From: Michael Walle michael@walle.cc
commit 0add6e9b88d0632a25323aaf4987dbacb0e4ae64 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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 @@ -1069,6 +1069,17 @@ 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;
do {