ath9k: Send legacy rated frames as unaggregated

Currently the aggregation is formed till the aggregation limit
is reached and the rate lookup is done for the first frame alone.
But there can be a legacy rated frames in tid queue. This patch
limits the subframe addition based on presence of legacy rate and
sends the legacy rated frames as unaggregated one.

Signed-off-by: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/xmit.c

@@ -571,6 +571,25 @@ static void ath_tx_complete_aggr(struct ath_softc *sc, struct ath_txq *txq,
 		ath_reset(sc, false);
 }
 
+static bool ath_lookup_legacy(struct ath_buf *bf)
+{
+	struct sk_buff *skb;
+	struct ieee80211_tx_info *tx_info;
+	struct ieee80211_tx_rate *rates;
+	int i;
+
+	skb = bf->bf_mpdu;
+	tx_info = IEEE80211_SKB_CB(skb);
+	rates = tx_info->control.rates;
+
+	for (i = 3; i >= 0; i--) {
+		if (!(rates[i].flags & IEEE80211_TX_RC_MCS))
+			return true;
+	}
+
+	return false;
+}
+
 static u32 ath_lookup_rate(struct ath_softc *sc, struct ath_buf *bf,
 			   struct ath_atx_tid *tid)
 {
@@ -750,7 +769,8 @@ static enum ATH_AGGR_STATUS ath_tx_form_aggr(struct ath_softc *sc,
 		al_delta = ATH_AGGR_DELIM_SZ + fi->framelen;
 
 		if (nframes &&
-		    (aggr_limit < (al + bpad + al_delta + prev_al))) {
+		    ((aggr_limit < (al + bpad + al_delta + prev_al)) ||
+		     ath_lookup_legacy(bf))) {
 			status = ATH_AGGR_LIMITED;
 			break;
 		}