From: Sherry Sun <sherry.sun@xxxxxxx> commit 2411fd94ceaa6e11326e95d6ebf876cbfed28d23 upstream. According to LPUART RM, Transmission Complete Flag becomes 0 if queuing a break character by writing 1 to CTRL[SBK], so here need to skip waiting for transmission complete when UARTCTRL_SBK is asserted, otherwise the kernel may stuck here. And actually set_termios() adds transmission completion waiting to avoid data loss or data breakage when changing the baud rate, but we don't need to worry about this when queuing break characters. Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx> Cc: stable <stable@xxxxxxxxxx> Link: https://lore.kernel.org/r/20230223093941.31790-1-sherry.sun@xxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/tty/serial/fsl_lpuart.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -2201,9 +2201,15 @@ lpuart32_set_termios(struct uart_port *p /* update the per-port timeout */ uart_update_timeout(port, termios->c_cflag, baud); - /* wait transmit engin complete */ - lpuart32_write(&sport->port, 0, UARTMODIR); - lpuart32_wait_bit_set(&sport->port, UARTSTAT, UARTSTAT_TC); + /* + * LPUART Transmission Complete Flag may never be set while queuing a break + * character, so skip waiting for transmission complete when UARTCTRL_SBK is + * asserted. + */ + if (!(old_ctrl & UARTCTRL_SBK)) { + lpuart32_write(&sport->port, 0, UARTMODIR); + lpuart32_wait_bit_set(&sport->port, UARTSTAT, UARTSTAT_TC); + } /* disable transmit and receive */ lpuart32_write(&sport->port, old_ctrl & ~(UARTCTRL_TE | UARTCTRL_RE),
