mac80211: implement fair queueing per txq

mac80211's software queues were designed to work
very closely with device tx queues. They are
required to make use of 802.11 packet aggregation
easily and efficiently.

Due to the way 802.11 aggregation is designed it
only makes sense to keep fair queuing as close to
hardware as possible to reduce induced latency and
inertia and provide the best flow responsiveness.

This change doesn't translate directly to
immediate and significant gains. End result
depends on driver's induced latency. Best results
can be achieved if driver keeps its own tx
queue/fifo fill level to a minimum.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/iface.c

@@ -779,6 +779,7 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
 			      bool going_down)
 {
 	struct ieee80211_local *local = sdata->local;
+	struct fq *fq = &local->fq;
 	unsigned long flags;
 	struct sk_buff *skb, *tmp;
 	u32 hw_reconf_flags = 0;
@@ -976,13 +977,10 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
 
 	if (sdata->vif.txq) {
 		struct txq_info *txqi = to_txq_info(sdata->vif.txq);
-		int n = skb_queue_len(&txqi->queue);
 
-		spin_lock_bh(&txqi->queue.lock);
-		ieee80211_purge_tx_queue(&local->hw, &txqi->queue);
-		atomic_sub(n, &sdata->num_tx_queued);
-		txqi->byte_cnt = 0;
-		spin_unlock_bh(&txqi->queue.lock);
+		spin_lock_bh(&fq->lock);
+		ieee80211_txq_purge(local, txqi);
+		spin_unlock_bh(&fq->lock);
 	}
 
 	if (local->open_count == 0)
@@ -1792,7 +1790,7 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
 
 		if (txq_size) {
 			txqi = netdev_priv(ndev) + size;
-			ieee80211_init_tx_queue(sdata, NULL, txqi, 0);
+			ieee80211_txq_init(sdata, NULL, txqi, 0);
 		}
 
 		sdata->dev = ndev;