[PATCH v3] serial: samsung: use dma_ops of DMA if attached

[Tamseel Shams <m.shams@samsung.com>]

When DMA is used for TX and RX by serial driver, it should
pass the DMA device pointer to DMA API instead of UART device
pointer. DMA device should be used for DMA API because only
the DMA device is aware of how the device connects to the memory.
There might be an extra level of address translation due to a
SMMU attached to the DMA device. When serial device pointer device
is used for DMA API, the DMA API will have no clue of the SMMU
attached to the DMA device.

This patch is necessary to fix the SMMU page faults
which is observed when a DMA(with SMMU enabled) is attached
to UART for transfer.

Signed-off-by: Tamseel Shams <m.shams@samsung.com>
Signed-off-by: Ajay Kumar <ajaykumar.rs@samsung.com>
---
Changes since v1:
1. Rebased the patch on "tty-next" branch of TTY driver tree

Changes since v2:
1. Updated the commit message.
2. Changed the comment description

 drivers/tty/serial/samsung_tty.c | 62 +++++++++++++++++++++++++-------
 1 file changed, 50 insertions(+), 12 deletions(-)

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index 9fbc61151c2e..7dd648cb7237 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -284,8 +284,13 @@ static void s3c24xx_serial_stop_tx(struct uart_port *port)
 	struct s3c24xx_uart_dma *dma = ourport->dma;
 	struct circ_buf *xmit = &port->state->xmit;
 	struct dma_tx_state state;
+	struct device *dma_map_ops_dev = ourport->port.dev;
 	int count;
 
+	/* Null pointer check for "dma" and "dma->tx_chan" */
+	if (dma && dma->tx_chan)
+		dma_map_ops_dev = dma->tx_chan->device->dev;
+
 	if (!ourport->tx_enabled)
 		return;
 
@@ -305,7 +310,7 @@ static void s3c24xx_serial_stop_tx(struct uart_port *port)
 		dmaengine_pause(dma->tx_chan);
 		dmaengine_tx_status(dma->tx_chan, dma->tx_cookie, &state);
 		dmaengine_terminate_all(dma->tx_chan);
-		dma_sync_single_for_cpu(ourport->port.dev,
+		dma_sync_single_for_cpu(dma_map_ops_dev,
 			dma->tx_transfer_addr, dma->tx_size, DMA_TO_DEVICE);
 		async_tx_ack(dma->tx_desc);
 		count = dma->tx_bytes_requested - state.residue;
@@ -331,14 +336,19 @@ static void s3c24xx_serial_tx_dma_complete(void *args)
 	struct circ_buf *xmit = &port->state->xmit;
 	struct s3c24xx_uart_dma *dma = ourport->dma;
 	struct dma_tx_state state;
+	struct device *dma_map_ops_dev = ourport->port.dev;
 	unsigned long flags;
 	int count;
 
+	/* Null pointer check for "dma" and "dma->tx_chan" */
+	if (dma && dma->tx_chan)
+		dma_map_ops_dev = dma->tx_chan->device->dev;
+
 	dmaengine_tx_status(dma->tx_chan, dma->tx_cookie, &state);
 	count = dma->tx_bytes_requested - state.residue;
 	async_tx_ack(dma->tx_desc);
 
-	dma_sync_single_for_cpu(ourport->port.dev, dma->tx_transfer_addr,
+	dma_sync_single_for_cpu(dma_map_ops_dev, dma->tx_transfer_addr,
 				dma->tx_size, DMA_TO_DEVICE);
 
 	spin_lock_irqsave(&port->lock, flags);
@@ -436,6 +446,11 @@ static int s3c24xx_serial_start_tx_dma(struct s3c24xx_uart_port *ourport,
 	struct uart_port *port = &ourport->port;
 	struct circ_buf *xmit = &port->state->xmit;
 	struct s3c24xx_uart_dma *dma = ourport->dma;
+	struct device *dma_map_ops_dev = ourport->port.dev;
+
+	/* Null pointer check for "dma" and "dma->tx_chan" */
+	if (dma && dma->tx_chan)
+		dma_map_ops_dev = dma->tx_chan->device->dev;
 
 	if (ourport->tx_mode != S3C24XX_TX_DMA)
 		enable_tx_dma(ourport);
@@ -443,7 +458,7 @@ static int s3c24xx_serial_start_tx_dma(struct s3c24xx_uart_port *ourport,
 	dma->tx_size = count & ~(dma_get_cache_alignment() - 1);
 	dma->tx_transfer_addr = dma->tx_addr + xmit->tail;
 
-	dma_sync_single_for_device(ourport->port.dev, dma->tx_transfer_addr,
+	dma_sync_single_for_device(dma_map_ops_dev, dma->tx_transfer_addr,
 				dma->tx_size, DMA_TO_DEVICE);
 
 	dma->tx_desc = dmaengine_prep_slave_single(dma->tx_chan,
@@ -510,12 +525,17 @@ static void s3c24xx_uart_copy_rx_to_tty(struct s3c24xx_uart_port *ourport,
 		struct tty_port *tty, int count)
 {
 	struct s3c24xx_uart_dma *dma = ourport->dma;
+	struct device *dma_map_ops_dev = ourport->port.dev;
 	int copied;
 
+	/* Null pointer check for "dma" and "dma->rx_chan" */
+	if (dma && dma->rx_chan)
+		dma_map_ops_dev = dma->rx_chan->device->dev;
+
 	if (!count)
 		return;
 
-	dma_sync_single_for_cpu(ourport->port.dev, dma->rx_addr,
+	dma_sync_single_for_cpu(dma_map_ops_dev, dma->rx_addr,
 				dma->rx_size, DMA_FROM_DEVICE);
 
 	ourport->port.icount.rx += count;
@@ -635,8 +655,13 @@ static void s3c24xx_serial_rx_dma_complete(void *args)
 static void s3c64xx_start_rx_dma(struct s3c24xx_uart_port *ourport)
 {
 	struct s3c24xx_uart_dma *dma = ourport->dma;
+	struct device *dma_map_ops_dev = ourport->port.dev;
+
+	/* Null pointer check for "dma" and "dma->rx_chan" */
+	if (dma && dma->rx_chan)
+		dma_map_ops_dev = dma->rx_chan->device->dev;
 
-	dma_sync_single_for_device(ourport->port.dev, dma->rx_addr,
+	dma_sync_single_for_device(dma_map_ops_dev, dma->rx_addr,
 				dma->rx_size, DMA_FROM_DEVICE);
 
 	dma->rx_desc = dmaengine_prep_slave_single(dma->rx_chan,
@@ -1045,6 +1070,7 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 	struct s3c24xx_uart_dma	*dma = p->dma;
 	struct dma_slave_caps dma_caps;
 	const char *reason = NULL;
+	struct device *dma_map_ops_dev = p->port.dev;
 	int ret;
 
 	/* Default slave configuration parameters */
@@ -1102,18 +1128,25 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 		goto err_release_tx;
 	}
 
-	dma->rx_addr = dma_map_single(p->port.dev, dma->rx_buf,
+	/* Null pointer check for "dma" and "dma->rx_chan" */
+	if (dma && dma->rx_chan)
+		dma_map_ops_dev = dma->rx_chan->device->dev;
+
+	dma->rx_addr = dma_map_single(dma_map_ops_dev, dma->rx_buf,
 				dma->rx_size, DMA_FROM_DEVICE);
-	if (dma_mapping_error(p->port.dev, dma->rx_addr)) {
+	if (dma_mapping_error(dma_map_ops_dev, dma->rx_addr)) {
 		reason = "DMA mapping error for RX buffer";
 		ret = -EIO;
 		goto err_free_rx;
 	}
 
+	/* Null pointer check for "dma" and "dma->tx_chan" */
+	if (dma && dma->tx_chan)
+		dma_map_ops_dev = dma->tx_chan->device->dev;
 	/* TX buffer */
-	dma->tx_addr = dma_map_single(p->port.dev, p->port.state->xmit.buf,
+	dma->tx_addr = dma_map_single(dma_map_ops_dev, p->port.state->xmit.buf,
 				UART_XMIT_SIZE, DMA_TO_DEVICE);
-	if (dma_mapping_error(p->port.dev, dma->tx_addr)) {
+	if (dma_mapping_error(dma_map_ops_dev, dma->tx_addr)) {
 		reason = "DMA mapping error for TX buffer";
 		ret = -EIO;
 		goto err_unmap_rx;
@@ -1122,7 +1155,9 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 	return 0;
 
 err_unmap_rx:
-	dma_unmap_single(p->port.dev, dma->rx_addr, dma->rx_size,
+	if (dma->rx_chan)
+		dma_map_ops_dev = dma->rx_chan->device->dev;
+	dma_unmap_single(dma_map_ops_dev, dma->rx_addr, dma->rx_size,
 			 DMA_FROM_DEVICE);
 err_free_rx:
 	kfree(dma->rx_buf);
@@ -1139,10 +1174,12 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
 static void s3c24xx_serial_release_dma(struct s3c24xx_uart_port *p)
 {
 	struct s3c24xx_uart_dma	*dma = p->dma;
+	struct device *dma_map_ops_dev = p->port.dev;
 
 	if (dma->rx_chan) {
+		dma_map_ops_dev = dma->rx_chan->device->dev;
 		dmaengine_terminate_all(dma->rx_chan);
-		dma_unmap_single(p->port.dev, dma->rx_addr,
+		dma_unmap_single(dma_map_ops_dev, dma->rx_addr,
 				dma->rx_size, DMA_FROM_DEVICE);
 		kfree(dma->rx_buf);
 		dma_release_channel(dma->rx_chan);
@@ -1150,8 +1187,9 @@ static void s3c24xx_serial_release_dma(struct s3c24xx_uart_port *p)
 	}
 
 	if (dma->tx_chan) {
+		dma_map_ops_dev = dma->tx_chan->device->dev;
 		dmaengine_terminate_all(dma->tx_chan);
-		dma_unmap_single(p->port.dev, dma->tx_addr,
+		dma_unmap_single(dma_map_ops_dev, dma->tx_addr,
 				UART_XMIT_SIZE, DMA_TO_DEVICE);
 		dma_release_channel(dma->tx_chan);
 		dma->tx_chan = NULL;
-- 
2.17.1