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regulator: core: introduce function to lock regulators and its supplies

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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>
This commit is contained in:
Sascha Hauer 2015-09-30 16:05:42 +02:00 committed by Mark Brown
parent 6ff33f3902
commit 9f01cd4a91
1 changed files with 39 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

39
drivers/regulator/core.c
View file

@ -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