Re: [PATCH v4 05/14] serial: 8250_mxpcie: offload XON/XOFF flow control to MUEx50 hardware

On 29. 07. 26, 8:05, Crescent Hsieh wrote:
> The MUEx50 UART can handle in-band software flow control (XON/XOFF)
> directly in hardware.
> 
> Program the on-chip XON/XOFF characters from termios settings and enable
> the corresponding MUEx50 flow control modes when IXON or IXOFF is
> requested. Provide throttle and unthrottle callbacks so RX can be
> stopped and resumed cleanly.
> 
> Signed-off-by: Crescent Hsieh <[email protected]>
> ---
>   drivers/tty/serial/8250/8250_mxpcie.c | 55 +++++++++++++++++++++++++--
>   1 file changed, 52 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_mxpcie.c b/drivers/tty/serial/8250/8250_mxpcie.c
> index 1124c7d951b3..0517caaf2d26 100644
> --- a/drivers/tty/serial/8250/8250_mxpcie.c
> +++ b/drivers/tty/serial/8250/8250_mxpcie.c
...> @@ -172,6 +184,23 @@ static void mxpcie8250_set_termios(struct 
uart_port *port,
>   		efr |= (MOXA_PUART_EFR_AUTO_RTS | MOXA_PUART_EFR_AUTO_CTS);
>   		up->port.status |= (UPSTAT_AUTORTS | UPSTAT_AUTOCTS);
>   	}
> +	/* Set on-chip software flow control character */
> +	serial_out(up, MOXA_PUART_XON1, START_CHAR(tty));
> +	serial_out(up, MOXA_PUART_XON2, START_CHAR(tty));
> +	serial_out(up, MOXA_PUART_XOFF1, STOP_CHAR(tty));
> +	serial_out(up, MOXA_PUART_XOFF2, STOP_CHAR(tty));
> +
> +	efr &= ~(MOXA_PUART_EFR_RX_FLOW_MASK | MOXA_PUART_EFR_TX_FLOW_MASK);

This is not needed, as you use FIELD_MODIFY(), right?

> +	val = I_IXON(tty) ? MOXA_PUART_EFR_RX_FLOW_XON1_XOFF1 : MOXA_PUART_EFR_RX_FLOW_DISABLED;
> +	efr = FIELD_MODIFY(MOXA_PUART_EFR_RX_FLOW_MASK, &efr, val);
> +
> +	val = I_IXOFF(tty) ? MOXA_PUART_EFR_TX_FLOW_XON1_XOFF1 : MOXA_PUART_EFR_TX_FLOW_DISABLED;
> +	efr = FIELD_MODIFY(MOXA_PUART_EFR_TX_FLOW_MASK, &efr, val);

Assigning back to efr is unnecessary. The reg is updated in-place.

thanks,
-- 
js
suse labs