e1000: prevent statistics from garbling during bus resets

If a PCI bus error/fault triggers a PCI bus reset, attempts to get
the ethernet packet count statistics from the hardware will fail,
returning garbage data upstream.  This patch skips statistics data
collection if the PCI device is not on the bus.
Signed-off-by: NLinas Vepstas <linas@austin.ibm.com>
Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Acked-by: NAuke Kok <auke-jan.h.kok@intel.com>

drivers/net/e1000/e1000_main.c

@@ -3045,14 +3045,20 @@ void
 e1000_update_stats(struct e1000_adapter *adapter)
 {
 	struct e1000_hw *hw = &adapter->hw;
+	struct pci_dev *pdev = adapter->pdev;
 	unsigned long flags;
 	uint16_t phy_tmp;
 
 #define PHY_IDLE_ERROR_COUNT_MASK 0x00FF
 
-	/* Prevent stats update while adapter is being reset */
+	/*
+	 * Prevent stats update while adapter is being reset, or if the pci
+	 * connection is down.
+	 */
 	if (adapter->link_speed == 0)
 		return;
+	if (pdev->error_state && pdev->error_state != pci_channel_io_normal)
+		return;
 
 	spin_lock_irqsave(&adapter->stats_lock, flags);