On Sat, Mar 7, 2020 at 4:51 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Fri, Mar 06, 2020 at 10:13:56AM -0800, Palmer Dabbelt wrote:
> > On Tue, 03 Mar 2020 00:41:40 PST (-0800), vincent.chen@xxxxxxxxxx wrote:
> > > Add CONSOLE_POLL support for future KGDB porting.
> > >
> > > Signed-off-by: Vincent Chen <vincent.chen@xxxxxxxxxx>
> > > ---
> > > drivers/tty/serial/sifive.c | 27 +++++++++++++++++++++++++++
> > > 1 file changed, 27 insertions(+)
> > >
> > > diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c
> > > index d5f81b98e4d7..acdbaca4de36 100644
> > > --- a/drivers/tty/serial/sifive.c
> > > +++ b/drivers/tty/serial/sifive.c
> > > @@ -818,6 +818,29 @@ static int __init sifive_serial_console_setup(struct console *co, char *options)
> > > return uart_set_options(&ssp->port, co, baud, parity, bits, flow);
> > > }
> > >
> > > +#ifdef CONFIG_CONSOLE_POLL
> > > +static int sifive_serial_poll_get_char(struct uart_port *port)
> > > +{
> > > + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
> > > + char is_empty, ch;
> > > +
> > > + ch = __ssp_receive_char(ssp, &is_empty);
> > > + if (is_empty)
> > > + return NO_POLL_CHAR;
> > > +
> > > + return ch;
> > > +}
> > > +
> > > +static void sifive_serial_poll_put_char(struct uart_port *port,
> > > + unsigned char c)
> > > +{
> > > + struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
> > > +
> > > + sifive_serial_console_putchar(port, c);
> > > + __ssp_wait_for_xmitr(ssp);
> >
> > So we still have that TX watermark bug in the SiFive UARTs. If this function
> > is supposed to wait until the word is actually out on the line then this isn't
> > sufficient, but if it's just supposed to wait until the next write won't block
> > then this is fine.
> >
> > I'm not really a serial person, so mabye someone else knows? For those
> > unfamiliar with the issue, there's a pretty good description in the patch to
> > fix it
> >
> > https://github.com/sifive/sifive-blocks/pull/90
> >
> > Poking around we don't have any PRE_RATE_CHANGE hook, so I'm going to take a
> > whack at adding one -- not really related to this patch, though.
>
> I do have to drop this patch from my tree, as it breaks the build, so it
> needs to be redone anyway :(
>
Thanks for the test to find out my mistake.
I will fix it and resend the 2nd version patch.
Thanks
