PM / devfreq: Check get_dev_status in devfreq_update_stats

Check .get_dev_status() in devfreq_update_stats in case it's abused
when a device does not provide it.

Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
index 70f44b3..2446344 100644
--- a/drivers/devfreq/governor.h
+++ b/drivers/devfreq/governor.h
@@ -91,6 +91,9 @@ int devfreq_update_target(struct devfreq *devfreq, unsigned long freq);
 
 static inline int devfreq_update_stats(struct devfreq *df)
 {
+	if (!df->profile->get_dev_status)
+		return -EINVAL;
+
 	return df->profile->get_dev_status(df->dev.parent, &df->last_status);
 }
 #endif /* _GOVERNOR_H */