[PATCH v2] regulator: core: Fix the init of DT defined fixed regulators

[Alban Bedel <alban.bedel@avionic-design.de>]

When a regulator is defined using DT and it has a single voltage the
regulator init always tries to apply this voltage. However it fails if
the regulator isn't settable because it is using an internal low level
function. To overcome this we now first query the regulator and only
set it if needed.

Signed-off-by: Alban Bedel <alban.bedel@avionic-design.de>
---
 drivers/regulator/core.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 9a09f3c..7375997 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -844,13 +844,22 @@ static int machine_constraints_voltage(struct regulator_dev *rdev,
 	/* do we need to apply the constraint voltage */
 	if (rdev->constraints->apply_uV &&
 	    rdev->constraints->min_uV == rdev->constraints->max_uV) {
-		ret = _regulator_do_set_voltage(rdev,
-						rdev->constraints->min_uV,
-						rdev->constraints->max_uV);
-		if (ret < 0) {
-			rdev_err(rdev, "failed to apply %duV constraint\n",
-				 rdev->constraints->min_uV);
-			return ret;
+		int current_uV = _regulator_get_voltage(rdev);
+		if (current_uV < 0) {
+			rdev_err(rdev, "failed to get the current voltage\n");
+			return current_uV;
+		}
+		if (current_uV < rdev->constraints->min_uV ||
+		    current_uV > rdev->constraints->max_uV) {
+			ret = _regulator_do_set_voltage(
+				rdev, rdev->constraints->min_uV,
+				rdev->constraints->max_uV);
+			if (ret < 0) {
+				rdev_err(rdev,
+					"failed to apply %duV constraint\n",
+					rdev->constraints->min_uV);
+				return ret;
+			}
 		}
 	}
 
-- 
1.9.3