[PATCH 3.16 245/328] serial: cpm_uart: return immediately from console poll

Ben Hutchings
2018-12-09T21:58:37Z

From: Christophe Leroy <christophe.leroy@c-s.fr>

commit be28c1e3ca29887e207f0cbcd294cefe5074bab6 upstream.

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.wessel@windriver.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/tty/serial/cpm_uart/cpm_uart_core.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--- a/drivers/tty/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
@@ -1062,8 +1062,8 @@ static int poll_wait_key(char *obuf, str
/* 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.
@@ -1097,7 +1097,11 @@ static int cpm_get_poll_char(struct uart
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--;