diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 6d0ce64163e5..ea41f2626458 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -1868,6 +1868,7 @@ static int serial8250_startup(struct uart_port *port)
 	}
 
 	if (is_real_interrupt(up->port.irq)) {
+		unsigned char iir1;
 		/*
 		 * Test for UARTs that do not reassert THRE when the
 		 * transmitter is idle and the interrupt has already
@@ -1881,7 +1882,7 @@ static int serial8250_startup(struct uart_port *port)
 		wait_for_xmitr(up, UART_LSR_THRE);
 		serial_out_sync(up, UART_IER, UART_IER_THRI);
 		udelay(1); /* allow THRE to set */
-		serial_in(up, UART_IIR);
+		iir1 = serial_in(up, UART_IIR);
 		serial_out(up, UART_IER, 0);
 		serial_out_sync(up, UART_IER, UART_IER_THRI);
 		udelay(1); /* allow a working UART time to re-assert THRE */
@@ -1894,7 +1895,7 @@ static int serial8250_startup(struct uart_port *port)
 		 * If the interrupt is not reasserted, setup a timer to
 		 * kick the UART on a regular basis.
 		 */
-		if (iir & UART_IIR_NO_INT) {
+		if (!(iir1 & UART_IIR_NO_INT) && (iir & UART_IIR_NO_INT)) {
 			pr_debug("ttyS%d - using backup timer\n", port->line);
 			up->timer.function = serial8250_backup_timeout;
 			up->timer.data = (unsigned long)up;