I found a use_count leakage towards supply regulator of rdev with
boot-on option.

┌───────────────────┐           ┌───────────────────┐
│  regulator_dev A  │           │  regulator_dev B  │
│     (boot-on)     │           │     (boot-on)     │
│    use_count=0    │◀──supply──│    use_count=1    │
│                   │           │                   │
└───────────────────┘           └───────────────────┘

In case of rdev(A) configured with `regulator-boot-on', the use_count
of supplying regulator(B) will increment inside
regulator_enable(rdev->supply).

Thus, B will acts like always-on, and further balanced
regulator_enable/disable cannot actually disable it anymore.

However, B was also configured with `regulator-boot-on', we wish it
could be disabled afterwards.

Signed-off-by: Rui Zhang <zr.zhang@vivo.com>
---
 drivers/regulator/core.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index e8c00a884f1f..1cfac32121c0 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1596,7 +1596,13 @@ static int set_machine_constraints(struct regulator_dev *rdev)
 		if (rdev->supply_name && !rdev->supply)
 			return -EPROBE_DEFER;
 
-		if (rdev->supply) {
+		/* If supplying regulator has already been enabled,
+		 * it's not intended to have use_count increment
+		 * when rdev is only boot-on.
+		 */
+		if (rdev->supply &&
+		    (rdev->constraints->always_on ||
+		     !regulator_is_enabled(rdev->supply))) {
 			ret = regulator_enable(rdev->supply);
 			if (ret < 0) {
 				_regulator_put(rdev->supply);

base-commit: 01f856ae6d0ca5ad0505b79bf2d22d7ca439b2a1
-- 
2.34.1

On Thu, 1 Dec 2022 11:38:06 +0800, Rui Zhang wrote:
> I found a use_count leakage towards supply regulator of rdev with
> boot-on option.
> 
> ┌───────────────────┐           ┌───────────────────┐
> │  regulator_dev A  │           │  regulator_dev B  │
> │     (boot-on)     │           │     (boot-on)     │
> │    use_count=0    │◀──supply──│    use_count=1    │
> │                   │           │                   │
> └───────────────────┘           └───────────────────┘
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator.git for-next

Thanks!

[1/1] regulator: core: fix use_count leakage when handling boot-on
      commit: 0591b14ce0398125439c759f889647369aa616a0

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark