diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 0494c08551e35485d0dd8c339bd31dd378713c1f..ee1e09495c41c10e020e2007ba6ac986cbbd0bea 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -537,6 +537,8 @@ 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);
@@ -550,6 +552,8 @@ 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);
 }