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

[Lad, Prabhakar]

Hi Wolfram,

On Wed, Jul 3, 2024 at 10:38 AM Wolfram Sang
<wsa+renesas@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Jun 26, 2024 at 02:23:39PM +0100, Prabhakar wrote:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxxx>
>
> 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@15c10000 {
        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.

Cheers,
Prabhakar