target/linux/generic/patches-3.18/077-06-bgmac-set-received-skb-headroom-to-NET_SKB_PAD.patch

   1 From: Felix Fietkau <nbd@openwrt.org>
   2 Date: Sun, 12 Apr 2015 10:13:28 +0200
   3 Subject: [PATCH] bgmac: set received skb headroom to NET_SKB_PAD
   4
   5 A packet buffer offset of 30 bytes is inefficient, because the first 2
   6 bytes end up in a different cacheline.
   7
   8 Signed-off-by: Felix Fietkau <nbd@openwrt.org>
   9 ---
  10
  11 --- a/drivers/net/ethernet/broadcom/bgmac.c
  12 +++ b/drivers/net/ethernet/broadcom/bgmac.c
  13 @@ -346,13 +346,13 @@ static int bgmac_dma_rx_skb_for_slot(str
  14                 return -ENOMEM;
  15
  16         /* Poison - if everything goes fine, hardware will overwrite it */
  17 -       rx = buf;
  18 +       rx = buf + BGMAC_RX_BUF_OFFSET;
  19         rx->len = cpu_to_le16(0xdead);
  20         rx->flags = cpu_to_le16(0xbeef);
  21
  22         /* Map skb for the DMA */
  23 -       dma_addr = dma_map_single(dma_dev, buf, BGMAC_RX_BUF_SIZE,
  24 -                                 DMA_FROM_DEVICE);
  25 +       dma_addr = dma_map_single(dma_dev, buf + BGMAC_RX_BUF_OFFSET,
  26 +                                 BGMAC_RX_BUF_SIZE, DMA_FROM_DEVICE);
  27         if (dma_mapping_error(dma_dev, dma_addr)) {
  28                 bgmac_err(bgmac, "DMA mapping error\n");
  29                 put_page(virt_to_head_page(buf));
  30 @@ -403,7 +403,7 @@ static int bgmac_dma_rx_read(struct bgma
  31         while (ring->start != ring->end) {
  32                 struct device *dma_dev = bgmac->core->dma_dev;
  33                 struct bgmac_slot_info *slot = &ring->slots[ring->start];
  34 -               struct bgmac_rx_header *rx = slot->buf;
  35 +               struct bgmac_rx_header *rx = slot->buf + BGMAC_RX_BUF_OFFSET;
  36                 struct sk_buff *skb;
  37                 void *buf = slot->buf;
  38                 u16 len, flags;
  39 @@ -454,8 +454,10 @@ static int bgmac_dma_rx_read(struct bgma
  40                                          BGMAC_RX_BUF_SIZE, DMA_FROM_DEVICE);
  41
  42                         skb = build_skb(buf, BGMAC_RX_ALLOC_SIZE);
  43 -                       skb_put(skb, BGMAC_RX_FRAME_OFFSET + len);
  44 -                       skb_pull(skb, BGMAC_RX_FRAME_OFFSET);
  45 +                       skb_put(skb, BGMAC_RX_FRAME_OFFSET +
  46 +                               BGMAC_RX_BUF_OFFSET + len);
  47 +                       skb_pull(skb, BGMAC_RX_FRAME_OFFSET +
  48 +                                BGMAC_RX_BUF_OFFSET);
  49
  50                         skb_checksum_none_assert(skb);
  51                         skb->protocol = eth_type_trans(skb, bgmac->net_dev);
  52 --- a/drivers/net/ethernet/broadcom/bgmac.h
  53 +++ b/drivers/net/ethernet/broadcom/bgmac.h
  54 @@ -360,9 +360,11 @@
  55
  56  #define BGMAC_RX_HEADER_LEN                    28              /* Last 24 bytes are unused. Well... */
  57  #define BGMAC_RX_FRAME_OFFSET                  30              /* There are 2 unused bytes between header and real data */
  58 +#define BGMAC_RX_BUF_OFFSET                    (NET_SKB_PAD + NET_IP_ALIGN - \
  59 +                                                BGMAC_RX_FRAME_OFFSET)
  60  #define BGMAC_RX_MAX_FRAME_SIZE                        1536            /* Copied from b44/tg3 */
  61  #define BGMAC_RX_BUF_SIZE                      (BGMAC_RX_FRAME_OFFSET + BGMAC_RX_MAX_FRAME_SIZE)
  62 -#define BGMAC_RX_ALLOC_SIZE                    (SKB_DATA_ALIGN(BGMAC_RX_BUF_SIZE) + \
  63 +#define BGMAC_RX_ALLOC_SIZE                    (SKB_DATA_ALIGN(BGMAC_RX_BUF_SIZE + BGMAC_RX_BUF_OFFSET) + \
  64                                                  SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
  65
  66  #define BGMAC_BFL_ENETROBO                     0x0010          /* has ephy roboswitch spi */