[linux-yocto] [PATCH 02/15] serial: 8250: don't change the fifo trigger level when using dma

[rebecca.swee.fun.chang at intel.com]

From: Heikki Krogerus <heikki.krogerus at linux.intel.com>

DMA engines usually expect the fifo trigger level to be
aligned with the burst size. It should not be changed even
with small baud rates. This will fix an issue with
Designware DMA engine where the data can not be transferred
over UART with lower baud rates then 2400.

Signed-off-by: Heikki Krogerus <heikki.krogerus at linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
(cherry picked from commit 2797f6fb6727d8ac5127f88aee1fd059db0be24b)
Signed-off-by: Chang Rebecca Swee Fun <rebecca.swee.fun.chang at intel.com>
---
 drivers/tty/serial/8250/8250_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index d28d7af..3d508f3 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -2322,7 +2322,7 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
 
 	if (up->capabilities & UART_CAP_FIFO && port->fifosize > 1) {
 		fcr = uart_config[port->type].fcr;
-		if (baud < 2400 || fifo_bug) {
+		if ((baud < 2400 && !up->dma) || fifo_bug) {
 			fcr &= ~UART_FCR_TRIGGER_MASK;
 			fcr |= UART_FCR_TRIGGER_1;
 		}
-- 
1.9.1