Commit 9f01cd4a authored Sep 30, 2015 by Sascha Hauer Committed by Mark Brown Oct 01, 2015

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(&regulator->rdev->mutex) ->
_regulator_get_voltage(regulator->rdev) ->
regulator_get_voltage(rdev->supply) ->
mutex_lock(&regulator->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>

parent 6ff33f39

drivers/regulator/core.c

+39 −0

Original line number	Diff line number	Diff line
		@@ -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