regulator: core: introduce function to lock regulators and its supplies
Each regulator_dev is locked with its own mutex. This is fine as long
as only one regulator_dev is locked, but makes lockdep unhappy when we
have to walk up the supply chain like it can happen in
regulator_get_voltage:
regulator_get_voltage ->
mutex_lock(®ulator->rdev->mutex) ->
_regulator_get_voltage(regulator->rdev) ->
regulator_get_voltage(rdev->supply) ->
mutex_lock(®ulator->rdev->mutex);
This causes lockdep to issue a possible deadlock warning.
There are at least two ways to work around this:
- We can always lock the whole supply chain using the functions
introduced with this patch.
- We could store the current voltage in struct regulator_rdev so
that we do not have to walk up the supply chain for the
_regulator_get_voltage case.
Anyway, regulator_lock_supply/regulator_unlock_supply will be needed
once we allow regulator_set_voltage to optimize the supply voltages.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 7a85ac9..1f9ff55 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -132,6 +132,45 @@
}
/**
+ * regulator_lock_supply - lock a regulator and its supplies
+ * @rdev: regulator source
+ */
+static void regulator_lock_supply(struct regulator_dev *rdev)
+{
+ struct regulator *supply;
+ int i = 0;
+
+ while (1) {
+ mutex_lock_nested(&rdev->mutex, i++);
+ supply = rdev->supply;
+
+ if (!rdev->supply)
+ return;
+
+ rdev = supply->rdev;
+ }
+}
+
+/**
+ * regulator_unlock_supply - unlock a regulator and its supplies
+ * @rdev: regulator source
+ */
+static void regulator_unlock_supply(struct regulator_dev *rdev)
+{
+ struct regulator *supply;
+
+ while (1) {
+ mutex_unlock(&rdev->mutex);
+ supply = rdev->supply;
+
+ if (!rdev->supply)
+ return;
+
+ rdev = supply->rdev;
+ }
+}
+
+/**
* of_get_regulator - get a regulator device node based on supply name
* @dev: Device pointer for the consumer (of regulator) device
* @supply: regulator supply name