regulator: da9211: Fix notifier mutex lock warning

The mutex for the regulator_dev must be controlled by the caller of
the regulator_notifier_call_chain(), as described in the comment
for that function.

Failure to mutex lock and unlock surrounding the notifier call results
in a kernel WARN_ON_ONCE() which will dump a backtrace for the
regulator_notifier_call_chain() when that function call is first made.
The mutex can be controlled using the regulator_lock/unlock() API.

Fixes: 1028a37d ("regulator: da9211: new regulator driver")
Suggested-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Signed-off-by: Steve Twiss <stwiss.opensource@diasemi.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/da9211-regulator.c

@@ -322,8 +322,10 @@ static irqreturn_t da9211_irq_handler(int irq, void *data)
 		goto error_i2c;
 
 	if (reg_val & DA9211_E_OV_CURR_A) {
+	        regulator_lock(chip->rdev[0]);
 		regulator_notifier_call_chain(chip->rdev[0],
 			REGULATOR_EVENT_OVER_CURRENT, NULL);
+	        regulator_unlock(chip->rdev[0]);
 
 		err = regmap_write(chip->regmap, DA9211_REG_EVENT_B,
 			DA9211_E_OV_CURR_A);
@@ -334,8 +336,10 @@ static irqreturn_t da9211_irq_handler(int irq, void *data)
 	}
 
 	if (reg_val & DA9211_E_OV_CURR_B) {
+	        regulator_lock(chip->rdev[1]);
 		regulator_notifier_call_chain(chip->rdev[1],
 			REGULATOR_EVENT_OVER_CURRENT, NULL);
+	        regulator_unlock(chip->rdev[1]);
 
 		err = regmap_write(chip->regmap, DA9211_REG_EVENT_B,
 			DA9211_E_OV_CURR_B);