serial: sh-sci: Call dma_async_issue_pending when transaction completes

dmaengine_submit() will not start the DMA operation, it merely adds
it to the pending queue.  If the queue is no longer running, it won't be
restarted until dma_async_issue_pending() is called.
Signed-off-by: Muhammad Hamza Farooq <mfarooq@visteon.com>
[geert: Add more description]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sh-sci.c

@@ -1104,6 +1104,7 @@ static void sci_rx_dma_release(struct sci_port *s, bool enable_pio)
 static void sci_dma_rx_complete(void *arg)
 {
 	struct sci_port *s = arg;
+	struct dma_chan *chan = s->chan_rx;
 	struct uart_port *port = &s->port;
 	struct dma_async_tx_descriptor *desc;
 	unsigned long flags;
@@ -1137,6 +1138,8 @@ static void sci_dma_rx_complete(void *arg)
 
 	s->active_rx = s->cookie_rx[!active];
 
+	dma_async_issue_pending(chan);
+
 	dev_dbg(port->dev, "%s: cookie %d #%d, new active cookie %d\n",
 		__func__, s->cookie_rx[active], active, s->active_rx);
 	spin_unlock_irqrestore(&port->lock, flags);