This is a note to let you know that I've just added the patch titled mmc: core: clear flags before allowing to retune to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mmc-core-clear-flags-before-allowing-to-retune.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 77347eda64ed5c9383961d1de9165f9d0b7d8df6 Mon Sep 17 00:00:00 2001 From: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx> Date: Thu, 24 Jun 2021 17:16:14 +0200 Subject: mmc: core: clear flags before allowing to retune 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; } Patches currently in stable-queue which might be from wsa+renesas@xxxxxxxxxxxxxxxxxxxx are queue-4.9/mmc-core-clear-flags-before-allowing-to-retune.patch