regulator: core: Allow regulator_set_voltage for fixed regulators

Make it okay to call regulator_set_voltage on regulators with fixed
voltage if the requested range overlaps the current/configured voltage.

Signed-off-by: Bjorn Andersson <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/core.c

···
 	struct regulator_dev *rdev = regulator->rdev;
 	int ret = 0;
 	int old_min_uV, old_max_uV;
+	int current_uV;
 
 	mutex_lock(&rdev->mutex);
 
···
 	 */
 	if (regulator->min_uV == min_uV && regulator->max_uV == max_uV)
 		goto out;
+
+	/* If we're trying to set a range that overlaps the current voltage,
+	 * return succesfully even though the regulator does not support
+	 * changing the voltage.
+	 */
+	if (!(rdev->constraints->valid_ops_mask & REGULATOR_CHANGE_VOLTAGE)) {
+		current_uV = _regulator_get_voltage(rdev);
+		if (min_uV <= current_uV && current_uV <= max_uV) {
+			regulator->min_uV = min_uV;
+			regulator->max_uV = max_uV;
+			goto out;
+		}
+	}
 
 	/* sanity check */
 	if (!rdev->desc->ops->set_voltage &&