serial: imx: set_termios(): clarify RTS/CTS bits calculation

Avoid repeating the same code for rs485 twice.

Make it obvious we clear CRTSCTS bit in termios->c_cflag whenever
sport->have_rtscts is false.

Make it obvious we clear UCR2_IRTS whenever CRTSCTS is set.
Reviewed-by: NSascha Hauer <s.hauer@pengutronix.de>
Tested-by: NSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NSergey Organov <sorganov@gmail.com>
Link: https://lore.kernel.org/r/1561558293-7683-4-git-send-email-sorganov@gmail.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -1566,35 +1566,25 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
 	if ((termios->c_cflag & CSIZE) == CS8)
 		ucr2 |= UCR2_WS;
 
-	if (termios->c_cflag & CRTSCTS) {
-		if (sport->have_rtscts) {
-			ucr2 &= ~UCR2_IRTS;
-
-			if (port->rs485.flags & SER_RS485_ENABLED) {
-				/*
-				 * RTS is mandatory for rs485 operation, so keep
-				 * it under manual control and keep transmitter
-				 * disabled.
-				 */
-				if (port->rs485.flags &
-				    SER_RS485_RTS_AFTER_SEND)
-					imx_uart_rts_active(sport, &ucr2);
-				else
-					imx_uart_rts_inactive(sport, &ucr2);
-			} else {
-				imx_uart_rts_auto(sport, &ucr2);
-			}
-		} else {
-			termios->c_cflag &= ~CRTSCTS;
-		}
-	} else if (port->rs485.flags & SER_RS485_ENABLED) {
-		/* disable transmitter */
+	if (!sport->have_rtscts)
+		termios->c_cflag &= ~CRTSCTS;
+
+	if (port->rs485.flags & SER_RS485_ENABLED) {
+		/*
+		 * RTS is mandatory for rs485 operation, so keep
+		 * it under manual control and keep transmitter
+		 * disabled.
+		 */
 		if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
 			imx_uart_rts_active(sport, &ucr2);
 		else
 			imx_uart_rts_inactive(sport, &ucr2);
-	}
 
+	} else if (termios->c_cflag & CRTSCTS)
+		imx_uart_rts_auto(sport, &ucr2);
+
+	if (termios->c_cflag & CRTSCTS)
+		ucr2 &= ~UCR2_IRTS;
 
 	if (termios->c_cflag & CSTOPB)
 		ucr2 |= UCR2_STPB;