sky2: sky2 FE+ receive status workaround

The Yukon FE+ chip appears to have a hardware glitch that causes bogus
receive status values to be posted. The data in the packet is good, but
the status value is random garbage. As a temporary workaround until the
problem is better understood, implement the workaround the vendor driver
used of ignoring the status value on this chip.

Since this means trusting dodgy hardware values; add additional checking
of the receive packet length.

Signed-off-by: Stephen Hemminger <[e-mail]>
Signed-off-by: Jeff Garzik <[e-mail]>

drivers/net/sky2.c

···
 	sky2->rx_next = (sky2->rx_next + 1) % sky2->rx_pending;
 	prefetch(sky2->rx_ring + sky2->rx_next);
 
+	if (length < ETH_ZLEN || length > sky2->rx_data_size)
+		goto len_error;
+
+	/* This chip has hardware problems that generates bogus status.
+	 * So do only marginal checking and expect higher level protocols
+	 * to handle crap frames.
+	 */
+	if (sky2->hw->chip_id == CHIP_ID_YUKON_FE_P &&
+	    sky2->hw->chip_rev == CHIP_REV_YU_FE2_A0 &&
+	    length != count)
+		goto okay;
+
 	if (status & GMR_FS_ANY_ERR)
 		goto error;
 
···
 
 	/* if length reported by DMA does not match PHY, packet was truncated */
 	if (length != count)
-		goto len_mismatch;
+		goto len_error;
 
+okay:
 	if (length < copybreak)
 		skb = receive_copy(sky2, re, length);
 	else
···
 
 	return skb;
 
-len_mismatch:
+len_error:
 	/* Truncation of overlength packets
 	   causes PHY length to not match MAC length */
 	++sky2->net_stats.rx_length_errors;
 	if (netif_msg_rx_err(sky2) && net_ratelimit())
-		pr_info(PFX "%s: rx length mismatch: length %d status %#x\n",
-			dev->name, length, status);
+		pr_info(PFX "%s: rx length error: status %#x length %d\n",
+			dev->name, status, length);
 	goto resubmit;
 
 error:
···
 	sky2->netdev = dev;
 	sky2->hw = hw;
 	sky2->msg_enable = netif_msg_init(debug, default_msg);
-
-	/* This chip has hardware problems that generates
-	 * bogus PHY receive status so by default shut up the message.
-	 */
-	if (hw->chip_id == CHIP_ID_YUKON_FE_P &&
-	    hw->chip_rev == CHIP_REV_YU_FE2_A0)
-		sky2->msg_enable &= ~NETIF_MSG_RX_ERR;
 
 	/* Auto speed and flow control */
 	sky2->autoneg = AUTONEG_ENABLE;