diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index 5cc967fe3b59..287153d32536 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -203,7 +203,8 @@ void serial8250_rpm_put(struct uart_8250_port *p);
 void serial8250_rpm_get_tx(struct uart_8250_port *p);
 void serial8250_rpm_put_tx(struct uart_8250_port *p);
 
-int serial8250_em485_config(struct uart_port *port, struct serial_rs485 *rs485);
+int serial8250_em485_config(struct uart_port *port, struct ktermios *termios,
+			    struct serial_rs485 *rs485);
 void serial8250_em485_start_tx(struct uart_8250_port *p);
 void serial8250_em485_stop_tx(struct uart_8250_port *p);
 void serial8250_em485_destroy(struct uart_8250_port *p);
diff --git a/drivers/tty/serial/8250/8250_dwlib.c b/drivers/tty/serial/8250/8250_dwlib.c
index c83e7eaf3877..d1ff3daeb0ba 100644
--- a/drivers/tty/serial/8250/8250_dwlib.c
+++ b/drivers/tty/serial/8250/8250_dwlib.c
@@ -85,7 +85,8 @@ void dw8250_do_set_termios(struct uart_port *p, struct ktermios *termios, struct
 }
 EXPORT_SYMBOL_GPL(dw8250_do_set_termios);
 
-static int dw8250_rs485_config(struct uart_port *p, struct serial_rs485 *rs485)
+static int dw8250_rs485_config(struct uart_port *p, struct ktermios *termios,
+			       struct serial_rs485 *rs485)
 {
 	u32 tcr;
 
diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
index 3d999eec4087..f5344cfe303c 100644
--- a/drivers/tty/serial/8250/8250_exar.c
+++ b/drivers/tty/serial/8250/8250_exar.c
@@ -112,7 +112,8 @@
 struct exar8250;
 
 struct exar8250_platform {
-	int (*rs485_config)(struct uart_port *, struct serial_rs485 *);
+	int (*rs485_config)(struct uart_port *port, struct ktermios *termios,
+			    struct serial_rs485 *rs485);
 	const struct serial_rs485 *rs485_supported;
 	int (*register_gpio)(struct pci_dev *, struct uart_8250_port *);
 	void (*unregister_gpio)(struct uart_8250_port *);
@@ -409,7 +410,7 @@ static void xr17v35x_unregister_gpio(struct uart_8250_port *port)
 	port->port.private_data = NULL;
 }
 
-static int generic_rs485_config(struct uart_port *port,
+static int generic_rs485_config(struct uart_port *port, struct ktermios *termios,
 				struct serial_rs485 *rs485)
 {
 	bool is_rs485 = !!(rs485->flags & SER_RS485_ENABLED);
@@ -441,7 +442,7 @@ static const struct exar8250_platform exar8250_default_platform = {
 	.rs485_supported = &generic_rs485_supported,
 };
 
-static int iot2040_rs485_config(struct uart_port *port,
+static int iot2040_rs485_config(struct uart_port *port, struct ktermios *termios,
 				struct serial_rs485 *rs485)
 {
 	bool is_rs485 = !!(rs485->flags & SER_RS485_ENABLED);
@@ -471,7 +472,7 @@ static int iot2040_rs485_config(struct uart_port *port,
 	value |= mode;
 	writeb(value, p + UART_EXAR_MPIOLVL_7_0);
 
-	return generic_rs485_config(port, rs485);
+	return generic_rs485_config(port, termios, rs485);
 }
 
 static const struct serial_rs485 iot2040_rs485_supported = {
diff --git a/drivers/tty/serial/8250/8250_fintek.c b/drivers/tty/serial/8250/8250_fintek.c
index 1fb86c73786c..eea693f5b577 100644
--- a/drivers/tty/serial/8250/8250_fintek.c
+++ b/drivers/tty/serial/8250/8250_fintek.c
@@ -191,7 +191,7 @@ static int fintek_8250_get_ldn_range(struct fintek_8250 *pdata, int *min,
 	return -ENODEV;
 }
 
-static int fintek_8250_rs485_config(struct uart_port *port,
+static int fintek_8250_rs485_config(struct uart_port *port, struct ktermios *termios,
 			      struct serial_rs485 *rs485)
 {
 	uint8_t config = 0;
diff --git a/drivers/tty/serial/8250/8250_lpc18xx.c b/drivers/tty/serial/8250/8250_lpc18xx.c
index 3a1cb51cbc91..d7cb3bb52069 100644
--- a/drivers/tty/serial/8250/8250_lpc18xx.c
+++ b/drivers/tty/serial/8250/8250_lpc18xx.c
@@ -32,7 +32,7 @@ struct lpc18xx_uart_data {
 	int line;
 };
 
-static int lpc18xx_rs485_config(struct uart_port *port,
+static int lpc18xx_rs485_config(struct uart_port *port, struct ktermios *termios,
 				struct serial_rs485 *rs485)
 {
 	struct uart_8250_port *up = up_to_u8250p(port);
diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index b6d71268aa7d..d31d2350a9db 100644
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1553,7 +1553,7 @@ pci_brcm_trumanage_setup(struct serial_private *priv,
 #define FINTEK_RTS_INVERT		BIT(5)
 
 /* We should do proper H/W transceiver setting before change to RS485 mode */
-static int pci_fintek_rs485_config(struct uart_port *port,
+static int pci_fintek_rs485_config(struct uart_port *port, struct ktermios *termios,
 			       struct serial_rs485 *rs485)
 {
 	struct pci_dev *pci_dev = to_pci_dev(port->dev);
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 19c612d732cf..5cb3673f9ee5 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -664,7 +664,8 @@ EXPORT_SYMBOL_GPL(serial8250_em485_supported);
  * if the uart is incapable of driving RTS as a Transmit Enable signal in
  * hardware, relying on software emulation instead.
  */
-int serial8250_em485_config(struct uart_port *port, struct serial_rs485 *rs485)
+int serial8250_em485_config(struct uart_port *port, struct ktermios *termios,
+			    struct serial_rs485 *rs485)
 {
 	struct uart_8250_port *up = up_to_u8250p(port);
 
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index eccd66625d25..c8f52945a4aa 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2197,7 +2197,7 @@ static int pl011_verify_port(struct uart_port *port, struct serial_struct *ser)
 	return ret;
 }
 
-static int pl011_rs485_config(struct uart_port *port,
+static int pl011_rs485_config(struct uart_port *port, struct ktermios *termios,
 			      struct serial_rs485 *rs485)
 {
 	struct uart_amba_port *uap =
diff --git a/drivers/tty/serial/ar933x_uart.c b/drivers/tty/serial/ar933x_uart.c
index ab2c5b2a1ce8..b73ce13683db 100644
--- a/drivers/tty/serial/ar933x_uart.c
+++ b/drivers/tty/serial/ar933x_uart.c
@@ -580,7 +580,7 @@ static const struct uart_ops ar933x_uart_ops = {
 	.verify_port	= ar933x_uart_verify_port,
 };
 
-static int ar933x_config_rs485(struct uart_port *port,
+static int ar933x_config_rs485(struct uart_port *port, struct ktermios *termios,
 				struct serial_rs485 *rs485conf)
 {
 	struct ar933x_uart_port *up =
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 74dd1d3ac46f..64dd6fea0a30 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -285,7 +285,7 @@ static void atmel_tasklet_schedule(struct atmel_uart_port *atmel_port,
 }
 
 /* Enable or disable the rs485 support */
-static int atmel_config_rs485(struct uart_port *port,
+static int atmel_config_rs485(struct uart_port *port, struct ktermios *termios,
 			      struct serial_rs485 *rs485conf)
 {
 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index d35414cb3e4e..8fe0494d4057 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1355,7 +1355,7 @@ static void lpuart_dma_rx_free(struct uart_port *port)
 	sport->dma_rx_cookie = -EINVAL;
 }
 
-static int lpuart_config_rs485(struct uart_port *port,
+static int lpuart_config_rs485(struct uart_port *port, struct ktermios *termios,
 			struct serial_rs485 *rs485)
 {
 	struct lpuart_port *sport = container_of(port,
@@ -1385,7 +1385,7 @@ static int lpuart_config_rs485(struct uart_port *port,
 	return 0;
 }
 
-static int lpuart32_config_rs485(struct uart_port *port,
+static int lpuart32_config_rs485(struct uart_port *port, struct ktermios *termios,
 			struct serial_rs485 *rs485)
 {
 	struct lpuart_port *sport = container_of(port,
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index f4edde54175f..3457006cea3f 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1907,7 +1907,7 @@ static void imx_uart_poll_put_char(struct uart_port *port, unsigned char c)
 #endif
 
 /* called with port.lock taken and irqs off or from .probe without locking */
-static int imx_uart_rs485_config(struct uart_port *port,
+static int imx_uart_rs485_config(struct uart_port *port, struct ktermios *termios,
 				 struct serial_rs485 *rs485conf)
 {
 	struct imx_port *sport = (struct imx_port *)port;
diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index d7d1791fcb57..5a8521fb9237 100644
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -1026,7 +1026,7 @@ static void max310x_rs_proc(struct work_struct *ws)
 			MAX310X_MODE2_ECHOSUPR_BIT, mode2);
 }
 
-static int max310x_rs485_config(struct uart_port *port,
+static int max310x_rs485_config(struct uart_port *port, struct ktermios *termios,
 				struct serial_rs485 *rs485)
 {
 	struct max310x_one *one = to_max310x_port(port);
diff --git a/drivers/tty/serial/mcf.c b/drivers/tty/serial/mcf.c
index 036f178e3d66..73c5287b8e5e 100644
--- a/drivers/tty/serial/mcf.c
+++ b/drivers/tty/serial/mcf.c
@@ -431,7 +431,8 @@ static int mcf_verify_port(struct uart_port *port, struct serial_struct *ser)
 /****************************************************************************/
 
 /* Enable or disable the RS485 support */
-static int mcf_config_rs485(struct uart_port *port, struct serial_rs485 *rs485)
+static int mcf_config_rs485(struct uart_port *port, struct ktermios *termios,
+			    struct serial_rs485 *rs485)
 {
 	unsigned char mr1, mr2;
 
diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 98622c35d896..1d1e48ff33d8 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1325,7 +1325,8 @@ static inline void serial_omap_add_console_port(struct uart_omap_port *up)
 
 /* Enable or disable the rs485 support */
 static int
-serial_omap_config_rs485(struct uart_port *port, struct serial_rs485 *rs485)
+serial_omap_config_rs485(struct uart_port *port, struct ktermios *termios,
+			 struct serial_rs485 *rs485)
 {
 	struct uart_omap_port *up = to_uart_omap_port(port);
 	unsigned int mode;
diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 2ceecaa4a478..8cb92a3b3fb8 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -1127,7 +1127,7 @@ static void sc16is7xx_set_termios(struct uart_port *port,
 	spin_unlock_irqrestore(&port->lock, flags);
 }
 
-static int sc16is7xx_config_rs485(struct uart_port *port,
+static int sc16is7xx_config_rs485(struct uart_port *port, struct ktermios *termios,
 				  struct serial_rs485 *rs485)
 {
 	struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 621fc15e2e54..44c3785445e3 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1359,7 +1359,7 @@ int uart_rs485_config(struct uart_port *port)
 
 	uart_sanitize_serial_rs485(port, rs485);
 
-	ret = port->rs485_config(port, rs485);
+	ret = port->rs485_config(port, NULL, rs485);
 	if (ret)
 		memset(rs485, 0, sizeof(*rs485));
 
@@ -1383,7 +1383,7 @@ static int uart_get_rs485_config(struct uart_port *port,
 	return 0;
 }
 
-static int uart_set_rs485_config(struct uart_port *port,
+static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
 			 struct serial_rs485 __user *rs485_user)
 {
 	struct serial_rs485 rs485;
@@ -1402,7 +1402,7 @@ static int uart_set_rs485_config(struct uart_port *port,
 	uart_sanitize_serial_rs485(port, &rs485);
 
 	spin_lock_irqsave(&port->lock, flags);
-	ret = port->rs485_config(port, &rs485);
+	ret = port->rs485_config(port, &tty->termios, &rs485);
 	if (!ret)
 		port->rs485 = rs485;
 	spin_unlock_irqrestore(&port->lock, flags);
@@ -1511,6 +1511,10 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
 	if (ret != -ENOIOCTLCMD)
 		goto out;
 
+	/* rs485_config requires more locking than others */
+	if (cmd == TIOCGRS485)
+		down_write(&tty->termios_rwsem);
+
 	mutex_lock(&port->mutex);
 	uport = uart_port_check(state);
 
@@ -1534,7 +1538,7 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
 		break;
 
 	case TIOCSRS485:
-		ret = uart_set_rs485_config(uport, uarg);
+		ret = uart_set_rs485_config(tty, uport, uarg);
 		break;
 
 	case TIOCSISO7816:
@@ -1551,6 +1555,8 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
 	}
 out_up:
 	mutex_unlock(&port->mutex);
+	if (cmd == TIOCGRS485)
+		up_write(&tty->termios_rwsem);
 out:
 	return ret;
 }
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index db3dd9731ee1..13992e64a7df 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -97,7 +97,7 @@ static void stm32_usart_config_reg_rs485(u32 *cr1, u32 *cr3, u32 delay_ADE,
 	*cr1 |= rs485_deat_dedt;
 }
 
-static int stm32_usart_config_rs485(struct uart_port *port,
+static int stm32_usart_config_rs485(struct uart_port *port, struct ktermios *termios,
 				    struct serial_rs485 *rs485conf)
 {
 	struct stm32_port *stm32_port = to_stm32_port(port);
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 5518b70177b3..17bbd0412a23 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -132,6 +132,7 @@ struct uart_port {
 				      unsigned int old);
 	void			(*handle_break)(struct uart_port *);
 	int			(*rs485_config)(struct uart_port *,
+						struct ktermios *termios,
 						struct serial_rs485 *rs485);
 	int			(*iso7816_config)(struct uart_port *,
 						  struct serial_iso7816 *iso7816);
