mmc: add host_caps checking avoid switch card improperly

Add a host capability checking to avoid the mmc stack
switch the card to HIGHSPEED mode when the card supports
HIGHSPEED while the host doesn't.

This patch avoid furthur transaction problem when the
mmc/sd card runs different mode to the host.

Signed-off-by: Macpaul Lin <macpaul@andestech.com>

diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index 21665ec..98abf1c 100644 (file)
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -785,6 +785,16 @@ retry_scr:
        if (!(__be32_to_cpu(switch_status[3]) & SD_HIGHSPEED_SUPPORTED))
                return 0;
 
+       /*
+        * If the host doesn't support SD_HIGHSPEED, do not switch card to
+        * HIGHSPEED mode even if the card support SD_HIGHSPPED.
+        * This can avoid furthur problem when the card runs in different
+        * mode between the host.
+        */
+       if (!((mmc->host_caps & MMC_MODE_HS_52MHz) &&
+               (mmc->host_caps & MMC_MODE_HS)))
+               return 0;
+
        err = sd_switch(mmc, SD_SWITCH_SWITCH, 0, 1, (u8 *)switch_status);
 
        if (err)