app: Fixes for PPP restart logic with Zephyr host

When running on DLC1, we still need to detach from the pipe
if PPP stops.

Also, drop the check from AT#XCMUX=2 when it runs on the recovery.
We don't keep track of the "current" channel anymore.

Signed-off-by: Seppo Takalo <seppo.takalo@nordicsemi.no>

Author: SeppoTakalo

app/src/sm_cmux.c

@@ -220,6 +220,7 @@ static int do_at_and_ppp_channel_switch(int new_at_channel)
 		LOG_DBG("Switching CMUX PPP channel to %d", !cmux.at_channel + 1);
 		sm_at_host_release(sm_at_host_get_ctx_from(ppp_pipe));
 		sm_ppp_attach(ppp_pipe);
+		sm_ppp_detach_after_disconnect();
 	}
 	return -SILENT_AT_COMMAND_RET;
 }
@@ -293,17 +294,13 @@ static int handle_at_xcmux(enum at_parser_cmd_type cmd_type, struct at_parser *p
 		const unsigned int at_channel = DLCI_TO_INDEX(at_dlci);
 
 		if (IS_ENABLED(CONFIG_SM_PPP)) {
-			if (!sm_ppp_is_stopped() && at_channel != cmux.at_channel) {
+			if (ppp_is_running() && at_channel != cmux.at_channel) {
 				/* The AT channel cannot be changed when PPP has a channel reserved.
 				 */
 				return -ENOTSUP;
 			}
 		}
 		if (sm_cmux_is_started()) {
-			if (at_channel == cmux.at_channel) {
-				/* No channel change requested and CMUX is already running */
-				return -EALREADY;
-			}
 			return do_at_and_ppp_channel_switch(at_channel);
 		}
 		cmux.at_channel = at_channel;

app/src/sm_ppp.c

@@ -241,7 +241,7 @@ static void delegate_ppp_event(enum ppp_action action, enum ppp_reason reason)
 	}
 }
 
-static bool ppp_is_running(void)
+bool ppp_is_running(void)
 {
 	return (ppp_state == PPP_STATE_RUNNING);
 }
@@ -719,7 +719,7 @@ static int handle_at_ppp(enum at_parser_cmd_type cmd_type, struct at_parser *par
 	} else {
 		rsp_send_ok();
 		sm_ppp_set_auto_start(false);
-		delegate_ppp_event(PPP_STOP, PPP_REASON_CMD);
+		sm_ppp_detach();
 	}
 	return -SILENT_AT_COMMAND_RET;
 }
@@ -943,4 +943,13 @@ void sm_ppp_detach(void)
 {
 	ppp_pipe = NULL;
 	sm_ppp_keep_pipe_attached = false;
+	sm_ppp_auto_start = false;
+	if (!sm_ppp_is_stopped()) {
+		delegate_ppp_event(PPP_STOP, PPP_REASON_CMD);
+	}
+}
+
+void sm_ppp_detach_after_disconnect(void)
+{
+	sm_ppp_keep_pipe_attached = false;
 }

app/src/sm_ppp.h

@@ -13,6 +13,7 @@
 extern bool sm_fwd_cgev_notifs;
 
 bool sm_ppp_is_stopped(void);
+bool ppp_is_running(void);
 void sm_ppp_set_auto_start(bool enable);
 
 /** Set the permanent modem pipe for PPP communication */
@@ -21,4 +22,7 @@ void sm_ppp_attach(struct modem_pipe *pipe);
 /** Detach the modem pipe from PPP communication */
 void sm_ppp_detach(void);
 
+/** Ask to detach from PIPE after disconnecting PPP */
+void sm_ppp_detach_after_disconnect(void);
+
 #endif