[PATCH] serial: cpm_uart: return immediately from console poll

[Christophe Leroy]

kgdb expects poll function to return immediately and
returning NO_POLL_CHAR when no character is available.

Fixes: f5316b4aea024 ("kgdb,8250,pl011: Return immediately from console poll")
Cc: Jason Wessel <jason.wes...@windriver.com>
Cc: <sta...@vger.kernel.org>
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
---
 drivers/tty/serial/cpm_uart/cpm_uart_core.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/cpm_uart/cpm_uart_core.c 
b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
index cd3f3fc4e0a5..280acc4dfa90 100644
--- a/drivers/tty/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
@@ -1093,8 +1093,8 @@ static int poll_wait_key(char *obuf, struct uart_cpm_port 
*pinfo)
        /* Get the address of the host memory buffer.
         */
        bdp = pinfo->rx_cur;
-       while (bdp->cbd_sc & BD_SC_EMPTY)
-               ;
+       if (bdp->cbd_sc & BD_SC_EMPTY)
+               return NO_POLL_CHAR;
 
        /* If the buffer address is in the CPM DPRAM, don't
         * convert it.
@@ -1129,7 +1129,11 @@ static int cpm_get_poll_char(struct uart_port *port)
                poll_chars = 0;
        }
        if (poll_chars <= 0) {
-               poll_chars = poll_wait_key(poll_buf, pinfo);
+               int ret = poll_wait_key(poll_buf, pinfo);
+
+               if (ret == NO_POLL_CHAR)
+                       return ret;
+               poll_chars = ret;
                pollp = poll_buf;
        }
        poll_chars--;
-- 
2.13.3