firmware: arm_scmi: Add helper to trace bad messages

Upon reception of malformed and unexpected timed-out SCMI messages, it is
not possible to trace those bad messages in their entirety, because usually
we cannot even retrieve the payload, or it is just not reliable.

Add a helper to trace at least the content of the header of the received
message while associating a meaningful tag and error code.
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240325204620.1437237-3-cristian.marussi@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/common.h

@@ -301,6 +301,17 @@ extern const struct scmi_desc scmi_optee_desc;
 
 void scmi_rx_callback(struct scmi_chan_info *cinfo, u32 msg_hdr, void *priv);
 
+enum scmi_bad_msg {
+	MSG_UNEXPECTED = -1,
+	MSG_INVALID = -2,
+	MSG_UNKNOWN = -3,
+	MSG_NOMEM = -4,
+	MSG_MBOX_SPURIOUS = -5,
+};
+
+void scmi_bad_message_trace(struct scmi_chan_info *cinfo, u32 msg_hdr,
+			    enum scmi_bad_msg err);
+
 /* shmem related declarations */
 struct scmi_shared_mem;
 

drivers/firmware/arm_scmi/driver.c

@@ -696,6 +696,45 @@ scmi_xfer_lookup_unlocked(struct scmi_xfers_info *minfo, u16 xfer_id)
 	return xfer ?: ERR_PTR(-EINVAL);
 }
 
+/**
+ * scmi_bad_message_trace  - A helper to trace weird messages
+ *
+ * @cinfo: A reference to the channel descriptor on which the message was
+ *	   received
+ * @msg_hdr: Message header to track
+ * @err: A specific error code used as a status value in traces.
+ *
+ * This helper can be used to trace any kind of weird, incomplete, unexpected,
+ * timed-out message that arrives and as such, can be traced only referring to
+ * the header content, since the payload is missing/unreliable.
+ */
+void scmi_bad_message_trace(struct scmi_chan_info *cinfo, u32 msg_hdr,
+			    enum scmi_bad_msg err)
+{
+	char *tag;
+	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
+
+	switch (MSG_XTRACT_TYPE(msg_hdr)) {
+	case MSG_TYPE_COMMAND:
+		tag = "!RESP";
+		break;
+	case MSG_TYPE_DELAYED_RESP:
+		tag = "!DLYD";
+		break;
+	case MSG_TYPE_NOTIFICATION:
+		tag = "!NOTI";
+		break;
+	default:
+		tag = "!UNKN";
+		break;
+	}
+
+	trace_scmi_msg_dump(info->id, cinfo->id,
+			    MSG_XTRACT_PROT_ID(msg_hdr),
+			    MSG_XTRACT_ID(msg_hdr), tag,
+			    MSG_XTRACT_TOKEN(msg_hdr), err, NULL, 0);
+}
+
 /**
  * scmi_msg_response_validate  - Validate message type against state of related
  * xfer