Re: [PATCH] mmc: Add quirk to disable DDR50 tuning

From: Erick Shepherd
Date: Wed Mar 26 2025 - 17:00:29 EST


> Perhaps make a helper function (untested):

Making a helper function seems like a good idea to me. How does this
look? I tested it using the SD card with our issue to confirm the I/O
errors no longer appear. I also tested it with another DDR50 SD card
to make sure the tuning is still executed in that case. I don't have a
SDR50 or SDR104 card on hand but could try to find them if you believe
the helper function needs to be tested further.

diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index cc757b850e79..fc3416027033 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -613,6 +613,29 @@ static int sd_set_current_limit(struct mmc_card *card, u8 *status)
return 0;
}

+/*
+ * Determine if the card should tune or not.
+ */
+static bool mmc_sd_use_tuning(struct mmc_card *card)
+{
+ /*
+ * SPI mode doesn't define CMD19 and tuning is only valid for SDR50 and
+ * SDR104 mode SD-cards. Note that tuning is mandatory for SDR104.
+ */
+ if (mmc_host_is_spi(card->host))
+ return false;
+
+ switch (card->host->ios.timing) {
+ case MMC_TIMING_UHS_SDR50:
+ case MMC_TIMING_UHS_SDR104:
+ return true;
+ case MMC_TIMING_UHS_DDR50:
+ return !mmc_card_no_uhs_ddr50_tuning(card);
+ }
+
+ return false;
+}
+
/*
* UHS-I specific initialization procedure
*/
@@ -656,14 +679,7 @@ static int mmc_sd_init_uhs_card(struct mmc_card *card)
if (err)
goto out;

- /*
- * SPI mode doesn't define CMD19 and tuning is only valid for SDR50 and
- * SDR104 mode SD-cards. Note that tuning is mandatory for SDR104.
- */
- if (!mmc_host_is_spi(card->host) &&
- (card->host->ios.timing == MMC_TIMING_UHS_SDR50 ||
- card->host->ios.timing == MMC_TIMING_UHS_DDR50 ||
- card->host->ios.timing == MMC_TIMING_UHS_SDR104)) {
+ if (mmc_sd_use_tuning(card)) {
err = mmc_execute_tuning(card);

/*

Regards,
Erick