linux-kernel - Re: [PATCH 20/33] serial: 8250: extract serial8250_set

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Message-ID: <1de58a33-b2f2-3425-752c-cabd2eda89bf@linux.intel.com>
Date: Wed, 11 Jun 2025 15:35:04 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
cc: gregkh@...uxfoundation.org, linux-serial@...r.kernel.org, 
    linux-kernel@...r.kernel.org
Subject: Re: [PATCH 20/33] serial: 8250: extract serial8250_set_afe()

On Wed, 11 Jun 2025, Jiri Slaby (SUSE) wrote:

> serial8250_do_set_termios() consists of many registers and up flags
> settings. Extract all these into separate functions. This time, setting
> of MCR for UART_CAP_AFE ports.
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> ---
>  drivers/tty/serial/8250/8250_port.c | 32 +++++++++++++++--------------
>  1 file changed, 17 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 52385314c426..b15371838366 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -2704,6 +2704,22 @@ static void serial8250_set_trigger_for_slow_speed(struct uart_port *port, struct
>  	up->fcr |= UART_FCR_TRIGGER_1;
>  }
>  
> +/*
> + * MCR-based auto flow control. When AFE is enabled, RTS will be deasserted when the receive FIFO
> + * contains more characters than the trigger, or the MCR RTS bit is cleared.
> + */
> +static void serial8250_set_afe(struct uart_port *port, struct ktermios *termios)
> +{
> +	struct uart_8250_port *up = up_to_u8250p(port);
> +
> +	if (!(up->capabilities & UART_CAP_AFE))
> +		return;
> +
> +	up->mcr &= ~UART_MCR_AFE;
> +	if (termios->c_cflag & CRTSCTS)
> +		up->mcr |= UART_MCR_AFE;
> +}
> +
>  void
>  serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
>  		          const struct ktermios *old)
> @@ -2729,21 +2745,7 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
>  
>  	up->lcr = cval;					/* Save computed LCR */
>  	serial8250_set_trigger_for_slow_speed(port, termios, baud);
> -
> -	/*
> -	 * MCR-based auto flow control.  When AFE is enabled, RTS will be
> -	 * deasserted when the receive FIFO contains more characters than
> -	 * the trigger, or the MCR RTS bit is cleared.
> -	 */
> -	if (up->capabilities & UART_CAP_AFE) {
> -		up->mcr &= ~UART_MCR_AFE;
> -		if (termios->c_cflag & CRTSCTS)
> -			up->mcr |= UART_MCR_AFE;
> -	}
> -
> -	/*
> -	 * Update the per-port timeout.
> -	 */
> +	serial8250_set_afe(port, termios);
>  	uart_update_timeout(port, termios->c_cflag, baud);
>  
>  	/*
> 

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

-- 
 i.