diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 4b40a5b449eeec048c0fc71b253f09c84dc32eb8..ebd33c0232e6390e3e2301ae7850e656c83943ae 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1727,10 +1727,26 @@ static int pl011_allocate_irq(struct uart_amba_port *uap)
  */
 static void pl011_enable_interrupts(struct uart_amba_port *uap)
 {
+	unsigned int i;
+
 	spin_lock_irq(&uap->port.lock);
 
 	/* Clear out any spuriously appearing RX interrupts */
 	pl011_write(UART011_RTIS | UART011_RXIS, uap, REG_ICR);
+
+	/*
+	 * RXIS is asserted only when the RX FIFO transitions from below
+	 * to above the trigger threshold.  If the RX FIFO is already
+	 * full to the threshold this can't happen and RXIS will now be
+	 * stuck off.  Drain the RX FIFO explicitly to fix this:
+	 */
+	for (i = 0; i < uap->fifosize * 2; ++i) {
+		if (pl011_read(uap, REG_FR) & UART01x_FR_RXFE)
+			break;
+
+		pl011_read(uap, REG_DR);
+	}
+
 	uap->im = UART011_RTIM;
 	if (!pl011_dma_rx_running(uap))
 		uap->im |= UART011_RXIM;