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authorMika Westerberg <mika.westerberg@iki.fi>2011-06-11 08:39:58 +0000
committerDavid S. Miller <davem@davemloft.net>2011-06-11 16:25:16 -0700
commitf1c089e3192f1afdfa76226dc38ef81b08ac810d (patch)
treee3968efef6b98608e5a49edf6c84097ff066badd
parent1f758a4341ac83289a549e6ba2d29a08cf639717 (diff)
net: ep93xx_eth: fix DMA API violations
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> Acked-by: Russell King <rmk+kernel@arm.linux.org.uk> Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com> Tested-by: Petr Stetiar <ynezz@true.cz> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/arm/ep93xx_eth.c18
1 files changed, 13 insertions, 5 deletions
diff --git a/drivers/net/arm/ep93xx_eth.c b/drivers/net/arm/ep93xx_eth.c
index bef38116abaf..0b46b8ea0e80 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);

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