[U-Boot] [PATCH] mmc: Do not poll using CMD13 when changing timing

[Marek Vasut]

When using CMD6 to switch eMMC card timing from HS200/HS400 to HS/legacy,
do not poll for the completion status using CMD13, but rather wait 50mS.

Once the card receives the CMD6 and starts executing it, the bus is in
undefined state until both the card finishes executing the command and
until the controller switches the bus to matching timing configuration.
During this time, it is not possible to transport any commands or data
across the bus, which includes the CMD13.

Signed-off-by: Marek Vasut <marek.vasut+renesas at gmail.com>
Cc: Jaehoon Chung <jh80.chung at samsung.com>
---
NOTE: Linux does the same thing.
---
 drivers/mmc/mmc.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index c7730c9233..ababacf65a 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -720,7 +720,8 @@ static int mmc_send_ext_csd(struct mmc *mmc, u8 *ext_csd)
 	return err;
 }
 
-int mmc_switch(struct mmc *mmc, u8 set, u8 index, u8 value)
+static int __mmc_switch(struct mmc *mmc, u8 set, u8 index, u8 value,
+			bool send_status)
 {
 	struct mmc_cmd cmd;
 	int timeout = 1000;
@@ -736,19 +737,29 @@ int mmc_switch(struct mmc *mmc, u8 set, u8 index, u8 value)
 	while (retries > 0) {
 		ret = mmc_send_cmd(mmc, &cmd, NULL);
 
-		/* Waiting for the ready status */
-		if (!ret) {
-			ret = mmc_send_status(mmc, timeout);
-			return ret;
+		if (ret) {
+			retries--;
+			continue;
+		}
+
+		if (!send_status) {
+			mdelay(50);
+			return 0;
 		}
 
-		retries--;
+		/* Waiting for the ready status */
+		return mmc_send_status(mmc, timeout);
 	}
 
 	return ret;
 
 }
 
+int mmc_switch(struct mmc *mmc, u8 set, u8 index, u8 value)
+{
+	return __mmc_switch(mmc, set, index, value, true);
+}
+
 #if !CONFIG_IS_ENABLED(MMC_TINY)
 static int mmc_set_card_speed(struct mmc *mmc, enum bus_mode mode,
 			      bool hsdowngrade)
@@ -780,8 +791,9 @@ static int mmc_set_card_speed(struct mmc *mmc, enum bus_mode mode,
 	default:
 		return -EINVAL;
 	}
-	err = mmc_switch(mmc, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_HS_TIMING,
-			 speed_bits);
+
+	err = __mmc_switch(mmc, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_HS_TIMING,
+			   speed_bits, !hsdowngrade);
 	if (err)
 		return err;
 
-- 
2.19.2