linux-kernel - [PATCH] regulator: core: fix use_count leakage when handling boot-on

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Date:   Tue, 22 Nov 2022 18:32:51 +0800
From:   Rui Zhang <zr.zhang@...o.com>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org
Cc:     kernel@...o.com, Rui Zhang <zr.zhang@...o.com>
Subject: [PATCH] regulator: core: fix use_count leakage when handling boot-on

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@...o.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);
--
2.34.1

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