lib: lte_link_control: Apply missing settings after +CFUN=0

Band lock, RAI notification subscription and DNS fallback
address were not applied after modem was put into minimal
functionality mode (AT+CFUN=0). Those settings are not
stored into NVM by the modem and the settings need to be
applied again.

Corrected the comments for PLMN lock in on_modem_init().
That setting is not volatile, but it is saved into NVM
by the modem.

Changed on_modem_init() callback to always continue execution
in case setting a configuration to modem fails. Earlier some of
the configurations caused the function to exit, while some did
not. The callback does not return any value, so it does its
best and tries to configure everything. Possible failures are
logged.

Jira: NRF91-2680

Signed-off-by: Tommi Kangas <[email protected]>

Author: tokangas

doc/nrf/releases_and_maturity/releases/release-notes-changelog.rst

@@ -809,6 +809,8 @@ Modem libraries
     * The order of the ``LTE_LC_MODEM_EVT_SEARCH_DONE`` modem event, and registration and cell related events.
       See the :ref:`migration guide <migration_3.2_required>` for more information.
 
+  * Fixed an issue where band lock, RAI notification subscription, and DNS fallback address were lost when the modem was put into :c:enumerator:`LTE_LC_FUNC_MODE_POWER_OFF` functional mode.
+
 * :ref:`nrf_modem_lib_readme` library:
 
   * Added the :c:func:`nrf_modem_lib_trace_peek_at` function to the :c:struct:`nrf_modem_lib_trace_backend` interface to peek trace data at a byte offset without consuming it.

lib/lte_link_control/include/modules/edrx.h

@@ -25,6 +25,11 @@ int edrx_param_set(enum lte_lc_lte_mode mode, const char *edrx);
 /* Request modem to enable or disable use of eDRX. */
 int edrx_request(bool enable);
 
+/* Apply current eDRX configuration. Used after +CFUN=0 to restore the eDRX notification
+ * subscription, which is not stored into NVM by the modem.
+ */
+void edrx_set(void);
+
 #ifdef __cplusplus
 }
 #endif

lib/lte_link_control/include/modules/rai.h

@@ -12,7 +12,7 @@ extern "C" {
 #endif
 
 /* Configure RAI. */
-int rai_set(void);
+void rai_set(void);
 
 #ifdef __cplusplus
 }

lib/lte_link_control/lte_lc_modem_hooks.c

@@ -9,12 +9,28 @@
 #include <modem/nrf_modem_lib.h>
 #include <zephyr/logging/log.h>
 
+#include "modules/edrx.h"
 #include "modules/rai.h"
 #include "modules/dns.h"
 #include "common/helpers.h"
 
 LOG_MODULE_DECLARE(lte_lc, CONFIG_LTE_LINK_CONTROL_LOG_LEVEL);
 
+#if defined(CONFIG_LTE_LOCK_BANDS)
+static void band_lock_set(void)
+{
+	int err;
+
+	/* Set LTE band lock (volatile setting).
+	 * Has to be done every time before activating the modem.
+	 */
+	err = nrf_modem_at_printf("AT%%XBANDLOCK=2,\""CONFIG_LTE_LOCK_BAND_MASK "\"");
+	if (err) {
+		LOG_ERR("Failed to lock LTE bands, err %d", err);
+	}
+}
+#endif /* CONFIG_LTE_LOCK_BANDS */
+
 #if defined(CONFIG_UNITY)
 void on_modem_init(int err, void *ctx)
 #else
@@ -37,7 +53,6 @@ static void on_modem_init(int err, void *ctx)
 		err = lte_lc_system_mode_set(lte_lc_sys_mode, lte_lc_sys_mode_pref);
 		if (err) {
 			LOG_ERR("Failed to set system mode and mode preference, err %d", err);
-			return;
 		}
 	}
 
@@ -47,37 +62,32 @@ static void on_modem_init(int err, void *ctx)
 						   CONFIG_LTE_PSM_REQ_RAT_SECONDS);
 		if (err) {
 			LOG_ERR("Failed to set PSM params, err %d", err);
-			return;
+		} else {
+			LOG_DBG("PSM configs set from seconds: tau=%ds, rat=%ds",
+				CONFIG_LTE_PSM_REQ_RPTAU_SECONDS,
+				CONFIG_LTE_PSM_REQ_RAT_SECONDS);
 		}
-
-		LOG_DBG("PSM configs set from seconds: tau=%ds, rat=%ds",
-			CONFIG_LTE_PSM_REQ_RPTAU_SECONDS,
-			CONFIG_LTE_PSM_REQ_RAT_SECONDS);
 	} else {
 		__ASSERT_NO_MSG(IS_ENABLED(CONFIG_LTE_PSM_REQ_FORMAT_STRING));
 
 		err = lte_lc_psm_param_set(CONFIG_LTE_PSM_REQ_RPTAU, CONFIG_LTE_PSM_REQ_RAT);
 		if (err) {
 			LOG_ERR("Failed to set PSM params, err %d", err);
-			return;
+		} else {
+			LOG_DBG("PSM configs set from string: tau=%s, rat=%s",
+				CONFIG_LTE_PSM_REQ_RPTAU, CONFIG_LTE_PSM_REQ_RAT);
 		}
-
-		LOG_DBG("PSM configs set from string: tau=%s, rat=%s",
-			CONFIG_LTE_PSM_REQ_RPTAU, CONFIG_LTE_PSM_REQ_RAT);
 	}
 
-	/* Request configured PSM and eDRX settings to save power. */
 	err = lte_lc_psm_req(IS_ENABLED(CONFIG_LTE_PSM_REQ));
 	if (err) {
 		LOG_ERR("Failed to configure PSM, err %d", err);
-		return;
 	}
 
 	if (IS_ENABLED(CONFIG_LTE_PROPRIETARY_PSM_REQ)) {
 		err = lte_lc_proprietary_psm_req(true);
 		if (err) {
 			LOG_ERR("Failed to configure proprietary PSM, err %d", err);
-			return;
 		}
 	} else {
 		/* Return value is ignored because this feature is not supported by all MFW
@@ -99,41 +109,69 @@ static void on_modem_init(int err, void *ctx)
 	err = lte_lc_edrx_req(IS_ENABLED(CONFIG_LTE_EDRX_REQ));
 	if (err) {
 		LOG_ERR("Failed to configure eDRX, err %d", err);
-		return;
-	}
-#endif
-
-#if defined(CONFIG_LTE_LOCK_BANDS)
-	/* Set LTE band lock (volatile setting).
-	 * Has to be done every time before activating the modem.
-	 */
-	err = nrf_modem_at_printf("AT%%XBANDLOCK=2,\""CONFIG_LTE_LOCK_BAND_MASK "\"");
-	if (err) {
-		LOG_ERR("Failed to lock LTE bands, err %d", err);
-		return;
 	}
 #endif
 
 #if defined(CONFIG_LTE_LOCK_PLMN)
-	/* Manually select Operator (volatile setting).
-	 * Has to be done every time before activating the modem.
-	 */
+	/* Manually select the PLMN. */
 	err = nrf_modem_at_printf("AT+COPS=1,2,\"" CONFIG_LTE_LOCK_PLMN_STRING "\"");
 	if (err) {
 		LOG_ERR("Failed to lock PLMN, err %d", err);
-		return;
 	}
 #elif defined(CONFIG_LTE_UNLOCK_PLMN)
-	/* Automatically select Operator (volatile setting). */
+	/* Automatically select the PLMN. */
 	err = nrf_modem_at_printf("AT+COPS=0");
 	if (err) {
 		LOG_ERR("Failed to unlock PLMN, err %d", err);
+	}
+#endif
+
+#if defined(CONFIG_LTE_LOCK_BANDS)
+	band_lock_set();
+#endif
+
+#if defined(CONFIG_LTE_LC_RAI_MODULE)
+	rai_set();
+#endif
+
+#if defined(CONFIG_LTE_LC_DNS_FALLBACK_MODULE)
+	dns_fallback_set();
+#endif
+}
+
+#if defined(CONFIG_UNITY)
+void lte_lc_on_modem_cfun(int mode, void *ctx)
+#else
+NRF_MODEM_LIB_ON_CFUN(lte_lc_cfun_hook, lte_lc_on_modem_cfun, NULL);
+
+static void lte_lc_on_modem_cfun(int mode, void *ctx)
+#endif /* CONFIG_UNITY */
+{
+	ARG_UNUSED(ctx);
+
+	/* Settings not stored into NVM are lost when modem is put into functional mode
+	 * LTE_LC_FUNC_MODE_POWER_OFF. Because of this some of the settings need to be applied
+	 * again.
+	 *
+	 * We want to avoid sending AT commands in the callback. However, when modem is
+	 * powered off, we are not expecting AT notifications that could cause an assertion or
+	 * a missing notification.
+	 */
+
+	if (mode != LTE_LC_FUNC_MODE_POWER_OFF) {
+		/* Nothing to do */
 		return;
 	}
+
+#if defined(CONFIG_LTE_LC_EDRX_MODULE)
+	edrx_set();
+#endif
+
+#if defined(CONFIG_LTE_LOCK_BANDS)
+	band_lock_set();
 #endif
 
 #if defined(CONFIG_LTE_LC_RAI_MODULE)
-	/* Configure Release Assistance Indication (RAI). */
 	rai_set();
 #endif
 

lib/lte_link_control/modules/edrx.c

@@ -133,30 +133,6 @@ static void edrx_ptw_send_work_fn(struct k_work *work_item)
 	}
 }
 
-#if defined(CONFIG_UNITY)
-void lte_lc_edrx_on_modem_cfun(int mode, void *ctx)
-#else
-NRF_MODEM_LIB_ON_CFUN(lte_lc_edrx_cfun_hook, lte_lc_edrx_on_modem_cfun, NULL);
-
-static void lte_lc_edrx_on_modem_cfun(int mode, void *ctx)
-#endif /* CONFIG_UNITY */
-{
-	ARG_UNUSED(ctx);
-
-	/* If eDRX is enabled and modem is powered off, subscription of unsolicited eDRX
-	 * notifications must be re-newed because modem forgets that information
-	 * although it stores eDRX value and PTW for both system modes.
-	 */
-	if (mode == LTE_LC_FUNC_MODE_POWER_OFF && requested_edrx_enable) {
-		lte_lc_edrx_current_values_clear();
-		/* We want to avoid sending AT commands in the callback. However,
-		 * when modem is powered off, we are not expecting AT notifications
-		 * that could cause an assertion or missing notification.
-		 */
-		edrx_request(requested_edrx_enable);
-	}
-}
-
 /* Get Paging Time Window multiplier for the LTE mode.
  * Multiplier is 1.28 s for LTE-M, and 2.56 s for NB-IoT, derived from
  * Figure 10.5.5.32/3GPP TS 24.008.
@@ -534,3 +510,11 @@ int edrx_param_set(enum lte_lc_lte_mode mode, const char *edrx)
 
 	return 0;
 }
+
+void edrx_set(void)
+{
+	if (requested_edrx_enable) {
+		lte_lc_edrx_current_values_clear();
+		edrx_request(requested_edrx_enable);
+	}
+}

lib/lte_link_control/modules/rai.c

@@ -100,7 +100,7 @@ static void at_handler_rai(const char *response)
 	event_handler_list_dispatch(&evt);
 }
 
-int rai_set(void)
+void rai_set(void)
 {
 	int err;
 
@@ -119,9 +119,6 @@ int rai_set(void)
 		}
 		if (err) {
 			LOG_ERR("Failed to configure RAI, err %d", err);
-			return -EFAULT;
 		}
 	}
-
-	return err;
 }