iwlwifi: Recover TX flow failure

Monitors the tx statistics to detect the drop in throughput.
When the throughput drops, the ratio of the actual_ack_count and the
expected_ack_count also drops.  At the same time, the aggregated
ba_timeout (the number of ba timeout retries) also rises.  If the
actual_ack_count/expected_ack_count ratio is 0 and the number of ba
timeout retries rises to BA_TIMEOUT_MAX, no tx packets can be delivered.
Reloading the uCode and bring the system back to normal operational
state.

Signed-off-by: Trieu 'Andrew' Nguyen <trieux.t.nguyen@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-agn.c b/drivers/net/wireless/iwlwifi/iwl-agn.c
index 82b1a3f..e69e625 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn.c
@@ -2916,10 +2916,21 @@
 			return ret;
 	case IEEE80211_AMPDU_TX_START:
 		IWL_DEBUG_HT(priv, "start Tx\n");
-		return iwl_tx_agg_start(priv, sta->addr, tid, ssn);
+		ret = iwl_tx_agg_start(priv, sta->addr, tid, ssn);
+		if (ret == 0) {
+			priv->_agn.agg_tids_count++;
+			IWL_DEBUG_HT(priv, "priv->_agn.agg_tids_count = %u\n",
+				     priv->_agn.agg_tids_count);
+		}
+		return ret;
 	case IEEE80211_AMPDU_TX_STOP:
 		IWL_DEBUG_HT(priv, "stop Tx\n");
 		ret = iwl_tx_agg_stop(priv, sta->addr, tid);
+		if ((ret == 0) && (priv->_agn.agg_tids_count > 0)) {
+			priv->_agn.agg_tids_count--;
+			IWL_DEBUG_HT(priv, "priv->_agn.agg_tids_count = %u\n",
+				     priv->_agn.agg_tids_count);
+		}
 		if (test_bit(STATUS_EXIT_PENDING, &priv->status))
 			return 0;
 		else
@@ -3303,6 +3314,7 @@
 	priv->iw_mode = NL80211_IFTYPE_STATION;
 	priv->current_ht_config.smps = IEEE80211_SMPS_STATIC;
 	priv->missed_beacon_threshold = IWL_MISSED_BEACON_THRESHOLD_DEF;
+	priv->_agn.agg_tids_count = 0;
 
 	/* initialize force reset */
 	priv->force_reset[IWL_RF_RESET].reset_duration =