app: Buffer URCs during datamode

URCs from modem and other SM threads are buffered during
the data mode. When datamode is exited, all the received
URCs will be received.

Note: Currently this prevents the TCP and UDP clients (and
servers) from receiving data in data mode, as the send is
done from a thread, which is considered URC. There is a
work item to refactor the TCP and UDP clients (and servers),
which will address this.

Signed-off-by: Markus Lassila <[email protected]>

Author: MarkusLassila

app/src/sm_at_host.c

@@ -133,6 +133,9 @@ static bool exit_datamode(void)
 
 	k_mutex_unlock(&mutex_mode);
 
+	/* Flush the TX buffer. */
+	sm_tx_write(NULL, 0, true, K_NO_WAIT);
+
 	return ret;
 }
 
@@ -725,20 +728,14 @@ AT_MONITOR(at_notify, ANY, notification_handler);
 
 static void notification_handler(const char *notification)
 {
-	if (get_sm_mode() == SM_AT_COMMAND_MODE) {
-
 #if defined(CONFIG_SM_PPP)
-		if (!sm_fwd_cgev_notifs
-		 && !strncmp(notification, "+CGEV: ", strlen("+CGEV: "))) {
-			/* CGEV notifications are silenced. Do not forward them. */
-			return;
-		}
-#endif
-		sm_at_send_internal(CRLF_STR, strlen(CRLF_STR), SM_DEBUG_PRINT_FULL);
-		sm_at_send_str(notification);
-	} else {
-		LOG_DBG("Drop notification: %s", notification);
+	if (!sm_fwd_cgev_notifs && !strncmp(notification, "+CGEV: ", strlen("+CGEV: "))) {
+		/* CGEV notifications are silenced. Do not forward them. */
+		return;
 	}
+#endif
+	sm_at_send_internal(CRLF_STR, strlen(CRLF_STR), SM_DEBUG_PRINT_FULL);
+	sm_at_send_str(notification);
 }
 
 void rsp_send_ok(void)

app/src/sm_cmux.c

@@ -198,6 +198,10 @@ static void nonblock_tx_work_fn(struct k_work *work)
 		LOG_ERR("No URC context");
 		return;
 	}
+	if (in_datamode()) {
+		/* Do not send URCs in datamode. */
+		return;
+	}
 
 	/* Do not lock the URC mutex. */
 	do {

app/src/sm_uart_handler.c

@@ -441,6 +441,11 @@ static void tx_write_nonblock_fn(struct k_work *)
 		return;
 	}
 
+	if (in_datamode()) {
+		/* Do not send URCs in datamode. */
+		return;
+	}
+
 	/* Do not lock the URC mutex.
 	 * This is the only reader and URC context ownership cannot be transferred as we
 	 * are in the same work queue that processes AT-commands.

doc/app/sm_data_mode.rst

@@ -12,7 +12,8 @@ The |SM| (SM) application can run in the two operation modes defined by the AT c
 When running in data mode, the application does the following:
 
 * It considers all the data received from the MCU over the UART bus as arbitrary data to be streamed through the LTE network by various service modules.
-* It considers all the data streamed from a remote service as arbitrary data to be sent to the MCU over the UART bus.
+* It buffers the URCs received from modem and threads and sends them to the MCU only after exiting data mode.
+* For TLS and UDP client (and servers), it considers all the data streamed from a remote service as arbitrary data to be sent to the MCU over the UART bus.
 
 Overview
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