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 <b38343@freescale.com>
Signed-off-by: Fugang Duan <B38611@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index ab958a5..d61b89e 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -946,8 +946,21 @@
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)