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From:   Steve Twiss <stwiss.opensource@diasemi.com>
Date:   Tue, 26 Feb 2019 15:38:56 +0000
Subject: [PATCH 07/13] regulator: ltc3676: Fix notifier mutex lock warning
To:     Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>
CC:     Support Opensource <support.opensource@diasemi.com>,
        LKML <linux-kernel@vger.kernel.org>
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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: 37b918a034fe ("regulator: Add LTC3676 support")
Suggested-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Signed-off-by: Steve Twiss <stwiss.opensource@diasemi.com>
---
 drivers/regulator/ltc3676.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/regulator/ltc3676.c b/drivers/regulator/ltc3676.c
index 71fd0f2..cd0f112 100644
--- a/drivers/regulator/ltc3676.c
+++ b/drivers/regulator/ltc3676.c
@@ -338,17 +338,23 @@ static irqreturn_t ltc3676_isr(int irq, void *dev_id)
 	if (irqstat & LTC3676_IRQSTAT_THERMAL_WARN) {
 		dev_warn(dev, "Over-temperature Warning\n");
 		event = REGULATOR_EVENT_OVER_TEMP;
-		for (i = 0; i < LTC3676_NUM_REGULATORS; i++)
+		for (i = 0; i < LTC3676_NUM_REGULATORS; i++) {
+			regulator_lock(ltc3676->regulators[i]);
 			regulator_notifier_call_chain(ltc3676->regulators[i],
 						      event, NULL);
+			regulator_unlock(ltc3676->regulators[i]);
+		}
 	}
 
 	if (irqstat & LTC3676_IRQSTAT_UNDERVOLT_WARN) {
 		dev_info(dev, "Undervoltage Warning\n");
 		event = REGULATOR_EVENT_UNDER_VOLTAGE;
-		for (i = 0; i < LTC3676_NUM_REGULATORS; i++)
+		for (i = 0; i < LTC3676_NUM_REGULATORS; i++) {
+			regulator_lock(ltc3676->regulators[i]);
 			regulator_notifier_call_chain(ltc3676->regulators[i],
 						      event, NULL);
+			regulator_unlock(ltc3676->regulators[i]);
+		}
 	}
 
 	/* Clear warning condition */
-- 
1.9.3