mmc: mmci: Switch to mmc_regulator_set_vqmmc()

Instead of reimplementing the logic in mmc_regulator_set_vqmmc(), use the
mmc code function directly.

This also allows us to fix a related issue on STM32MP1, when a voltage
switch of 1.8V is done for the eMMC, but the current level is already set
to 1.8V. More precisely, in this scenario the call to the
->post_sig_volt_switch() hangs, indefinitely waiting for the voltage switch
to complete. Fix this problem by checking if mmc_regulator_set_vqmmc()
returned 1 and then skip invoking the callback.
Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20200416163649.336967-3-marex@denx.de
[Ulf: Updated the commit message]
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/mmci.c

@@ -1861,31 +1861,17 @@ 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;
-
-	if (!IS_ERR(mmc->supply.vqmmc)) {
+	int ret;
 
-		switch (ios->signal_voltage) {
-		case MMC_SIGNAL_VOLTAGE_330:
-			ret = regulator_set_voltage(mmc->supply.vqmmc,
-						2700000, 3600000);
-			break;
-		case MMC_SIGNAL_VOLTAGE_180:
-			ret = regulator_set_voltage(mmc->supply.vqmmc,
-						1700000, 1950000);
-			break;
-		case MMC_SIGNAL_VOLTAGE_120:
-			ret = regulator_set_voltage(mmc->supply.vqmmc,
-						1100000, 1300000);
-			break;
-		}
+	ret = mmc_regulator_set_vqmmc(mmc, ios);
 
-		if (!ret && host->ops && host->ops->post_sig_volt_switch)
-			ret = host->ops->post_sig_volt_switch(host, ios);
+	if (!ret && host->ops && host->ops->post_sig_volt_switch)
+		ret = host->ops->post_sig_volt_switch(host, ios);
+	else if (ret)
+		ret = 0;
 
-		if (ret)
-			dev_warn(mmc_dev(mmc), "Voltage switch failed\n");
-	}
+	if (ret < 0)
+		dev_warn(mmc_dev(mmc), "Voltage switch failed\n");
 
 	return ret;
 }