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

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Message-ID:
 <TY3PR01MB11346909D4DE29AFE7D229B0786B4A@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Mon, 22 Dec 2025 11:04:24 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: geert <geert@...ux-m68k.org>
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 Geert,

> -----Original Message-----
> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Sent: 22 December 2025 10:58
> 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?

As per RZ/G2M hardware manual(R-Car M3-W) SoC has mmc/sdhi support only for SD2 and SD3. 
SD0 and SD1, SoC don't provide  8 data pins to support MMC mode.

57.1.2 Block Diagram mentions "Note: * MMC interface is only CH2 and CH3."

Cheers,
Biju