[PATCH 4.19 291/421] mmc: core: clear flags before allowing to retune

From: Greg Kroah-Hartman
Date: Mon Jul 19 2021 - 12:23:37 EST

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
@@ -980,11 +980,14 @@ 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;
+ }

return err;