serial: uartps: Move the spinlock after the read of the tx empty

commit 107475685a upstream.

Currently we are doing a read of the status register.
Move the spinlock after that as the reads need not be spinlock
protected. This patch prevents relaxing the cpu with spinlock held.

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Cc: Pavel Machek <pavel@denx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/xilinx_uartps.c

@@ -686,8 +686,6 @@ static void cdns_uart_set_termios(struct uart_port *port,
 	unsigned int ctrl_reg, mode_reg, val;
 	int err;
 
-	spin_lock_irqsave(&port->lock, flags);
-
 	/* Wait for the transmit FIFO to empty before making changes */
 	if (!(readl(port->membase + CDNS_UART_CR) &
 				CDNS_UART_CR_TX_DIS)) {
@@ -699,6 +697,7 @@ static void cdns_uart_set_termios(struct uart_port *port,
 			return;
 		}
 	}
+	spin_lock_irqsave(&port->lock, flags);
 
 	/* Disable the TX and RX to set baud rate */
 	ctrl_reg = readl(port->membase + CDNS_UART_CR);