Since the introduction of regulator->enable_count, a driver that did
an exclusive get on an already-enabled regulator would end up with
enable_count initialized to 0 but rdev->use_count initialized to 1.
With that starting point the regulator is effectively stuck enabled,
because if the driver attempted to disable it it would fail the
enable_count underflow check in _regulator_handle_consumer_disable().

The EXCLUSIVE_GET path in _regulator_get() now initializes
enable_count along with rdev->use_count so that the regulator can be
disabled without underflowing the former.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Fixes: 5451781dadf85 ("regulator: core: Only count load for enabled consumers")
---

I tripped on this problem a bit in some recent experimentation with
the regulator API -- at first I figured I was misusing something, but
after looking a bit closer I *think* it's a bug (perhaps unnoticed
until now because EXCLUSIVE_GET doesn't seem to be very widely used),
but I'm not real knowledgeable about the regulator subsystem so
apologies if I've misdiagnosed.

 drivers/regulator/core.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index d2553970a67b..c4d844ffad7a 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -2133,10 +2133,13 @@ struct regulator *_regulator_get(struct device *dev, const char *id,
 		rdev->exclusive = 1;
 
 		ret = _regulator_is_enabled(rdev);
-		if (ret > 0)
+		if (ret > 0) {
 			rdev->use_count = 1;
-		else
+			regulator->enable_count = 1;
+		} else {
 			rdev->use_count = 0;
+			regulator->enable_count = 0;
+		}
 	}
 
 	link = device_link_add(dev, &rdev->dev, DL_FLAG_STATELESS);
-- 
2.36.0

On Wed, 4 May 2022 21:31:52 -0700, Zev Weiss wrote:
> Since the introduction of regulator->enable_count, a driver that did
> an exclusive get on an already-enabled regulator would end up with
> enable_count initialized to 0 but rdev->use_count initialized to 1.
> With that starting point the regulator is effectively stuck enabled,
> because if the driver attempted to disable it it would fail the
> enable_count underflow check in _regulator_handle_consumer_disable().
> 
> [...]

Applied to

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

Thanks!

[1/1] regulator: core: Fix enable_count imbalance with EXCLUSIVE_GET
      commit: c3e3ca05dae37f8f74bb80358efd540911cbc2c8

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