linux-kernel - Re: [PATCH V2 09/15] arm64: dts: imx8mn-evk: set off-on-delay-us in regulator

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Date:   Thu, 3 Nov 2022 18:25:35 +0800
From:   Peng Fan <peng.fan@....nxp.com>
To:     Marco Felsch <m.felsch@...gutronix.de>
Cc:     robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        shawnguo@...nel.org, s.hauer@...gutronix.de,
        devicetree@...r.kernel.org, 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 V2 09/15] arm64: dts: imx8mn-evk: set off-on-delay-us in
 regulator



On 10/28/2022 11:02 PM, Marco Felsch wrote:
> On 22-10-24, 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>
>> ---
>>   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>;
> 
> All others are using 20000us, did you changed the HW?

This is i.MX8MN. This value should be safe I think,
since it goes through several NXP releases.

Thanks,
Peng.

> 
> Regards,
>    Marco
> 
>>   		enable-active-high;
>>   	};
>>   
>> -- 
>> 2.37.1
>>
>>
>>