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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: 48a6092fb4 ("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>
This commit is contained in:
Erwan Le Ray 2021-03-04 17:22:58 +01:00 committed by Greg Kroah-Hartman
parent f4518a8a75
commit f264c6f6ae
1 changed files with 11 additions and 1 deletions
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12
drivers/tty/serial/stm32-usart.c
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@ -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);