[U-Boot] fsl_esdhc: GPIO regulator as VQMMC supply?

[Peng Fan <peng.fan@nxp.com>]

> Subject: fsl_esdhc: GPIO regulator as VQMMC supply?
> 
> Hi,
> 
> I’m trying to implement the VQMMC supply for the an eMMC on my board
> using a GPIO regulator, i.e.
> 
> reg_sd_vsel: regulator-sd-vsel {
>   pinctrl-names = "default";
>   pinctrl-0 = <&pinctrl_sd_vsel>;
>   compatible = "regulator-gpio";
>   regulator-name = "sd-vsel";
>   regulator-min-microvolt = <1800000>;
>   regulator-max-microvolt = <3300000>;
>   gpios = <&gpio1 1 GPIO_ACTIVE_HIGH>;
>   states = <1800000 1 3300000 0>;
>   gpios-states = <0>; /* default: 3.3V */ };
> 
> &usdhc3 {
>   vqmmc-supply = <&reg_sd_vsel>;
> };
> 
> This is using an i.MX7D SoC, so my [eu]sdhc driver is fsl_esdhc. In
> fsl_esdhc_probe, regulator_set_enable is called for vqmmc-supply. This fails
> for GPIO regulators because they only have a set_value method and no
> set_enable method. How is this best resolved? Does it make sense to add a
> set_enable method to the GPIO regulator or should the esdhc driver handle
> the -ENOSYS return value gracefully? Or should I write my device tree
> differently?

Add set_enable callback to gpio regulator seems make sense.

Regards,
Peng

> 
> Hints are much appreciated. Thanks!
> 
> Best regards,
> Sven