diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 69b7a3e1e418e200944b0b0429b6341d71ecff26..04212c823a91d5a343327292d8ffd95be1465473 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -248,6 +248,13 @@ struct pl011_dmatx_data {
 	bool			queued;
 };
 
+enum pl011_rs485_tx_state {
+	OFF,
+	WAIT_AFTER_RTS,
+	SEND,
+	WAIT_AFTER_SEND,
+};
+
 /*
  * We wrap our port structure around the generic uart_port.
  */
@@ -261,8 +268,10 @@ struct uart_amba_port {
 	unsigned int		fifosize;	/* vendor-specific */
 	unsigned int		fixed_baud;	/* vendor-set fixed baud rate */
 	char			type[12];
-	bool			rs485_tx_started;
-	unsigned int		rs485_tx_drain_interval; /* usecs */
+	ktime_t			rs485_tx_drain_interval; /* nano */
+	enum pl011_rs485_tx_state	rs485_tx_state;
+	struct hrtimer		trigger_start_tx;
+	struct hrtimer		trigger_stop_tx;
 #ifdef CONFIG_DMA_ENGINE
 	/* DMA stuff */
 	unsigned int		dmacr;		/* dma control reg */
@@ -1260,30 +1269,31 @@ static inline bool pl011_dma_rx_running(struct uart_amba_port *uap)
 
 static void pl011_rs485_tx_stop(struct uart_amba_port *uap)
 {
-	/*
-	 * To be on the safe side only time out after twice as many iterations
-	 * as fifo size.
-	 */
-	const int MAX_TX_DRAIN_ITERS = uap->port.fifosize * 2;
 	struct uart_port *port = &uap->port;
-	int i = 0;
 	u32 cr;
 
-	/* Wait until hardware tx queue is empty */
-	while (!pl011_tx_empty(port)) {
-		if (i > MAX_TX_DRAIN_ITERS) {
-			dev_warn(port->dev,
-				 "timeout while draining hardware tx queue\n");
-			break;
-		}
+	if (uap->rs485_tx_state == SEND)
+		uap->rs485_tx_state = WAIT_AFTER_SEND;
 
-		udelay(uap->rs485_tx_drain_interval);
-		i++;
+	if (uap->rs485_tx_state == WAIT_AFTER_SEND) {
+		/* Schedule hrtimer if tx queue not empty */
+		if (!pl011_tx_empty(port)) {
+			hrtimer_start(&uap->trigger_stop_tx,
+				      uap->rs485_tx_drain_interval,
+				      HRTIMER_MODE_REL);
+			return;
+		}
+		if (port->rs485.delay_rts_after_send > 0) {
+			hrtimer_start(&uap->trigger_stop_tx,
+				      ms_to_ktime(port->rs485.delay_rts_after_send),
+				      HRTIMER_MODE_REL);
+			return;
+		}
+		/* Continue without any delay */
+	} else if (uap->rs485_tx_state == WAIT_AFTER_RTS) {
+		hrtimer_try_to_cancel(&uap->trigger_start_tx);
 	}
 
-	if (port->rs485.delay_rts_after_send)
-		mdelay(port->rs485.delay_rts_after_send);
-
 	cr = pl011_read(uap, REG_CR);
 
 	if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
@@ -1296,7 +1306,7 @@ static void pl011_rs485_tx_stop(struct uart_amba_port *uap)
 	cr |= UART011_CR_RXE;
 	pl011_write(cr, uap, REG_CR);
 
-	uap->rs485_tx_started = false;
+	uap->rs485_tx_state = OFF;
 }
 
 static void pl011_stop_tx(struct uart_port *port)
@@ -1304,11 +1314,18 @@ static void pl011_stop_tx(struct uart_port *port)
 	struct uart_amba_port *uap =
 	    container_of(port, struct uart_amba_port, port);
 
+	if (port->rs485.flags & SER_RS485_ENABLED &&
+	    uap->rs485_tx_state == WAIT_AFTER_RTS) {
+		pl011_rs485_tx_stop(uap);
+		return;
+	}
+
 	uap->im &= ~UART011_TXIM;
 	pl011_write(uap->im, uap, REG_IMSC);
 	pl011_dma_tx_stop(uap);
 
-	if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started)
+	if (port->rs485.flags & SER_RS485_ENABLED &&
+	    uap->rs485_tx_state != OFF)
 		pl011_rs485_tx_stop(uap);
 }
 
@@ -1328,10 +1345,19 @@ static void pl011_rs485_tx_start(struct uart_amba_port *uap)
 	struct uart_port *port = &uap->port;
 	u32 cr;
 
+	if (uap->rs485_tx_state == WAIT_AFTER_RTS) {
+		uap->rs485_tx_state = SEND;
+		return;
+	}
+	if (uap->rs485_tx_state == WAIT_AFTER_SEND) {
+		hrtimer_try_to_cancel(&uap->trigger_stop_tx);
+		uap->rs485_tx_state = SEND;
+		return;
+	}
+	/* uap->rs485_tx_state == OFF */
 	/* Enable transmitter */
 	cr = pl011_read(uap, REG_CR);
 	cr |= UART011_CR_TXE;
-
 	/* Disable receiver if half-duplex */
 	if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))
 		cr &= ~UART011_CR_RXE;
@@ -1343,10 +1369,14 @@ static void pl011_rs485_tx_start(struct uart_amba_port *uap)
 
 	pl011_write(cr, uap, REG_CR);
 
-	if (port->rs485.delay_rts_before_send)
-		mdelay(port->rs485.delay_rts_before_send);
-
-	uap->rs485_tx_started = true;
+	if (port->rs485.delay_rts_before_send > 0) {
+		uap->rs485_tx_state = WAIT_AFTER_RTS;
+		hrtimer_start(&uap->trigger_start_tx,
+			      ms_to_ktime(port->rs485.delay_rts_before_send),
+			      HRTIMER_MODE_REL);
+	} else {
+		uap->rs485_tx_state = SEND;
+	}
 }
 
 static void pl011_start_tx(struct uart_port *port)
@@ -1355,13 +1385,44 @@ static void pl011_start_tx(struct uart_port *port)
 	    container_of(port, struct uart_amba_port, port);
 
 	if ((uap->port.rs485.flags & SER_RS485_ENABLED) &&
-	    !uap->rs485_tx_started)
+	    uap->rs485_tx_state != SEND) {
 		pl011_rs485_tx_start(uap);
+		if (uap->rs485_tx_state == WAIT_AFTER_RTS)
+			return;
+	}
 
 	if (!pl011_dma_tx_start(uap))
 		pl011_start_tx_pio(uap);
 }
 
+static enum hrtimer_restart pl011_trigger_start_tx(struct hrtimer *t)
+{
+	struct uart_amba_port *uap =
+	    container_of(t, struct uart_amba_port, trigger_start_tx);
+	unsigned long flags;
+
+	uart_port_lock_irqsave(&uap->port, &flags);
+	if (uap->rs485_tx_state == WAIT_AFTER_RTS)
+		pl011_start_tx(&uap->port);
+	uart_port_unlock_irqrestore(&uap->port, flags);
+
+	return HRTIMER_NORESTART;
+}
+
+static enum hrtimer_restart pl011_trigger_stop_tx(struct hrtimer *t)
+{
+	struct uart_amba_port *uap =
+	    container_of(t, struct uart_amba_port, trigger_stop_tx);
+	unsigned long flags;
+
+	uart_port_lock_irqsave(&uap->port, &flags);
+	if (uap->rs485_tx_state == WAIT_AFTER_SEND)
+		pl011_rs485_tx_stop(uap);
+	uart_port_unlock_irqrestore(&uap->port, flags);
+
+	return HRTIMER_NORESTART;
+}
+
 static void pl011_stop_rx(struct uart_port *port)
 {
 	struct uart_amba_port *uap =
@@ -1953,7 +2014,7 @@ static void pl011_shutdown(struct uart_port *port)
 
 	pl011_dma_shutdown(uap);
 
-	if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started)
+	if ((port->rs485.flags & SER_RS485_ENABLED && uap->rs485_tx_state != OFF))
 		pl011_rs485_tx_stop(uap);
 
 	free_irq(uap->port.irq, uap);
@@ -2098,7 +2159,7 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios,
 	 * with the given baud rate. We use this as the poll interval when we
 	 * wait for the tx queue to empty.
 	 */
-	uap->rs485_tx_drain_interval = DIV_ROUND_UP(bits * 1000 * 1000, baud);
+	uap->rs485_tx_drain_interval = ns_to_ktime(DIV_ROUND_UP(bits * NSEC_PER_SEC, baud));
 
 	pl011_setup_status_masks(port, termios);
 
@@ -2807,6 +2868,11 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
 		}
 	}
 
+	hrtimer_init(&uap->trigger_start_tx, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	hrtimer_init(&uap->trigger_stop_tx, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	uap->trigger_start_tx.function = pl011_trigger_start_tx;
+	uap->trigger_stop_tx.function = pl011_trigger_stop_tx;
+
 	ret = pl011_setup_port(&dev->dev, uap, &dev->res, portnr);
 	if (ret)
 		return ret;
