On Fri, Mar 07, 2025 at 10:19:50AM +0800, Sherry Sun wrote:
> According to the LPUART reference manual, TXRTSE and TXRTSPOL of MODIR
> register only can be changed when the transmitter is disabled.
> So disable the transmitter before changing RS485 related registers and
> re-enable it after the change is done.
>
> Fixes: 67b01837861c ("tty: serial: lpuart: Add RS485 support for 32-bit uart flavour")
> Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
Reviewed-by: Frank Li <Frank.Li@xxxxxxx>
> ---
> drivers/tty/serial/fsl_lpuart.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
> index 91d02c55c470..4dc2f3e2b8e0 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -1484,6 +1484,16 @@ static int lpuart32_config_rs485(struct uart_port *port, struct ktermios *termio
>
> unsigned long modem = lpuart32_read(&sport->port, UARTMODIR)
> & ~(UARTMODIR_TXRTSPOL | UARTMODIR_TXRTSE);
> + u32 ctrl;
> +
> + /* TXRTSE and TXRTSPOL only can be changed when transmitter is disabled. */
> + ctrl = lpuart32_read(&sport->port, UARTCTRL);
> + if (ctrl & UARTCTRL_TE) {
> + /* wait transmit engin complete */
> + lpuart32_wait_bit_set(&sport->port, UARTSTAT, UARTSTAT_TC);
> + lpuart32_write(&sport->port, ctrl & ~UARTCTRL_TE, UARTCTRL);
> + }
> +
> lpuart32_write(&sport->port, modem, UARTMODIR);
>
> if (rs485->flags & SER_RS485_ENABLED) {
> @@ -1503,6 +1513,10 @@ static int lpuart32_config_rs485(struct uart_port *port, struct ktermios *termio
> }
>
> lpuart32_write(&sport->port, modem, UARTMODIR);
> +
> + if (ctrl & UARTCTRL_TE)
> + lpuart32_write(&sport->port, ctrl, UARTCTRL);
> +
> return 0;
> }
>
> --
> 2.34.1
>
