Re: [PATCH v6 1/7] serial: Do not hold the port lock when setting rx-during-tx GPIO

[Maarten Brock]

Lino Sanfilippo wrote on 2023-12-29 16:03:
> Hi,
>
> On 25.12.23 at 13:31, Maarten Brock wrote:
> > Lino Sanfilippo wrote on 2023-12-25 12:35:
> > > diff --git a/drivers/tty/serial/serial_core.c 
> > > b/drivers/tty/serial/serial_core.c
> > > +static void uart_set_rs485_rx_during_tx(struct uart_port *port,
> > > +                    const struct serial_rs485 *rs485)
> > > +{
> > > +    if (!(rs485->flags & SER_RS485_ENABLED))
> > > +        return;
> >
> > How about checking port->rs485_rx_during_tx_gpio here against NULL 
> > instead of
> > before every call?
>
> gpiod_set_value_cansleep() already checks for a NULL pointer, so doing
> this check in the caller is not needed.

Ah, sorry, you're right.

> > > +    gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
> > > +                 !!(rs485->flags & SER_RS485_RX_DURING_TX));
> > > +}
> > > +
> > > @@ -1457,6 +1472,7 @@ static int uart_set_rs485_config(struct
> > > tty_struct *tty, struct uart_port *port,
> > >          return ret;
> > >      uart_sanitize_serial_rs485(port, &rs485);
> > >      uart_set_rs485_termination(port, &rs485);
> > > +    uart_set_rs485_rx_during_tx(port, &rs485);
> > >
> > >      uart_port_lock_irqsave(port, &flags);
> > >      ret = port->rs485_config(port, &tty->termios, &rs485);
> > > @@ -1468,8 +1484,14 @@ static int uart_set_rs485_config(struct
> > > tty_struct *tty, struct uart_port *port,
> > >              port->ops->set_mctrl(port, port->mctrl);
> > >      }
> > >      uart_port_unlock_irqrestore(port, flags);
> > > -    if (ret)
> > > +    if (ret) {
> > > +        /* restore old GPIO settings */
> > > +        gpiod_set_value_cansleep(port->rs485_term_gpio,
> > > +            !!(port->rs485.flags & SER_RS485_TERMINATE_BUS));
> > > +        gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
> > > +            !!(port->rs485.flags & SER_RS485_RX_DURING_TX));
> >
> > This does not look like restoring.
>
> Hmm. The rx-during-tx and terminate-bus GPIOs may have changed before 
> the
> drivers rs485_config() was called. If that function fails, the GPIOs
> are set back to the values they had before (i.e what is still stored in
> the ports serial_rs485 struct). So what is wrong with the term 
> "restore"?

Oops, I missed that too that port-rs485 is not updated in this case.

Kind Regards,
Maarten Brock