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net/macb: Offset first RX buffer by two bytes 

Make the ethernet frame payload word-aligned, possibly making the
memcpy into the skb a bit faster. This will be even more important
after we eliminate the copy altogether.

Also eliminate the redundant RX_OFFSET constant -- it has the same
definition and purpose as NET_IP_ALIGN.

Signed-off-by: Havard Skinnemoen <havard@skinnemoen.net>
[nicolas.ferre@atmel.com: adapt to newer kernel]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Tested-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Havard Skinnemoen 2012-10-31 06:04:58 +00:00 committed by David S. Miller
parent e86cd53afc
commit 29bc2e1e55
1 changed files with 16 additions and 7 deletions
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23
drivers/net/ethernet/cadence/macb.c
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@ -33,9 +33,6 @@
#define RX_RING_SIZE 512 /* must be power of 2 */
#define RX_RING_BYTES (sizeof(struct macb_dma_desc) * RX_RING_SIZE)
/* Make the IP header word-aligned (the ethernet header is 14 bytes) */
#define RX_OFFSET 2
#define TX_RING_SIZE 128 /* must be power of 2 */
#define TX_RING_BYTES (sizeof(struct macb_dma_desc) * TX_RING_SIZE)
@ -498,7 +495,7 @@ static int macb_rx_frame(struct macb *bp, unsigned int first_frag,
{
unsigned int len;
unsigned int frag;
unsigned int offset = 0;
unsigned int offset;
struct sk_buff *skb;
struct macb_dma_desc *desc;
@ -509,7 +506,16 @@ static int macb_rx_frame(struct macb *bp, unsigned int first_frag,
macb_rx_ring_wrap(first_frag),
macb_rx_ring_wrap(last_frag), len);
skb = netdev_alloc_skb(bp->dev, len + RX_OFFSET);
/*
* The ethernet header starts NET_IP_ALIGN bytes into the
* first buffer. Since the header is 14 bytes, this makes the
* payload word-aligned.
*
* Instead of calling skb_reserve(NET_IP_ALIGN), we just copy
* the two padding bytes into the skb so that we avoid hitting
* the slowpath in memcpy(), and pull them off afterwards.
*/
skb = netdev_alloc_skb(bp->dev, len + NET_IP_ALIGN);
if (!skb) {
bp->stats.rx_dropped++;
for (frag = first_frag; ; frag++) {
@ -525,7 +531,8 @@ static int macb_rx_frame(struct macb *bp, unsigned int first_frag,
return 1;
}
skb_reserve(skb, RX_OFFSET);
offset = 0;
len += NET_IP_ALIGN;
skb_checksum_none_assert(skb);
skb_put(skb, len);
@ -549,10 +556,11 @@ static int macb_rx_frame(struct macb *bp, unsigned int first_frag,
/* Make descriptor updates visible to hardware */
wmb();
__skb_pull(skb, NET_IP_ALIGN);
skb->protocol = eth_type_trans(skb, bp->dev);
bp->stats.rx_packets++;
bp->stats.rx_bytes += len;
bp->stats.rx_bytes += skb->len;
netdev_vdbg(bp->dev, "received skb of length %u, csum: %08x\n",
skb->len, skb->csum);
netif_receive_skb(skb);
@ -1012,6 +1020,7 @@ static void macb_init_hw(struct macb *bp)
__macb_set_hwaddr(bp);
config = macb_mdc_clk_div(bp);
config |= MACB_BF(RBOF, NET_IP_ALIGN); /* Make eth data aligned */
config |= MACB_BIT(PAE); /* PAuse Enable */
config |= MACB_BIT(DRFCS); /* Discard Rx FCS */
config |= MACB_BIT(BIG); /* Receive oversized frames */