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Commit 29bc2e1e authored by Havard Skinnemoen's avatar Havard Skinnemoen Committed by David S. Miller
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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: default avatarHavard Skinnemoen <havard@skinnemoen.net>
[nicolas.ferre@atmel.com: adapt to newer kernel]
Signed-off-by: default avatarNicolas Ferre <nicolas.ferre@atmel.com>
Tested-by: default avatarJoachim Eastwood <manabian@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e86cd53a

drivers/net/ethernet/cadence/macb.c

+16 −7
Original line number Diff line number Diff line
@@ -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 */