Incorrect characters are observed on console during boot. This issue occurs
when init/main.c is modifying termios settings to open /dev/console on the
rootfs.
This patch adds a waiting loop in set_termios to wait for TX shift register
empty (and TX FIFO if any) before stopping serial port.
Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver")
Signed-off-by: Erwan Le Ray <erwan.leray@xxxxxxxxxxx>
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 33a479062948..7710de947aa3 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -738,8 +738,9 @@ static void stm32_usart_set_termios(struct uart_port *port,
unsigned int baud, bits;
u32 usartdiv, mantissa, fraction, oversampling;
tcflag_t cflag = termios->c_cflag;
- u32 cr1, cr2, cr3;
+ u32 cr1, cr2, cr3, isr;
unsigned long flags;
+ int ret;
if (!stm32_port->hw_flow_control)
cflag &= ~CRTSCTS;
@@ -748,6 +749,15 @@ static void stm32_usart_set_termios(struct uart_port *port,
spin_lock_irqsave(&port->lock, flags);
+ ret = readl_relaxed_poll_timeout_atomic(port->membase + ofs->isr,
+ isr,
+ (isr & USART_SR_TC),
+ 10, 100000);
+
+ /* Send the TC error message only when ISR_TC is not set. */
+ if (ret)
+ dev_err(port->dev, "Transmission is not complete\n");
+
/* Stop serial port and reset value */
writel_relaxed(0, port->membase + ofs->cr1);
--
2.17.1
