[PATCH v3 1/5] ep93xx: set DMA masks for the ep93xx_eth

Since the driver uses the DMA API, we should pass it valid DMA masks.

Signed-off-by: Mika Westerberg <redacted>
Acked-by: Russell King <redacted>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Tested-by: Petr Stetiar <redacted>
---
 arch/arm/mach-ep93xx/core.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/arch/arm/mach-ep93xx/core.c b/arch/arm/mach-ep93xx/core.c
index 8207954..1d4b65f 100644
--- a/arch/arm/mach-ep93xx/core.c
+++ b/arch/arm/mach-ep93xx/core.c

@@ -402,11 +402,15 @@ static struct resource ep93xx_eth_resource[] = {
 	}
 };
 
+static u64 ep93xx_eth_dma_mask = DMA_BIT_MASK(32);
+
 static struct platform_device ep93xx_eth_device = {
 	.name		= "ep93xx-eth",
 	.id		= -1,
 	.dev		= {
-		.platform_data	= &ep93xx_eth_data,
+		.platform_data		= &ep93xx_eth_data,
+		.coherent_dma_mask	= DMA_BIT_MASK(32),
+		.dma_mask		= &ep93xx_eth_dma_mask,
 	},
 	.num_resources	= ARRAY_SIZE(ep93xx_eth_resource),
 	.resource	= ep93xx_eth_resource,

-- 
1.7.4.4

We shouldn't use NULL for any DMA API functions, unless we are dealing with
ISA or EISA device. So pass correct struct dev pointer to these functions.

Signed-off-by: Mika Westerberg <redacted>
---
I modified this patch according to Hartley's comments; There is no separate
dma_dev pointer in ep93xx_priv structure but we use SET_NETDEV_DEV() to store
pointer to the platform device which we use as the device for DMA API.

Because this patch is different than the original one, I dropped all the acks
and tested-by's.

 drivers/net/arm/ep93xx_eth.c |   23 +++++++++++++----------
 1 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/net/arm/ep93xx_eth.c b/drivers/net/arm/ep93xx_eth.c
index 5a77001..f65dfb6 100644
--- a/drivers/net/arm/ep93xx_eth.c
+++ b/drivers/net/arm/ep93xx_eth.c

@@ -284,7 +284,7 @@ static int ep93xx_rx(struct net_device *dev, int processed, int budget)
 		skb = dev_alloc_skb(length + 2);
 		if (likely(skb != NULL)) {
 			skb_reserve(skb, 2);
-			dma_sync_single_for_cpu(NULL, ep->descs->rdesc[entry].buf_addr,
+			dma_sync_single_for_cpu(dev->dev.parent, ep->descs->rdesc[entry].buf_addr,
 						length, DMA_FROM_DEVICE);
 			skb_copy_to_linear_data(skb, ep->rx_buf[entry], length);
 			skb_put(skb, length);

@@ -362,7 +362,7 @@ static int ep93xx_xmit(struct sk_buff *skb, struct net_device *dev)
 	ep->descs->tdesc[entry].tdesc1 =
 		TDESC1_EOF | (entry << 16) | (skb->len & 0xfff);
 	skb_copy_and_csum_dev(skb, ep->tx_buf[entry]);
-	dma_sync_single_for_cpu(NULL, ep->descs->tdesc[entry].buf_addr,
+	dma_sync_single_for_cpu(dev->dev.parent, ep->descs->tdesc[entry].buf_addr,
 				skb->len, DMA_TO_DEVICE);
 	dev_kfree_skb(skb);
 

@@ -457,6 +457,7 @@ static irqreturn_t ep93xx_irq(int irq, void *dev_id)
 
 static void ep93xx_free_buffers(struct ep93xx_priv *ep)
 {
+	struct device *dev = ep->dev->dev.parent;
 	int i;
 
 	for (i = 0; i < RX_QUEUE_ENTRIES; i += 2) {

@@ -464,7 +465,7 @@ static void ep93xx_free_buffers(struct ep93xx_priv *ep)
 
 		d = ep->descs->rdesc[i].buf_addr;
 		if (d)
-			dma_unmap_single(NULL, d, PAGE_SIZE, DMA_FROM_DEVICE);
+			dma_unmap_single(dev, d, PAGE_SIZE, DMA_FROM_DEVICE);
 
 		if (ep->rx_buf[i] != NULL)
 			free_page((unsigned long)ep->rx_buf[i]);

@@ -475,13 +476,13 @@ static void ep93xx_free_buffers(struct ep93xx_priv *ep)
 
 		d = ep->descs->tdesc[i].buf_addr;
 		if (d)
-			dma_unmap_single(NULL, d, PAGE_SIZE, DMA_TO_DEVICE);
+			dma_unmap_single(dev, d, PAGE_SIZE, DMA_TO_DEVICE);
 
 		if (ep->tx_buf[i] != NULL)
 			free_page((unsigned long)ep->tx_buf[i]);
 	}
 
-	dma_free_coherent(NULL, sizeof(struct ep93xx_descs), ep->descs,
+	dma_free_coherent(dev, sizeof(struct ep93xx_descs), ep->descs,
 							ep->descs_dma_addr);
 }
 

@@ -491,9 +492,10 @@ static void ep93xx_free_buffers(struct ep93xx_priv *ep)
  */
 static int ep93xx_alloc_buffers(struct ep93xx_priv *ep)
 {
+	struct device *dev = ep->dev->dev.parent;
 	int i;
 
-	ep->descs = dma_alloc_coherent(NULL, sizeof(struct ep93xx_descs),
+	ep->descs = dma_alloc_coherent(dev, sizeof(struct ep93xx_descs),
 				&ep->descs_dma_addr, GFP_KERNEL | GFP_DMA);
 	if (ep->descs == NULL)
 		return 1;

@@ -506,8 +508,8 @@ static int ep93xx_alloc_buffers(struct ep93xx_priv *ep)
 		if (page == NULL)
 			goto err;
 
-		d = dma_map_single(NULL, page, PAGE_SIZE, DMA_FROM_DEVICE);
-		if (dma_mapping_error(NULL, d)) {
+		d = dma_map_single(dev, page, PAGE_SIZE, DMA_FROM_DEVICE);
+		if (dma_mapping_error(dev, d)) {
 			free_page((unsigned long)page);
 			goto err;
 		}

@@ -529,8 +531,8 @@ static int ep93xx_alloc_buffers(struct ep93xx_priv *ep)
 		if (page == NULL)
 			goto err;
 
-		d = dma_map_single(NULL, page, PAGE_SIZE, DMA_TO_DEVICE);
-		if (dma_mapping_error(NULL, d)) {
+		d = dma_map_single(dev, page, PAGE_SIZE, DMA_TO_DEVICE);
+		if (dma_mapping_error(dev, d)) {
 			free_page((unsigned long)page);
 			goto err;
 		}

@@ -829,6 +831,7 @@ static int ep93xx_eth_probe(struct platform_device *pdev)
 	}
 	ep = netdev_priv(dev);
 	ep->dev = dev;
+	SET_NETDEV_DEV(dev, &pdev->dev);
 	netif_napi_add(dev, &ep->napi, ep93xx_poll, 64);
 
 	platform_set_drvdata(pdev, dev);

-- 
1.7.4.4

From: Mika Westerberg <redacted>
Date: Sat, 11 Jun 2011 21:39:55 +0300

We shouldn't use NULL for any DMA API functions, unless we are dealing with
ISA or EISA device. So pass correct struct dev pointer to these functions.

Signed-off-by: Mika Westerberg <redacted>

Applied.

We can use simply kmalloc() to allocate the buffers. This also simplifies the
code and allows us to perform DMA sync operations more easily.

Memory is allocated with only GFP_KERNEL since there are no DMA allocation
restrictions on this platform.

Signed-off-by: Mika Westerberg <redacted>
Acked-by: Russell King <redacted>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Tested-by: Petr Stetiar <redacted>
---
 drivers/net/arm/ep93xx_eth.c |   51 ++++++++++++++++-------------------------
 1 files changed, 20 insertions(+), 31 deletions(-)

diff --git a/drivers/net/arm/ep93xx_eth.c b/drivers/net/arm/ep93xx_eth.c
index f65dfb6..97bf6b1 100644
--- a/drivers/net/arm/ep93xx_eth.c
+++ b/drivers/net/arm/ep93xx_eth.c

@@ -460,36 +460,32 @@ static void ep93xx_free_buffers(struct ep93xx_priv *ep)
 	struct device *dev = ep->dev->dev.parent;
 	int i;
 
-	for (i = 0; i < RX_QUEUE_ENTRIES; i += 2) {
+	for (i = 0; i < RX_QUEUE_ENTRIES; i++) {
 		dma_addr_t d;
 
 		d = ep->descs->rdesc[i].buf_addr;
 		if (d)
-			dma_unmap_single(dev, d, PAGE_SIZE, DMA_FROM_DEVICE);
+			dma_unmap_single(dev, d, PKT_BUF_SIZE, DMA_FROM_DEVICE);
 
 		if (ep->rx_buf[i] != NULL)
-			free_page((unsigned long)ep->rx_buf[i]);
+			kfree(ep->rx_buf[i]);
 	}
 
-	for (i = 0; i < TX_QUEUE_ENTRIES; i += 2) {
+	for (i = 0; i < TX_QUEUE_ENTRIES; i++) {
 		dma_addr_t d;
 
 		d = ep->descs->tdesc[i].buf_addr;
 		if (d)
-			dma_unmap_single(dev, d, PAGE_SIZE, DMA_TO_DEVICE);
+			dma_unmap_single(dev, d, PKT_BUF_SIZE, DMA_TO_DEVICE);
 
 		if (ep->tx_buf[i] != NULL)
-			free_page((unsigned long)ep->tx_buf[i]);
+			kfree(ep->tx_buf[i]);
 	}
 
 	dma_free_coherent(dev, sizeof(struct ep93xx_descs), ep->descs,
 							ep->descs_dma_addr);
 }
 
-/*
- * The hardware enforces a sub-2K maximum packet size, so we put
- * two buffers on every hardware page.
- */
 static int ep93xx_alloc_buffers(struct ep93xx_priv *ep)
 {
 	struct device *dev = ep->dev->dev.parent;

@@ -500,48 +496,41 @@ static int ep93xx_alloc_buffers(struct ep93xx_priv *ep)
 	if (ep->descs == NULL)
 		return 1;
 
-	for (i = 0; i < RX_QUEUE_ENTRIES; i += 2) {
-		void *page;
+	for (i = 0; i < RX_QUEUE_ENTRIES; i++) {
+		void *buf;
 		dma_addr_t d;
 
-		page = (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
-		if (page == NULL)
+		buf = kmalloc(PKT_BUF_SIZE, GFP_KERNEL);
+		if (buf == NULL)
 			goto err;
 
-		d = dma_map_single(dev, page, PAGE_SIZE, DMA_FROM_DEVICE);
+		d = dma_map_single(dev, buf, PKT_BUF_SIZE, DMA_FROM_DEVICE);
 		if (dma_mapping_error(dev, d)) {
-			free_page((unsigned long)page);
+			kfree(buf);
 			goto err;
 		}
 
-		ep->rx_buf[i] = page;
+		ep->rx_buf[i] = buf;
 		ep->descs->rdesc[i].buf_addr = d;
 		ep->descs->rdesc[i].rdesc1 = (i << 16) | PKT_BUF_SIZE;
-
-		ep->rx_buf[i + 1] = page + PKT_BUF_SIZE;
-		ep->descs->rdesc[i + 1].buf_addr = d + PKT_BUF_SIZE;
-		ep->descs->rdesc[i + 1].rdesc1 = ((i + 1) << 16) | PKT_BUF_SIZE;
 	}
 
-	for (i = 0; i < TX_QUEUE_ENTRIES; i += 2) {
-		void *page;
+	for (i = 0; i < TX_QUEUE_ENTRIES; i++) {
+		void *buf;
 		dma_addr_t d;
 
-		page = (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
-		if (page == NULL)
+		buf = kmalloc(PKT_BUF_SIZE, GFP_KERNEL);
+		if (buf == NULL)
 			goto err;
 
-		d = dma_map_single(dev, page, PAGE_SIZE, DMA_TO_DEVICE);
+		d = dma_map_single(dev, buf, PKT_BUF_SIZE, DMA_TO_DEVICE);
 		if (dma_mapping_error(dev, d)) {
-			free_page((unsigned long)page);
+			kfree(buf);
 			goto err;
 		}
 
-		ep->tx_buf[i] = page;
+		ep->tx_buf[i] = buf;
 		ep->descs->tdesc[i].buf_addr = d;
-
-		ep->tx_buf[i + 1] = page + PKT_BUF_SIZE;
-		ep->descs->tdesc[i + 1].buf_addr = d + PKT_BUF_SIZE;
 	}
 
 	return 0;

-- 
1.7.4.4

From: Mika Westerberg <redacted>
Date: Sat, 11 Jun 2011 21:39:56 +0300

We can use simply kmalloc() to allocate the buffers. This also simplifies the
code and allows us to perform DMA sync operations more easily.

Memory is allocated with only GFP_KERNEL since there are no DMA allocation
restrictions on this platform.

Signed-off-by: Mika Westerberg <redacted>
Acked-by: Russell King <redacted>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Tested-by: Petr Stetiar <redacted>

Applied.

Commit a197b59ae6e8 (mm: fail GFP_DMA allocations when ZONE_DMA is not
configured) made page allocator to return NULL if GFP_DMA is set but
CONFIG_ZONE_DMA is disabled.

This causes ep93xx_eth to fail:

 WARNING: at mm/page_alloc.c:2251 __alloc_pages_nodemask+0x11c/0x638()
 Modules linked in:
 [<c0035498>] (unwind_backtrace+0x0/0xf4) from [<c0043da4>] (warn_slowpath_common+0x48/0x60)
 [<c0043da4>] (warn_slowpath_common+0x48/0x60) from [<c0043dd8>] (warn_slowpath_null+0x1c/0x24)
 [<c0043dd8>] (warn_slowpath_null+0x1c/0x24) from [<c0083b6c>] (__alloc_pages_nodemask+0x11c/0x638)
 [<c0083b6c>] (__alloc_pages_nodemask+0x11c/0x638) from [<c00366fc>] (__dma_alloc+0x8c/0x3ec)
 [<c00366fc>] (__dma_alloc+0x8c/0x3ec) from [<c0036adc>] (dma_alloc_coherent+0x54/0x60)
 [<c0036adc>] (dma_alloc_coherent+0x54/0x60) from [<c0227808>] (ep93xx_open+0x20/0x864)
 [<c0227808>] (ep93xx_open+0x20/0x864) from [<c0283144>] (__dev_open+0xb8/0x108)
 [<c0283144>] (__dev_open+0xb8/0x108) from [<c0280528>] (__dev_change_flags+0x70/0x128)
 [<c0280528>] (__dev_change_flags+0x70/0x128) from [<c0283054>] (dev_change_flags+0x10/0x48)
 [<c0283054>] (dev_change_flags+0x10/0x48) from [<c001a720>] (ip_auto_config+0x190/0xf68)
 [<c001a720>] (ip_auto_config+0x190/0xf68) from [<c00233b0>] (do_one_initcall+0x34/0x18c)
 [<c00233b0>] (do_one_initcall+0x34/0x18c) from [<c0008400>] (kernel_init+0x94/0x134)
 [<c0008400>] (kernel_init+0x94/0x134) from [<c0030858>] (kernel_thread_exit+0x0/0x8)

Since there is no restrictions for DMA on ep93xx, we can fix this by just
removing the GFP_DMA flag from the call.

Signed-off-by: Mika Westerberg <redacted>
Acked-by: Russell King <redacted>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Tested-by: Petr Stetiar <redacted>
---
 drivers/net/arm/ep93xx_eth.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/net/arm/ep93xx_eth.c b/drivers/net/arm/ep93xx_eth.c
index 97bf6b1..bef3811 100644
--- a/drivers/net/arm/ep93xx_eth.c
+++ b/drivers/net/arm/ep93xx_eth.c

@@ -492,7 +492,7 @@ static int ep93xx_alloc_buffers(struct ep93xx_priv *ep)
 	int i;
 
 	ep->descs = dma_alloc_coherent(dev, sizeof(struct ep93xx_descs),
-				&ep->descs_dma_addr, GFP_KERNEL | GFP_DMA);
+				&ep->descs_dma_addr, GFP_KERNEL);
 	if (ep->descs == NULL)
 		return 1;
 

-- 
1.7.4.4

From: Mika Westerberg <redacted>
Date: Sat, 11 Jun 2011 21:39:57 +0300

Commit a197b59ae6e8 (mm: fail GFP_DMA allocations when ZONE_DMA is not
configured) made page allocator to return NULL if GFP_DMA is set but
CONFIG_ZONE_DMA is disabled.

This causes ep93xx_eth to fail:

 WARNING: at mm/page_alloc.c:2251 __alloc_pages_nodemask+0x11c/0x638()
 Modules linked in:
 [<c0035498>] (unwind_backtrace+0x0/0xf4) from [<c0043da4>] (warn_slowpath_common+0x48/0x60)
 [<c0043da4>] (warn_slowpath_common+0x48/0x60) from [<c0043dd8>] (warn_slowpath_null+0x1c/0x24)
 [<c0043dd8>] (warn_slowpath_null+0x1c/0x24) from [<c0083b6c>] (__alloc_pages_nodemask+0x11c/0x638)
 [<c0083b6c>] (__alloc_pages_nodemask+0x11c/0x638) from [<c00366fc>] (__dma_alloc+0x8c/0x3ec)
 [<c00366fc>] (__dma_alloc+0x8c/0x3ec) from [<c0036adc>] (dma_alloc_coherent+0x54/0x60)
 [<c0036adc>] (dma_alloc_coherent+0x54/0x60) from [<c0227808>] (ep93xx_open+0x20/0x864)
 [<c0227808>] (ep93xx_open+0x20/0x864) from [<c0283144>] (__dev_open+0xb8/0x108)
 [<c0283144>] (__dev_open+0xb8/0x108) from [<c0280528>] (__dev_change_flags+0x70/0x128)
 [<c0280528>] (__dev_change_flags+0x70/0x128) from [<c0283054>] (dev_change_flags+0x10/0x48)
 [<c0283054>] (dev_change_flags+0x10/0x48) from [<c001a720>] (ip_auto_config+0x190/0xf68)
 [<c001a720>] (ip_auto_config+0x190/0xf68) from [<c00233b0>] (do_one_initcall+0x34/0x18c)
 [<c00233b0>] (do_one_initcall+0x34/0x18c) from [<c0008400>] (kernel_init+0x94/0x134)
 [<c0008400>] (kernel_init+0x94/0x134) from [<c0030858>] (kernel_thread_exit+0x0/0x8)

Since there is no restrictions for DMA on ep93xx, we can fix this by just
removing the GFP_DMA flag from the call.

Signed-off-by: Mika Westerberg <redacted>
Acked-by: Russell King <redacted>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Tested-by: Petr Stetiar <redacted>

Applied.

Russell King said:

So, to summarize what its doing:

1. It allocates buffers for rx and tx.
2. It maps them with dma_map_single().
      This transfers ownership of the buffer to the DMA device.
3. In ep93xx_xmit,
3a. It copies the data into the buffer with skb_copy_and_csum_dev()
      This violates the DMA buffer ownership rules - the CPU should
      not be writing to this buffer while it is (in principle) owned
      by the DMA device.
3b. It then calls dma_sync_single_for_cpu() for the buffer.
      This transfers ownership of the buffer to the CPU, which surely
      is the wrong direction.
4. In ep93xx_rx,
4a. It calls dma_sync_single_for_cpu() for the buffer.
      This at least transfers the DMA buffer ownership to the CPU
      before the CPU reads the buffer
4b. It then uses skb_copy_to_linear_data() to copy the data out.
      At no point does it transfer ownership back to the DMA device.
5. When the driver is removed, it dma_unmap_single()'s the buffer.
      This transfers ownership of the buffer to the CPU.
6. It frees the buffer.

While it may work on ep93xx, it's not respecting the DMA API rules,
and with DMA debugging enabled it will probably encounter quite a few
warnings.

This patch fixes these violations.

Signed-off-by: Mika Westerberg <redacted>
Acked-by: Russell King <redacted>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Tested-by: Petr Stetiar <redacted>
---
 drivers/net/arm/ep93xx_eth.c |   18 +++++++++++++-----
 1 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/net/arm/ep93xx_eth.c b/drivers/net/arm/ep93xx_eth.c
index bef3811..0b46b8e 100644
--- a/drivers/net/arm/ep93xx_eth.c
+++ b/drivers/net/arm/ep93xx_eth.c

@@ -283,10 +283,14 @@ static int ep93xx_rx(struct net_device *dev, int processed, int budget)
 
 		skb = dev_alloc_skb(length + 2);
 		if (likely(skb != NULL)) {
+			struct ep93xx_rdesc *rxd = &ep->descs->rdesc[entry];
 			skb_reserve(skb, 2);
-			dma_sync_single_for_cpu(dev->dev.parent, ep->descs->rdesc[entry].buf_addr,
+			dma_sync_single_for_cpu(dev->dev.parent, rxd->buf_addr,
 						length, DMA_FROM_DEVICE);
 			skb_copy_to_linear_data(skb, ep->rx_buf[entry], length);
+			dma_sync_single_for_device(dev->dev.parent,
+						   rxd->buf_addr, length,
+						   DMA_FROM_DEVICE);
 			skb_put(skb, length);
 			skb->protocol = eth_type_trans(skb, dev);
 

@@ -348,6 +352,7 @@ poll_some_more:
 static int ep93xx_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct ep93xx_priv *ep = netdev_priv(dev);
+	struct ep93xx_tdesc *txd;
 	int entry;
 
 	if (unlikely(skb->len > MAX_PKT_SIZE)) {

@@ -359,11 +364,14 @@ static int ep93xx_xmit(struct sk_buff *skb, struct net_device *dev)
 	entry = ep->tx_pointer;
 	ep->tx_pointer = (ep->tx_pointer + 1) & (TX_QUEUE_ENTRIES - 1);
 
-	ep->descs->tdesc[entry].tdesc1 =
-		TDESC1_EOF | (entry << 16) | (skb->len & 0xfff);
+	txd = &ep->descs->tdesc[entry];
+
+	txd->tdesc1 = TDESC1_EOF | (entry << 16) | (skb->len & 0xfff);
+	dma_sync_single_for_cpu(dev->dev.parent, txd->buf_addr, skb->len,
+				DMA_TO_DEVICE);
 	skb_copy_and_csum_dev(skb, ep->tx_buf[entry]);
-	dma_sync_single_for_cpu(dev->dev.parent, ep->descs->tdesc[entry].buf_addr,
-				skb->len, DMA_TO_DEVICE);
+	dma_sync_single_for_device(dev->dev.parent, txd->buf_addr, skb->len,
+				   DMA_TO_DEVICE);
 	dev_kfree_skb(skb);
 
 	spin_lock_irq(&ep->tx_pending_lock);

-- 
1.7.4.4

From: Mika Westerberg <redacted>
Date: Sat, 11 Jun 2011 21:39:58 +0300

Russell King said:

quoted

So, to summarize what its doing:

1. It allocates buffers for rx and tx.
2. It maps them with dma_map_single().
      This transfers ownership of the buffer to the DMA device.
3. In ep93xx_xmit,
3a. It copies the data into the buffer with skb_copy_and_csum_dev()
      This violates the DMA buffer ownership rules - the CPU should
      not be writing to this buffer while it is (in principle) owned
      by the DMA device.
3b. It then calls dma_sync_single_for_cpu() for the buffer.
      This transfers ownership of the buffer to the CPU, which surely
      is the wrong direction.
4. In ep93xx_rx,
4a. It calls dma_sync_single_for_cpu() for the buffer.
      This at least transfers the DMA buffer ownership to the CPU
      before the CPU reads the buffer
4b. It then uses skb_copy_to_linear_data() to copy the data out.
      At no point does it transfer ownership back to the DMA device.
5. When the driver is removed, it dma_unmap_single()'s the buffer.
      This transfers ownership of the buffer to the CPU.
6. It frees the buffer.

While it may work on ep93xx, it's not respecting the DMA API rules,
and with DMA debugging enabled it will probably encounter quite a few
warnings.

This patch fixes these violations.

Signed-off-by: Mika Westerberg <redacted>
Acked-by: Russell King <redacted>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Tested-by: Petr Stetiar <redacted>

Applied.

From: Mika Westerberg <redacted>
Date: Sat, 11 Jun 2011 21:39:54 +0300

Since the driver uses the DMA API, we should pass it valid DMA masks.

Signed-off-by: Mika Westerberg <redacted>
Acked-by: Russell King <redacted>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Tested-by: Petr Stetiar <redacted>

Applied.