diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index fe8c447..5f1ab92 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -181,6 +181,8 @@
 				  const char *governor_name,
 				  void *data);
 extern int devfreq_remove_device(struct devfreq *devfreq);
+
+/* Supposed to be called by PM_SLEEP/PM_RUNTIME callbacks */
 extern int devfreq_suspend_device(struct devfreq *devfreq);
 extern int devfreq_resume_device(struct devfreq *devfreq);