serial: imx: Avoid post-PIO cleanup if TX DMA is started

The imx_transmit_buffer function should return if TX DMA has already
been started and not just skip over the buffer PIO write loop. (Which
did fix the initial problem, but could have unintentional side-effects)

Tested on an i.MX6Q board with half-duplex RS-485 and with RS-232.

Cc: Clemens Gruber <clemens.gruber@pqgruber.com>
Cc: Uwe-Kleine König <u.kleine-koenig@pengutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Fixes: 514ab34dbad6 ("serial: imx: Prevent TX buffer PIO write when a DMA has been started")
Signed-off-by: Ian Jamison <ian.dev@arkver.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 d879a9b86424f11a49071a995a2dae226062d163..dfeff3951f934627f8ed45e892ee5d30cec3216b 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -457,7 +457,10 @@ static inline void imx_transmit_buffer(struct imx_port *sport)
                }
        }
 
-       while (!uart_circ_empty(xmit) && !sport->dma_is_txing &&
+       if (sport->dma_is_txing)
+               return;
+
+       while (!uart_circ_empty(xmit) &&
               !(readl(sport->port.membase + uts_reg(sport)) & UTS_TXFULL)) {
                /* send xmit->buf[xmit->tail]
                 * out the port here */