[PATCH v2 2/2] regulator: fp9931: Fix Runtime PM usage count underflow in v3p3 ops

[robby.cai@oss.nxp.com]

From: Robby Cai <robby.cai@nxp.com>

The fp9931_v3p3_enable() callback acquires a Runtime PM reference which
remains held until fp9931_v3p3_disable() releases it.

Device-level Runtime PM lifetime is also managed through the shared
VCOM enable path: fp9931_set_enable() acquires a reference and
fp9931_clear_enable() releases it.

As a result, the Runtime PM usage count may already have reached 0
before fp9931_v3p3_disable() is invoked. In that case,
fp9931_v3p3_disable() calls pm_runtime_put_autosuspend() on an
already-zero count, triggering:

  fp9931 1-0018: Runtime PM usage count underflow!

Holding a Runtime PM reference across the V3P3 regulator lifetime is
unnecessary. V3P3 only needs the device to be runtime-active for the
duration of the register access.

Fix this by scoping the Runtime PM reference lifetime to the register
access itself, pairing pm_runtime_resume_and_get() and
pm_runtime_put_autosuspend() within each callback.

Fixes: 12d821bd13d4 ("regulator: Add FP9931/JD9930 driver")
Signed-off-by: Robby Cai <robby.cai@nxp.com>
---
 drivers/regulator/fp9931.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/regulator/fp9931.c b/drivers/regulator/fp9931.c
index ff743a8b0dfe..0d926546221a 100644
--- a/drivers/regulator/fp9931.c
+++ b/drivers/regulator/fp9931.c
@@ -214,8 +214,7 @@ static int fp9931_v3p3_enable(struct regulator_dev *rdev)
 		return ret;
 
 	ret = regulator_enable_regmap(rdev);
-	if (ret < 0)
-		pm_runtime_put_autosuspend(data->dev);
+	pm_runtime_put_autosuspend(data->dev);
 
 	return ret;
 }
@@ -225,6 +224,10 @@ static int fp9931_v3p3_disable(struct regulator_dev *rdev)
 	struct fp9931_data *data = rdev_get_drvdata(rdev);
 	int ret;
 
+	ret = pm_runtime_resume_and_get(data->dev);
+	if (ret < 0)
+		return ret;
+
 	ret = regulator_disable_regmap(rdev);
 	pm_runtime_put_autosuspend(data->dev);
 
-- 
2.50.1