diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index d938b2b..eb1d00a 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1196,9 +1196,14 @@
  *
  * This is the central routine for suspending USB devices.  It calls the
  * suspend methods for all the interface drivers in @udev and then calls
- * the suspend method for @udev itself.  If an error occurs at any stage,
- * all the interfaces which were suspended are resumed so that they remain
- * in the same state as the device.
+ * the suspend method for @udev itself.  When the routine is called in
+ * autosuspend, if an error occurs at any stage, all the interfaces
+ * which were suspended are resumed so that they remain in the same
+ * state as the device, but when called from system sleep, all error
+ * from suspend methods of interfaces and the non-root-hub device itself
+ * are simply ignored, so all suspended interfaces are only resumed
+ * to the device's state when @udev is root-hub and its suspend method
+ * returns failure.
  *
  * Autosuspend requests originating from a child device or an interface
  * driver may be made without the protection of @udev's device lock, but
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 52464fb..8d4bc17 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -976,7 +976,12 @@
  *	the "usbfs" filesystem.  This lets devices provide ways to
  *	expose information to user space regardless of where they
  *	do (or don't) show up otherwise in the filesystem.
- * @suspend: Called when the device is going to be suspended by the system.
+ * @suspend: Called when the device is going to be suspended by the
+ *	system either from system sleep or runtime suspend context. The
+ *	return value will be ignored in system sleep context, so do NOT
+ *	try to continue using the device if suspend fails in this case.
+ *	Instead, let the resume or reset-resume routine recover from
+ *	the failure.
  * @resume: Called when the device is being resumed by the system.
  * @reset_resume: Called when the suspended device has been reset instead
  *	of being resumed.