--- /dev/null
+From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
+Date: Tue, 18 Dec 2018 17:02:06 -0800
+Subject: [PATCH] mac80211: Add TXQ scheduling API
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+This adds an API to mac80211 to handle scheduling of TXQs. The interface
+between driver and mac80211 for TXQ handling is changed by adding two new
+functions: ieee80211_next_txq(), which will return the next TXQ to schedule
+in the current round-robin rotation, and ieee80211_return_txq(), which the
+driver uses to indicate that it has finished scheduling a TXQ (which will
+then be put back in the scheduling rotation if it isn't empty).
+
+The driver must call ieee80211_txq_schedule_start() at the start of each
+scheduling session, and ieee80211_txq_schedule_end() at the end. The API
+then guarantees that the same TXQ is not returned twice in the same
+session (so a driver can loop on ieee80211_next_txq() without worrying
+about breaking the loop.
+
+Usage of the new API is optional, so drivers can be ported one at a time.
+In this patch, the actual scheduling performed by mac80211 is simple
+round-robin, but a subsequent commit adds airtime fairness awareness to the
+scheduler.
+
+Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
+[minor kernel-doc fix, propagate sparse locking checks out]
+Signed-off-by: Johannes Berg <johannes.berg@intel.com>
+---
+
+--- a/include/net/mac80211.h
++++ b/include/net/mac80211.h
+@@ -107,9 +107,15 @@
+ * The driver is expected to initialize its private per-queue data for stations
+ * and interfaces in the .add_interface and .sta_add ops.
+ *
+- * The driver can't access the queue directly. To dequeue a frame, it calls
+- * ieee80211_tx_dequeue(). Whenever mac80211 adds a new frame to a queue, it
+- * calls the .wake_tx_queue driver op.
++ * The driver can't access the queue directly. To dequeue a frame from a
++ * txq, it calls ieee80211_tx_dequeue(). Whenever mac80211 adds a new frame to a
++ * queue, it calls the .wake_tx_queue driver op.
++ *
++ * Drivers can optionally delegate responsibility for scheduling queues to
++ * mac80211, to take advantage of airtime fairness accounting. In this case, to
++ * obtain the next queue to pull frames from, the driver calls
++ * ieee80211_next_txq(). The driver is then expected to return the txq using
++ * ieee80211_return_txq().
+ *
+ * For AP powersave TIM handling, the driver only needs to indicate if it has
+ * buffered packets in the driver specific data structures by calling
+@@ -5979,7 +5985,8 @@ void ieee80211_unreserve_tid(struct ieee
+ * ieee80211_tx_dequeue - dequeue a packet from a software tx queue
+ *
+ * @hw: pointer as obtained from ieee80211_alloc_hw()
+- * @txq: pointer obtained from station or virtual interface
++ * @txq: pointer obtained from station or virtual interface, or from
++ * ieee80211_next_txq()
+ *
+ * Returns the skb if successful, %NULL if no frame was available.
+ */
+@@ -5987,6 +5994,54 @@ struct sk_buff *ieee80211_tx_dequeue(str
+ struct ieee80211_txq *txq);
+
+ /**
++ * ieee80211_next_txq - get next tx queue to pull packets from
++ *
++ * @hw: pointer as obtained from ieee80211_alloc_hw()
++ * @ac: AC number to return packets from.
++ *
++ * Should only be called between calls to ieee80211_txq_schedule_start()
++ * and ieee80211_txq_schedule_end().
++ * Returns the next txq if successful, %NULL if no queue is eligible. If a txq
++ * is returned, it should be returned with ieee80211_return_txq() after the
++ * driver has finished scheduling it.
++ */
++struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac);
++
++/**
++ * ieee80211_return_txq - return a TXQ previously acquired by ieee80211_next_txq()
++ *
++ * @hw: pointer as obtained from ieee80211_alloc_hw()
++ * @txq: pointer obtained from station or virtual interface
++ *
++ * Should only be called between calls to ieee80211_txq_schedule_start()
++ * and ieee80211_txq_schedule_end().
++ */
++void ieee80211_return_txq(struct ieee80211_hw *hw, struct ieee80211_txq *txq);
++
++/**
++ * ieee80211_txq_schedule_start - acquire locks for safe scheduling of an AC
++ *
++ * @hw: pointer as obtained from ieee80211_alloc_hw()
++ * @ac: AC number to acquire locks for
++ *
++ * Acquire locks needed to schedule TXQs from the given AC. Should be called
++ * before ieee80211_next_txq() or ieee80211_return_txq().
++ */
++void ieee80211_txq_schedule_start(struct ieee80211_hw *hw, u8 ac)
++ __acquires(txq_lock);
++
++/**
++ * ieee80211_txq_schedule_end - release locks for safe scheduling of an AC
++ *
++ * @hw: pointer as obtained from ieee80211_alloc_hw()
++ * @ac: AC number to acquire locks for
++ *
++ * Release locks previously acquired by ieee80211_txq_schedule_end().
++ */
++void ieee80211_txq_schedule_end(struct ieee80211_hw *hw, u8 ac)
++ __releases(txq_lock);
++
++/**
+ * ieee80211_txq_get_depth - get pending frame/byte count of given txq
+ *
+ * The values are not guaranteed to be coherent with regard to each other, i.e.
+--- a/net/mac80211/agg-tx.c
++++ b/net/mac80211/agg-tx.c
+@@ -229,7 +229,7 @@ ieee80211_agg_start_txq(struct sta_info
+ clear_bit(IEEE80211_TXQ_STOP, &txqi->flags);
+ local_bh_disable();
+ rcu_read_lock();
+- drv_wake_tx_queue(sta->sdata->local, txqi);
++ schedule_and_wake_txq(sta->sdata->local, txqi);
+ rcu_read_unlock();
+ local_bh_enable();
+ }
+--- a/net/mac80211/driver-ops.h
++++ b/net/mac80211/driver-ops.h
+@@ -1176,6 +1176,15 @@ static inline void drv_wake_tx_queue(str
+ local->ops->wake_tx_queue(&local->hw, &txq->txq);
+ }
+
++static inline void schedule_and_wake_txq(struct ieee80211_local *local,
++ struct txq_info *txqi)
++{
++ spin_lock_bh(&local->active_txq_lock[txqi->txq.ac]);
++ ieee80211_return_txq(&local->hw, &txqi->txq);
++ spin_unlock_bh(&local->active_txq_lock[txqi->txq.ac]);
++ drv_wake_tx_queue(local, txqi);
++}
++
+ static inline int drv_start_nan(struct ieee80211_local *local,
+ struct ieee80211_sub_if_data *sdata,
+ struct cfg80211_nan_conf *conf)
+--- a/net/mac80211/ieee80211_i.h
++++ b/net/mac80211/ieee80211_i.h
+@@ -829,6 +829,8 @@ enum txq_info_flags {
+ * a fq_flow which is already owned by a different tin
+ * @def_cvars: codel vars for @def_flow
+ * @frags: used to keep fragments created after dequeue
++ * @schedule_order: used with ieee80211_local->active_txqs
++ * @schedule_round: counter to prevent infinite loops on TXQ scheduling
+ */
+ struct txq_info {
+ struct fq_tin tin;
+@@ -836,6 +838,8 @@ struct txq_info {
+ struct codel_vars def_cvars;
+ struct codel_stats cstats;
+ struct sk_buff_head frags;
++ struct list_head schedule_order;
++ u16 schedule_round;
+ unsigned long flags;
+
+ /* keep last! */
+@@ -1127,6 +1131,11 @@ struct ieee80211_local {
+ struct codel_vars *cvars;
+ struct codel_params cparams;
+
++ /* protects active_txqs and txqi->schedule_order */
++ spinlock_t active_txq_lock[IEEE80211_NUM_ACS];
++ struct list_head active_txqs[IEEE80211_NUM_ACS];
++ u16 schedule_round[IEEE80211_NUM_ACS];
++
+ const struct ieee80211_ops *ops;
+
+ /*
+--- a/net/mac80211/main.c
++++ b/net/mac80211/main.c
+@@ -652,6 +652,11 @@ struct ieee80211_hw *ieee80211_alloc_hw_
+ spin_lock_init(&local->rx_path_lock);
+ spin_lock_init(&local->queue_stop_reason_lock);
+
++ for (i = 0; i < IEEE80211_NUM_ACS; i++) {
++ INIT_LIST_HEAD(&local->active_txqs[i]);
++ spin_lock_init(&local->active_txq_lock[i]);
++ }
++
+ INIT_LIST_HEAD(&local->chanctx_list);
+ mutex_init(&local->chanctx_mtx);
+
+--- a/net/mac80211/sta_info.c
++++ b/net/mac80211/sta_info.c
+@@ -1244,7 +1244,7 @@ void ieee80211_sta_ps_deliver_wakeup(str
+ if (!txq_has_queue(sta->sta.txq[i]))
+ continue;
+
+- drv_wake_tx_queue(local, to_txq_info(sta->sta.txq[i]));
++ schedule_and_wake_txq(local, to_txq_info(sta->sta.txq[i]));
+ }
+ }
+
+--- a/net/mac80211/tx.c
++++ b/net/mac80211/tx.c
+@@ -1441,6 +1441,7 @@ void ieee80211_txq_init(struct ieee80211
+ codel_vars_init(&txqi->def_cvars);
+ codel_stats_init(&txqi->cstats);
+ __skb_queue_head_init(&txqi->frags);
++ INIT_LIST_HEAD(&txqi->schedule_order);
+
+ txqi->txq.vif = &sdata->vif;
+
+@@ -1464,6 +1465,9 @@ void ieee80211_txq_purge(struct ieee8021
+
+ fq_tin_reset(fq, tin, fq_skb_free_func);
+ ieee80211_purge_tx_queue(&local->hw, &txqi->frags);
++ spin_lock_bh(&local->active_txq_lock[txqi->txq.ac]);
++ list_del_init(&txqi->schedule_order);
++ spin_unlock_bh(&local->active_txq_lock[txqi->txq.ac]);
+ }
+
+ void ieee80211_txq_set_params(struct ieee80211_local *local)
+@@ -1580,7 +1584,7 @@ static bool ieee80211_queue_skb(struct i
+ ieee80211_txq_enqueue(local, txqi, skb);
+ spin_unlock_bh(&fq->lock);
+
+- drv_wake_tx_queue(local, txqi);
++ schedule_and_wake_txq(local, txqi);
+
+ return true;
+ }
+@@ -3602,6 +3606,60 @@ out:
+ }
+ EXPORT_SYMBOL(ieee80211_tx_dequeue);
+
++struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
++{
++ struct ieee80211_local *local = hw_to_local(hw);
++ struct txq_info *txqi = NULL;
++
++ lockdep_assert_held(&local->active_txq_lock[ac]);
++
++ txqi = list_first_entry_or_null(&local->active_txqs[ac],
++ struct txq_info,
++ schedule_order);
++
++ if (!txqi || txqi->schedule_round == local->schedule_round[ac])
++ return NULL;
++
++ list_del_init(&txqi->schedule_order);
++ txqi->schedule_round = local->schedule_round[ac];
++ return &txqi->txq;
++}
++EXPORT_SYMBOL(ieee80211_next_txq);
++
++void ieee80211_return_txq(struct ieee80211_hw *hw,
++ struct ieee80211_txq *txq)
++{
++ struct ieee80211_local *local = hw_to_local(hw);
++ struct txq_info *txqi = to_txq_info(txq);
++
++ lockdep_assert_held(&local->active_txq_lock[txq->ac]);
++
++ if (list_empty(&txqi->schedule_order) &&
++ (!skb_queue_empty(&txqi->frags) || txqi->tin.backlog_packets))
++ list_add_tail(&txqi->schedule_order,
++ &local->active_txqs[txq->ac]);
++}
++EXPORT_SYMBOL(ieee80211_return_txq);
++
++void ieee80211_txq_schedule_start(struct ieee80211_hw *hw, u8 ac)
++ __acquires(txq_lock)
++{
++ struct ieee80211_local *local = hw_to_local(hw);
++
++ spin_lock_bh(&local->active_txq_lock[ac]);
++ local->schedule_round[ac]++;
++}
++EXPORT_SYMBOL(ieee80211_txq_schedule_start);
++
++void ieee80211_txq_schedule_end(struct ieee80211_hw *hw, u8 ac)
++ __releases(txq_lock)
++{
++ struct ieee80211_local *local = hw_to_local(hw);
++
++ spin_unlock_bh(&local->active_txq_lock[ac]);
++}
++EXPORT_SYMBOL(ieee80211_txq_schedule_end);
++
+ void __ieee80211_subif_start_xmit(struct sk_buff *skb,
+ struct net_device *dev,
+ u32 info_flags)
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