drm: msm: dsi: Don't attempt changing voltage of switches

In some configurations the supplies are voltage switches and not LDOs,
making the set voltage call to fail. Check with the regulator framework
if the supply can change voltage before attempting.
Signed-off-by: NBjorn Andersson <bjorn.andersson@sonymobile.com>
Reviewed-by: NArchit Taneja <architt@codeaurora.org>
Signed-off-by: NRob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/dsi/dsi_host.c

@@ -278,7 +278,7 @@ static int dsi_regulator_init(struct msm_dsi_host *msm_host)
 	}
 
 	for (i = 0; i < num; i++) {
-		if ((regs[i].min_voltage >= 0) && (regs[i].max_voltage >= 0)) {
+		if (regulator_can_change_voltage(s[i].consumer)) {
 			ret = regulator_set_voltage(s[i].consumer,
 				regs[i].min_voltage, regs[i].max_voltage);
 			if (ret < 0) {

drivers/gpu/drm/msm/dsi/phy/dsi_phy.c

@@ -178,7 +178,7 @@ static int dsi_phy_regulator_init(struct msm_dsi_phy *phy)
 	}
 
 	for (i = 0; i < num; i++) {
-		if ((regs[i].min_voltage >= 0) && (regs[i].max_voltage >= 0)) {
+		if (regulator_can_change_voltage(s[i].consumer)) {
 			ret = regulator_set_voltage(s[i].consumer,
 				regs[i].min_voltage, regs[i].max_voltage);
 			if (ret < 0) {