linux-kernel - Re: [PATCH v2] arm64: dts: imx8mq-kontron-pitx-imx8m: remove vqmmc-supply node

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Date:   Tue, 14 Sep 2021 10:20:21 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Heiko Thiery <heiko.thiery@...il.com>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Fabio Estevam <festevam@...il.com>,
        Shengjiu Wang <shengjiu.wang@....com>,
        Joakim Zhang <qiangqing.zhang@....com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Michael Walle <michael@...le.cc>,
        Rob Herring <robh+dt@...nel.org>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>
Subject: Re: [PATCH v2] arm64: dts: imx8mq-kontron-pitx-imx8m: remove
 vqmmc-supply node

Am Dienstag, dem 14.09.2021 um 09:26 +0200 schrieb Heiko Thiery:
> The sw4 output (V_1V8_S0 voltage) from the PMIC is the main supply for
> the 1V8 power domain. It is not only used as supply for the eMMC.
> So this voltage can not be changed and is not allowed to switched off.
> Therefore we do not want to provide this regulator to the SDHC driver to
> control this voltage.
> 
This specific requirement should not be solved by removing the
regulator connection from the SDHCI node, but instead by constraining
the regulator voltage range to a fixed 3.3V and marking the regulator
as always-on to reflect the hardware requirements in the DT.

Also if your eMMC vqmmc is a fixed 3.3V, I don't think you need the
faster pinctrl states, as you can't use the faster pin states anyways,
as they require a 1.8V signaling voltage.

Regards,
Lucas
 
> Fixes: 5dbadc848259 ("arm64: dts: fsl: add support for Kontron pitx-imx8m board")
> Signed-off-by: Heiko Thiery <heiko.thiery@...il.com>
> ---
> 
> v2:
>  - slightly reword the commit message (thanks Michael)
>  - add Fixes tag (thanks Fabio)
> 
> 
>  arch/arm64/boot/dts/freescale/imx8mq-kontron-pitx-imx8m.dts | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mq-kontron-pitx-imx8m.dts b/arch/arm64/boot/dts/freescale/imx8mq-kontron-pitx-imx8m.dts
> index f593e4ff62e1..436d98135ba9 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mq-kontron-pitx-imx8m.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8mq-kontron-pitx-imx8m.dts
> @@ -348,7 +348,6 @@ &usdhc1 {
>  	pinctrl-0 = <&pinctrl_usdhc1>;
>  	pinctrl-1 = <&pinctrl_usdhc1_100mhz>;
>  	pinctrl-2 = <&pinctrl_usdhc1_200mhz>;
> -	vqmmc-supply = <&sw4_reg>;
>  	bus-width = <8>;
>  	non-removable;
>  	no-sd;