linux-kernel - Re: [PATCH v4 1/3] dt-bindings: mmc: renesas,sdhi: Document RZ/V2H(P) support

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Message-ID: <CA+V-a8uQz4fbCHeG-88Re3sxa3ye+5NfZ=NRdgV-58=9tHpN+A@mail.gmail.com>
Date: Mon, 22 Jul 2024 14:19:10 +0100
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc: Geert Uytterhoeven <geert+renesas@...der.be>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>, 
	Ulf Hansson <ulf.hansson@...aro.org>, Rob Herring <robh@...nel.org>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, Biju Das <biju.das.jz@...renesas.com>, 
	linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-mmc@...r.kernel.org, 
	Magnus Damm <magnus.damm@...il.com>, Conor Dooley <conor+dt@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>
Subject: Re: [PATCH v4 1/3] dt-bindings: mmc: renesas,sdhi: Document RZ/V2H(P) support

Hi Wolfram,

On Thu, Jul 4, 2024 at 7:27 PM Lad, Prabhakar
<prabhakar.csengg@...il.com> wrote:
>
> Hi Wolfram,
>
> On Wed, Jul 3, 2024 at 10:38 AM Wolfram Sang
> <wsa+renesas@...g-engineering.com> wrote:
> >
> > On Wed, Jun 26, 2024 at 02:23:39PM +0100, Prabhakar wrote:
> > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > >
> > > The SD/MMC block on the RZ/V2H(P) ("R9A09G057") SoC is similar to that
> > > of the R-Car Gen3, but it has some differences:
> > > - HS400 is not supported.
> > > - It supports the SD_IOVS bit to control the IO voltage level.
> > > - It supports fixed address mode.
> > >
> > > To accommodate these differences, a SoC-specific 'renesas,sdhi-r9a09g057'
> > > compatible string is added.
> > >
> > > A 'vqmmc-regulator' object is introduced to handle the power enable (PWEN)
> > > and voltage level switching for the SD/MMC.
> > >
> > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> >
> > Can we have an example here? I can read DTS snippets better than YAML
> > code :/ Also wondering about the "regulator-compatible" property but
> > maybe the example makes the problem clear?
> >
> You mean in the commit message or comment section? (I had added below
> in the cover letter)
>
> SoC DTSI node:
> sdhi1: mmc@...10000 {
>         compatible = "renesas,sdhi-r9a09g057";
>         reg = <0x0 0x15c10000 0 0x10000>;
>         interrupts = <GIC_SPI 737 IRQ_TYPE_LEVEL_HIGH>,
>                         <GIC_SPI 738 IRQ_TYPE_LEVEL_HIGH>;
>         clocks = <&cpg CPG_MOD 167>,
>                         <&cpg CPG_MOD 169>,
>                         <&cpg CPG_MOD 168>,
>                         <&cpg CPG_MOD 170>;
>         clock-names = "core", "clkh", "cd", "aclk";
>         resets = <&cpg 168>;
>         power-domains = <&cpg>;
>         status = "disabled";
>
>         vqmmc_sdhi1: vqmmc-regulator {
>                 regulator-compatible = "vqmmc-r9a09g057-regulator";
>                 regulator-name = "sdhi1-vqmmc-regulator";
>                 regulator-min-microvolt = <1800000>;
>                 regulator-max-microvolt = <3300000>;
>                 status = "disabled";
>         };
> };
>
> Board DTS:
> &sdhi1 {
>         pinctrl-0 = <&sdhi1_pins>;
>         pinctrl-1 = <&sdhi1_pins>;
>         pinctrl-names = "default", "state_uhs";
>         vmmc-supply = <&reg_3p3v>;
>         vqmmc-supply = <&vqmmc_sdhi1>;
>         bus-width = <4>;
>         sd-uhs-sdr50;
>         sd-uhs-sdr104;
>         status = "okay";
> };
>
> &vqmmc_sdhi1 {
>      status = "okay";
> };
>
> Based on feedback from Conor, we cannot use the regulator-compatible
> property. This would require us to implement separate drivers (one for
> VMMC and another for VQMMC), which I believe would necessitate the use
> of regmap. Currently, this seems unnecessary for controlling the two
> bits as a regulator. As Geert previously pointed out, the PWEN and
> IOVS pins can always be multiplexed as GPIOs on the RZ/V2H SoC (as is
> done on R-Car devices). Therefore, I am inclined to drop the internal
> regulator support for now.
>
> Let me know your thoughts.
>
Gentle ping.

Cheers,
Prabhakar