remoteproc/omap: Check for undefined mailbox messages

Add some checks in the mailbox callback function to limit
any processing in the mailbox callback function to only
certain currently valid messages, and drop all the remaining
messages. A debug message is added to print any such invalid
messages when the appropriate trace control is enabled.

Co-developed-by: Subramaniam Chanderashekarapuram <subramaniam.ca@ti.com>
Signed-off-by: Subramaniam Chanderashekarapuram <subramaniam.ca@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Andrew F. Davis <afd@ti.com>
Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200324110035.29907-10-t-kristo@ti.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/omap_remoteproc.c

@@ -130,6 +130,12 @@ static void omap_rproc_mbox_callback(struct mbox_client *client, void *data)
 		dev_info(dev, "received echo reply from %s\n", name);
 		break;
 	default:
+		if (msg >= RP_MBOX_READY && msg < RP_MBOX_END_MSG)
+			return;
+		if (msg > oproc->rproc->max_notifyid) {
+			dev_dbg(dev, "dropping unknown message 0x%x", msg);
+			return;
+		}
 		/* msg contains the index of the triggered vring */
 		if (rproc_vq_interrupt(oproc->rproc, msg) == IRQ_NONE)
 			dev_dbg(dev, "no message was found in vqid %d\n", msg);

drivers/remoteproc/omap_remoteproc.h

@@ -56,6 +56,12 @@
  *
  * @RP_MBOX_ABORT_REQUEST: a "please crash" request, used for testing the
  * recovery mechanism (to some extent).
+ *
+ * Introduce new message definitions if any here.
+ *
+ * @RP_MBOX_END_MSG: Indicates end of known/defined messages from remote core
+ * This should be the last definition.
+ *
  */
 enum omap_rp_mbox_messages {
 	RP_MBOX_READY		= 0xFFFFFF00,
@@ -64,6 +70,7 @@ enum omap_rp_mbox_messages {
 	RP_MBOX_ECHO_REQUEST	= 0xFFFFFF03,
 	RP_MBOX_ECHO_REPLY	= 0xFFFFFF04,
 	RP_MBOX_ABORT_REQUEST	= 0xFFFFFF05,
+	RP_MBOX_END_MSG		= 0xFFFFFF06,
 };
 
 #endif /* _OMAP_RPMSG_H */