drivers: PL011: avoid potential unregister_driver call

Although we care about not unregistering the driver if there are
still ports connected during the .remove callback, we do miss this
check in the pl011_probe function. So if the current port allocation
fails, but there are other ports already registered, we will kill
those.
So factor out the port removal into a separate function and use that
in the probe function, too.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
Tested-by: Naresh Bhat <nbhat@cavium.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/amba-pl011.c

@@ -2135,6 +2135,23 @@ static int pl011_probe_dt_alias(int index, struct device *dev)
 	return ret;
 }
 
+/* unregisters the driver also if no more ports are left */
+static void pl011_unregister_port(struct uart_amba_port *uap)
+{
+	int i;
+	bool busy = false;
+
+	for (i = 0; i < ARRAY_SIZE(amba_ports); i++) {
+		if (amba_ports[i] == uap)
+			amba_ports[i] = NULL;
+		else if (amba_ports[i])
+			busy = true;
+	}
+	pl011_dma_remove(uap);
+	if (!busy)
+		uart_unregister_driver(&amba_reg);
+}
+
 static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
 {
 	struct uart_amba_port *uap;
@@ -2200,10 +2217,8 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
 	}
 
 	ret = uart_add_one_port(&amba_reg, &uap->port);
-	if (ret) {
-		amba_ports[i] = NULL;
-		uart_unregister_driver(&amba_reg);
-	}
+	if (ret)
+		pl011_unregister_port(uap);
 
 	return ret;
 }
@@ -2211,20 +2226,9 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
 static int pl011_remove(struct amba_device *dev)
 {
 	struct uart_amba_port *uap = amba_get_drvdata(dev);
-	bool busy = false;
-	int i;
 
 	uart_remove_one_port(&amba_reg, &uap->port);
-
-	for (i = 0; i < ARRAY_SIZE(amba_ports); i++)
-		if (amba_ports[i] == uap)
-			amba_ports[i] = NULL;
-		else if (amba_ports[i])
-			busy = true;
-
-	pl011_dma_remove(uap);
-	if (!busy)
-		uart_unregister_driver(&amba_reg);
+	pl011_unregister_port(uap);
 	return 0;
 }