[PATCH 3.16 14/63] mmc: core: fix using wrong io voltage if mmc_select_hs200 fails

[Ben Hutchings]

3.16.81-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Dong Aisheng <aisheng.dong@xxxxxxx>

commit e51534c806609c806d81bfb034f02737461f855c upstream.

Currently MMC core will keep going if HS200/HS timing switch failed
with -EBADMSG error by the assumption that the old timing is still valid.

However, for mmc_select_hs200 case, the signal voltage may have already
been switched. If the timing switch failed, we should fall back to
the old voltage in case the card is continue run with legacy timing.

If fall back signal voltage failed, we explicitly report an EIO error
to force retry during the next power cycle.

Signed-off-by: Dong Aisheng <aisheng.dong@xxxxxxx>
Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
[bwh: Backported to 3.16:
 - Delete now-unused err label
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -1079,8 +1079,10 @@ static int mmc_select_hs400(struct mmc_c
 static int mmc_select_hs200(struct mmc_card *card)
 {
 	struct mmc_host *host = card->host;
+	unsigned int old_signal_voltage;
 	int err = -EINVAL;
 
+	old_signal_voltage = host->ios.signal_voltage;
 	if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS200_1_2V)
 		err = __mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_120);
 
@@ -1089,7 +1091,7 @@ static int mmc_select_hs200(struct mmc_c
 
 	/* If fails try again during next card power cycle */
 	if (err)
-		goto err;
+		return err;
 
 	/*
 	 * Set the bus width(4 or 8) with host's support and
@@ -1104,7 +1106,12 @@ static int mmc_select_hs200(struct mmc_c
 		if (!err)
 			mmc_set_timing(host, MMC_TIMING_MMC_HS200);
 	}
-err:
+
+	if (err) {
+		/* fall back to the old signal voltage, if fails report error */
+		if (__mmc_set_signal_voltage(host, old_signal_voltage))
+			err = -EIO;
+	}
 	return err;
 }