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

[Jiri Slaby]

On 11. 06. 25, 14:58, Ilpo Järvinen wrote:
> 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 UART_CAP_EFR at all (nor uses
> UPF_BOOT_AUTOCONF)??

Impossible as far as I can tell nowadays. Likely since:
commit 6be254c2113d18984bae002b3b3dfc133cf56ac5
Author: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Date:   Wed Jul 31 20:05:56 2019 +0300

    serial: 8250_exar: No need to autoconfigure Exar ports

Andy?

The question is whether we need the code or we can drop it 8-).

> > +		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)


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