linux-kernel - [PATCH] regulator: core: Clean up on enable failure

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Date:   Fri, 19 Aug 2022 14:43:36 -0500
From:   Andrew Halaney <ahalaney@...hat.com>
To:     lgirdwood@...il.com, broonie@...nel.org
Cc:     linux-kernel@...r.kernel.org, bmasney@...hat.com,
        dianders@...omium.org, Andrew Halaney <ahalaney@...hat.com>
Subject: [PATCH] regulator: core: Clean up on enable failure

If regulator_enable() fails, enable_count is incremented still.
A consumer, assuming no matching regulator_disable() is necessary on
failure, will then get this error message upon regulator_put()
since enable_count is non-zero:

    [    1.277418] WARNING: CPU: 3 PID: 1 at drivers/regulator/core.c:2304 _regulator_put.part.0+0x168/0x170

The consumer could try to fix this in their driver by cleaning up on
error from regulator_enable() (i.e. call regulator_disable()), but that
results in the following since regulator_enable() failed and didn't
increment user_count:

    [    1.258112] unbalanced disables for vreg_l17c
    [    1.262606] WARNING: CPU: 4 PID: 1 at drivers/regulator/core.c:2899 _regulator_disable+0xd4/0x190

Fix this by decrementing enable_count upon failure to enable.

With this in place, just the reason for failure to enable is printed
as expected and developers can focus on the root cause of their issue
instead of thinking their usage of the regulator consumer api is
incorrect. For example, in my case:

    [    1.240426] vreg_l17c: invalid input voltage found

Fixes: 5451781dadf8 ("regulator: core: Only count load for enabled consumers")
Signed-off-by: Andrew Halaney <ahalaney@...hat.com>
---

I'm new to using the regulator framework, but I _believe_ this is a
cosmetic bug that's fixed by this patch. I went down a bit of a rabbit
hole because of the original WARN() message, so I'm trying to prevent
others from doing the same :)

Please let me know what you think, I tested on the misconfigured system
and on a working system and things seemed to work as expected.

Thanks,
Andrew

 drivers/regulator/core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index d8373cb04f90..d3e8dc32832d 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -2733,13 +2733,18 @@ static int _regulator_do_enable(struct regulator_dev *rdev)
  */
 static int _regulator_handle_consumer_enable(struct regulator *regulator)
 {
+	int ret;
 	struct regulator_dev *rdev = regulator->rdev;

 	lockdep_assert_held_once(&rdev->mutex.base);

 	regulator->enable_count++;
-	if (regulator->uA_load && regulator->enable_count == 1)
-		return drms_uA_update(rdev);
+	if (regulator->uA_load && regulator->enable_count == 1) {
+		ret = drms_uA_update(rdev);
+		if (ret)
+			regulator->enable_count--;
+		return ret;
+	}

 	return 0;
 }
-- 
2.37.1