serial: uartps: Fix uartps_major handling

There are two parts which should be fixed. The first one is to assigned
uartps_major at the end of probe() to avoid complicated logic when
something fails.
The second part is initialized uartps_major number to 0 when last device is
removed. This will ensure that on next probe driver will ask for new
dynamic major number.

Fixes: ab26266 ("serial: uartps: Use the same dynamic major number for all ports")
Reported-by: Paul Thomas <[email protected]>
Cc: stable <[email protected]>
Signed-off-by: Michal Simek <[email protected]>
Link: https://lore.kernel.org/r/d2652cda992833315c4f96f06953eb547f928918.1570194248.git.michal.simek@xilinx.com
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Michal Simek

drivers/tty/serial/xilinx_uartps.c

@@ -1550,7 +1550,6 @@ static int cdns_uart_probe(struct platform_device *pdev)
 		goto err_out_id;
 	}
 
-	uartps_major = cdns_uart_uart_driver->tty_driver->major;
 	cdns_uart_data->cdns_uart_driver = cdns_uart_uart_driver;
 
 	/*
@@ -1680,6 +1679,7 @@ static int cdns_uart_probe(struct platform_device *pdev)
 		console_port = NULL;
 #endif
 
+	uartps_major = cdns_uart_uart_driver->tty_driver->major;
 	cdns_uart_data->cts_override = of_property_read_bool(pdev->dev.of_node,
 							     "cts-override");
 	return 0;
@@ -1741,6 +1741,12 @@ static int cdns_uart_remove(struct platform_device *pdev)
 		console_port = NULL;
 #endif
 
+	/* If this is last instance major number should be initialized */
+	mutex_lock(&bitmap_lock);
+	if (bitmap_empty(bitmap, MAX_UART_INSTANCES))
+		uartps_major = 0;
+	mutex_unlock(&bitmap_lock);
+
 	uart_unregister_driver(cdns_uart_data->cdns_uart_driver);
 	return rc;
 }