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charset="utf-8" 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 uar= t flavour") Signed-off-by: Sherry Sun Reviewed-by: Frank Li --- 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_lpuar= t.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 *p= ort, struct ktermios *termio =20 unsigned long modem =3D lpuart32_read(&sport->port, UARTMODIR) & ~(UARTMODIR_TXRTSPOL | UARTMODIR_TXRTSE); + u32 ctrl; + + /* TXRTSE and TXRTSPOL only can be changed when transmitter is disabled. = */ + ctrl =3D 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); =20 if (rs485->flags & SER_RS485_ENABLED) { @@ -1503,6 +1513,10 @@ static int lpuart32_config_rs485(struct uart_port *p= ort, struct ktermios *termio } =20 lpuart32_write(&sport->port, modem, UARTMODIR); + + if (ctrl & UARTCTRL_TE) + lpuart32_write(&sport->port, ctrl, UARTCTRL); + return 0; } =20 --=20 2.34.1