regulator: ltc3589: 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: 3eb2c7ec ("regulator: Add LTC3589 support")
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/ltc3589.c

@@ -419,16 +419,22 @@ static irqreturn_t ltc3589_isr(int irq, void *dev_id)
 
 	if (irqstat & LTC3589_IRQSTAT_THERMAL_WARN) {
 		event = REGULATOR_EVENT_OVER_TEMP;
-		for (i = 0; i < LTC3589_NUM_REGULATORS; i++)
+		for (i = 0; i < LTC3589_NUM_REGULATORS; i++) {
+		        regulator_lock(ltc3589->regulators[i]);
 			regulator_notifier_call_chain(ltc3589->regulators[i],
 						      event, NULL);
+		        regulator_unlock(ltc3589->regulators[i]);
+		}
 	}
 
 	if (irqstat & LTC3589_IRQSTAT_UNDERVOLT_WARN) {
 		event = REGULATOR_EVENT_UNDER_VOLTAGE;
-		for (i = 0; i < LTC3589_NUM_REGULATORS; i++)
+		for (i = 0; i < LTC3589_NUM_REGULATORS; i++) {
+		        regulator_lock(ltc3589->regulators[i]);
 			regulator_notifier_call_chain(ltc3589->regulators[i],
 						      event, NULL);
+		        regulator_unlock(ltc3589->regulators[i]);
+		}
 	}
 
 	/* Clear warning condition */