[PATCH] sky2: optimize checksum offload information

Since many packets have the same checksum starting offset and insertion
location; the driver can save the last information and only tell hardware
when it changes.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/sky2.c

@@ -1280,12 +1280,17 @@ static int sky2_xmit_frame(struct sk_buff *skb, struct net_device *dev)
 		if (skb->nh.iph->protocol == IPPROTO_UDP)
 			ctrl |= UDPTCP;
 
-		le = get_tx_le(sky2);
-		le->tx.csum.start = cpu_to_le16(hdr);
-		le->tx.csum.offset = cpu_to_le16(offset);
-		le->length = 0;	/* initial checksum value */
-		le->ctrl = 1;	/* one packet */
-		le->opcode = OP_TCPLISW | HW_OWNER;
+		if (hdr != sky2->tx_csum_start || offset != sky2->tx_csum_offset) {
+			sky2->tx_csum_start = hdr;
+			sky2->tx_csum_offset = offset;
+
+			le = get_tx_le(sky2);
+			le->tx.csum.start = cpu_to_le16(hdr);
+			le->tx.csum.offset = cpu_to_le16(offset);
+			le->length = 0;	/* initial checksum value */
+			le->ctrl = 1;	/* one packet */
+			le->opcode = OP_TCPLISW | HW_OWNER;
+		}
 	}
 
 	le = get_tx_le(sky2);

drivers/net/sky2.h

@@ -1843,6 +1843,8 @@ struct sky2_port {
 	u32		     tx_addr64;
 	u16		     tx_pending;
 	u16		     tx_last_mss;
+	u16		     tx_csum_start;
+	u16		     tx_csum_offset;
 
 	struct ring_info     *rx_ring ____cacheline_aligned_in_smp;
 	struct sky2_rx_le    *rx_le;