--- a/drivers/serial/serial_stm32.c
+++ b/drivers/serial/serial_stm32.c
@@ -209,7 +209,7 @@
 	 * before uart initialization, wait for TC bit (Transmission Complete)
 	 * in case there is still chars from previous bootstage to transmit
 	 */
-	ret = read_poll_timeout(readl, isr, isr & USART_ISR_TC, 10, 150,
+	ret = read_poll_timeout(readl, isr, isr & USART_ISR_TC, 10, 1500,
 				plat->base + ISR_OFFSET(stm32f4));
 	if (ret) {
 		clk_disable(&clk);