diff --git a/Documentation/serial/n_gsm.txt b/Documentation/serial/n_gsm.txt
index a5d91126a8f7..875361bb7cb4 100644
--- a/Documentation/serial/n_gsm.txt
+++ b/Documentation/serial/n_gsm.txt
@@ -77,6 +77,13 @@ for example, it's possible :
 
 6- first close all virtual ports before closing the physical port.
 
+Note that after closing the physical port the modem is still in multiplexing
+mode. This may prevent a successful re-opening of the port later. To avoid
+this situation either reset the modem if your hardware allows that or send
+a disconnect command frame manually before initializing the multiplexing mode
+for the second time. The byte sequence for the disconnect command frame is:
+0xf9, 0x03, 0xef, 0x03, 0xc3, 0x16, 0xf9.
+
 Additional Documentation
 ------------------------
 More practical details on the protocol and how it's supported by industrial
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 2667a205a5ab..363a8ca824ad 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2015,6 +2015,33 @@ static void gsm_error(struct gsm_mux *gsm,
 	gsm->io_error++;
 }
 
+static int gsm_disconnect(struct gsm_mux *gsm)
+{
+	struct gsm_dlci *dlci = gsm->dlci[0];
+	struct gsm_control *gc;
+
+	if (!dlci)
+		return 0;
+
+	/* In theory disconnecting DLCI 0 is sufficient but for some
+	   modems this is apparently not the case. */
+	gc = gsm_control_send(gsm, CMD_CLD, NULL, 0);
+	if (gc)
+		gsm_control_wait(gsm, gc);
+
+	del_timer_sync(&gsm->t2_timer);
+	/* Now we are sure T2 has stopped */
+
+	gsm_dlci_begin_close(dlci);
+	wait_event_interruptible(gsm->event,
+				dlci->state == DLCI_CLOSED);
+
+	if (signal_pending(current))
+		return -EINTR;
+
+	return 0;
+}
+
 /**
  *	gsm_cleanup_mux		-	generic GSM protocol cleanup
  *	@gsm: our mux
@@ -2029,7 +2056,6 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm)
 	int i;
 	struct gsm_dlci *dlci = gsm->dlci[0];
 	struct gsm_msg *txq, *ntxq;
-	struct gsm_control *gc;
 
 	gsm->dead = 1;
 
@@ -2045,21 +2071,11 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm)
 	if (i == MAX_MUX)
 		return;
 
-	/* In theory disconnecting DLCI 0 is sufficient but for some
-	   modems this is apparently not the case. */
-	if (dlci) {
-		gc = gsm_control_send(gsm, CMD_CLD, NULL, 0);
-		if (gc)
-			gsm_control_wait(gsm, gc);
-	}
 	del_timer_sync(&gsm->t2_timer);
 	/* Now we are sure T2 has stopped */
-	if (dlci) {
+	if (dlci)
 		dlci->dead = 1;
-		gsm_dlci_begin_close(dlci);
-		wait_event_interruptible(gsm->event,
-					dlci->state == DLCI_CLOSED);
-	}
+
 	/* Free up any link layer users */
 	mutex_lock(&gsm->mutex);
 	for (i = 0; i < NUM_DLCI; i++)
@@ -2519,12 +2535,12 @@ static int gsmld_config(struct tty_struct *tty, struct gsm_mux *gsm,
 	 */
 
 	if (need_close || need_restart) {
-		gsm_dlci_begin_close(gsm->dlci[0]);
-		/* This will timeout if the link is down due to N2 expiring */
-		wait_event_interruptible(gsm->event,
-				gsm->dlci[0]->state == DLCI_CLOSED);
-		if (signal_pending(current))
-			return -EINTR;
+		int ret;
+
+		ret = gsm_disconnect(gsm);
+
+		if (ret)
+			return ret;
 	}
 	if (need_restart)
 		gsm_cleanup_mux(gsm);