Re: [PATCH 23/33] serial: 8250: extract serial8250_set_efr()

[Ilpo Järvinen]

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 EFR for UART_CAP_EFR ports.
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@xxxxxxxxxx>
> ---
>  drivers/tty/serial/8250/8250_port.c | 43 +++++++++++++++++------------
>  1 file changed, 25 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 2c045a4369fc..0f16398cc86f 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -2768,6 +2768,30 @@ static void serial8250_set_ier(struct uart_port *port, struct ktermios *termios)
>  	serial_port_out(port, UART_IER, up->ier);
>  }
>  
> +static void serial8250_set_efr(struct uart_port *port, struct ktermios *termios)
> +{
> +	struct uart_8250_port *up = up_to_u8250p(port);
> +	u8 efr_reg = UART_EFR;
> +	u8 efr = 0;
> +
> +	if (!(up->capabilities & UART_CAP_EFR))
> +		return;
> +
> +	/*
> +	 * TI16C752/Startech hardware flow control.  FIXME:
> +	 * - TI16C752 requires control thresholds to be set.
> +	 * - UART_MCR_RTS is ineffective if auto-RTS mode is enabled.
> +	 */
> +	if (termios->c_cflag & CRTSCTS)
> +		efr |= UART_EFR_CTS;
> +
> +	if (port->flags & UPF_EXAR_EFR)

I wonder if it is possible to trigger this at all? Only 8250_exar.c sets 
this flag and does not contain have UART_CAP_EFR at all (nor uses 
UPF_BOOT_AUTOCONF)??

> +		efr_reg = UART_XR_EFR;
> +
> +	serial_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B);
> +	serial_port_out(port, efr_reg, efr);
> +}
> +
>  void
>  serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
>  		          const struct ktermios *old)
> @@ -2797,24 +2821,7 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
>  	uart_update_timeout(port, termios->c_cflag, baud);
>  	serial8250_set_errors_and_ignores(port, termios);
>  	serial8250_set_ier(port, termios);
> -
> -	if (up->capabilities & UART_CAP_EFR) {
> -		unsigned char efr = 0;
> -		/*
> -		 * TI16C752/Startech hardware flow control.  FIXME:
> -		 * - TI16C752 requires control thresholds to be set.
> -		 * - UART_MCR_RTS is ineffective if auto-RTS mode is enabled.
> -		 */
> -		if (termios->c_cflag & CRTSCTS)
> -			efr |= UART_EFR_CTS;
> -
> -		serial_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B);
> -		if (port->flags & UPF_EXAR_EFR)
> -			serial_port_out(port, UART_XR_EFR, efr);
> -		else
> -			serial_port_out(port, UART_EFR, efr);
> -	}
> -
> +	serial8250_set_efr(port, termios);
>  	serial8250_set_divisor(port, baud, quot, frac);
>  
>  	/*
> 

-- 
 i.