[PATCH 1/5] net: ep93xx_eth: pass struct device to DMA API functions

[PATCH 1/5] net: ep93xx_eth: pass struct device to DMA API functions

[Mika Westerberg]

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 <mika.westerberg@iki.fi>
---
 drivers/net/arm/ep93xx_eth.c |   26 ++++++++++++++++----------
 1 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/net/arm/ep93xx_eth.c b/drivers/net/arm/ep93xx_eth.c
index 5a77001..8779d3b 100644
--- a/drivers/net/arm/ep93xx_eth.c
+++ b/drivers/net/arm/ep93xx_eth.c
@@ -159,6 +159,8 @@ struct ep93xx_priv
 	void __iomem		*base_addr;
 	int			irq;
 
+	struct device		*dma_dev;
+
 	struct ep93xx_descs	*descs;
 	dma_addr_t		descs_dma_addr;
 
@@ -284,7 +286,8 @@ 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(ep->dma_dev,
+						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 +365,7 @@ 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(ep->dma_dev, ep->descs->tdesc[entry].buf_addr,
 				skb->len, DMA_TO_DEVICE);
 	dev_kfree_skb(skb);
 
@@ -457,6 +460,7 @@ static irqreturn_t ep93xx_irq(int irq, void *dev_id)
 
 static void ep93xx_free_buffers(struct ep93xx_priv *ep)
 {
+	struct device *dev = ep->dma_dev;
 	int i;
 
 	for (i = 0; i < RX_QUEUE_ENTRIES; i += 2) {
@@ -464,7 +468,7 @@ 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 +479,13 @@ 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 +495,10 @@ static void ep93xx_free_buffers(struct ep93xx_priv *ep)
  */
 static int ep93xx_alloc_buffers(struct ep93xx_priv *ep)
 {
+	struct device *dev = ep->dma_dev;
 	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 +511,8 @@ 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 +534,8 @@ 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 +834,7 @@ static int ep93xx_eth_probe(struct platform_device *pdev)
 	}
 	ep = netdev_priv(dev);
 	ep->dev = dev;
+	ep->dma_dev = &pdev->dev;
 	netif_napi_add(dev, &ep->napi, ep93xx_poll, 64);
 
 	platform_set_drvdata(pdev, dev);
-- 
1.7.4.4

[PATCH 2/5] net: ep93xx_eth: allocate buffers using kmalloc()

[Mika Westerberg]

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 <mika.westerberg@iki.fi>
---
 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 8779d3b..0c9df11 100644
--- a/drivers/net/arm/ep93xx_eth.c
+++ b/drivers/net/arm/ep93xx_eth.c
@@ -463,36 +463,32 @@ static void ep93xx_free_buffers(struct ep93xx_priv *ep)
 	struct device *dev = ep->dma_dev;
 	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->dma_dev;
@@ -503,48 +499,41 @@ 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

[PATCH 3/5] net: ep93xx_eth: drop GFP_DMA from call to dma_alloc_coherent()

[Mika Westerberg]

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 <mika.westerberg@iki.fi>
---
 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 0c9df11..56b51a1 100644
--- a/drivers/net/arm/ep93xx_eth.c
+++ b/drivers/net/arm/ep93xx_eth.c
@@ -495,7 +495,7 @@ 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

[PATCH 4/5] net: ep93xx_eth: fix DMA API violations

[Mika Westerberg]

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 <mika.westerberg@iki.fi>
---
 drivers/net/arm/ep93xx_eth.c |   19 +++++++++++++------
 1 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/drivers/net/arm/ep93xx_eth.c b/drivers/net/arm/ep93xx_eth.c
index 56b51a1..c2a7847 100644
--- a/drivers/net/arm/ep93xx_eth.c
+++ b/drivers/net/arm/ep93xx_eth.c
@@ -285,11 +285,14 @@ 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(ep->dma_dev,
-						ep->descs->rdesc[entry].buf_addr,
+
+			dma_sync_single_for_cpu(ep->dma_dev, rxd->buf_addr,
 						length, DMA_FROM_DEVICE);
 			skb_copy_to_linear_data(skb, ep->rx_buf[entry], length);
+			dma_sync_single_for_device(ep->dma_dev, rxd->buf_addr,
+						length, DMA_FROM_DEVICE);
 			skb_put(skb, length);
 			skb->protocol = eth_type_trans(skb, dev);
 
@@ -351,6 +354,7 @@ 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)) {
@@ -362,11 +366,14 @@ 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(ep->dma_dev, txd->buf_addr, skb->len,
+				DMA_TO_DEVICE);
 	skb_copy_and_csum_dev(skb, ep->tx_buf[entry]);
-	dma_sync_single_for_cpu(ep->dma_dev, ep->descs->tdesc[entry].buf_addr,
-				skb->len, DMA_TO_DEVICE);
+	dma_sync_single_for_device(ep->dma_dev, txd->buf_addr, skb->len,
+				   DMA_TO_DEVICE);
 	dev_kfree_skb(skb);
 
 	spin_lock_irq(&ep->tx_pending_lock);
-- 
1.7.4.4

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

[Mika Westerberg]

As the driver is now passing platform device to the DMA mapping functions,
we should give it valid DMA masks.

Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi>
---
 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

Re: [PATCH 1/5] net: ep93xx_eth: pass struct device to DMA API functions

[Russell King - ARM Linux]

On Thu, Jun 02, 2011 at 12:38:13PM +0300, Mika Westerberg wrote:
> 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.

Thanks for doing this - it certainly makes things more correct, even
if the original problem has been resolved by the troublesome GFP_DMA
commit having been reverted.  As such I think this patch series should
still be applied.

I think the series should be re-ordered so that patch 5 is first however,
as you can do that with or without the remainder of the patches.

For the entire series:

Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>