tg3: Use NET_IP_ALIGN

This patch replaces hardcoded 2's with the NET_IP_ALIGN constant or
TG3_RAW_IP_ALIGN where appropriate.  Some platforms can redefine the
NET_IP_ALIGN definition to zero if unaligned DMA transfers cost more
than the IP header alignment gains.  This patch represents a
performance improvement when using the 5701 on these platforms.
The copy path can be avoided.

TG3_RAW_IP_ALIGN is used in cases where we always want to align the
IP header on dword boundaries.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 7 deletions

diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index 9ba18e1bc34..0a82ea878ae 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -132,6 +132,8 @@
 /* minimum number of free TX descriptors required to wake up TX process */
 #define TG3_TX_WAKEUP_THRESH(tp)                ((tp)->tx_pending / 4)
 
+#define TG3_RAW_IP_ALIGN 2
+
 /* number of ETHTOOL_GSTATS u64's */
 #define TG3_NUM_STATS           (sizeof(struct tg3_ethtool_stats)/sizeof(u64))
 
@@ -4231,12 +4233,15 @@ static int tg3_rx(struct tg3 *tp, int budget)
                         goto next_pkt;
                 }
 
-                len = ((desc->idx_len & RXD_LEN_MASK) >> RXD_LEN_SHIFT) - 4; /* omit crc */
+                len = ((desc->idx_len & RXD_LEN_MASK) >> RXD_LEN_SHIFT) -
+                      ETH_FCS_LEN;
 
                 if (len > RX_COPY_THRESHOLD
-                        && tp->rx_offset == 2
-                        /* rx_offset != 2 iff this is a 5701 card running
-                         * in PCI-X mode [see tg3_get_invariants()] */
+                        && tp->rx_offset == NET_IP_ALIGN
+                        /* rx_offset will likely not equal NET_IP_ALIGN
+                         * if this is a 5701 card running in PCI-X mode
+                         * [see tg3_get_invariants()]
+                         */
                 ) {
                         int skb_size;
 
@@ -4256,11 +4261,12 @@ static int tg3_rx(struct tg3 *tp, int budget)
                         tg3_recycle_rx(tp, opaque_key,
                                        desc_idx, *post_ptr);
 
-                        copy_skb = netdev_alloc_skb(tp->dev, len + 2);
+                        copy_skb = netdev_alloc_skb(tp->dev,
+                                                    len + TG3_RAW_IP_ALIGN);
                         if (copy_skb == NULL)
                                 goto drop_it_no_recycle;
 
-                        skb_reserve(copy_skb, 2);
+                        skb_reserve(copy_skb, TG3_RAW_IP_ALIGN);
                         skb_put(copy_skb, len);
                         pci_dma_sync_single_for_cpu(tp->pdev, dma_addr, len, PCI_DMA_FROMDEVICE);
                         skb_copy_from_linear_data(skb, copy_skb->data, len);
@@ -12614,7 +12620,7 @@ static int __devinit tg3_get_invariants(struct tg3 *tp)
         else
                 tp->tg3_flags &= ~TG3_FLAG_POLL_SERDES;
 
-        tp->rx_offset = 2;
+        tp->rx_offset = NET_IP_ALIGN;
         if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5701 &&
             (tp->tg3_flags & TG3_FLAG_PCIX_MODE) != 0)
                 tp->rx_offset = 0;