From ee5e7c1091a703c6a465d8145e9b55e09adb6f37 Mon Sep 17 00:00:00 2001 From: Robin Gong Date: Tue, 9 Dec 2014 18:11:33 +0900 Subject: [PATCH] serial: imx: start rx_dma once RXFIFO is not empty Start rx_dma once RXFIFO is not empty that can avoid dma request lost and causes data delay issue. Signed-off-by: Robin Gong Signed-off-by: Fugang Duan Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/imx.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index ab958a59cae9..d61b89e4a96e 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -946,8 +946,21 @@ static void dma_rx_callback(void *data) tty_flip_buffer_push(port); start_rx_dma(sport); - } else + } else if (readl(sport->port.membase + USR2) & USR2_RDR) { + /* + * start rx_dma directly once data in RXFIFO, more efficient + * than before: + * 1. call imx_rx_dma_done to stop dma if no data received + * 2. wait next RDR interrupt to start dma transfer. + */ + start_rx_dma(sport); + } else { + /* + * stop dma to prevent too many IDLE event trigged if no data + * in RXFIFO + */ imx_rx_dma_done(sport); + } } static int start_rx_dma(struct imx_port *sport)