mv643xx_eth: use sw csum for big packets

Some controllers (KW, Dove) limits the TX IP/layer4 checksum offloading to a max size.

Signed-off-by: Saeed Bishara <[e-mail]>
Acked-by: Lennert Buytenhek <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/mv643xx_eth.c

···
 	unsigned int t_clk;
 	int extended_rx_coal_limit;
 	int tx_bw_control;
+	int tx_csum_limit;
 };
 
 #define TX_BW_CONTROL_ABSENT		0
···
 	l4i_chk = 0;
 
 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		int hdr_len;
 		int tag_bytes;
 
 		BUG_ON(skb->protocol != htons(ETH_P_IP) &&
 		       skb->protocol != htons(ETH_P_8021Q));
 
-		tag_bytes = (void *)ip_hdr(skb) - (void *)skb->data - ETH_HLEN;
-		if (unlikely(tag_bytes & ~12)) {
+		hdr_len = (void *)ip_hdr(skb) - (void *)skb->data;
+		tag_bytes = hdr_len - ETH_HLEN;
+		if (skb->len - hdr_len > mp->shared->tx_csum_limit ||
+		    unlikely(tag_bytes & ~12)) {
 			if (skb_checksum_help(skb) == 0)
 				goto no_csum;
 			kfree_skb(skb);
···
 	 * Detect hardware parameters.
 	 */
 	msp->t_clk = (pd != NULL && pd->t_clk != 0) ? pd->t_clk : 133000000;
+	msp->tx_csum_limit = pd->tx_csum_limit ? pd->tx_csum_limit : 9 * 1024;
 	infer_hw_params(msp);
 
 	platform_set_drvdata(pdev, msp);

include/linux/mv643xx_eth.h

···
 	struct mbus_dram_target_info	*dram;
 	struct platform_device	*shared_smi;
 	unsigned int		t_clk;
+	/*
+	 * Max packet size for Tx IP/Layer 4 checksum, when set to 0, default
+	 * limit of 9KiB will be used.
+	 */
+	int			tx_csum_limit;
 };
 
 #define MV643XX_ETH_PHY_ADDR_DEFAULT	0