diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 29f05db0d49bae74478cfcc4e2a52c0ccd343105..367692a35398d8578b9b1910fa71927b98aee578 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -538,6 +538,8 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
 			      SC16IS7XX_MCR_CLKSEL_BIT,
 			      prescaler);
 
+	mutex_lock(&s->efr_lock);
+
 	/* Open the LCR divisors for configuration */
 	sc16is7xx_port_write(port, SC16IS7XX_LCR_REG,
 			     SC16IS7XX_LCR_CONF_MODE_A);
@@ -551,6 +553,8 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
 	/* Put LCR back to the normal mode */
 	sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, lcr);
 
+	mutex_unlock(&s->efr_lock);
+
 	return DIV_ROUND_CLOSEST(clk / 16, div);
 }