On Sat, Mar 7, 2020 at 4:51 PM Greg KH [off-list ref] wrote:

On Fri, Mar 06, 2020 at 10:13:56AM -0800, Palmer Dabbelt wrote:

quoted

On Tue, 03 Mar 2020 00:41:40 PST (-0800), vincent.chen@sifive.com wrote:

quoted

Add CONSOLE_POLL support for future KGDB porting.

Signed-off-by: Vincent Chen <redacted>
---
 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