bgmac: set received skb headroom to NET_SKB_PAD

A packet buffer offset of 30 bytes is inefficient, because the first 2
bytes end up in a different cacheline.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 11 insertions, 7 deletions

diff --git a/drivers/net/ethernet/broadcom/bgmac.c b/drivers/net/ethernet/broadcom/bgmac.c
index 9c3b2ff33e63..424a68ce5aa0 100644
--- a/drivers/net/ethernet/broadcom/bgmac.c
+++ b/drivers/net/ethernet/broadcom/bgmac.c
@@ -346,13 +346,13 @@ static int bgmac_dma_rx_skb_for_slot(struct bgmac *bgmac,
                 return -ENOMEM;
 
         /* Poison - if everything goes fine, hardware will overwrite it */
-        rx = buf;
+        rx = buf + BGMAC_RX_BUF_OFFSET;
         rx->len = cpu_to_le16(0xdead);
         rx->flags = cpu_to_le16(0xbeef);
 
         /* Map skb for the DMA */
-        dma_addr = dma_map_single(dma_dev, buf, BGMAC_RX_BUF_SIZE,
-                                  DMA_FROM_DEVICE);
+        dma_addr = dma_map_single(dma_dev, buf + BGMAC_RX_BUF_OFFSET,
+                                  BGMAC_RX_BUF_SIZE, DMA_FROM_DEVICE);
         if (dma_mapping_error(dma_dev, dma_addr)) {
                 bgmac_err(bgmac, "DMA mapping error\n");
                 put_page(virt_to_head_page(buf));
@@ -403,7 +403,7 @@ static int bgmac_dma_rx_read(struct bgmac *bgmac, struct bgmac_dma_ring *ring,
         while (ring->start != ring->end) {
                 struct device *dma_dev = bgmac->core->dma_dev;
                 struct bgmac_slot_info *slot = &ring->slots[ring->start];
-                struct bgmac_rx_header *rx = slot->buf;
+                struct bgmac_rx_header *rx = slot->buf + BGMAC_RX_BUF_OFFSET;
                 struct sk_buff *skb;
                 void *buf = slot->buf;
                 u16 len, flags;
@@ -454,8 +454,10 @@ static int bgmac_dma_rx_read(struct bgmac *bgmac, struct bgmac_dma_ring *ring,
                                          BGMAC_RX_BUF_SIZE, DMA_FROM_DEVICE);
 
                         skb = build_skb(buf, BGMAC_RX_ALLOC_SIZE);
-                        skb_put(skb, BGMAC_RX_FRAME_OFFSET + len);
-                        skb_pull(skb, BGMAC_RX_FRAME_OFFSET);
+                        skb_put(skb, BGMAC_RX_FRAME_OFFSET +
+                                BGMAC_RX_BUF_OFFSET + len);
+                        skb_pull(skb, BGMAC_RX_FRAME_OFFSET +
+                                 BGMAC_RX_BUF_OFFSET);
 
                         skb_checksum_none_assert(skb);
                         skb->protocol = eth_type_trans(skb, bgmac->net_dev);
diff --git a/drivers/net/ethernet/broadcom/bgmac.h b/drivers/net/ethernet/broadcom/bgmac.h
index abd50d128e6c..3db0d5211c5d 100644
--- a/drivers/net/ethernet/broadcom/bgmac.h
+++ b/drivers/net/ethernet/broadcom/bgmac.h
@@ -360,9 +360,11 @@
 
 #define BGMAC_RX_HEADER_LEN                     28              /* Last 24 bytes are unused. Well... */
 #define BGMAC_RX_FRAME_OFFSET                   30              /* There are 2 unused bytes between header and real data */
+#define BGMAC_RX_BUF_OFFSET                     (NET_SKB_PAD + NET_IP_ALIGN - \
+                                                 BGMAC_RX_FRAME_OFFSET)
 #define BGMAC_RX_MAX_FRAME_SIZE                 1536            /* Copied from b44/tg3 */
 #define BGMAC_RX_BUF_SIZE                       (BGMAC_RX_FRAME_OFFSET + BGMAC_RX_MAX_FRAME_SIZE)
-#define BGMAC_RX_ALLOC_SIZE                     (SKB_DATA_ALIGN(BGMAC_RX_BUF_SIZE) + \
+#define BGMAC_RX_ALLOC_SIZE                     (SKB_DATA_ALIGN(BGMAC_RX_BUF_SIZE + BGMAC_RX_BUF_OFFSET) + \
                                                  SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
 
 #define BGMAC_BFL_ENETROBO                      0x0010          /* has ephy roboswitch spi */