regulator: core: Use parent voltage from the supply when bypassed

When a regulator is in bypass mode it is functioning as a switch
returning the voltage set in the regulator will not give the voltage
being output by the regulator as it's just passing through its supply.
This means that when we are getting the voltage from a regulator we
should check to see if it is in bypass mode and if it is we should
report the voltage from the supply rather than that which is set on the
regulator.

Reported-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
[treding@nvidia.com: return early for bypass mode]
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -3109,6 +3109,20 @@ EXPORT_SYMBOL_GPL(regulator_sync_voltage);
 static int _regulator_get_voltage(struct regulator_dev *rdev)
 {
 	int sel, ret;
+	bool bypassed;
+
+	if (rdev->desc->ops->get_bypass) {
+		ret = rdev->desc->ops->get_bypass(rdev, &bypassed);
+		if (ret < 0)
+			return ret;
+		if (bypassed) {
+			/* if bypassed the regulator must have a supply */
+			if (!rdev->supply)
+				return -EINVAL;
+
+			return _regulator_get_voltage(rdev->supply->rdev);
+		}
+	}
 
 	if (rdev->desc->ops->get_voltage_sel) {
 		sel = rdev->desc->ops->get_voltage_sel(rdev);