--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -784,17 +784,23 @@ static void ath_tx_sched_aggr(struct ath
 		 status != ATH_AGGR_BAW_CLOSED);
 }
 
-void ath_tx_aggr_start(struct ath_softc *sc, struct ieee80211_sta *sta,
-		       u16 tid, u16 *ssn)
+int ath_tx_aggr_start(struct ath_softc *sc, struct ieee80211_sta *sta,
+		      u16 tid, u16 *ssn)
 {
 	struct ath_atx_tid *txtid;
 	struct ath_node *an;
 
 	an = (struct ath_node *)sta->drv_priv;
 	txtid = ATH_AN_2_TID(an, tid);
+
+	if (txtid->state & (AGGR_CLEANUP | AGGR_ADDBA_COMPLETE))
+		return -EAGAIN;
+
 	txtid->state |= AGGR_ADDBA_PROGRESS;
 	txtid->paused = true;
 	*ssn = txtid->seq_start;
+
+	return 0;
 }
 
 void ath_tx_aggr_stop(struct ath_softc *sc, struct ieee80211_sta *sta, u16 tid)
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -346,8 +346,8 @@ void ath_tx_tasklet(struct ath_softc *sc
 void ath_tx_edma_tasklet(struct ath_softc *sc);
 void ath_tx_cabq(struct ieee80211_hw *hw, struct sk_buff *skb);
 bool ath_tx_aggr_check(struct ath_softc *sc, struct ath_node *an, u8 tidno);
-void ath_tx_aggr_start(struct ath_softc *sc, struct ieee80211_sta *sta,
-		       u16 tid, u16 *ssn);
+int ath_tx_aggr_start(struct ath_softc *sc, struct ieee80211_sta *sta,
+		      u16 tid, u16 *ssn);
 void ath_tx_aggr_stop(struct ath_softc *sc, struct ieee80211_sta *sta, u16 tid);
 void ath_tx_aggr_resume(struct ath_softc *sc, struct ieee80211_sta *sta, u16 tid);
 void ath9k_enable_ps(struct ath_softc *sc);
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -1968,8 +1968,9 @@ static int ath9k_ampdu_action(struct iee
 		break;
 	case IEEE80211_AMPDU_TX_START:
 		ath9k_ps_wakeup(sc);
-		ath_tx_aggr_start(sc, sta, tid, ssn);
-		ieee80211_start_tx_ba_cb_irqsafe(vif, sta->addr, tid);
+		ret = ath_tx_aggr_start(sc, sta, tid, ssn);
+		if (!ret)
+			ieee80211_start_tx_ba_cb_irqsafe(vif, sta->addr, tid);
 		ath9k_ps_restore(sc);
 		break;
 	case IEEE80211_AMPDU_TX_STOP: