdVUdU4J+cg7V-rMK63TkEKJp_Nyxh=+34rdtuo1wGUNRw@mail.gmail.com> (raw)
In-Reply-To: <PS1PR06MB1162A82F35F00D18D5D22FC08A5B0@PS1PR06MB1162.apcprd06.prod.outlook.com>

Hi Chris,

On Wed, Feb 15, 2017 at 6:33 PM, Chris Brandt <Chris.Brandt@renesas.com> wrote:
> On Tuesday, February 14, 2017, Geert Uytterhoeven wrote:
>> > +Required properties:
>> > +  - compatible: must be one or more of the following:
>> > +    - "renesas,r7s72100-reset" for the r7s72100 SoC
>> > +    - "renesas,wdt-reset"
>> > +                This is a fallback for the above renesas,*-reset
>> > +entries
>>
>> Please use "renesas,r7s72100-wdt". DT describes the hardware (watchdog),
>> not the software policy (use it for reset only, as a max. timeout of 125
>> ms is too short for a usable watchdog).
>
> I had a look at:
>
>   Documentation/devicetree/bindings/watchdog/renesas-wdt.txt
>
> Which has:
>
> Required properties:
> - compatible : Should be "renesas,<soctype>-wdt", and
>                "renesas,rcar-gen3-wdt" as fallback.
>                Examples with soctypes are:
>                  - "renesas,r8a7795-wdt" (R-Car H3)
>                  - "renesas,r8a7796-wdt" (R-Car M3-W)
>
>
> So in my 'renesas-reset.txt' should I do:

As "reset" is software policy, perhaps you should instead extend the existing
binding document Documentation/devicetree/bindings/watchdog/renesas-wdt.txt?

Nothing says you have to use the same Linux driver for R-Car Gen3 and
RZ/A1.

> A. "renesas,r7s72100-wdt", "renesas,rz-wdt"

Please don't use plain "rz", as RZ/A, RZ/G, and RZ/T are completely different
beasts.

>
>   or just:
>
> B. "renesas,r7s72100-wdt"   (no fallback, change the driver to add new SoCs)

Do you know if future RZ/A SoCs will use the exact same type of WDT?
If yes, you can document both "renesas,r7s72100-wdt" and "renesas,rza-wdt",
and let the driver match against the latter.
Else I'd just document and match against "renesas,r7s72100-wdt".

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds