[PATCH 1/2] ath9k: Drain txq before sending a nullfunc frame.

[Vivek Natarajan <vnatarajan@atheros.com>]

In a highly noisy environment, a data frame which is queued before
a nullfunc frame on a different hw queue may be sent over the air
after the tx completion of nullfunc frame. This causes the station
to enter power save and the AP to see the station as awake and
continues to send the data traffic. Fix this by draining all tx
queues before we send the null function frame with PM bit set.

Signed-off-by: Vivek Natarajan <vnatarajan@atheros.com>
---
 drivers/net/wireless/ath/ath9k/xmit.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
index 68a1c76..0cb6017 100644
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -1710,7 +1710,6 @@ static struct ath_buf *ath_tx_setup_buffer(struct ieee80211_hw *hw,
 			    bf->bf_buf_addr,
 			    txq->axq_qnum);
 
-
 	return bf;
 }
 
@@ -1813,6 +1812,15 @@ int ath_tx_start(struct ieee80211_hw *hw, struct sk_buff *skb,
 	if (unlikely(!bf))
 		return -ENOMEM;
 
+	if (ieee80211_is_nullfunc(hdr->frame_control) &&
+	    ieee80211_has_pm(hdr->frame_control)) {
+		/* Drain all the pending frames before we send a nullfunc frame
+		 * to avoid any power save state mismatch between the station
+		 * and the AP.
+		 */
+		ath_drain_all_txq(sc, false);
+	}
+
 	q = skb_get_queue_mapping(skb);
 	spin_lock_bh(&txq->axq_lock);
 	if (txq == sc->tx.txq_map[q] &&
-- 
1.6.3.3