serial: bfin_sport_uart: shorten the SPORT TX waiting loop

The waiting loop to stop SPORT TX from TX interrupt is too long.  This may
block the SPORT RX interrupts and cause the RX FIFO to overflow. So, do
stop sport TX only after the last char in TX FIFO is moved into the shift
register.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/serial/bfin_sport_uart.c b/drivers/serial/bfin_sport_uart.c
index c88f8ad3ff821d16fef218c5021adede8c9c6cf1..6991c3605f9cec662bba10132407377ef4fc6623 100644 (file)
--- a/drivers/serial/bfin_sport_uart.c
+++ b/drivers/serial/bfin_sport_uart.c
@@ -271,7 +271,13 @@ static void sport_uart_tx_chars(struct sport_uart_port *up)
        }
 
        if (uart_circ_empty(xmit) || uart_tx_stopped(&up->port)) {
-               sport_stop_tx(&up->port);
+               /* The waiting loop to stop SPORT TX from TX interrupt is
+                * too long. This may block SPORT RX interrupts and cause
+                * RX FIFO overflow. So, do stop sport TX only after the last
+                * char in TX FIFO is moved into the shift register.
+                */
+               if (SPORT_GET_STAT(up) & TXHRE)
+                       sport_stop_tx(&up->port);
                return;
        }