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 <[e-mail]>
Signed-off-by: Jesse Brandeburg <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/e1000e/e1000.h

···
 	unsigned long led_status;
 
 	unsigned int flags;
+	unsigned int flags2;
 	struct work_struct downshift_task;
 	struct work_struct update_phy_task;
 };
···
 struct e1000_info {
 	enum e1000_mac_type	mac;
 	unsigned int		flags;
+	unsigned int            flags2;
 	u32			pba;
 	s32			(*get_variants)(struct e1000_adapter *);
 	struct e1000_mac_operations *mac_ops;
···
 #define FLAG_TSO_FORCE                    (1 << 29)
 #define FLAG_RX_RESTART_NOW               (1 << 30)
 #define FLAG_MSI_TEST_FAILED              (1 << 31)
+
+/* CRC Stripping defines */
+#define FLAG2_CRC_STRIPPING               (1 << 0)
 
 #define E1000_RX_DESC_PS(R, i)	    \
 	(&(((union e1000_rx_desc_packet_split *)((R).desc))[i]))

drivers/net/e1000e/netdev.c

···
 			goto next_desc;
 		}
 
+		/* adjust length to remove Ethernet CRC */
+		if (!(adapter->flags2 & FLAG2_CRC_STRIPPING))
+			length -= 4;
+
 		total_rx_bytes += length;
 		total_rx_packets++;
 
···
 			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 */
···
 			skb->data_len += length;
 			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;
···
 	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;
···
 	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;

drivers/net/e1000e/param.c

···
  */
 E1000_PARAM(WriteProtectNVM, "Write-protect NVM [WARNING: disabling this can lead to corrupted NVM]");
 
+/*
+ * Enable CRC Stripping
+ *
+ * Valid Range: 0, 1
+ *
+ * Default Value: 1 (enabled)
+ */
+E1000_PARAM(CrcStripping, "Enable CRC Stripping, disable if your BMC needs " \
+                          "the CRC");
+
 struct e1000_option {
 	enum { enable_option, range_option, list_option } type;
 	const char *name;
···
 			if ((adapter->flags & FLAG_HAS_SMART_POWER_DOWN)
 			    && spd)
 				adapter->flags |= FLAG_SMART_POWER_DOWN;
+		}
+	}
+	{ /* CRC Stripping */
+		const struct e1000_option opt = {
+			.type = enable_option,
+			.name = "CRC Stripping",
+			.err  = "defaulting to enabled",
+			.def  = OPTION_ENABLED
+		};
+
+		if (num_CrcStripping > bd) {
+			unsigned int crc_stripping = CrcStripping[bd];
+			e1000_validate_option(&crc_stripping, &opt, adapter);
+			if (crc_stripping == OPTION_ENABLED)
+				adapter->flags2 |= FLAG2_CRC_STRIPPING;
 		}
 	}
 	{ /* Kumeran Lock Loss Workaround */