Re: [PATCH] arm64: dts: imx8mm-verdin: Link reg_nvcc_sd to usdhc2

[Francesco Dolcini <francesco@dolcini.it>]

Hello Wojciech,
thanks very much for your patch.

On Thu, Apr 17, 2025 at 01:20:11PM +0200, Wojciech Dubowik wrote:
> Link LDO5 labeled reg_nvcc_sd from PMIC to align with
> hardware configuration specified in the datasheet.
> 
> Without this definition LDO5 will be powered down, disabling
> SD card after bootup. This has been introduced in commit
> f5aab0438ef1 (regulator: pca9450: Fix enable register for LDO5).
> 
> Fixes: f5aab0438ef1 (regulator: pca9450: Fix enable register for LDO5)
> Cc: stable@vger.kernel.org
> 
> Signed-off-by: Wojciech Dubowik <Wojciech.Dubowik@mt.com>
> ---
>  arch/arm64/boot/dts/freescale/imx8mm-verdin.dtsi | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mm-verdin.dtsi b/arch/arm64/boot/dts/freescale/imx8mm-verdin.dtsi
> index 7251ad3a0017..6307c5caf3bc 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mm-verdin.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mm-verdin.dtsi
> @@ -785,6 +785,7 @@ &usdhc2 {
>  	pinctrl-2 = <&pinctrl_usdhc2_200mhz>, <&pinctrl_usdhc2_cd>;
>  	pinctrl-3 = <&pinctrl_usdhc2_sleep>, <&pinctrl_usdhc2_cd_sleep>;
>  	vmmc-supply = <&reg_usdhc2_vmmc>;
> +	vqmmc-supply = <&reg_nvcc_sd>;

I am worried just doing this will have some side effects.

Before this patch, the switch between 1v8 and 3v3 was done because we
have a GPIO, connected to the PMIC, controlled by the USDHC2 instance
(MX8MM_IOMUXC_GPIO1_IO04_USDHC2_VSELECT, see pinctrl_usdhc2).

With your change both the PMIC will be programmed with a different
voltage over i2c and the GPIO will also toggle. It does not sound like
what we want to do.

Maybe we should have a "regulator-gpio" with vin-supply =
<&reg_nvcc_sd>, as we recently did here
https://lore.kernel.org/all/20250414123827.428339-1-ivitro@gmail.com/T/#m2964f1126a6732a66a6e704812f2b786e8237354
?

Francesco