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

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Message-ID: <CAMuHMdV52FEGdW3Jqtn_=yhZ8h1hf5h9nn8d15Pkgmq7VJwnSA@mail.gmail.com>
Date: Mon, 22 Dec 2025 11:58:24 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Biju Das <biju.das.jz@...renesas.com>
Cc: Josua Mayer <josua@...id-run.com>, Ulf Hansson <ulf.hansson@...aro.org>, 
	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>, 
	"wsa+renesas" <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" <linux-mmc@...r.kernel.org>, 
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] dt-bindings: mmc: renesas,sdhi: Add mux-states property

Hi Biju,

On Mon, 1 Dec 2025 at 14:03, Biju Das <biju.das.jz@...renesas.com> wrote:
> > -----Original Message-----
> > From: Josua Mayer <josua@...id-run.com>
> > Add mux controller support for when sdio lines are muxed between a host and multiple cards.
> >
> > 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 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>

> > --- 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.
>
> Maybe describe 0 - state for SD and 1 - state for 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>;
>
> On R-Car mmc/sd mux available only on SD2/SD3, so I guess you picked wrong node SD0??

What do you mean by this comment?
AFAIUI, this muxing is board-specific, and not related to the on-SoC
SDHI controller instance?

Thanks!

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