Re: Re: [PATCH V3] serial/uart/8250: Add tunable RX interrupt trigger I/F of FIFO buffers

[Yoshihiro YUNOMAE]

Hi Heikki,

Thank you for your reply.

(2014/03/14 23:16), Heikki Krogerus wrote:
> Hi,
>
> On Fri, Mar 14, 2014 at 11:21:54AM +0900, Yoshihiro YUNOMAE wrote:
> >   void serial8250_clear_and_reinit_fifos(struct uart_8250_port *p)
> >   {
> > -	unsigned char fcr;
> > -
> >   	serial8250_clear_fifos(p);
> > -	fcr = uart_config[p->port.type].fcr;
> > -	serial_out(p, UART_FCR, fcr);
> > +	p->fcr = uart_config[p->port.type].fcr;
> > +	serial_out(p, UART_FCR, p->fcr);
>
> You should allow also the probe drivers to set this..
>
>          if (!p->fcr)
>                  p->fcr = uart_config[p->port.type].fcr;

Oh, I'll fix it.

> >   }
> >   EXPORT_SYMBOL_GPL(serial8250_clear_and_reinit_fifos);
> >
> > @@ -2325,10 +2323,19 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
> >   		if ((baud < 2400 && !up->dma) || fifo_bug) {
> >   			fcr &= ~UART_FCR_TRIGGER_MASK;
> >   			fcr |= UART_FCR_TRIGGER_1;
> > +			/* Don't use user setting RX trigger */
> > +			up->fcr = 0;
>
> I don't know about this but..
>
> >   		}
> >   	}
> >
> >   	/*
> > +	 * If up->fcr exists, a user has opened this port, changed RX trigger,
> > +	 * or read RX trigger before. So, we don't need to change up->fcr here.
> > +	 */
> > +	if (!up->fcr)
> > +		up->fcr = fcr;
>
> Why not just set fcr = up->fcr in the beginning of the function?

Ah, we don't need to set up->fcr = 0 in the previous flow when we
implement as follows:

unsigned char fcr = up->fcr;

 ... <snip> ...

    /*
     * If fcr exists, a user has opened this port, changed RX
     * trigger, or read RX trigger before. If so, we do not change
     * fcr.
     */
    if (!fcr)
        fcr = uart_config[port_type].fcr;
    if ((baud < 2400 && !up->dma) || fifo_bug) {
        fcr &= ~UART_FCR_TRIGGER_MASK;
        fcr |= UART_FCR_TRIGGER_1;
    }

up->fcr = fcr;

> <snip>
>
> > +static int do_set_rx_int_trig(struct tty_port *port, unsigned char val)
> > +{
> > +	struct uart_state *state = container_of(port, struct uart_state, port);
> > +	struct uart_port *uport = state->uart_port;
> > +	struct uart_8250_port *up =
> > +		container_of(uport, struct uart_8250_port, port);
> > +	unsigned char fcr;
> > +	int rx_trig;
> > +
> > +	if (!(up->capabilities & UART_CAP_FIFO) || uport->fifosize <= 1)
> > +		return -EINVAL;
> > +
> > +	rx_trig = convert_val2rxtrig(up, val);
> > +	if (rx_trig < 0)
> > +		return rx_trig;
> > +
> > +	serial8250_clear_fifos(up);
> > +	if (!up->fcr)
> > +		/* termios is not set yet */
> > +		fcr = uart_config[up->port.type].fcr;
> > +	else
> > +		fcr = up->fcr;
> > +	fcr &= ~UART_FCR_TRIGGER_MASK;
> > +	fcr |= (unsigned char)rx_trig;
> > +	up->fcr = fcr;
> > +	serial_out(up, UART_FCR, up->fcr);
> > +	return 0;
> > +}
>
> Where are you setting UART_FCR_ENABLE_FIFO bit? Am I missing
> something?

In these implementation, the driver sets up->fcr as
uart_config[up->port.type].fcr first and changes only RX trigger. So,
we don't need to set the bit in a direct way.

Thank you,
Yoshihiro YUNOMAE

--
Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: yoshihiro.yunomae.ez@xxxxxxxxxxx


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