application: serial_lte_modem: Automation of LwM2M requests

Add CONFIG_SLM_CARRIER_AUTO_CONTROL to control automatical handling
of below requests from LwM2M in SLM, instead of by host MCU:
- Link down/up
- Power off modem
- Reboot

By default this CONFIG is enabled.

JIRA-ticket: NCSDK-28267
JIRA-ticket: NCSDK-28431

Signed-off-by: Jun Qing Zou <jun.qing.zou@nordicsemi.no>

applications/serial_lte_modem/doc/CARRIER_AT_commands.rst

@@ -31,27 +31,27 @@ These may be the following:
 
 * ``#XCARRIEREVT: 1,<status>``
 
-  Request to set the modem to full functional mode.
+  Request to use the ``AT+CFUN=1`` AT command to set the modem to full functional mode.
   ``<status>`` returns two possible values:
 
-  * ``0`` - Request handled successfully.
-  * ``-1`` - Request handling was deferred and must be performed by the application at its earliest convenience.
+  * ``0`` - Request handling is fulfilled automatically.
+  * ``-1`` - Request handling is deferred and must be fulfilled by the application at its earliest convenience.
 
 * ``#XCARRIEREVT: 2,<status>``
 
-  Request to set the modem to flight functional mode.
+  Request to use the ``AT+CFUN=4`` AT command to set the modem to flight functional mode.
   ``<status>`` returns two possible values:
 
-  * ``0`` - Request handled successfully.
-  * ``-1`` - Request handling was deferred and must be performed by the application at its earliest convenience.
+  * ``0`` - Request handling is fulfilled automatically.
+  * ``-1`` - Request handling is deferred and must be fulfilled by the application at its earliest convenience.
 
 * ``#XCARRIEREVT: 3,<status>``
 
-  Request to set the modem to minimum functional mode.
+  Request to use the ``AT+CFUN=0`` AT command to set the modem to minimum functional mode.
   ``<status>`` returns two possible values:
 
-  * ``0`` - Request handled successfully.
-  * ``-1`` - Request handling was deferred and must be performed by the application at its earliest convenience.
+  * ``0`` - Request handling is fulfilled automatically.
+  * ``-1`` - Request handling is deferred and must be fulfilled by the application at its earliest convenience.
 
 * ``#XCARRIEREVT: 4,0``
 
@@ -94,12 +94,12 @@ These may be the following:
 
 * ``#XCARRIEREVT: 10,<status>``
 
-  Request to perform an application reboot.
+  Request to perform an application reboot, for example using the ``AT#XRESET`` AT command.
 
   ``<status>`` returns two possible values:
 
-  * ``0`` - Request handled successfully.
-  * ``-1`` - Request handling was deferred and must be performed by the application at its earliest convenience.
+  * ``0`` - Request handling is fulfilled automatically.
+  * ``-1`` - Request handling is deferred and must be fulfilled by the application at its earliest convenience.
 
 * ``#XCARRIEREVT: 11,0``
 

applications/serial_lte_modem/src/lwm2m_carrier/Kconfig

@@ -25,4 +25,13 @@ config SLM_CARRIER_AUTO_STARTUP
 	  Enable automatic startup of the library on device boot. If this configuration is
 	  disabled, automatic startup is controlled through a dedicated AT command.
 
+config SLM_CARRIER_AUTO_CONTROL
+	bool "Automatic handling of LwM2M requests"
+	depends on SLM_AUTO_CONNECT
+	default y
+	help
+	  Enable automatic power off, reboot, link up or link down when requested by the LwM2M
+	  stack. If this is disabled, the host MCU must perform these operations via AT commands
+	  when requested.
+
 endif # SLM_CARRIER

applications/serial_lte_modem/src/lwm2m_carrier/slm_at_carrier.c

@@ -148,29 +148,53 @@ static void reconnect_wk(struct k_work *work)
 int lwm2m_carrier_event_handler(const lwm2m_carrier_event_t *event)
 {
 	int err = 0;
-	static bool fota_started;
 
 	switch (event->type) {
+#if defined(CONFIG_SLM_CARRIER_AUTO_CONTROL)
 	case LWM2M_CARRIER_EVENT_LTE_LINK_UP:
 		LOG_DBG("LWM2M_CARRIER_EVENT_LTE_LINK_UP");
-		if (fota_started) {
-			fota_started = false;
-			k_work_reschedule(&reconnect_work, K_MSEC(100));
-		} else {
-			/* AT+CFUN=1 to be issued. */
+		k_work_reschedule(&reconnect_work, SLM_UART_RESPONSE_DELAY);
+		break;
+	case LWM2M_CARRIER_EVENT_LTE_LINK_DOWN:
+		LOG_DBG("LWM2M_CARRIER_EVENT_LTE_LINK_DOWN");
+		err = slm_util_at_printf("AT+CFUN=4");
+		if (err) {
+			err = -1;
+		}
+		break;
+	case LWM2M_CARRIER_EVENT_LTE_POWER_OFF:
+		LOG_DBG("LWM2M_CARRIER_EVENT_LTE_POWER_OFF");
+		err = slm_util_at_printf("AT+CFUN=0");
+		if (err) {
 			err = -1;
 		}
 		break;
+	case LWM2M_CARRIER_EVENT_REBOOT:
+		LOG_DBG("LWM2M_CARRIER_EVENT_REBOOT");
+		/* Return 0 to reboot right after a URC. */
+		break;
+#else
+	case LWM2M_CARRIER_EVENT_LTE_LINK_UP:
+		LOG_DBG("LWM2M_CARRIER_EVENT_LTE_LINK_UP");
+		/* AT+CFUN=1 to be issued. */
+		err = -1;
+		break;
 	case LWM2M_CARRIER_EVENT_LTE_LINK_DOWN:
 		LOG_DBG("LWM2M_CARRIER_EVENT_LTE_LINK_DOWN");
 		/* AT+CFUN=4 to be issued. */
 		err = -1;
 		break;
 	case LWM2M_CARRIER_EVENT_LTE_POWER_OFF:
 		LOG_DBG("LWM2M_CARRIER_EVENT_LTE_POWER_OFF");
-		/* TODO: defer setting the modem to minimum funtional mode. */
-		err = slm_util_at_printf("AT+CFUN=0");
+		/* AT+CFUN=0 to be issued. */
+		err = -1;
+		break;
+	case LWM2M_CARRIER_EVENT_REBOOT:
+		LOG_DBG("LWM2M_CARRIER_EVENT_REBOOT");
+		/* Return -1 to defer the reboot until the application decides to do so. */
+		err = -1;
 		break;
+#endif /* CONFIG_SLM_CARRIER_AUTO_CONTROL */
 	case LWM2M_CARRIER_EVENT_BOOTSTRAPPED:
 		LOG_DBG("LWM2M_CARRIER_EVENT_BOOTSTRAPPED");
 		break;
@@ -185,16 +209,10 @@ int lwm2m_carrier_event_handler(const lwm2m_carrier_event_t *event)
 		return 0;
 	case LWM2M_CARRIER_EVENT_FOTA_START:
 		LOG_DBG("LWM2M_CARRIER_EVENT_FOTA_START");
-		fota_started = true;
 		break;
 	case LWM2M_CARRIER_EVENT_FOTA_SUCCESS:
 		LOG_DBG("LWM2M_CARRIER_EVENT_FOTA_SUCCESS");
 		break;
-	case LWM2M_CARRIER_EVENT_REBOOT:
-		LOG_DBG("LWM2M_CARRIER_EVENT_REBOOT");
-		/* Return -1 to defer the reboot until the application decides to do so. */
-		err = -1;
-		break;
 	case LWM2M_CARRIER_EVENT_MODEM_DOMAIN:
 		LOG_DBG("LWM2M_CARRIER_EVENT_MODEM_DOMAIN");
 		break;
@@ -220,6 +238,13 @@ int lwm2m_carrier_event_handler(const lwm2m_carrier_event_t *event)
 
 	rsp_send("\r\n#XCARRIEREVT: %d,%d\r\n", event->type, err);
 
+#if defined(CONFIG_SLM_CARRIER_AUTO_CONTROL)
+	/* Allow time for the URC be flushed before reboot */
+	if (event->type == LWM2M_CARRIER_EVENT_REBOOT && err == 0) {
+		k_sleep(SLM_UART_RESPONSE_DELAY);
+	}
+#endif
+
 	return err;
 }