tty: serial: Add CONSOLE_POLL support to SiFive UART

Add CONSOLE_POLL support for future KGDB porting.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Changes since v1:
1. Fix the compile error reported by kbuild test robot
Link: https://lore.kernel.org/r/1584492027-23236-1-git-send-email-vincent.chen@sifive.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c
index d34031e842d0087eb861666d309df5676fff4cd8..13eadcb8aec4e1554cca30ad399577cf1dace2ae 100644 (file)
--- a/drivers/tty/serial/sifive.c
+++ b/drivers/tty/serial/sifive.c
@@ -729,6 +729,29 @@ static const char *sifive_serial_type(struct uart_port *port)
        return port->type == PORT_SIFIVE_V0 ? "SiFive UART v0" : NULL;
 }
 
+#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);
+
+       __ssp_wait_for_xmitr(ssp);
+       __ssp_transmit_char(ssp, c);
+}
+#endif /* CONFIG_CONSOLE_POLL */
+
 /*
  * Early console support
  */
@@ -897,6 +920,10 @@ static const struct uart_ops sifive_serial_uops = {
        .request_port   = sifive_serial_request_port,
        .config_port    = sifive_serial_config_port,
        .verify_port    = sifive_serial_verify_port,
+#ifdef CONFIG_CONSOLE_POLL
+       .poll_get_char  = sifive_serial_poll_get_char,
+       .poll_put_char  = sifive_serial_poll_put_char,
+#endif
 };
 
 static struct uart_driver sifive_serial_uart_driver = {