e1000e: Avoid wrong check on TX hang

Based on the original patch submitted my Michael Wang
<wangyun@linux.vnet.ibm.com>.
Descriptors may not be write-back while checking TX hang with flag
FLAG2_DMA_BURST on.
So when we detect hang, we just flush the descriptor and detect
again for once.

-v2 change 1 to true and 0 to false and remove extra ()

CC: Michael Wang <wangyun@linux.vnet.ibm.com>
CC: Flavio Leitner <fbl@redhat.com>
Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/e1000e/e1000.h

@@ -309,6 +309,7 @@ struct e1000_adapter {
 	u32 txd_cmd;
 
 	bool detect_tx_hung;
+	bool tx_hang_recheck;
 	u8 tx_timeout_factor;
 
 	u32 tx_int_delay;

drivers/net/ethernet/intel/e1000e/netdev.c

@@ -1014,6 +1014,7 @@ static void e1000_print_hw_hang(struct work_struct *work)
 	struct e1000_adapter *adapter = container_of(work,
 	                                             struct e1000_adapter,
 	                                             print_hang_task);
+	struct net_device *netdev = adapter->netdev;
 	struct e1000_ring *tx_ring = adapter->tx_ring;
 	unsigned int i = tx_ring->next_to_clean;
 	unsigned int eop = tx_ring->buffer_info[i].next_to_watch;
@@ -1025,6 +1026,21 @@ static void e1000_print_hw_hang(struct work_struct *work)
 	if (test_bit(__E1000_DOWN, &adapter->state))
 		return;
 
+	if (!adapter->tx_hang_recheck &&
+	    (adapter->flags2 & FLAG2_DMA_BURST)) {
+		/* May be block on write-back, flush and detect again
+		 * flush pending descriptor writebacks to memory
+		 */
+		ew32(TIDV, adapter->tx_int_delay | E1000_TIDV_FPD);
+		/* execute the writes immediately */
+		e1e_flush();
+		adapter->tx_hang_recheck = true;
+		return;
+	}
+	/* Real hang detected */
+	adapter->tx_hang_recheck = false;
+	netif_stop_queue(netdev);
+
 	e1e_rphy(hw, PHY_STATUS, &phy_status);
 	e1e_rphy(hw, PHY_1000T_STATUS, &phy_1000t_status);
 	e1e_rphy(hw, PHY_EXT_STATUS, &phy_ext_status);
@@ -1145,10 +1161,10 @@ static bool e1000_clean_tx_irq(struct e1000_adapter *adapter)
 		if (tx_ring->buffer_info[i].time_stamp &&
 		    time_after(jiffies, tx_ring->buffer_info[i].time_stamp
 			       + (adapter->tx_timeout_factor * HZ)) &&
-		    !(er32(STATUS) & E1000_STATUS_TXOFF)) {
+		    !(er32(STATUS) & E1000_STATUS_TXOFF))
 			schedule_work(&adapter->print_hang_task);
-			netif_stop_queue(netdev);
-		}
+		else
+			adapter->tx_hang_recheck = false;
 	}
 	adapter->total_tx_bytes += total_tx_bytes;
 	adapter->total_tx_packets += total_tx_packets;
@@ -3838,6 +3854,7 @@ static int e1000_open(struct net_device *netdev)
 
 	e1000_irq_enable(adapter);
 
+	adapter->tx_hang_recheck = false;
 	netif_start_queue(netdev);
 
 	adapter->idle_check = true;