mmc: Enable signal voltage to be selected from mmc core

Add a new function *mmc_set_signal_voltage* in mmc core
which can be used during mmc initialization to select the
signal voltage. Platform driver should use the set_ios
callback function to select the signal voltage.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>

drivers/mmc/mmc.c

@@ -30,6 +30,8 @@ static const unsigned int sd_au_size[] = {
 	SZ_16M / 512,	(SZ_16M + SZ_8M) / 512,	SZ_32M / 512,	SZ_64M / 512,
 };
 
+static int mmc_set_signal_voltage(struct mmc *mmc, uint signal_voltage);
+
 #if CONFIG_IS_ENABLED(MMC_TINY)
 static struct mmc mmc_static;
 struct mmc *find_mmc_device(int dev_num)
@@ -1257,6 +1259,12 @@ struct mode_width_tuning {
 	uint widths;
 };
 
+static int mmc_set_signal_voltage(struct mmc *mmc, uint signal_voltage)
+{
+	mmc->signal_voltage = signal_voltage;
+	return mmc_set_ios(mmc);
+}
+
 static const struct mode_width_tuning sd_modes_by_pref[] = {
 	{
 		.mode = SD_HS,
@@ -1964,6 +1972,14 @@ int mmc_start_init(struct mmc *mmc)
 		return err;
 #endif
 	mmc->ddr_mode = 0;
+
+	/* First try to set 3.3V. If it fails set to 1.8V */
+	err = mmc_set_signal_voltage(mmc, MMC_SIGNAL_VOLTAGE_330);
+	if (err != 0)
+		err = mmc_set_signal_voltage(mmc, MMC_SIGNAL_VOLTAGE_180);
+	if (err != 0)
+		printf("failed to set signal voltage\n");
+
 	mmc_set_bus_width(mmc, 1);
 	mmc_set_clock(mmc, 1);
 

include/mmc.h

@@ -272,6 +272,13 @@
 #define ENHNCD_SUPPORT		(0x2)
 #define PART_ENH_ATTRIB		(0x1f)
 
+enum mmc_voltage {
+	MMC_SIGNAL_VOLTAGE_000 = 0,
+	MMC_SIGNAL_VOLTAGE_120,
+	MMC_SIGNAL_VOLTAGE_180,
+	MMC_SIGNAL_VOLTAGE_330
+};
+
 /* Maximum block size for MMC */
 #define MMC_MAX_BLOCK_LEN	512
 
@@ -457,6 +464,7 @@ struct mmc {
 	int high_capacity;
 	uint bus_width;
 	uint clock;
+	enum mmc_voltage signal_voltage;
 	uint card_caps;
 	uint ocr;
 	uint dsr;