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

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Date:   Mon, 24 Oct 2022 11:13:45 +0800
From:   "Peng Fan (OSS)" <peng.fan@....nxp.com>
To:     robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        shawnguo@...nel.org, s.hauer@...gutronix.de
Cc:     kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, Peng Fan <peng.fan@....com>
Subject: [PATCH V2 09/15] arm64: dts: imx8mn-evk: set off-on-delay-us in regulator

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>;
 		enable-active-high;
 	};

-- 
2.37.1