From 29bc2e1e5504627c08ae2ce298e2209701289c40 Mon Sep 17 00:00:00 2001 From: Havard Skinnemoen Date: Wed, 31 Oct 2012 06:04:58 +0000 Subject: [PATCH] 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 [nicolas.ferre@atmel.com: adapt to newer kernel] Signed-off-by: Nicolas Ferre Tested-by: Joachim Eastwood Signed-off-by: David S. Miller --- drivers/net/ethernet/cadence/macb.c | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-) diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c index d5b52ff6d586..c1f20b067abf 100644 --- a/drivers/net/ethernet/cadence/macb.c +++ b/drivers/net/ethernet/cadence/macb.c @@ -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 */ -- 2.20.1