From: Felix Fietkau <nbd@openwrt.org>
Date: Tue, 18 Nov 2014 23:58:51 +0100
Subject: [PATCH] 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>
---

--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1257,6 +1257,8 @@ struct ieee80211_vif {
 	u8 cab_queue;
 	u8 hw_queue[IEEE80211_NUM_ACS];
 
+	struct ieee80211_txq *txq;
+
 	struct ieee80211_chanctx_conf __rcu *chanctx_conf;
 
 	u32 driver_flags;
@@ -1519,6 +1521,8 @@ struct ieee80211_sta {
 	bool tdls_initiator;
 	bool mfp;
 
+	struct ieee80211_txq *txq[IEEE80211_NUM_TIDS];
+
 	/* must be last */
 	u8 drv_priv[0] __aligned(sizeof(void *));
 };
@@ -1547,6 +1551,27 @@ struct ieee80211_tx_control {
 };
 
 /**
+ * struct ieee80211_txq - Software intermediate tx queue
+ *
+ * @vif: &struct ieee80211_vif pointer from the add_interface callback.
+ * @sta: station table entry, may be NULL for per-vif queue
+ * @tid: the TID for this queue (unset for per-vif queue)
+ * @ac: the AC for this queue
+ *
+ * The driver can obtain packets from this queue by calling
+ * ieee80211_tx_dequeue().
+ */
+struct ieee80211_txq {
+	struct ieee80211_vif *vif;
+	struct ieee80211_sta *sta;
+	u8 tid;
+	u8 ac;
+
+	/* must be last */
+	u8 drv_priv[0] __aligned(sizeof(void *));
+};
+
+/**
  * enum ieee80211_hw_flags - hardware flags
  *
  * These flags are used to indicate hardware capabilities to
@@ -1770,6 +1795,8 @@ enum ieee80211_hw_flags {
  *	within &struct ieee80211_sta.
  * @chanctx_data_size: size (in bytes) of the drv_priv data area
  *	within &struct ieee80211_chanctx_conf.
+ * @txq_data_size: size (in bytes) of the drv_priv data area
+ *	within @struct ieee80211_txq.
  *
  * @max_rates: maximum number of alternate rate retry stages the hw
  *	can handle.
@@ -1818,6 +1845,9 @@ enum ieee80211_hw_flags {
  * @n_cipher_schemes: a size of an array of cipher schemes definitions.
  * @cipher_schemes: a pointer to an array of cipher scheme definitions
  *	supported by HW.
+ *
+ * @txq_ac_max_pending: maximum number of frames per AC pending in all txq
+ *	entries for a vif.
  */
 struct ieee80211_hw {
 	struct ieee80211_conf conf;
@@ -1830,6 +1860,7 @@ struct ieee80211_hw {
 	int vif_data_size;
 	int sta_data_size;
 	int chanctx_data_size;
+	int txq_data_size;
 	u16 queues;
 	u16 max_listen_interval;
 	s8 max_signal;
@@ -1846,6 +1877,7 @@ struct ieee80211_hw {
 	u8 uapsd_max_sp_len;
 	u8 n_cipher_schemes;
 	const struct ieee80211_cipher_scheme *cipher_schemes;
+	int txq_ac_max_pending;
 };
 
 /**
@@ -3007,6 +3039,8 @@ enum ieee80211_reconfig_type {
  *	response template is provided, together with the location of the
  *	switch-timing IE within the template. The skb can only be used within
  *	the function call.
+ *
+ * @wake_tx_queue: Called when new packets have been added to the queue.
  */
 struct ieee80211_ops {
 	void (*tx)(struct ieee80211_hw *hw,
@@ -3238,6 +3272,9 @@ struct ieee80211_ops {
 	void (*tdls_recv_channel_switch)(struct ieee80211_hw *hw,
 					 struct ieee80211_vif *vif,
 					 struct ieee80211_tdls_ch_sw_params *params);
+
+	void (*wake_tx_queue)(struct ieee80211_hw *hw,
+			      struct ieee80211_txq *txq);
 };
 
 /**
@@ -5249,4 +5286,17 @@ void ieee80211_unreserve_tid(struct ieee
  */
 size_t ieee80211_ie_split(const u8 *ies, size_t ielen,
 			  const u8 *ids, int n_ids, size_t offset);
+
+/**
+ * ieee80211_tx_dequeue - dequeue a packet from a software tx queue
+ *
+ * @hw: pointer as obtained from ieee80211_alloc_hw()
+ * @txq: pointer obtained from .add_tx_queue() call
+ *
+ * Returns the sjb if successful, ERR_PTR(-EAGAIN) if no frame was available.
+ */
+struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
+				     struct ieee80211_txq *txq);
+
+
 #endif /* MAC80211_H */
--- a/net/mac80211/driver-ops.h
+++ b/net/mac80211/driver-ops.h
@@ -1367,4 +1367,21 @@ drv_tdls_recv_channel_switch(struct ieee
 	trace_drv_return_void(local);
 }
 
+static inline void drv_wake_tx_queue(struct ieee80211_local *local,
+				     struct txq_info *txq)
+{
+	struct ieee80211_sub_if_data *sdata = vif_to_sdata(txq->txq.vif);
+
+	if (!check_sdata_in_driver(sdata))
+		return;
+
+	if (txq->txq.sta)
+		trace_drv_wake_sta_tx_queue(local, sdata, txq->txq.sta,
+					    txq->txq.tid);
+	else
+		trace_drv_wake_vif_tx_queue(local, sdata);
+
+	local->ops->wake_tx_queue(&local->hw, &txq->txq);
+}
+
 #endif /* __MAC80211_DRIVER_OPS */
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -809,6 +809,13 @@ struct mac80211_qos_map {
 	struct rcu_head rcu_head;
 };
 
+struct txq_info {
+	struct sk_buff_head queue;
+
+	/* keep last! */
+	struct ieee80211_txq txq;
+};
+
 struct ieee80211_sub_if_data {
 	struct list_head list;
 
@@ -853,6 +860,7 @@ struct ieee80211_sub_if_data {
 	bool control_port_no_encrypt;
 	int encrypt_headroom;
 
+	atomic_t txqs_len[IEEE80211_NUM_ACS];
 	struct ieee80211_tx_queue_params tx_conf[IEEE80211_NUM_ACS];
 	struct mac80211_qos_map __rcu *qos_map;
 
@@ -1905,6 +1913,12 @@ static inline bool ieee80211_can_run_wor
 	return true;
 }
 
+void ieee80211_init_tx_queue(struct ieee80211_sub_if_data *sdata,
+			     struct sta_info *sta,
+			     struct txq_info *txq, int tid);
+void ieee80211_flush_tx_queue(struct ieee80211_local *local,
+			      struct ieee80211_txq *txq);
+
 void ieee80211_send_auth(struct ieee80211_sub_if_data *sdata,
 			 u16 transaction, u16 auth_alg, u16 status,
 			 const u8 *extra, size_t extra_len, const u8 *bssid,
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -969,6 +969,9 @@ static void ieee80211_do_stop(struct iee
 	}
 	spin_unlock_irqrestore(&local->queue_stop_reason_lock, flags);
 
+	if (sdata->vif.txq)
+		ieee80211_flush_tx_queue(local, sdata->vif.txq);
+
 	if (local->open_count == 0)
 		ieee80211_clear_tx_pending(local);
 
@@ -1773,6 +1776,15 @@ int ieee80211_if_add(struct ieee80211_lo
 	ieee80211_setup_sdata(sdata, type);
 
 	if (ndev) {
+		struct txq_info *txqi = NULL;
+
+		if (local->ops->wake_tx_queue) {
+			txqi = kzalloc(sizeof(*txqi) +
+				      local->hw.txq_data_size, GFP_KERNEL);
+			if (txqi)
+				ieee80211_init_tx_queue(sdata, NULL, txqi, 0);
+		}
+
 		if (params) {
 			ndev->ieee80211_ptr->use_4addr = params->use_4addr;
 			if (type == NL80211_IFTYPE_STATION)
@@ -1785,6 +1797,7 @@ int ieee80211_if_add(struct ieee80211_lo
 
 		ret = register_netdevice(ndev);
 		if (ret) {
+			kfree(txqi);
 			free_netdev(ndev);
 			return ret;
 		}
@@ -1802,6 +1815,7 @@ int ieee80211_if_add(struct ieee80211_lo
 
 void ieee80211_if_remove(struct ieee80211_sub_if_data *sdata)
 {
+	struct txq_info *txqi;
 	ASSERT_RTNL();
 
 	mutex_lock(&sdata->local->iflist_mtx);
@@ -1810,6 +1824,11 @@ void ieee80211_if_remove(struct ieee8021
 
 	synchronize_rcu();
 
+	if (sdata->vif.txq) {
+		txqi = container_of(sdata->vif.txq, struct txq_info, txq);
+		kfree(txqi);
+	}
+
 	if (sdata->dev) {
 		unregister_netdevice(sdata->dev);
 	} else {
@@ -1833,6 +1852,7 @@ void ieee80211_sdata_stop(struct ieee802
 void ieee80211_remove_interfaces(struct ieee80211_local *local)
 {
 	struct ieee80211_sub_if_data *sdata, *tmp;
+	struct txq_info *txqi;
 	LIST_HEAD(unreg_list);
 	LIST_HEAD(wdev_list);
 
@@ -1851,6 +1871,12 @@ void ieee80211_remove_interfaces(struct 
 	list_for_each_entry_safe(sdata, tmp, &local->interfaces, list) {
 		list_del(&sdata->list);
 
+		if (sdata->vif.txq) {
+			txqi = container_of(sdata->vif.txq, struct txq_info,
+					   txq);
+			kfree(txqi);
+		}
+
 		if (sdata->dev)
 			unregister_netdevice_queue(sdata->dev, &unreg_list);
 		else
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -1019,6 +1019,9 @@ int ieee80211_register_hw(struct ieee802
 
 	local->dynamic_ps_forced_timeout = -1;
 
+	if (!local->hw.txq_ac_max_pending)
+		local->hw.txq_ac_max_pending = 64;
+
 	result = ieee80211_wep_init(local);
 	if (result < 0)
 		wiphy_debug(local->hw.wiphy, "Failed to initialize wep: %d\n",
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -118,6 +118,11 @@ static void __cleanup_single_sta(struct 
 		atomic_dec(&ps->num_sta_ps);
 	}
 
+	if (sta->txq) {
+		for (i = 0; i < IEEE80211_NUM_TIDS; i++)
+			ieee80211_flush_tx_queue(local, sta->sta.txq[i]);
+	}
+
 	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
 		local->total_ps_buffered -= skb_queue_len(&sta->ps_tx_buf[ac]);
 		ieee80211_purge_tx_queue(&local->hw, &sta->ps_tx_buf[ac]);
@@ -234,6 +239,7 @@ void sta_info_free(struct ieee80211_loca
 
 	sta_dbg(sta->sdata, "Destroyed STA %pM\n", sta->sta.addr);
 
+	kfree(sta->txq);
 	kfree(rcu_dereference_raw(sta->sta.rates));
 	kfree(sta);
 }
@@ -285,11 +291,12 @@ struct sta_info *sta_info_alloc(struct i
 				const u8 *addr, gfp_t gfp)
 {
 	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_hw *hw = &local->hw;
 	struct sta_info *sta;
 	struct timespec uptime;
 	int i;
 
-	sta = kzalloc(sizeof(*sta) + local->hw.sta_data_size, gfp);
+	sta = kzalloc(sizeof(*sta) + hw->sta_data_size, gfp);
 	if (!sta)
 		return NULL;
 
@@ -321,11 +328,23 @@ struct sta_info *sta_info_alloc(struct i
 	for (i = 0; i < ARRAY_SIZE(sta->chain_signal_avg); i++)
 		ewma_init(&sta->chain_signal_avg[i], 1024, 8);
 
-	if (sta_prepare_rate_control(local, sta, gfp)) {
-		kfree(sta);
-		return NULL;
+	if (local->ops->wake_tx_queue) {
+		int size = sizeof(struct txq_info) +
+			   ALIGN(hw->txq_data_size, sizeof(void *));
+
+		sta->txq = kcalloc(IEEE80211_NUM_TIDS, size, gfp);
+		if (!sta->txq)
+			goto free;
+
+		for (i = 0; i < IEEE80211_NUM_TIDS; i++) {
+			struct txq_info *txq = sta->txq + i * size;
+			ieee80211_init_tx_queue(sdata, sta, txq, i);
+		}
 	}
 
+	if (sta_prepare_rate_control(local, sta, gfp))
+		goto free_txq;
+
 	for (i = 0; i < IEEE80211_NUM_TIDS; i++) {
 		/*
 		 * timer_to_tid must be initialized with identity mapping
@@ -346,7 +365,7 @@ struct sta_info *sta_info_alloc(struct i
 	if (sdata->vif.type == NL80211_IFTYPE_AP ||
 	    sdata->vif.type == NL80211_IFTYPE_AP_VLAN) {
 		struct ieee80211_supported_band *sband =
-			local->hw.wiphy->bands[ieee80211_get_sdata_band(sdata)];
+			hw->wiphy->bands[ieee80211_get_sdata_band(sdata)];
 		u8 smps = (sband->ht_cap.cap & IEEE80211_HT_CAP_SM_PS) >>
 				IEEE80211_HT_CAP_SM_PS_SHIFT;
 		/*
@@ -371,6 +390,12 @@ struct sta_info *sta_info_alloc(struct i
 	sta_dbg(sdata, "Allocated STA %pM\n", sta->sta.addr);
 
 	return sta;
+
+free_txq:
+	kfree(sta->txq);
+free:
+	kfree(sta);
+	return NULL;
 }
 
 static int sta_info_insert_check(struct sta_info *sta)
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -368,6 +368,7 @@ struct sta_info {
 	struct sk_buff_head ps_tx_buf[IEEE80211_NUM_ACS];
 	struct sk_buff_head tx_filtered[IEEE80211_NUM_ACS];
 	unsigned long driver_buffered_tids;
+	struct txq_info *txq;
 
 	/* Updated from RX path only, no locking requirements */
 	unsigned long rx_packets;
--- a/net/mac80211/trace.h
+++ b/net/mac80211/trace.h
@@ -2312,6 +2312,40 @@ TRACE_EVENT(drv_tdls_recv_channel_switch
 	)
 );
 
+DEFINE_EVENT(local_sdata_evt, drv_wake_vif_tx_queue,
+	TP_PROTO(struct ieee80211_local *local,
+		 struct ieee80211_sub_if_data *sdata),
+	TP_ARGS(local, sdata)
+);
+
+TRACE_EVENT(drv_wake_sta_tx_queue,
+	TP_PROTO(struct ieee80211_local *local,
+		 struct ieee80211_sub_if_data *sdata,
+		 struct ieee80211_sta *sta,
+		 u8 tid),
+
+	TP_ARGS(local, sdata, sta, tid),
+
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		VIF_ENTRY
+		STA_ENTRY
+		__field(u8, tid)
+	),
+
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		VIF_ASSIGN;
+		STA_ASSIGN;
+		__entry->tid = tid;
+	),
+
+	TP_printk(
+		LOCAL_PR_FMT  VIF_PR_FMT  STA_PR_FMT " tid: 0x%x",
+		LOCAL_PR_ARG, VIF_PR_ARG, STA_PR_ARG, __entry->tid
+	)
+);
+
 #ifdef CPTCFG_MAC80211_MESSAGE_TRACING
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM mac80211_msg
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1201,13 +1201,76 @@ ieee80211_tx_prepare(struct ieee80211_su
 	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_control control = {
+		.sta = pubsta
+	};
+	struct ieee80211_txq *txq = NULL;
+	struct txq_info *txqi;
+	u8 ac;
+
+	if (ieee80211_is_mgmt(hdr->frame_control) ||
+	    ieee80211_is_ctl(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 = container_of(txq, struct 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 sk_buff *skb;
+	u8 ac = txq->ac;
+
+	skb = skb_dequeue(&txqi->queue);
+	if (!skb)
+		return ERR_PTR(-EAGAIN);
+
+	atomic_dec(&sdata->txqs_len[ac]);
+	if (__netif_subqueue_stopped(sdata->dev, ac))
+		ieee80211_propagate_queue_wake(local, sdata->vif.hw_queue[ac]);
+
+	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;
 
@@ -1265,10 +1328,9 @@ static bool ieee80211_tx_frags(struct ie
 		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;
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -308,6 +308,11 @@ void ieee80211_propagate_queue_wake(stru
 		for (ac = 0; ac < n_acs; ac++) {
 			int ac_queue = sdata->vif.hw_queue[ac];
 
+			if (local->ops->wake_tx_queue &&
+			    (atomic_read(&sdata->txqs_len[ac]) >
+			     local->hw.txq_ac_max_pending))
+				continue;
+
 			if (ac_queue == queue ||
 			    (sdata->vif.cab_queue == queue &&
 			     local->queue_stop_reasons[ac_queue] == 0 &&
@@ -3307,3 +3312,36 @@ u8 *ieee80211_add_wmm_info_ie(u8 *buf, u
 
 	return buf;
 }
+
+void ieee80211_init_tx_queue(struct ieee80211_sub_if_data *sdata,
+			     struct sta_info *sta,
+			     struct txq_info *txqi, int tid)
+{
+	skb_queue_head_init(&txqi->queue);
+	txqi->txq.vif = &sdata->vif;
+
+	if (sta) {
+		txqi->txq.sta = &sta->sta;
+		sta->sta.txq[tid] = &txqi->txq;
+		txqi->txq.ac = ieee802_1d_to_ac[tid & 7];
+	} else {
+		sdata->vif.txq = &txqi->txq;
+		txqi->txq.ac = IEEE80211_AC_BE;
+	}
+}
+
+void ieee80211_flush_tx_queue(struct ieee80211_local *local,
+			      struct ieee80211_txq *txq)
+{
+	struct txq_info *txqi = container_of(txq, struct txq_info, txq);
+	struct ieee80211_sub_if_data *sdata = vif_to_sdata(txq->vif);
+	struct sk_buff *skb;
+	int n = 0;
+
+	while ((skb = skb_dequeue(&txqi->queue)) != NULL) {
+		n++;
+		ieee80211_free_txskb(&local->hw, skb);
+	}
+
+	atomic_sub(n, &sdata->txqs_len[txq->ac]);
+}