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From:   Steve Twiss <stwiss.opensource@diasemi.com>
Date:   Tue, 26 Feb 2019 15:54:01 +0000
Subject: [PATCH 13/13] regulator: wm831x ldo: 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>,
        Cirrus Patches <patches@opensource.cirrus.com>
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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: d1c6b4fe668b ("regulator: Add WM831x LDO support")
Suggested-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Signed-off-by: Steve Twiss <stwiss.opensource@diasemi.com>
---
 drivers/regulator/wm831x-ldo.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/regulator/wm831x-ldo.c b/drivers/regulator/wm831x-ldo.c
index e4a6f88..fcd038e 100644
--- a/drivers/regulator/wm831x-ldo.c
+++ b/drivers/regulator/wm831x-ldo.c
@@ -51,9 +51,11 @@ static irqreturn_t wm831x_ldo_uv_irq(int irq, void *data)
 {
 	struct wm831x_ldo *ldo = data;
 
+	regulator_lock(ldo->regulator);
 	regulator_notifier_call_chain(ldo->regulator,
 				      REGULATOR_EVENT_UNDER_VOLTAGE,
 				      NULL);
+	regulator_unlock(ldo->regulator);
 
 	return IRQ_HANDLED;
 }
-- 
1.9.3