[PATCH 2/2] ARM: i.MX8MM: increase off-on delay on the SD Vcc regulator

Marco Felsch m.felsch at pengutronix.de
Thu Jun 16 07:02:46 PDT 2022

This commit is ported from u-boot commit 247bbeb74c ("ARM: dts: imx8m:
increase off-on delay on the SD Vcc regulator"). Currently barebox
supports only SDR25/HS mode but it gets important as soon as barebox
supports faster modes.

    ARM: dts: imx8m: increase off-on delay on the SD Vcc regulator

    Some SD Card controller and power circuitry has increased capacitance,
    which keeps the internal logic remains powered after regulator is switch
    off. This is generally the case when card is switched to SD104 mode,
    where a power cycle should be performed. In case if the card internal
    logic remains powered, it causes a subsequent failure of mode
    transition, effectively leading to failed enumeration.

    Introduce a delay of 20 msec in order to provide a possibility for
    internal card circuitry to drain voltages and perform a power cycle

    Similar fix is done in commit c49d0ac38a76 ("ARM: dts: rmobile: Increase
    off-on delay on the SD Vcc regulator") targeted Renesas SOCs.

    Signed-off-by: Andrey Zhizhikin <andrey.zhizhikin at leica-geosystems.com>
    Cc: Stefano Babic <sbabic at denx.de>

Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
 arch/arm/dts/imx8mm-evk.dts | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/dts/imx8mm-evk.dts b/arch/arm/dts/imx8mm-evk.dts
index 854e9db869..6c06ad7e47 100644
--- a/arch/arm/dts/imx8mm-evk.dts
+++ b/arch/arm/dts/imx8mm-evk.dts
@@ -24,6 +24,10 @@
+&reg_usdhc2_vmmc {
+	off-on-delay-us = <20000>;
 &usdhc2 {
 	#address-cells = <1>;
 	#size-cells = <1>;

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