From: Erwan Le Ray erwan.leray@foss.st.com
[ Upstream commit f264c6f6aece81a9f8fbdf912b20bd3feb476a7a ]
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@foss.st.com Link: https://lore.kernel.org/r/20210304162308.8984-4-erwan.leray@foss.st.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/serial/stm32-usart.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index c6ca8f964c69..eae54b8cf5e2 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);