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

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Date:   Tue, 25 Oct 2022 23:38:36 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Magnus Damm <magnus.damm@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-renesas-soc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Biju Das <biju.das.jz@...renesas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH 2/2] arm64: dts: renesas: rzg2ul-smarc: Add
 /omit-if-no-ref/ to pinmux

Hi Geert,

Thank you for the review.

On Tue, Oct 25, 2022 at 9:13 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Prabhakar,
>
> On Thu, Sep 15, 2022 at 6:53 PM Prabhakar <prabhakar.csengg@...il.com> wrote:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...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@...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?

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

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

Cheers,
Prabhakar

> > --- a/arch/arm64/boot/dts/renesas/rzg2ul-smarc-pinfunction.dtsi
> > +++ b/arch/arm64/boot/dts/renesas/rzg2ul-smarc-pinfunction.dtsi
> > @@ -12,12 +12,14 @@ &pinctrl {
> >         pinctrl-0 = <&sound_clk_pins>;
>                         ^^^^^^^^^^^^^^
> >         pinctrl-names = "default";
> >
> > +       /omit-if-no-ref/
> >         can0_pins: can0 {
> >                 pinmux = <RZG2L_PORT_PINMUX(1, 1, 3)>, /* TX */
> >                          <RZG2L_PORT_PINMUX(1, 2, 3)>; /* RX */
> >         };
> >
> >  #if (SW_ET0_EN_N)
> > +       /omit-if-no-ref/
> >         can0-stb-hog {
> >                 gpio-hog;
> >                 gpios = <RZG2L_GPIO(2, 2) GPIO_ACTIVE_HIGH>;
>
> > @@ -94,11 +103,13 @@ sd1_mux_uhs {
> >                 };
> >         };
> >
> > +       /omit-if-no-ref/
> >         sound_clk_pins: sound_clk {
>
> FTR, this one is always referenced.
>
> >                 pins = "AUDIO_CLK1", "AUDIO_CLK2";
> >                 input-enable;
> >         };
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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