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

Ilpo Järvinen
2025-06-11T12:58:38Z

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@kernel.org>
> ---
> 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.