e1000e: fix IPMI traffic

Some users reported that they have machines with BMCs enabled that cannot
receive IPMI traffic after e1000e is loaded.
http://marc.info/?l=e1000-devel&m=121909039127414&w=2
http://marc.info/?l=e1000-devel&m=121365543823387&w=2

This fixes the issue if they load with the new parameter = 0 by disabling
crc stripping, but leaves the performance feature on for most users.
Based on work done by Hong Zhang.

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/e1000e/netdev.c b/drivers/net/e1000e/netdev.c
index f6ebebb..91795f7 100644
--- a/drivers/net/e1000e/netdev.c
+++ b/drivers/net/e1000e/netdev.c
@@ -499,6 +499,10 @@
 			goto next_desc;
 		}
 
+		/* adjust length to remove Ethernet CRC */
+		if (!(adapter->flags2 & FLAG2_CRC_STRIPPING))
+			length -= 4;
+
 		total_rx_bytes += length;
 		total_rx_packets++;
 
@@ -804,6 +808,10 @@
 			pci_dma_sync_single_for_device(pdev, ps_page->dma,
 				PAGE_SIZE, PCI_DMA_FROMDEVICE);
 
+			/* remove the CRC */
+			if (!(adapter->flags2 & FLAG2_CRC_STRIPPING))
+				l1 -= 4;
+
 			skb_put(skb, l1);
 			goto copydone;
 		} /* if */
@@ -825,6 +833,12 @@
 			skb->truesize += length;
 		}
 
+		/* strip the ethernet crc, problem is we're using pages now so
+		 * this whole operation can get a little cpu intensive
+		 */
+		if (!(adapter->flags2 & FLAG2_CRC_STRIPPING))
+			pskb_trim(skb, skb->len - 4);
+
 copydone:
 		total_rx_bytes += skb->len;
 		total_rx_packets++;
@@ -2301,8 +2315,12 @@
 	else
 		rctl |= E1000_RCTL_LPE;
 
-	/* Enable hardware CRC frame stripping */
-	rctl |= E1000_RCTL_SECRC;
+	/* Some systems expect that the CRC is included in SMBUS traffic. The
+	 * hardware strips the CRC before sending to both SMBUS (BMC) and to
+	 * host memory when this is enabled
+	 */
+	if (adapter->flags2 & FLAG2_CRC_STRIPPING)
+		rctl |= E1000_RCTL_SECRC;
 
 	/* Setup buffer sizes */
 	rctl &= ~E1000_RCTL_SZ_4096;
@@ -4766,6 +4784,7 @@
 	adapter->ei = ei;
 	adapter->pba = ei->pba;
 	adapter->flags = ei->flags;
+	adapter->flags2 = ei->flags2;
 	adapter->hw.adapter = adapter;
 	adapter->hw.mac.type = ei->mac;
 	adapter->msg_enable = (1 << NETIF_MSG_DRV | NETIF_MSG_PROBE) - 1;