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

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Date:   Mon, 19 Jul 2021 16:51:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Adrian Hunter <adrian.hunter@...el.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: [PATCH 4.19 291/421] mmc: core: clear flags before allowing to retune

From: Wolfram Sang <wsa+renesas@...g-engineering.com>

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

---
 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;
 		mmc_retune_enable(host);
+	}
 
 	return err;
 }