Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/include/linux/mailbox_controller.h b/include/linux/mailbox_controller.h
index 74deadb..36d6ce6 100644
--- a/include/linux/mailbox_controller.h
+++ b/include/linux/mailbox_controller.h
@@ -1,8 +1,4 @@
-/*
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
+/* SPDX-License-Identifier: GPL-2.0-only */
 
 #ifndef __MAILBOX_CONTROLLER_H
 #define __MAILBOX_CONTROLLER_H
@@ -24,6 +20,9 @@
  *		transmission of data is reported by the controller via
  *		mbox_chan_txdone (if it has some TX ACK irq). It must not
  *		sleep.
+ * @flush:	Called when a client requests transmissions to be blocking but
+ *		the context doesn't allow sleeping. Typically the controller
+ *		will implement a busy loop waiting for the data to flush out.
  * @startup:	Called when a client requests the chan. The controller
  *		could ask clients for additional parameters of communication
  *		to be provided via client's chan_data. This call may
@@ -46,6 +45,7 @@
  */
 struct mbox_chan_ops {
 	int (*send_data)(struct mbox_chan *chan, void *data);
+	int (*flush)(struct mbox_chan *chan, unsigned long timeout);
 	int (*startup)(struct mbox_chan *chan);
 	void (*shutdown)(struct mbox_chan *chan);
 	bool (*last_tx_done)(struct mbox_chan *chan);
@@ -131,4 +131,9 @@
 void mbox_chan_received_data(struct mbox_chan *chan, void *data); /* atomic */
 void mbox_chan_txdone(struct mbox_chan *chan, int r); /* atomic */
 
+int devm_mbox_controller_register(struct device *dev,
+				  struct mbox_controller *mbox);
+void devm_mbox_controller_unregister(struct device *dev,
+				     struct mbox_controller *mbox);
+
 #endif /* __MAILBOX_CONTROLLER_H */