From 0add6e9b88d0632a25323aaf4987dbacb0e4ae64 Mon Sep 17 00:00:00 2001

From: Michael Walle <michael@walle.cc>

Date: Fri, 23 Oct 2020 00:23:37 +0200

Subject: [PATCH] mmc: sdhci-of-esdhc: set timeout to max before tuning

Git-commit: 0add6e9b88d0632a25323aaf4987dbacb0e4ae64

Patch-mainline: v5.10-rc2

References: git-fixes

On rare occations there is the following error:

  mmc0: Tuning timeout, falling back to fixed sampling clock

There are SD cards which takes a significant longer time to reply to the

first CMD19 command. The eSDHC takes the data timeout value into account

during the tuning period. The SDHCI core doesn't explicitly set this

timeout for the tuning procedure. Thus on the slow cards, there might be

a spurious "Buffer Read Ready" interrupt, which in turn triggers a wrong

sequence of events. In the end this will lead to an unsuccessful tuning

procedure and to the above error.

To workaround this, set the timeout to the maximum value (which is the

best we can do) and the SDHCI core will take care of the proper timeout

handling.

Fixes: ba49cbd0936e ("mmc: sdhci-of-esdhc: add tuning support")

Signed-off-by: Michael Walle <michael@walle.cc>

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

Cc: stable@vger.kernel.org

Link: https://lore.kernel.org/r/20201022222337.19857-1-michael@walle.cc

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 drivers/mmc/host/sdhci-of-esdhc.c |   11 +++++++++++

 1 file changed, 11 insertions(+)

--- a/drivers/mmc/host/sdhci-of-esdhc.c

+++ b/drivers/mmc/host/sdhci-of-esdhc.c

@@ -830,6 +830,17 @@ static int esdhc_execute_tuning(struct m

 	esdhc_tuning_block_enable(host, true);

+	/*

+	 * The eSDHC controller takes the data timeout value into account

+	 * during tuning. If the SD card is too slow sending the response, the

+	 * timer will expire and a "Buffer Read Ready" interrupt without data

+	 * is triggered. This leads to tuning errors.

+	 *

+	 * Just set the timeout to the maximum value because the core will

+	 * already take care of it in sdhci_send_tuning().

+	 */

+	sdhci_writeb(host, 0xe, SDHCI_TIMEOUT_CONTROL);

+

 	hs400_tuning = host->flags & SDHCI_HS400_TUNING;

 	ret = sdhci_execute_tuning(mmc, opcode);