Re: [PATCH 24/33] serial: 8250: extract serial8250_set_fcr()

Ilpo Järvinen
2025-06-11T13:01:56Z

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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 FCR.
>
> serial8250_do_set_termios() looks sane at this point.
>
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>

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

--
i.

> ---
> drivers/tty/serial/8250/8250_port.c | 41 ++++++++++++++++++-----------
> 1 file changed, 26 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 0f16398cc86f..85b75ff0699e 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -2792,6 +2792,30 @@ static void serial8250_set_efr(struct uart_port *port, struct ktermios *termios)
> serial_port_out(port, efr_reg, efr);
> }
>
> +static void serial8250_set_fcr(struct uart_port *port, struct ktermios *termios)
> +{
> + struct uart_8250_port *up = up_to_u8250p(port);
> + bool is_16750 = port->type == PORT_16750;
> +
> + if (is_16750)
> + serial_port_out(port, UART_FCR, up->fcr);
> +
> + /*
> + * LCR DLAB must be reset to enable 64-byte FIFO mode. If the FCR is written without DLAB
> + * set, this mode will be disabled.
> + */
> + serial_port_out(port, UART_LCR, up->lcr);
> +
> + if (is_16750)
> + return;
> +
> + /* emulated UARTs (Lucent Venus 167x) need two steps */
> + if (up->fcr & UART_FCR_ENABLE_FIFO)
> + serial_port_out(port, UART_FCR, UART_FCR_ENABLE_FIFO);
> +
> + serial_port_out(port, UART_FCR, up->fcr);
> +}
> +
> void
> serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
> const struct ktermios *old)
> @@ -2823,22 +2847,9 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
> serial8250_set_ier(port, termios);
> serial8250_set_efr(port, termios);
> serial8250_set_divisor(port, baud, quot, frac);
> -
> - /*
> - * LCR DLAB must be set to enable 64-byte FIFO mode. If the FCR
> - * is written without DLAB set, this mode will be disabled.
> - */
> - if (port->type == PORT_16750)
> - serial_port_out(port, UART_FCR, up->fcr);
> -
> - serial_port_out(port, UART_LCR, up->lcr); /* reset DLAB */
> - if (port->type != PORT_16750) {
> - /* emulated UARTs (Lucent Venus 167x) need two steps */
> - if (up->fcr & UART_FCR_ENABLE_FIFO)
> - serial_port_out(port, UART_FCR, UART_FCR_ENABLE_FIFO);
> - serial_port_out(port, UART_FCR, up->fcr); /* set fcr */
> - }
> + serial8250_set_fcr(port, termios);
> serial8250_set_mctrl(port, port->mctrl);
> +
> uart_port_unlock_irqrestore(port, flags);
> serial8250_rpm_put(up);
>
>