Re: [PATCH 1/4] serial: 8250_dw: add em485 support

[Giulio Benetti]

Il 06/06/2018 18:51, Andy Shevchenko ha scritto:
> On Wed, Jun 6, 2018 at 12:51 PM, Giulio Benetti
> <giulio.benetti@xxxxxxxxxxxxxxxx> wrote:
> > Need to use rs485 transceiver so let's use existing em485 485 emulation
> > layer on top of 8250.
> >
> > Add rs485_config callback to port.
>
> Besides the fact the series lacks of cover letter, I think it should

Sorry for that, next patchsets will have cover-letters.

> be postponed until we get a clear understanding how RS485 is supposed
> to be initialized and what exact problems you are trying to address.
>
> > Signed-off-by: Giulio Benetti <giulio.benetti@xxxxxxxxxxxxxxxx>
> > ---
> >   drivers/tty/serial/8250/8250_dw.c | 31 +++++++++++++++++++++++++++++++
> >   1 file changed, 31 insertions(+)
> >
> > diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
> > index 6fcdb90f616a..45366e6e5411 100644
> > --- a/drivers/tty/serial/8250/8250_dw.c
> > +++ b/drivers/tty/serial/8250/8250_dw.c
> > @@ -314,6 +314,36 @@ static void dw8250_set_ldisc(struct uart_port *p, struct ktermios *termios)
> >          serial8250_do_set_ldisc(p, termios);
> >   }
> >
> > +static int dw8250_rs485_config(struct uart_port *p,
> > +                              struct serial_rs485 *rs485)
> > +{
> > +       struct uart_8250_port *up = up_to_u8250p(p);
> > +
> > +       /* Clamp the delays to [0, 100ms] */
> > +       rs485->delay_rts_before_send = min(rs485->delay_rts_before_send, 100U);
> > +       rs485->delay_rts_after_send  = min(rs485->delay_rts_after_send, 100U);
> > +
> > +       p->rs485 = *rs485;
> > +
> > +       /*
> > +        * Both serial8250_em485_init and serial8250_em485_destroy
> > +        * are idempotent
> > +        */
> > +       if (rs485->flags & SER_RS485_ENABLED) {
> > +               int ret = serial8250_em485_init(up);
> > +
> > +               if (ret) {
> > +                       rs485->flags &= ~SER_RS485_ENABLED;
> > +                       p->rs485.flags &= ~SER_RS485_ENABLED;
> > +               }
> > +               return ret;
> > +       }
> > +
> > +       serial8250_em485_destroy(up);
> > +
> > +       return 0;
> > +}
> > +
> >   /*
> >    * dw8250_fallback_dma_filter will prevent the UART from getting just any free
> >    * channel on platforms that have DMA engines, but don't have any channels
> > @@ -449,6 +479,7 @@ static int dw8250_probe(struct platform_device *pdev)
> >          p->serial_out   = dw8250_serial_out;
> >          p->set_ldisc    = dw8250_set_ldisc;
> >          p->set_termios  = dw8250_set_termios;
> > +       p->rs485_config = dw8250_rs485_config;
> >
> >          p->membase = devm_ioremap(dev, regs->start, resource_size(regs));
> >          if (!p->membase)
> > --
> > 2.17.1

--
Giulio Benetti
CTO

MICRONOVA SRL
Sede: Via A. Niedda 3 - 35010 Vigonza (PD)
Tel. 049/8931563 - Fax 049/8931346
Cod.Fiscale - P.IVA 02663420285
Capitale Sociale â 26.000 i.v.
Iscritta al Reg. Imprese di Padova N. 02663420285
Numero R.E.A. 258642