mmc: core: Improve fallback to speed modes if eMMC HS200 fails

In the error path of mmc_select_hs200() we are trying our best to restore
the card/host into a valid state. This makes sense, especially if we
encounter a simple switch error (-EBADMSG). However, rather than then
continue with using the legacy speed mode, let's try the other better speed
modes first. Additionally, let's update the card->mmc_avail_type to avoid
us from trying a broken HS200 mode again.

In an Amlogic S905W based TV box where the switch to HS200 mode fails for
the eMMC, this allows us to use the eMMC in DDR mode in favor of the legacy
mode, which greatly improves the performance.

Suggested-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/20220303164522.129583-1-ulf.hansson@linaro.org

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 43d1b9b..3f5d0d7 100644 (file)
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -1523,13 +1523,23 @@ static int mmc_select_timing(struct mmc_card *card)
        if (!mmc_can_ext_csd(card))
                goto bus_speed;
 
-       if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS400ES)
+       if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS400ES) {
                err = mmc_select_hs400es(card);
-       else if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS200)
+               goto out;
+       }
+
+       if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS200) {
                err = mmc_select_hs200(card);
-       else if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS)
+               if (err == -EBADMSG)
+                       card->mmc_avail_type &= ~EXT_CSD_CARD_TYPE_HS200;
+               else
+                       goto out;
+       }
+
+       if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS)
                err = mmc_select_hs(card);
 
+out:
        if (err && err != -EBADMSG)
                return err;