diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 9f2fcd1c1916..9547aa8f4520 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -591,6 +591,8 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
 			      SC16IS7XX_MCR_CLKSEL_BIT,
 			      prescaler == 1 ? 0 : SC16IS7XX_MCR_CLKSEL_BIT);
 
+	mutex_lock(&one->efr_lock);
+
 	/* Backup LCR and access special register set (DLL/DLH) */
 	lcr = sc16is7xx_port_read(port, SC16IS7XX_LCR_REG);
 	sc16is7xx_port_write(port, SC16IS7XX_LCR_REG,
@@ -605,6 +607,8 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
 	/* Restore LCR and access to general register set */
 	sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, lcr);
 
+	mutex_unlock(&one->efr_lock);
+
 	return DIV_ROUND_CLOSEST((clk / prescaler) / 16, div);
 }