From 9f01cd4a915e13dda6a61b989229015687ffd58f Mon Sep 17 00:00:00 2001 From: Sascha Hauer Date: Wed, 30 Sep 2015 16:05:42 +0200 Subject: [PATCH] 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 Signed-off-by: Mark Brown --- drivers/regulator/core.c | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c index 7a85ac9e32c5..1f9ff55b3620 100644 --- a/drivers/regulator/core.c +++ b/drivers/regulator/core.c @@ -131,6 +131,45 @@ static bool have_full_constraints(void) return has_full_constraints || of_have_populated_dt(); } +/** + * 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 -- 2.39.5