mv643xx_eth: rework receive skb cache alignment
On the platforms that mv643xx_eth is used on, the manual skb->data
alignment logic in mv643xx_eth can be simplified, as the only case we
need to handle is where NET_SKB_PAD is not a multiple of the cache
line size. If this is the case, the extra padding we need can be
computed at compile time, while if NET_SKB_PAD _is_ a multiple of
the cache line size, the code can be optimised out entirely.
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/mv643xx_eth.c b/drivers/net/mv643xx_eth.c
index cc16f3e..05bb1c5 100644
--- a/drivers/net/mv643xx_eth.c
+++ b/drivers/net/mv643xx_eth.c
@@ -174,6 +174,7 @@
*/
#define DEFAULT_RX_QUEUE_SIZE 128
#define DEFAULT_TX_QUEUE_SIZE 256
+#define SKB_DMA_REALIGN ((PAGE_SIZE - NET_SKB_PAD) % SMP_CACHE_BYTES)
/*
@@ -649,23 +650,20 @@
refilled = 0;
while (refilled < budget && rxq->rx_desc_count < rxq->rx_ring_size) {
struct sk_buff *skb;
- int unaligned;
int rx;
struct rx_desc *rx_desc;
skb = __skb_dequeue(&mp->rx_recycle);
if (skb == NULL)
- skb = dev_alloc_skb(mp->skb_size +
- dma_get_cache_alignment() - 1);
+ skb = dev_alloc_skb(mp->skb_size);
if (skb == NULL) {
mp->oom = 1;
goto oom;
}
- unaligned = (u32)skb->data & (dma_get_cache_alignment() - 1);
- if (unaligned)
- skb_reserve(skb, dma_get_cache_alignment() - unaligned);
+ if (SKB_DMA_REALIGN)
+ skb_reserve(skb, SKB_DMA_REALIGN);
refilled++;
rxq->rx_desc_count++;
@@ -964,8 +962,7 @@
if (skb != NULL) {
if (skb_queue_len(&mp->rx_recycle) <
mp->rx_ring_size &&
- skb_recycle_check(skb, mp->skb_size +
- dma_get_cache_alignment() - 1))
+ skb_recycle_check(skb, mp->skb_size))
__skb_queue_head(&mp->rx_recycle, skb);
else
dev_kfree_skb(skb);
@@ -2336,6 +2333,14 @@
* size field are ignored by the hardware.
*/
mp->skb_size = (skb_size + 7) & ~7;
+
+ /*
+ * If NET_SKB_PAD is smaller than a cache line,
+ * netdev_alloc_skb() will cause skb->data to be misaligned
+ * to a cache line boundary. If this is the case, include
+ * some extra space to allow re-aligning the data area.
+ */
+ mp->skb_size += SKB_DMA_REALIGN;
}
static int mv643xx_eth_open(struct net_device *dev)