serial: 8250: factor out serial8250_{set,clear}_THRI() helpers

Factor out similar code pieces that set or clear UART_IER_THRI bit to
serial8250_{set,clear}_THRI() helpers.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250.h

@@ -128,6 +128,24 @@ static inline void serial_dl_write(struct uart_8250_port *up, int value)
 	up->dl_write(up, value);
 }
 
+static inline bool serial8250_set_THRI(struct uart_8250_port *up)
+{
+	if (up->ier & UART_IER_THRI)
+		return false;
+	up->ier |= UART_IER_THRI;
+	serial_out(up, UART_IER, up->ier);
+	return true;
+}
+
+static inline bool serial8250_clear_THRI(struct uart_8250_port *up)
+{
+	if (!(up->ier & UART_IER_THRI))
+		return false;
+	up->ier &= ~UART_IER_THRI;
+	serial_out(up, UART_IER, up->ier);
+	return true;
+}
+
 struct uart_8250_port *serial8250_get_port(int line);
 
 void serial8250_rpm_get(struct uart_8250_port *p);

drivers/tty/serial/8250/8250_dma.c

@@ -34,10 +34,8 @@ static void __dma_tx_complete(void *param)
 		uart_write_wakeup(&p->port);
 
 	ret = serial8250_tx_dma(p);
-	if (ret) {
-		p->ier |= UART_IER_THRI;
-		serial_port_out(&p->port, UART_IER, p->ier);
-	}
+	if (ret)
+		serial8250_set_THRI(p);
 
 	spin_unlock_irqrestore(&p->port.lock, flags);
 }
@@ -100,10 +98,7 @@ int serial8250_tx_dma(struct uart_8250_port *p)
 	dma_async_issue_pending(dma->txchan);
 	if (dma->tx_err) {
 		dma->tx_err = 0;
-		if (p->ier & UART_IER_THRI) {
-			p->ier &= ~UART_IER_THRI;
-			serial_out(p, UART_IER, p->ier);
-		}
+		serial8250_clear_THRI(p);
 	}
 	return 0;
 err:

drivers/tty/serial/8250/8250_omap.c

@@ -923,15 +923,13 @@ static void omap_8250_dma_tx_complete(void *param)
 		ret = omap_8250_tx_dma(p);
 		if (ret)
 			en_thri = true;
-
 	} else if (p->capabilities & UART_CAP_RPM) {
 		en_thri = true;
 	}
 
 	if (en_thri) {
 		dma->tx_err = 1;
-		p->ier |= UART_IER_THRI;
-		serial_port_out(&p->port, UART_IER, p->ier);
+		serial8250_set_THRI(p);
 	}
 
 	spin_unlock_irqrestore(&p->port.lock, flags);
@@ -959,10 +957,7 @@ static int omap_8250_tx_dma(struct uart_8250_port *p)
 			ret = -EBUSY;
 			goto err;
 		}
-		if (p->ier & UART_IER_THRI) {
-			p->ier &= ~UART_IER_THRI;
-			serial_out(p, UART_IER, p->ier);
-		}
+		serial8250_clear_THRI(p);
 		return 0;
 	}
 
@@ -1020,10 +1015,7 @@ static int omap_8250_tx_dma(struct uart_8250_port *p)
 	if (dma->tx_err)
 		dma->tx_err = 0;
 
-	if (p->ier & UART_IER_THRI) {
-		p->ier &= ~UART_IER_THRI;
-		serial_out(p, UART_IER, p->ier);
-	}
+	serial8250_clear_THRI(p);
 	if (skip_byte)
 		serial_out(p, UART_TX, xmit->buf[xmit->tail]);
 	return 0;

drivers/tty/serial/8250/8250_port.c

@@ -1502,11 +1502,8 @@ static void __stop_tx_rs485(struct uart_8250_port *p)
 
 static inline void __do_stop_tx(struct uart_8250_port *p)
 {
-	if (p->ier & UART_IER_THRI) {
-		p->ier &= ~UART_IER_THRI;
-		serial_out(p, UART_IER, p->ier);
+	if (serial8250_clear_THRI(p))
 		serial8250_rpm_put_tx(p);
-	}
 }
 
 static inline void __stop_tx(struct uart_8250_port *p)
@@ -1555,10 +1552,7 @@ static inline void __start_tx(struct uart_port *port)
 	if (up->dma && !up->dma->tx_dma(up))
 		return;
 
-	if (!(up->ier & UART_IER_THRI)) {
-		up->ier |= UART_IER_THRI;
-		serial_port_out(port, UART_IER, up->ier);
-
+	if (serial8250_set_THRI(up)) {
 		if (up->bugs & UART_BUG_TXEN) {
 			unsigned char lsr;