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, greg k-h