Commit f264c6f6 authored by Erwan Le Ray's avatar Erwan Le Ray Committed by Greg Kroah-Hartman
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serial: stm32: fix incorrect characters on console 



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: 48a6092f ("serial: stm32-usart: Add STM32 USART Driver")
Signed-off-by: default avatarErwan Le Ray <erwan.leray@foss.st.com>
Link: https://lore.kernel.org/r/20210304162308.8984-4-erwan.leray@foss.st.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f4518a8a

drivers/tty/serial/stm32-usart.c

+11 −1
Original line number Diff line number Diff line
@@ -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);