[PATCH] mmc: mmci: Only call .post_sig_volt_switch if voltage switch happened

[Marek Vasut <marex@denx.de>]

Call the post voltage switch handler only if the voltage switch actually
happened. It is well possible that the regulator is already set correctly
and no voltage switch happened, so there is no need to take any further
action.

This fixes a real issue on STM32MP1 where, if the eMMC is supplied with
VccQ=1.8 V, the post voltage switch code will spin indefinitelly waiting
for the voltage switch to complete, even though no voltage switch really
happened.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Ludovic Barre <ludovic.barre@st.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: linux-stm32@st-md-mailman.stormreply.com
To: linux-mmc@vger.kernel.org
---
 drivers/mmc/host/mmci.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index 647567def612..11c2f417cbe8 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -1861,10 +1861,12 @@ static int mmci_get_cd(struct mmc_host *mmc)
 static int mmci_sig_volt_switch(struct mmc_host *mmc, struct mmc_ios *ios)
 {
 	struct mmci_host *host = mmc_priv(mmc);
-	int ret = 0;
+	int old_voltage, new_voltage, ret = 0;
 
 	if (!IS_ERR(mmc->supply.vqmmc)) {
 
+		old_voltage = regulator_get_voltage(mmc->supply.vqmmc);
+
 		switch (ios->signal_voltage) {
 		case MMC_SIGNAL_VOLTAGE_330:
 			ret = regulator_set_voltage(mmc->supply.vqmmc,
@@ -1880,7 +1882,10 @@ static int mmci_sig_volt_switch(struct mmc_host *mmc, struct mmc_ios *ios)
 			break;
 		}
 
-		if (!ret && host->ops && host->ops->post_sig_volt_switch)
+		new_voltage = regulator_get_voltage(mmc->supply.vqmmc);
+
+		if (!ret && old_voltage != new_voltage &&
+		    host->ops && host->ops->post_sig_volt_switch)
 			ret = host->ops->post_sig_volt_switch(host, ios);
 
 		if (ret)
-- 
2.25.1