regulator: ltc3676: Fix notifier mutex lock warning

BugLink: https://bugs.launchpad.net/bugs/1837517
[ Upstream commit 769fc8d4182c1d1875db7859852afeb436714c5c ]

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>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/regulator/ltc3676.c b/drivers/regulator/ltc3676.c
index 71fd0f2a4b76e6d427bdb8a3d183909d6f39e725..cd0f11254c7782b0812d811a3909289e69aa7b3e 100644 (file)
--- 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 */