[PATCH] power: regulator: Fix power on/off delay issue

[Ye Li]

SD initialization failure happens with some UHS-I SD cards on
iMX8MM/iMX93/iMX91 EVK after
commit 4fcba5d556b4 ("regulator: implement basic reference counter").
When sending operation condition to SD card, the OCR does not return
correct status. The root cause is regulator on/off delay is missed
in MMC power cycle with above commit, so SD card is not completely
power off.

When SD startup, the sequence of MMC power cycle is:
mmc_power_init(get vmmc_supply dev) -> mmc_power_off -> udelay(2000)
-> mmc_power_on

Before above commit, as a fixed regulator, the GPIO is set as:
  GPIO inactive (in mmc_power_init) ->
  GPIO inactive and delay off-on-delay-us (in mmc_power_off) ->
  udelay(2000) ->
  GPIO active (in mmc_power_on)

After the commit:
  GPIO inactive (in mmc_power_init) ->
  enable_count is 0, regulator_set_enable returns -EALREADY immediately,
      so GPIO is inactive but No off-on-delay-us (in mmc_power_off) ->
  udelay(2000) ->
  GPIO active (in mmc_power_on)

Add the on/off delay and startup delay after GPIO request in
regulator_common_of_to_plat which is called in regulator device probing.
So in mmc_power_init, after GPIO is set to default inactive, the
off-on-delay-us is applied.

Signed-off-by: Ye Li <ye.li at nxp.com>
---
 drivers/power/regulator/regulator_common.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/power/regulator/regulator_common.c b/drivers/power/regulator/regulator_common.c
index 85af8d599ad..158284a3309 100644
--- a/drivers/power/regulator/regulator_common.c
+++ b/drivers/power/regulator/regulator_common.c
@@ -46,6 +46,12 @@ int regulator_common_of_to_plat(struct udevice *dev,
 			dev_read_u32_default(dev, "u-boot,off-on-delay-us", 0);
 	}
 
+	if ((flags & GPIOD_IS_OUT_ACTIVE) && plat->startup_delay_us)
+		udelay(plat->startup_delay_us);
+
+	if (!(flags & GPIOD_IS_OUT_ACTIVE) && plat->off_on_delay_us)
+		udelay(plat->off_on_delay_us);
+
 	return 0;
 }
 
-- 
2.37.1