Subject: [PATCH] sky2: turn off Rx checksum on bad hardware

From: Stephen Hemminger <[email-masked]>
Date: Thu, 8 Mar 2007 12:42:30 -0800

On Yukon FE, occasional hardware receive checksum errors are seen.
An early indication of the problem is single bit differences in the two
checksum engines.  Use this as a detection mechanism to turn off Rx
checksumming.

Signed-off-by: Stephen Hemminger <[email-masked]>

---
 drivers/net/sky2.c |   24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

--- sky2-dev.orig/drivers/net/sky2.c	2007-03-05 16:49:31.000000000 -0800
+++ sky2-dev/drivers/net/sky2.c	2007-03-05 16:49:45.000000000 -0800
@@ -2165,9 +2165,27 @@
 			/* fall through */
 #endif
 		case OP_RXCHKS:
-			skb = sky2->rx_ring[sky2->rx_next].skb;
-			skb->ip_summed = CHECKSUM_COMPLETE;
-			skb->csum = status & 0xffff;
+			if (!sky2->rx_csum)
+				break;
+
+			/* Both checksum counters are programmed to start at
+			 * the same offset, so unless there is a problem they
+			 * should match. This failure is an early indication that
+			 * hardware receive checksumming won't work.
+			 */
+			if (likely(status >> 16 == (status & 0xffff))) {
+				skb = sky2->rx_ring[sky2->rx_next].skb;
+				skb->ip_summed = CHECKSUM_COMPLETE;
+				skb->csum = status & 0xffff;
+			} else {
+				printk(KERN_NOTICE PFX "%s: hardware receive "
+				       "checksum problem (status = %#x)\n",
+				       dev->name, status);
+				sky2->rx_csum = 0;
+				sky2_write32(sky2->hw,
+					     Q_ADDR(rxqaddr[le->link], Q_CSR),
+					     BMU_DIS_RX_CHKSUM);
+			}
 			break;
 
 		case OP_TXINDEXLE: