[PATCH] ARM: dts: i.MX8MP: increase off-on delay on the SD Vcc regulator

[Marco Felsch]

This commit is required to fix the SD card detection mechanism. Without
this commit the SD card (auto-)detection fails when booted from this
sd-card:

  mmc1: Query interface conditions failed: -110
  mmc1: SD operation condition set timed out

The commit is ported from U-Boot:

| commit 247bbeb74c186963d9365db3136d0285618bd9a7
| Author: Andrey Zhizhikin <andrey.zhizhikin at leica-geosystems.com>
| Date:   Sat Dec 5 17:29:17 2020 +0000
|
|     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
|     correctly.
|
|     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/imx8mp-evk.dts | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/dts/imx8mp-evk.dts b/arch/arm/dts/imx8mp-evk.dts
index 3264ade4b8..77b438287c 100644
--- a/arch/arm/dts/imx8mp-evk.dts
+++ b/arch/arm/dts/imx8mp-evk.dts
@@ -35,6 +35,10 @@
 	reset-deassert-us = <100000>;
 };
 
+&reg_usdhc2_vmmc {
+	off-on-delay-us = <20000>;
+};
+
 &usdhc2 {
 	#address-cells = <1>;
 	#size-cells = <1>;
-- 
2.30.2