[PATCH 4.9 164/245] mmc: core: clear flags before allowing to retune

[Greg Kroah-Hartman]

From: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>

commit 77347eda64ed5c9383961d1de9165f9d0b7d8df6 upstream.

It might be that something goes wrong during tuning so the MMC core will
immediately trigger a retune. In our case it was:

 - we sent a tuning block
 - there was an error so we need to send an abort cmd to the eMMC
 - the abort cmd had a CRC error
 - retune was set by the MMC core

This lead to a vicious circle causing a performance regression of 75%.
So, clear retuning flags before we enable retuning to start with a known
cleared state.

Reported-by Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
Suggested-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
Fixes: bd11e8bd03ca ("mmc: core: Flag re-tuning is needed on CRC errors")
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20210624151616.38770-2-wsa+renesas@xxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/mmc/core/core.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1171,11 +1171,14 @@ int mmc_execute_tuning(struct mmc_card *
 
 	err = host->ops->execute_tuning(host, opcode);
 
-	if (err)
+	if (err) {
 		pr_err("%s: tuning execution failed: %d\n",
 			mmc_hostname(host), err);
-	else
+	} else {
+		host->retune_now = 0;
+		host->need_retune = 0;
 		mmc_retune_enable(host);
+	}
 
 	return err;
 }