ixgbe: dcb: IEEE PFC stats and reset logic incorrect

PFC stats are only tabulated when PFC is enabled. However in IEEE
mode the ieee_pfc pfc_tc bits were not checked and the calculation
was aborted.

This results in statistics not being reported through ethtool and
possible a false Tx hang occurring when receiving pause frames.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe_dcb_nl.c

@@ -662,6 +662,13 @@ static int ixgbe_dcbnl_ieee_setpfc(struct net_device *dev,
 			return -ENOMEM;
 	}
 
+	if (pfc->pfc_en) {
+		adapter->last_lfc_mode = adapter->hw.fc.current_mode;
+		adapter->hw.fc.current_mode = ixgbe_fc_pfc;
+	} else {
+		adapter->hw.fc.current_mode = adapter->last_lfc_mode;
+	}
+
 	prio_tc = adapter->ixgbe_ieee_ets->prio_tc;
 	memcpy(adapter->ixgbe_ieee_pfc, pfc, sizeof(*adapter->ixgbe_ieee_pfc));
 	return ixgbe_dcb_hw_pfc_config(&adapter->hw, pfc->pfc_en, prio_tc);

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

@@ -637,7 +637,11 @@ static void ixgbe_update_xoff_received(struct ixgbe_adapter *adapter)
 			clear_bit(__IXGBE_HANG_CHECK_ARMED,
 				  &adapter->tx_ring[i]->state);
 		return;
-	} else if (!(adapter->dcb_cfg.pfc_mode_enable))
+	} else if (((adapter->dcbx_cap & DCB_CAP_DCBX_VER_CEE) &&
+		    !(adapter->dcb_cfg.pfc_mode_enable)) ||
+		   ((adapter->dcbx_cap & DCB_CAP_DCBX_VER_IEEE) &&
+		    adapter->ixgbe_ieee_pfc &&
+		    !(adapter->ixgbe_ieee_pfc->pfc_en)))
 		return;
 
 	/* update stats for each tc, only valid with PFC enabled */