linux-kernel - Re: [PATCH V5 08/12] arm64: dts: imx8mn-evk: set off-on-delay-us in regulator

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Message-ID: <20221115100719.brt72kve6sulxd5a@pengutronix.de>
Date:   Tue, 15 Nov 2022 11:07:19 +0100
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     "Peng Fan (OSS)" <peng.fan@....nxp.com>
Cc:     shawnguo@...nel.org, s.hauer@...gutronix.de,
        Peng Fan <peng.fan@....com>, linux-kernel@...r.kernel.org,
        linux-imx@....com, kernel@...gutronix.de, festevam@...il.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V5 08/12] arm64: dts: imx8mn-evk: set off-on-delay-us in
 regulator

On 22-11-15, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@....com>
> 
> Some SD Card controller and power circuitry has increased capacitance,
> so the usual toggling of regulator to power the card off and on
> is insufficient.
> 
> According to SD spec, for sd card power reset operation, the sd card
> supply voltage needs to be lower than 0.5v and keep over 1ms, otherwise,
> next time power back the sd card supply voltage to 3.3v, sd card can't
> support SD3.0 mode again.
> 
> This patch add the off-on-delay-us, make sure the sd power reset behavior
> is align with the specification. Without this patch, when do quick system
> suspend/resume test, some sd card can't work at SD3.0 mode after system
> resume back.
> 
> Signed-off-by: Peng Fan <peng.fan@....com>

Reviewed-by: Marco Felsch <m.felsch@...gutronix.de>

> ---
>  arch/arm64/boot/dts/freescale/imx8mn-evk.dtsi | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mn-evk.dtsi b/arch/arm64/boot/dts/freescale/imx8mn-evk.dtsi
> index 261c36540079..2b4395854283 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mn-evk.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mn-evk.dtsi
> @@ -36,6 +36,7 @@ reg_usdhc2_vmmc: regulator-usdhc2 {
>  		regulator-min-microvolt = <3300000>;
>  		regulator-max-microvolt = <3300000>;
>  		gpio = <&gpio2 19 GPIO_ACTIVE_HIGH>;
> +		off-on-delay-us = <12000>;
>  		enable-active-high;
>  	};
>  
> -- 
> 2.37.1
> 
> 
>