Re: [PATCH 2/2] arm64: dts: renesas: rzg2ul-smarc: Add /omit-if-no-ref/ to pinmux

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Cc: Magnus Damm <magnus.damm@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	linux-renesas-soc@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Biju Das <biju.das.jz@bp.renesas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Subject: Re: [PATCH 2/2] arm64: dts: renesas: rzg2ul-smarc: Add /omit-if-no-ref/ to pinmux
Date: Wed, 26 Oct 2022 09:28:55 +0200	[thread overview]
Message-ID: <CAMuHMdWkg-k2efZoy=U+j-xji0Agp38qRy-8cjb7K7QiJrL-ZQ@mail.gmail.com> (raw)
In-Reply-To: <CA+V-a8sidwGQVSb7UV56opqE9ViS_y7nVPWx8Krx7t6P1BExCg@mail.gmail.com>

Hi Prabhakar,

On Wed, Oct 26, 2022 at 12:39 AM Lad, Prabhakar
<prabhakar.csengg@gmail.com> wrote:
> On Tue, Oct 25, 2022 at 9:13 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > On Thu, Sep 15, 2022 at 6:53 PM Prabhakar <prabhakar.csengg@gmail.com> wrote:
> > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > >
> > > In preparation to re-use the RZ/G2UL SMARC SoM and carrier DTS/I with the
> > > RZ/Five add /omit-if-no-ref/ keyword to pinmux entries as the support for
> > > RZ/Five SMARC EVK will be gradually added.
> > >
> > > Once we have full blown support for RZ/Five SMARC EVK we can get rid of
> > > the /omit-if-no-ref/ keyword.
> > >
> > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> >
> > Thanks for your patch!
> >
> > I finally had a deeper look at this...
> >
> > Why do you want to disable these nodes? While they are indeed not
> > used yet on RZ/Five, they are valid hardware descriptions for the
> > RZ/Five SMARC EVK, and their presence doesn't harm anything.
> >
> > I do see a valid use case for marking pin control subnodes with
> > /omit-if-no-ref/: you can provide all possible configurations as a
> > convenience for the user, so the user no longer has to look up the
> > numeric parameters of the RZG2L_PORT_PINMUX() macros.
> > But IMHO those would belong in the SoC-specific .dtsi, not in a
> > board .dtsi.  See e.g. the massive use of /omit-if-no-ref/ in sunxi
> > and rockchip .dtsi files.
> >
> > Am I missing something?
> >
> My intention was to keep the DTB as minimal as possible so that it
> includes just the required pinmuxes which were enabled on the RZ/Five.
> For example [0], [1] we do delete the pinctrl for the nodes which are
> marked as disabled. Do you think we should drop it?

You mean

    /delete-property/ pinctrl-0;
    /delete-property/ pinctrl-names;

?
These do not delete pinctrl subnodes, but pinctrl properties in disabled
device nodes pointing to pinctrl subnodes.  The actual pinctrl subnodes
are still present.

> But now that things are falling in place for RZ/Five we can ignore this patch.

Agreed.

> [0] arch/arm64/boot/dts/renesas/rzg2lc-smarc.dtsi
> [1] arch/arm64/boot/dts/renesas/rzg2ul-smarc.dtsi

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