diff --git a/drivers/regulator/hi6421-regulator.c b/drivers/regulator/hi6421-regulator.c
index 42dc5fb8c899..62c5f5445d44 100644
--- a/drivers/regulator/hi6421-regulator.c
+++ b/drivers/regulator/hi6421-regulator.c
@@ -477,7 +477,8 @@ static int hi6421_regulator_buck_set_mode(struct regulator_dev *rdev,
 	return 0;
 }
 
-unsigned int hi6421_regulator_ldo_get_optimum_mode(struct regulator_dev *rdev,
+static unsigned int
+hi6421_regulator_ldo_get_optimum_mode(struct regulator_dev *rdev,
 			int input_uV, int output_uV, int load_uA)
 {
 	struct hi6421_regulator_info *info = rdev_get_drvdata(rdev);