[PATCH 03/13] tty: serial: atmel: Call dma_async_issue_pending()

[Tudor Ambarus]

The driver wrongly assummed that tx_submit() will start the transfer,
which is not the case, now that the at_xdmac driver is fixed. tx_submit
is supposed to push the current transaction descriptor to a pending queue,
waiting for issue_pending to be called. issue_pending must start the
transfer, not tx_submit. While touching atmel_prepare_rx_dma(), introduce
a local variable for the RX dma channel.

Fixes: 34df42f59a60 ("serial: at91: add rx dma support")
Fixes: 08f738be88bb ("serial: at91: add tx dma support")
Signed-off-by: Tudor Ambarus <tudor.ambarus at microchip.com>
---
 drivers/tty/serial/atmel_serial.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 376f7a9c2868..b3e593f3c17f 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -1009,6 +1009,8 @@ static void atmel_tx_dma(struct uart_port *port)
 				atmel_port->cookie_tx);
 			return;
 		}
+
+		dma_async_issue_pending(chan);
 	}
 
 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
@@ -1191,6 +1193,7 @@ static void atmel_rx_from_dma(struct uart_port *port)
 static int atmel_prepare_rx_dma(struct uart_port *port)
 {
 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+	struct dma_chan *chan_rx;
 	struct device *mfd_dev = port->dev->parent;
 	struct dma_async_tx_descriptor *desc;
 	dma_cap_mask_t		mask;
@@ -1203,11 +1206,13 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
 	dma_cap_zero(mask);
 	dma_cap_set(DMA_CYCLIC, mask);
 
-	atmel_port->chan_rx = dma_request_slave_channel(mfd_dev, "rx");
-	if (atmel_port->chan_rx == NULL)
+	chan_rx = dma_request_slave_channel(mfd_dev, "rx");
+	if (chan_rx == NULL)
 		goto chan_err;
+	atmel_port->chan_rx = chan_rx;
+
 	dev_info(port->dev, "using %s for rx DMA transfers\n",
-		dma_chan_name(atmel_port->chan_rx));
+		 dma_chan_name(chan_rx));
 
 	spin_lock_init(&atmel_port->lock_rx);
 	sg_init_table(&atmel_port->sg_rx, 1);
@@ -1239,8 +1244,7 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
 	config.src_addr = port->mapbase + ATMEL_US_RHR;
 	config.src_maxburst = 1;
 
-	ret = dmaengine_slave_config(atmel_port->chan_rx,
-				     &config);
+	ret = dmaengine_slave_config(chan_rx, &config);
 	if (ret) {
 		dev_err(port->dev, "DMA rx slave configuration failed\n");
 		goto chan_err;
@@ -1249,7 +1253,7 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
 	 * Prepare a cyclic dma transfer, assign 2 descriptors,
 	 * each one is half ring buffer size
 	 */
-	desc = dmaengine_prep_dma_cyclic(atmel_port->chan_rx,
+	desc = dmaengine_prep_dma_cyclic(chan_rx,
 					 sg_dma_address(&atmel_port->sg_rx),
 					 sg_dma_len(&atmel_port->sg_rx),
 					 sg_dma_len(&atmel_port->sg_rx)/2,
@@ -1269,12 +1273,14 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
 		goto chan_err;
 	}
 
+	dma_async_issue_pending(chan_rx);
+
 	return 0;
 
 chan_err:
 	dev_err(port->dev, "RX channel not available, switch to pio\n");
 	atmel_port->use_dma_rx = false;
-	if (atmel_port->chan_rx)
+	if (chan_rx)
 		atmel_release_rx_dma(port);
 	return -EINVAL;
 }
-- 
2.25.1