[PATCH 3/3] hwmon: (adm1031) Serialize update rate changes

[Gui-Dong Han]

update_interval_store() updates the hardware rate bits in
ADM1031_REG_FAN_FILTER and then updates data->update_interval. Those
steps are currently split across unlocked and locked sections. This also
leaves the register read-modify-write sequence unprotected.

Hold data->update_lock across the whole sequence so that the register
update and the cached software state remain synchronized.

Fixes: 87c33daadbfe ("hwmon: (adm1031) Allow setting update rate")
Signed-off-by: Gui-Dong Han <hanguidong02@xxxxxxxxx>
---
 drivers/hwmon/adm1031.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/adm1031.c b/drivers/hwmon/adm1031.c
index 887fba9ea149..a46db83471f2 100644
--- a/drivers/hwmon/adm1031.c
+++ b/drivers/hwmon/adm1031.c
@@ -897,13 +897,14 @@ static ssize_t update_interval_store(struct device *dev,
 	}
 	/* if not found, we point to the last entry (lowest update interval) */
 
+	mutex_lock(&data->update_lock);
+
 	/* set the new update rate while preserving other settings */
 	reg = adm1031_read_value(client, ADM1031_REG_FAN_FILTER);
 	reg &= ~ADM1031_UPDATE_RATE_MASK;
 	reg |= i << ADM1031_UPDATE_RATE_SHIFT;
 	adm1031_write_value(client, ADM1031_REG_FAN_FILTER, reg);
 
-	mutex_lock(&data->update_lock);
 	data->update_interval = update_intervals[i];
 	mutex_unlock(&data->update_lock);
 
-- 
2.43.0