diff --git a/Documentation/firmware_class/README b/Documentation/firmware_class/README
index e9fce78c4137..43fada989e65 100644
--- a/Documentation/firmware_class/README
+++ b/Documentation/firmware_class/README
@@ -119,3 +119,10 @@
    on the setup, so I think that the choice on what firmware to make
    persistent should be left to userspace.
 
+ about firmware cache:
+ --------------------
+ After firmware cache mechanism is introduced during system sleep,
+ request_firmware can be called safely inside device's suspend and
+ resume callback, and callers need't cache the firmware by
+ themselves any more for dealing with firmware loss during system
+ resume.
diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 7888af7941a0..d81460309182 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -988,6 +988,9 @@ static int _request_firmware_load(struct firmware_priv *fw_priv, bool uevent,
  *      firmware image for this or any other device.
  *
  *	Caller must hold the reference count of @device.
+ *
+ *	The function can be called safely inside device's suspend and
+ *	resume callback.
  **/
 int
 request_firmware(const struct firmware **firmware_p, const char *name,