[U-Boot] [PATCH] mmc: correct the HS400 initialization process

[BOUGH CHEN]

After the commit b9a2a0e2e9c0 ("mmc: Add support for downgrading
HS200/HS400 to HS mode"), it add a parameter in mmc_set_card_speed()
which indicates that the HS200/HS400 to HS downgrade is happening.

During the HS400 initialization, first select to HS200, and config
the related clock rate, then downgrade to HS mode. So here also need
to config the downgrade value to be true, make sure in the function
mmc_set_card_speed(), after switch to HS mode, first config the
clock rate, then read the EXT_CSD. Otherwise read EXT_CSD in HS mode
at wrong clock rate, e.g. 200MHz, may lead to uncertain result.

Test on i.MX8QM MEK board, some Micron eMMC will stuck in transfer
mode in this case, and USDHC will never get data transfer complete
status, cause the uboot hang.

Signed-off-by: Haibo Chen <haibo.chen at nxp.com>
---
 drivers/mmc/mmc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index 1c1527cc74..55d3560b30 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -1892,8 +1892,7 @@ static int mmc_select_hs400(struct mmc *mmc)
 	}
 
 	/* Set back to HS */
-	mmc_set_card_speed(mmc, MMC_HS, false);
-	mmc_set_clock(mmc, mmc_mode2freq(mmc, MMC_HS), false);
+	mmc_set_card_speed(mmc, MMC_HS, true);
 
 	err = mmc_switch(mmc, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_BUS_WIDTH,
 			 EXT_CSD_BUS_WIDTH_8 | EXT_CSD_DDR_FLAG);
-- 
2.17.1