[E1000] Added Tx FIFO flush routine

* Added method to flush Tx FIFO after link disconnect; the hardware
  hangs on to Tx skb's that were in flight prior to link loss

drivers/net/e1000/e1000_main.c

@@ -1246,6 +1246,40 @@ e1000_set_multi(struct net_device *netdev)
 		e1000_leave_82542_rst(adapter);
 }
 
+static void
+e1000_tx_flush(struct e1000_adapter *adapter)
+{
+	uint32_t ctrl, tctl, txcw, icr;
+
+	e1000_irq_disable(adapter);
+
+	if(adapter->hw.mac_type < e1000_82543) {
+		/* Transmit Unit Reset */
+		tctl = E1000_READ_REG(&adapter->hw, TCTL);
+		E1000_WRITE_REG(&adapter->hw, TCTL, tctl | E1000_TCTL_RST);
+		E1000_WRITE_REG(&adapter->hw, TCTL, tctl);
+		e1000_clean_tx_ring(adapter);
+		e1000_configure_tx(adapter);
+	} else {
+		txcw = E1000_READ_REG(&adapter->hw, TXCW);
+		E1000_WRITE_REG(&adapter->hw, TXCW, txcw & ~E1000_TXCW_ANE);
+
+		ctrl = E1000_READ_REG(&adapter->hw, CTRL);
+		E1000_WRITE_REG(&adapter->hw, CTRL, ctrl | E1000_CTRL_SLU |
+				E1000_CTRL_ILOS);
+
+		mdelay(10);
+
+		e1000_clean_tx_irq(adapter);
+		E1000_WRITE_REG(&adapter->hw, CTRL, ctrl);
+		E1000_WRITE_REG(&adapter->hw, TXCW, txcw);
+
+		/* clear the link status change interrupts this caused */
+		icr = E1000_READ_REG(&adapter->hw, ICR);
+	}
+
+	e1000_irq_enable(adapter);
+}
 
 /* need to wait a few seconds after link up to get diagnostic information from the phy */
 
@@ -1348,6 +1382,15 @@ e1000_watchdog(unsigned long data)
 	e1000_update_stats(adapter);
 	e1000_update_adaptive(&adapter->hw);
 
+	if(!netif_carrier_ok(netdev)) {
+		if(E1000_DESC_UNUSED(txdr) + 1 < txdr->count) {
+			unsigned long flags;
+			spin_lock_irqsave(&netdev->xmit_lock, flags);
+			e1000_tx_flush(adapter);
+			spin_unlock_irqrestore(&netdev->xmit_lock, flags);
+		}
+	}
+
 
 	/* Cause software interrupt to ensure rx ring is cleaned */
 	E1000_WRITE_REG(&adapter->hw, ICS, E1000_ICS_RXDMT0);