diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index fc166cc2c856d..f2cef5f7ae5ae 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -325,6 +325,42 @@ static void stm32_usart_tx_interrupt_disable(struct uart_port *port)
 		stm32_usart_clr_bits(port, ofs->cr1, USART_CR1_TXEIE);
 }
 
+static void stm32_usart_rs485_rts_enable(struct uart_port *port)
+{
+	struct stm32_port *stm32_port = to_stm32_port(port);
+	struct serial_rs485 *rs485conf = &port->rs485;
+
+	if (stm32_port->hw_flow_control ||
+	    !(rs485conf->flags & SER_RS485_ENABLED))
+		return;
+
+	if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {
+		mctrl_gpio_set(stm32_port->gpios,
+			       stm32_port->port.mctrl | TIOCM_RTS);
+	} else {
+		mctrl_gpio_set(stm32_port->gpios,
+			       stm32_port->port.mctrl & ~TIOCM_RTS);
+	}
+}
+
+static void stm32_usart_rs485_rts_disable(struct uart_port *port)
+{
+	struct stm32_port *stm32_port = to_stm32_port(port);
+	struct serial_rs485 *rs485conf = &port->rs485;
+
+	if (stm32_port->hw_flow_control ||
+	    !(rs485conf->flags & SER_RS485_ENABLED))
+		return;
+
+	if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {
+		mctrl_gpio_set(stm32_port->gpios,
+			       stm32_port->port.mctrl & ~TIOCM_RTS);
+	} else {
+		mctrl_gpio_set(stm32_port->gpios,
+			       stm32_port->port.mctrl | TIOCM_RTS);
+	}
+}
+
 static void stm32_usart_transmit_chars_pio(struct uart_port *port)
 {
 	struct stm32_port *stm32_port = to_stm32_port(port);
@@ -566,41 +602,20 @@ static void stm32_usart_disable_ms(struct uart_port *port)
 /* Transmit stop */
 static void stm32_usart_stop_tx(struct uart_port *port)
 {
-	struct stm32_port *stm32_port = to_stm32_port(port);
-	struct serial_rs485 *rs485conf = &port->rs485;
-
 	stm32_usart_tx_interrupt_disable(port);
 
-	if (rs485conf->flags & SER_RS485_ENABLED) {
-		if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {
-			mctrl_gpio_set(stm32_port->gpios,
-					stm32_port->port.mctrl & ~TIOCM_RTS);
-		} else {
-			mctrl_gpio_set(stm32_port->gpios,
-					stm32_port->port.mctrl | TIOCM_RTS);
-		}
-	}
+	stm32_usart_rs485_rts_disable(port);
 }
 
 /* There are probably characters waiting to be transmitted. */
 static void stm32_usart_start_tx(struct uart_port *port)
 {
-	struct stm32_port *stm32_port = to_stm32_port(port);
-	struct serial_rs485 *rs485conf = &port->rs485;
 	struct circ_buf *xmit = &port->state->xmit;
 
 	if (uart_circ_empty(xmit) && !port->x_char)
 		return;
 
-	if (rs485conf->flags & SER_RS485_ENABLED) {
-		if (rs485conf->flags & SER_RS485_RTS_ON_SEND) {
-			mctrl_gpio_set(stm32_port->gpios,
-					stm32_port->port.mctrl | TIOCM_RTS);
-		} else {
-			mctrl_gpio_set(stm32_port->gpios,
-					stm32_port->port.mctrl & ~TIOCM_RTS);
-		}
-	}
+	stm32_usart_rs485_rts_enable(port);
 
 	stm32_usart_transmit_chars(port);
 }