linux-kernel - Re: [PATCH v2 1/2] dt-bindings: mmc: renesas,sdhi: Add mux-states property

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Message-ID: <CAPDyKFrD2x0U49w2Fpzrc98wKXtyyN-B1P69OMJk27+0Yzsg8Q@mail.gmail.com>
Date: Tue, 9 Dec 2025 13:08:46 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Josua Mayer <josua@...id-run.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Geert Uytterhoeven <geert+renesas@...der.be>, 
	Magnus Damm <magnus.damm@...il.com>, Wolfram Sang <wsa+renesas@...g-engineering.com>, 
	Mikhail Anikin <mikhail.anikin@...id-run.com>, Yazan Shhady <yazan.shhady@...id-run.com>, 
	Jon Nettleton <jon@...id-run.com>, linux-mmc@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v2 1/2] dt-bindings: mmc: renesas,sdhi: Add mux-states property

On Mon, 1 Dec 2025 at 13:31, Josua Mayer <josua@...id-run.com> wrote:
>
> Add mux controller support for when sdio lines are muxed between a host
> and multiple cards.

We have the SD, SDIO, (e)MMC interfaces with their corresponding pins.
Using "sdio lines" becomes confusing as it kind of indicates this is
for "SDIO" only.

>
> There are several devices supporting a choice of eMMC or SD on a single
> board by both dip switch and gpio, e.g. Renesas RZ/G2L SMARC SoM and
> SolidRun RZ/G2L SoM.
>
> In-tree dts for the Renesas boards currently rely on preprocessor macros
> to hog gpios and define the card.
>
> By adding mux-states property to sdio controller description, boards can

Again, please don't use "sdio" here.

> correctly describe the mux that already exists in hardware - and drivers
> can coordinate between mux selection and probing for cards.
>
> Signed-off-by: Josua Mayer <josua@...id-run.com>
> ---
>  Documentation/devicetree/bindings/mmc/renesas,sdhi.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/mmc/renesas,sdhi.yaml b/Documentation/devicetree/bindings/mmc/renesas,sdhi.yaml
> index c754ea71f51f7..754ccb1c30efb 100644
> --- a/Documentation/devicetree/bindings/mmc/renesas,sdhi.yaml
> +++ b/Documentation/devicetree/bindings/mmc/renesas,sdhi.yaml
> @@ -106,6 +106,11 @@ properties:
>    iommus:
>      maxItems: 1
>
> +  mux-states:
> +    description:
> +      mux controller node to route the SDIO signals from SoC to cards.

I suggest we change from "SDIO" to "SD/SDIO/eMMC".

> +    maxItems: 1
> +
>    power-domains:
>      maxItems: 1
>
> @@ -275,6 +280,7 @@ examples:
>          max-frequency = <195000000>;
>          power-domains = <&sysc R8A7790_PD_ALWAYS_ON>;
>          resets = <&cpg 314>;
> +        mux-states = <&mux 0>;
>      };
>
>      sdhi1: mmc@...20000 {
>
> --
> 2.51.0
>
>

Kind regards
Uffe