mac80211: add an intermediate software queue implementation

This allows drivers to request per-vif and per-sta-tid queues from which
they can pull frames. This makes it easier to keep the hardware queues
short, and to improve fairness between clients and vifs.

The task of scheduling packet transmission is left up to the driver -
queueing is controlled by mac80211. Drivers can only dequeue packets by
calling ieee80211_tx_dequeue. This makes it possible to add active queue
management later without changing drivers using this code.

This can also be used as a starting point to implement A-MSDU
aggregation in a way that does not add artificially induced latency.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
[resolved minor context conflict, minor changes, endian annotations]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 105 insertions, 10 deletions

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 9f7fb4e..667111e 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -767,12 +767,22 @@ ieee80211_tx_h_rate_ctrl(struct ieee80211_tx_data *tx)
 	return TX_CONTINUE;
 }
 
+static __le16 ieee80211_tx_next_seq(struct sta_info *sta, int tid)
+{
+	u16 *seq = &sta->tid_seq[tid];
+	__le16 ret = cpu_to_le16(*seq);
+
+	/* Increase the sequence number. */
+	*seq = (*seq + 0x10) & IEEE80211_SCTL_SEQ;
+
+	return ret;
+}
+
 static ieee80211_tx_result debug_noinline
 ieee80211_tx_h_sequence(struct ieee80211_tx_data *tx)
 {
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;
-	u16 *seq;
 	u8 *qc;
 	int tid;
 
@@ -823,13 +833,10 @@ ieee80211_tx_h_sequence(struct ieee80211_tx_data *tx)
 
 	qc = ieee80211_get_qos_ctl(hdr);
 	tid = *qc & IEEE80211_QOS_CTL_TID_MASK;
-	seq = &tx->sta->tid_seq[tid];
 	tx->sta->tx_msdu[tid]++;
 
-	hdr->seq_ctrl = cpu_to_le16(*seq);
-
-	/* Increase the sequence number. */
-	*seq = (*seq + 0x10) & IEEE80211_SCTL_SEQ;
+	if (!tx->sta->sta.txq[0])
+		hdr->seq_ctrl = ieee80211_tx_next_seq(tx->sta, tid);
 
 	return TX_CONTINUE;
 }
@@ -1070,7 +1077,7 @@ static bool ieee80211_tx_prep_agg(struct ieee80211_tx_data *tx,
 		 * nothing -- this aggregation session is being started
 		 * but that might still fail with the driver
 		 */
-	} else {
+	} else if (!tx->sta->sta.txq[tid]) {
 		spin_lock(&tx->sta->lock);
 		/*
 		 * Need to re-check now, because we may get here
@@ -1211,13 +1218,102 @@ ieee80211_tx_prepare(struct ieee80211_sub_if_data *sdata,
 	return TX_CONTINUE;
 }
 
+static void ieee80211_drv_tx(struct ieee80211_local *local,
+			     struct ieee80211_vif *vif,
+			     struct ieee80211_sta *pubsta,
+			     struct sk_buff *skb)
+{
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
+	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct ieee80211_tx_control control = {
+		.sta = pubsta,
+	};
+	struct ieee80211_txq *txq = NULL;
+	struct txq_info *txqi;
+	u8 ac;
+
+	if (info->control.flags & IEEE80211_TX_CTRL_PS_RESPONSE)
+		goto tx_normal;
+
+	if (!ieee80211_is_data(hdr->frame_control))
+		goto tx_normal;
+
+	if (pubsta) {
+		u8 tid = skb->priority & IEEE80211_QOS_CTL_TID_MASK;
+
+		txq = pubsta->txq[tid];
+	} else if (vif) {
+		txq = vif->txq;
+	}
+
+	if (!txq)
+		goto tx_normal;
+
+	ac = txq->ac;
+	txqi = to_txq_info(txq);
+	atomic_inc(&sdata->txqs_len[ac]);
+	if (atomic_read(&sdata->txqs_len[ac]) >= local->hw.txq_ac_max_pending)
+		netif_stop_subqueue(sdata->dev, ac);
+
+	skb_queue_tail(&txqi->queue, skb);
+	drv_wake_tx_queue(local, txqi);
+
+	return;
+
+tx_normal:
+	drv_tx(local, &control, skb);
+}
+
+struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
+				     struct ieee80211_txq *txq)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+	struct ieee80211_sub_if_data *sdata = vif_to_sdata(txq->vif);
+	struct txq_info *txqi = container_of(txq, struct txq_info, txq);
+	struct ieee80211_hdr *hdr;
+	struct sk_buff *skb = NULL;
+	u8 ac = txq->ac;
+
+	spin_lock_bh(&txqi->queue.lock);
+
+	if (test_bit(IEEE80211_TXQ_STOP, &txqi->flags))
+		goto out;
+
+	skb = __skb_dequeue(&txqi->queue);
+	if (!skb)
+		goto out;
+
+	atomic_dec(&sdata->txqs_len[ac]);
+	if (__netif_subqueue_stopped(sdata->dev, ac))
+		ieee80211_propagate_queue_wake(local, sdata->vif.hw_queue[ac]);
+
+	hdr = (struct ieee80211_hdr *)skb->data;
+	if (txq->sta && ieee80211_is_data_qos(hdr->frame_control)) {
+		struct sta_info *sta = container_of(txq->sta, struct sta_info,
+						    sta);
+		struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+
+		hdr->seq_ctrl = ieee80211_tx_next_seq(sta, txq->tid);
+		if (test_bit(IEEE80211_TXQ_AMPDU, &txqi->flags))
+			info->flags |= IEEE80211_TX_CTL_AMPDU;
+		else
+			info->flags &= ~IEEE80211_TX_CTL_AMPDU;
+	}
+
+out:
+	spin_unlock_bh(&txqi->queue.lock);
+
+	return skb;
+}
+EXPORT_SYMBOL(ieee80211_tx_dequeue);
+
 static bool ieee80211_tx_frags(struct ieee80211_local *local,
 			       struct ieee80211_vif *vif,
 			       struct ieee80211_sta *sta,
 			       struct sk_buff_head *skbs,
 			       bool txpending)
 {
-	struct ieee80211_tx_control control;
 	struct sk_buff *skb, *tmp;
 	unsigned long flags;
 
@@ -1275,10 +1371,9 @@ static bool ieee80211_tx_frags(struct ieee80211_local *local,
 		spin_unlock_irqrestore(&local->queue_stop_reason_lock, flags);
 
 		info->control.vif = vif;
-		control.sta = sta;
 
 		__skb_unlink(skb, skbs);
-		drv_tx(local, &control, skb);
+		ieee80211_drv_tx(local, vif, sta, skb);
 	}
 
 	return true;