Commit 7fd96ce4 authored by Lennert Buytenhek's avatar Lennert Buytenhek Committed by David S. Miller
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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: default avatarLennert Buytenhek <buytenh@marvell.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent becfad97

drivers/net/mv643xx_eth.c

+13 −8
Original line number Diff line number Diff line
@@ -174,6 +174,7 @@ static char mv643xx_eth_driver_version[] = "1.4"; 
 */

#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 @@ static int rxq_refill(struct rx_queue *rxq, int budget) 
	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 @@ static int txq_reclaim(struct tx_queue *txq, int budget, int force) 
		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 @@ static void mv643xx_eth_recalc_skb_size(struct mv643xx_eth_private *mp) 
	 * 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)

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