2 files changed, 5 insertions, 0 deletions

diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index c281e5562876..58789b027708 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -78,6 +78,8 @@ static void msg_submit(struct mbox_chan *chan)
 
         data = chan->msg_data[idx];
 
+        if (chan->cl->tx_prepare)
+                chan->cl->tx_prepare(chan->cl, data);
         /* Try to submit a message to the MBOX controller */
         err = chan->mbox->ops->send_data(chan, data);
         if (!err) {
diff --git a/include/linux/mailbox_client.h b/include/linux/mailbox_client.h
index 307d9cab2026..1726ccbd8009 100644
--- a/include/linux/mailbox_client.h
+++ b/include/linux/mailbox_client.h
@@ -25,6 +25,8 @@ struct mbox_chan;
  *                      if the client receives some ACK packet for transmission.
  *                      Unused if the controller already has TX_Done/RTR IRQ.
  * @rx_callback:        Atomic callback to provide client the data received
+ * @tx_prepare:         Atomic callback to ask client to prepare the payload
+ *                      before initiating the transmission if required.
  * @tx_done:            Atomic callback to tell client of data transmission
  */
 struct mbox_client {
@@ -34,6 +36,7 @@ struct mbox_client {
         bool knows_txdone;
 
         void (*rx_callback)(struct mbox_client *cl, void *mssg);
+        void (*tx_prepare)(struct mbox_client *cl, void *mssg);
         void (*tx_done)(struct mbox_client *cl, void *mssg, int r);
 };