driver: modem: gsm_ppp: Wait for cell registration before attaching

Author: ycsin

drivers/modem/Kconfig.gsm

@@ -62,6 +62,14 @@ config GSM_PPP_AUTOSTART
 	  modem connects to network. See contents of "drivers/gsm_ppp.h"
 	  to get an idea of the API.
 
+config MODEM_GSM_REGISTER_TIMEOUT
+	int "Timeout for registering to cell tower"
+	default 60
+	help
+	  Before attaching to packet service, the cell tower registration is
+	  checked using AT+CREG. This setting dictates how much time in seconds
+	  we give the modem before giving up.
+
 config MODEM_GSM_ATTACH_TIMEOUT
 	int "Timeout for attaching to packet service"
 	default 30

drivers/modem/gsm_ppp.c

@@ -35,6 +35,7 @@ LOG_MODULE_REGISTER(modem_gsm, CONFIG_MODEM_LOG_LEVEL);
 #define GSM_RX_STACK_SIZE               CONFIG_MODEM_GSM_RX_STACK_SIZE
 #define GSM_RECV_MAX_BUF                30
 #define GSM_RECV_BUF_SIZE               128
+#define GSM_REGISTER_DELAY_MSEC         1000
 #define GSM_ATTACH_RETRY_DELAY_MSEC     1000
 
 #define GSM_RSSI_RETRY_DELAY_MSEC       2000
@@ -69,6 +70,16 @@ static const char TIME_STRING_FORMAT[] = "\"yy/MM/dd,hh:mm:ss?zz\"";
 #define SIZE_OF_NUL 1
 #endif
 
+/* Modem network registration state */
+enum network_state {
+	GSM_NOT_REGISTERED = 0,
+	GSM_HOME_NETWORK,
+	GSM_SEARCHING,
+	GSM_REGISTRATION_DENIED,
+	GSM_UNKNOWN,
+	GSM_ROAMING,
+};
+
 /* During the modem setup, we first create DLCI control channel and then
  * PPP and AT channels. Currently the modem does not create possible GNSS
  * channel.
@@ -95,6 +106,9 @@ static struct gsm_modem {
 	uint8_t *ppp_recv_buf;
 	size_t ppp_recv_buf_len;
 
+	enum network_state net_state;
+	int register_retries;
+
 	enum setup_state state;
 	const struct device *ppp_dev;
 	const struct device *at_dev;
@@ -464,8 +478,8 @@ static const struct setup_cmd setup_cmds[] = {
 	SETUP_CMD("AT+CGSN", "", on_cmd_atcmdinfo_imei, 0U, ""),
 #endif
 
-	/* disable unsolicited network registration codes */
-	SETUP_CMD_NOHANDLE("AT+CREG=0"),
+	/* enable network registration report */
+	SETUP_CMD_NOHANDLE("AT+CREG=1"),
 
 	/* create PDP context */
 	SETUP_CMD_NOHANDLE("AT+CGDCONT=1,\"IP\",\"" CONFIG_MODEM_GSM_APN "\""),
@@ -589,6 +603,36 @@ int32_t gsm_ppp_get_local_time(const struct device *dev, struct tm *tm, int32_t
 }
 #endif /* CONFIG_NEWLIB_LIBC */
 
+MODEM_CMD_DEFINE(on_cmd_net_reg_sts)
+{
+	enum network_state net_sts = (enum network_state)atoi(argv[1]);
+
+	switch (net_sts) {
+	case GSM_NOT_REGISTERED:
+		LOG_INF("Network not registered.");
+		break;
+	case GSM_HOME_NETWORK:
+		LOG_INF("Network registered, home network.");
+		break;
+	case GSM_SEARCHING:
+		LOG_INF("Searching for network...");
+		break;
+	case GSM_REGISTRATION_DENIED:
+		LOG_INF("Network registration denied.");
+		break;
+	case GSM_UNKNOWN:
+		LOG_INF("Network unknown.");
+		break;
+	case GSM_ROAMING:
+		LOG_INF("Network registered, roaming.");
+		break;
+	}
+
+	gsm.net_state = net_sts;
+
+	return 0;
+}
+
 MODEM_CMD_DEFINE(on_cmd_atcmdinfo_attached)
 {
 	int error = -EAGAIN;
@@ -609,6 +653,9 @@ MODEM_CMD_DEFINE(on_cmd_atcmdinfo_attached)
 static const struct modem_cmd read_cops_cmd =
 	MODEM_CMD("+COPS", on_cmd_atcmdinfo_cops, 3U, ",");
 
+static const struct modem_cmd check_net_reg_cmd =
+	MODEM_CMD("+CREG: ", on_cmd_net_reg_sts, 2U, ",");
+
 static const struct modem_cmd check_attached_cmd =
 	MODEM_CMD("+CGATT:", on_cmd_atcmdinfo_attached, 1U, ",");
 
@@ -733,6 +780,11 @@ static void gsm_finalize_connection(struct gsm_modem *gsm)
 		goto attached;
 	}
 
+	/* If modem is searching for network, we should skip the setup step */
+	if ((gsm->net_state == GSM_SEARCHING) && gsm->register_retries) {
+		goto registering;
+	}
+
 	/* If attach check failed, we should not redo every setup step */
 	if (gsm->attach_retries) {
 		goto attaching;
@@ -788,6 +840,49 @@ static void gsm_finalize_connection(struct gsm_modem *gsm)
 		return;
 	}
 
+registering:
+	/* Wait for cell tower registration */
+	ret = modem_cmd_send_nolock(&gsm->context.iface,
+				    &gsm->context.cmd_handler,
+				    &check_net_reg_cmd, 1,
+				    "AT+CREG?",
+				    &gsm->sem_response,
+				    GSM_CMD_SETUP_TIMEOUT);
+	if ((ret < 0) || ((gsm->net_state != GSM_ROAMING) &&
+			 (gsm->net_state != GSM_HOME_NETWORK))) {
+		if (!gsm->register_retries) {
+			gsm->register_retries = CONFIG_MODEM_GSM_REGISTER_TIMEOUT *
+				MSEC_PER_SEC / GSM_REGISTER_DELAY_MSEC;
+		} else {
+			gsm->register_retries--;
+
+			/* Reset RF if timed out */
+			if (!gsm->register_retries) {
+				(void)modem_cmd_send_nolock(
+					&gsm->context.iface,
+					&gsm->context.cmd_handler,
+					&response_cmds[0],
+					ARRAY_SIZE(response_cmds),
+					"AT+CFUN=0", &gsm->sem_response,
+					GSM_CMD_AT_TIMEOUT);
+
+				k_sleep(K_SECONDS(1));
+
+				(void)modem_cmd_send_nolock(
+					&gsm->context.iface,
+					&gsm->context.cmd_handler,
+					&response_cmds[0],
+					ARRAY_SIZE(response_cmds),
+					"AT+CFUN=1", &gsm->sem_response,
+					GSM_CMD_AT_TIMEOUT);
+			}
+		}
+
+		(void)k_work_reschedule(&gsm->gsm_configure_work,
+					K_MSEC(GSM_REGISTER_DELAY_MSEC));
+		return;
+	}
+
 attaching:
 	/* Don't initialize PPP until we're attached to packet service */
 	ret = modem_cmd_send_nolock(&gsm->context.iface,
@@ -1229,6 +1324,8 @@ static int gsm_init(const struct device *dev)
 			gsm, NULL, NULL, K_PRIO_COOP(7), 0, K_NO_WAIT);
 	k_thread_name_set(&gsm_rx_thread, "gsm_rx");
 
+	gsm->net_state = GSM_NOT_REGISTERED;
+
 	gsm->iface = ppp_net_if();
 	if (!gsm->iface) {
 		LOG_ERR("Couldn't find ppp net_if!");