linux-kernel - Re: [PATCH v1 1/2] dt-bindings: mmc: sdhci-of-aspeed: Add power-gpio and power-switch-gpio

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Message-ID: <CAPDyKFr=Gtwu4v22FBaax5EjRbXTNez1N2ZQxP=v0LKGFTCovw@mail.gmail.com>
Date:   Mon, 12 Apr 2021 09:38:40 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Steven Lee <steven_lee@...eedtech.com>
Cc:     Andrew Jeffery <andrew@...id.au>, Rob Herring <robh+dt@...nel.org>,
        Joel Stanley <joel@....id.au>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ryan Chen <ryanchen.aspeed@...il.com>,
        "moderated list:ASPEED SD/MMC DRIVER" <linux-aspeed@...ts.ozlabs.org>,
        "moderated list:ASPEED SD/MMC DRIVER" <openbmc@...ts.ozlabs.org>,
        "open list:ASPEED SD/MMC DRIVER" <linux-mmc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:ARM/ASPEED MACHINE SUPPORT" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        ryan_chen@...eedtech.com, chin-ting_kuo@...eedtech.com
Subject: Re: [PATCH v1 1/2] dt-bindings: mmc: sdhci-of-aspeed: Add power-gpio
 and power-switch-gpio

On Thu, 8 Apr 2021 at 03:52, Steven Lee <steven_lee@...eedtech.com> wrote:
>
> AST2600-A2 EVB provides the reference design for enabling SD bus power
> and toggling SD bus signal voltage by GPIO pins.
> Add the definition and example for power-gpio and power-switch-gpio
> properties.
>
> In the reference design, GPIOV0 of AST2600-A2 EVB is connected to power
> load switch that providing 3.3v to SD1 bus vdd. GPIOV1 is connected to
> a 1.8v and a 3.3v power load switch that providing signal voltage to
> SD1 bus.
> If GPIOV0 is active high, SD1 bus is enabled. Otherwise, SD1 bus is
> disabled.
> If GPIOV1 is active high, 3.3v power load switch is enabled, SD1 signal
> voltage is 3.3v. Otherwise, 1.8v power load switch will be enabled, SD1
> signal voltage becomes 1.8v.
>
> AST2600-A2 EVB also support toggling signal voltage for SD2 bus.
> The design is the same as SD1 bus. It uses GPIOV2 as power-gpio and GPIOV3
> as power-switch-gpio.

Thanks for sharing the details, it certainly helps while reviewing.

>
> Signed-off-by: Steven Lee <steven_lee@...eedtech.com>
> ---
>  .../devicetree/bindings/mmc/aspeed,sdhci.yaml | 25 +++++++++++++++++++
>  1 file changed, 25 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/mmc/aspeed,sdhci.yaml b/Documentation/devicetree/bindings/mmc/aspeed,sdhci.yaml
> index 987b287f3bff..515a74614f3c 100644
> --- a/Documentation/devicetree/bindings/mmc/aspeed,sdhci.yaml
> +++ b/Documentation/devicetree/bindings/mmc/aspeed,sdhci.yaml
> @@ -37,6 +37,14 @@ properties:
>    clocks:
>      maxItems: 1
>      description: The SD/SDIO controller clock gate
> +  power-gpio:
> +    description:
> +      The GPIO for enabling/disabling SD bus power.
> +    maxItems: 1
> +  power-switch-gpio:
> +    description:
> +      The GPIO for toggling the signal voltage between 3.3v and 1.8v.
> +    maxItems: 1


>
>  patternProperties:
>    "^sdhci@[0-9a-f]+$":
> @@ -61,6 +69,14 @@ patternProperties:
>        sdhci,auto-cmd12:
>          type: boolean
>          description: Specifies that controller should use auto CMD12
> +      power-gpio:
> +        description:
> +          The GPIO for enabling/disabling SD bus power.
> +        maxItems: 1
> +      power-switch-gpio:
> +        description:
> +          The GPIO for toggling the signal voltage between 3.3v and 1.8v.
> +        maxItems: 1
>      required:

Please do not model these as GPIO pins like this. Instead, it's better
to model them as gpio regulators, since the mmc core manages them as
regulators.

We have a vmmc regulator (corresponding to vdd) and a vqmmc regulator
(corresponding the signal-voltage level). These are also described in
the common mmc DT bindings, see
Documentation/devicetree/bindings/mmc/mmc-controller.yaml.

>        - compatible
>        - reg
> @@ -80,6 +96,7 @@ required:
>  examples:
>    - |
>      #include <dt-bindings/clock/aspeed-clock.h>
> +    #include <dt-bindings/gpio/aspeed-gpio.h>
>      sdc@...40000 {
>              compatible = "aspeed,ast2500-sd-controller";
>              reg = <0x1e740000 0x100>;
> @@ -94,6 +111,10 @@ examples:
>                      interrupts = <26>;
>                      sdhci,auto-cmd12;
>                      clocks = <&syscon ASPEED_CLK_SDIO>;
> +                    power-gpio = <&gpio0 ASPEED_GPIO(V, 0)
> +                                     GPIO_ACTIVE_HIGH>;
> +                    power-switch-gpio = <&gpio0 ASPEED_GPIO(V, 1)
> +                                     GPIO_ACTIVE_HIGH>;
>              };
>
>              sdhci1: sdhci@200 {
> @@ -102,5 +123,9 @@ examples:
>                      interrupts = <26>;
>                      sdhci,auto-cmd12;
>                      clocks = <&syscon ASPEED_CLK_SDIO>;
> +                    power-gpio = <&gpio0 ASPEED_GPIO(V, 2)
> +                                     GPIO_ACTIVE_HIGH>;
> +                    power-switch-gpio = <&gpio0 ASPEED_GPIO(V, 3)
> +                                     GPIO_ACTIVE_HIGH>;
>              };
>      };

Kind regards
Uffe