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 10:13:12 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Prabhakar <prabhakar.csengg@...il.com>
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 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?

> --- 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