[RFC] mmc: meson-gx-mmc: add delay during poweroff

[Da Xue <da@libre.computer>]

Regulators controlling the SD card power need some settling time for SD
cards to fully reset from UHS modes. The regulator framework seems to
ignore falling times set in the device tree causing a few boards with the
same hardware implementation to hang on reboot because the SD card still
had some voltage and did not reset properly to be initialized again.

Add a delay sufficiently long for the voltage to drop so that the SD card
can reset properly. Otherwise the reboot will hang at missing SD card
especially with Samsung cards.

Signed-off-by: Da Xue <da@libre.computer>
---
 drivers/mmc/host/meson-gx-mmc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
index 694bb443d5f3..a39906079d29 100644
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -605,6 +605,7 @@ static void meson_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 	case MMC_POWER_OFF:
 		mmc_regulator_set_ocr(mmc, mmc->supply.vmmc, 0);
 		mmc_regulator_disable_vqmmc(mmc);
+		msleep(50);
 
 		break;
 
-- 
2.39.5