regulator: core: Only increment use_count when enable_count changes

The use_count of a regulator should only be incremented when the
enable_count changes from 0 to 1. Similarly, the use_count should
only be decremented when the enable_count changes from 1 to 0.

In the previous implementation, use_count was sometimes decremented
to 0 when some consumer called unbalanced disable,
leading to unexpected disable even the regulator is enabled by
other consumers. With this change, the use_count accurately reflects
the number of users which the regulator is enabled.

This should make things more robust in the case where a consumer does
leak references.
Signed-off-by: Rui Zhang <zr.zhang@vivo.com>
Link: https://lore.kernel.org/r/20231103074231.8031-1-zr.zhang@vivo.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -2918,6 +2918,7 @@ static int _regulator_enable(struct regulator *regulator)
 		/* Fallthrough on positive return values - already enabled */
 	}
 
+	if (regulator->enable_count == 1)
 		rdev->use_count++;
 
 	return 0;
@@ -2993,10 +2994,12 @@ static int _regulator_disable(struct regulator *regulator)
 
 	lockdep_assert_held_once(&rdev->mutex.base);
 
-	if (WARN(rdev->use_count <= 0,
+	if (WARN(regulator->enable_count == 0,
 		 "unbalanced disables for %s\n", rdev_get_name(rdev)))
 		return -EIO;
 
+	if (regulator->enable_count == 1) {
+	/* disabling last enable_count from this regulator */
 		/* are we the last user and permitted to disable ? */
 		if (rdev->use_count == 1 &&
 		    (rdev->constraints && !rdev->constraints->always_on)) {
@@ -3025,6 +3028,7 @@ static int _regulator_disable(struct regulator *regulator)
 		} else if (rdev->use_count > 1) {
 			rdev->use_count--;
 		}
+	}
 
 	if (ret == 0)
 		ret = _regulator_handle_consumer_disable(regulator);