From: Felix Fietkau <nbd@openwrt.org>
To: linux-wireless@vger.kernel.org
Cc: johannes@sipsolutions.net
Subject: [PATCH] mac80211: add an intermediate software queue implementation
Date: Wed, 19 Nov 2014 00:14:55 +0100
Message-Id: <1416352495-82172-1-git-send-email-nbd@openwrt.org> (sfid-20141119_001502_620004_F6772A5B)
Sender: linux-wireless-owner@vger.kernel.org

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>
---
 include/net/mac80211.h     | 50 ++++++++++++++++++++++++++++++++++
 net/mac80211/driver-ops.h  | 17 ++++++++++++
 net/mac80211/ieee80211_i.h | 14 ++++++++++
 net/mac80211/iface.c       | 10 +++++++
 net/mac80211/main.c        |  3 +++
 net/mac80211/sta_info.c    | 26 ++++++++++++++++--
 net/mac80211/sta_info.h    |  1 +
 net/mac80211/trace.h       | 34 +++++++++++++++++++++++
 net/mac80211/tx.c          | 67 +++++++++++++++++++++++++++++++++++++++++++---
 net/mac80211/util.c        | 35 ++++++++++++++++++++++++
 10 files changed, 252 insertions(+), 5 deletions(-)

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 5f203a6..f1ea966 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1192,6 +1192,8 @@ 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;
@@ -1448,6 +1450,8 @@ struct ieee80211_sta {
 	bool tdls;
 	bool tdls_initiator;
 
+	struct ieee80211_txq *txq[IEEE80211_NUM_TIDS];
+
 	/* must be last */
 	u8 drv_priv[0] __aligned(sizeof(void *));
 };
@@ -1476,6 +1480,27 @@ 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
@@ -1698,6 +1723,8 @@ 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.
@@ -1746,6 +1773,9 @@ 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;
@@ -1758,6 +1788,7 @@ 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;
@@ -1774,6 +1805,7 @@ struct ieee80211_hw {
 	u8 uapsd_max_sp_len;
 	u8 n_cipher_schemes;
 	const struct ieee80211_cipher_scheme *cipher_schemes;
+	int txq_ac_max_pending;
 };
 
 /**
@@ -2878,6 +2910,8 @@ enum ieee80211_reconfig_type {
  *
  * @get_txpower: get current maximum tx power (in dBm) based on configuration
  *	and hardware limits.
+ *
+ * @wake_tx_queue: Called when new packets have been added to the queue.
  */
 struct ieee80211_ops {
 	void (*tx)(struct ieee80211_hw *hw,
@@ -3089,6 +3123,9 @@ struct ieee80211_ops {
 	u32 (*get_expected_throughput)(struct ieee80211_sta *sta);
 	int (*get_txpower)(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 			   int *dbm);
+
+	void (*wake_tx_queue)(struct ieee80211_hw *hw,
+			      struct ieee80211_txq *txq);
 };
 
 /**
@@ -5006,4 +5043,17 @@ void ieee80211_tdls_oper_request(struct ieee80211_vif *vif, const u8 *peer,
  */
 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 0 if successful, -EAGAIN if no frame was available.
+ */
+int ieee80211_tx_dequeue(struct ieee80211_hw *hw, struct ieee80211_txq *txq,
+			 struct sk_buff **skb);
+
+
 #endif /* MAC80211_H */
diff --git a/net/mac80211/driver-ops.h b/net/mac80211/driver-ops.h
index 9759dd1..1dbc646 100644
--- a/net/mac80211/driver-ops.h
+++ b/net/mac80211/driver-ops.h
@@ -1296,4 +1296,21 @@ static inline int drv_get_txpower(struct ieee80211_local *local,
 	return ret;
 }
 
+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 */
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 842e066..8dee646 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -793,6 +793,13 @@ 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;
 
@@ -837,6 +844,8 @@ struct ieee80211_sub_if_data {
 	bool control_port_no_encrypt;
 	int encrypt_headroom;
 
+	struct txq_info *txq;
+	atomic_t txq_len[IEEE80211_NUM_ACS];
 	struct ieee80211_tx_queue_params tx_conf[IEEE80211_NUM_ACS];
 	struct mac80211_qos_map __rcu *qos_map;
 
@@ -1865,6 +1874,11 @@ void ieee80211_add_pending_skbs(struct ieee80211_local *local,
 				struct sk_buff_head *skbs);
 void ieee80211_flush_queues(struct ieee80211_local *local,
 			    struct ieee80211_sub_if_data *sdata);
+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,
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 9df26ad..86dd429 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -967,6 +967,9 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
 	}
 	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);
 
@@ -1753,6 +1756,13 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
 	/* setup type-dependent data */
 	ieee80211_setup_sdata(sdata, type);
 
+	if (local->ops->wake_tx_queue) {
+		sdata->txq = kzalloc(sizeof(*sdata->txq) +
+				     local->hw.txq_data_size, GFP_KERNEL);
+		if (sdata->txq)
+			ieee80211_init_tx_queue(sdata, NULL, sdata->txq, 0);
+	}
+
 	if (ndev) {
 		if (params) {
 			ndev->ieee80211_ptr->use_4addr = params->use_4addr;
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 282a4f3..c742f7f 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -1004,6 +1004,9 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 
 	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",
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index adc2537..dd948c3 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -119,6 +119,11 @@ static void __cleanup_single_sta(struct sta_info *sta)
 		sta_info_recalc_tim(sta);
 	}
 
+	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]);
@@ -241,6 +246,8 @@ void sta_info_free(struct ieee80211_local *local, struct sta_info *sta)
 		kfree(sta->tx_lat);
 	}
 
+	kfree(sta->txq);
+
 	sta_dbg(sta->sdata, "Destroyed STA %pM\n", sta->sta.addr);
 
 	kfree(rcu_dereference_raw(sta->sta.rates));
@@ -294,12 +301,13 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 				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;
 	struct ieee80211_tx_latency_bin_ranges *tx_latency;
 	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;
 
@@ -357,6 +365,20 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 	for (i = 0; i < ARRAY_SIZE(sta->chain_signal_avg); i++)
 		ewma_init(&sta->chain_signal_avg[i], 1024, 8);
 
+	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;
 
@@ -380,7 +402,7 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 	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;
 		/*
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index bcda2ac..3f73284 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -371,6 +371,7 @@ 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;
+	void *txq;
 
 	/* Updated from RX path only, no locking requirements */
 	unsigned long rx_packets;
diff --git a/net/mac80211/trace.h b/net/mac80211/trace.h
index 809a498..84780ad 100644
--- a/net/mac80211/trace.h
+++ b/net/mac80211/trace.h
@@ -2194,6 +2194,40 @@ TRACE_EVENT(drv_get_txpower,
 	)
 );
 
+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 CONFIG_MAC80211_MESSAGE_TRACING
 #undef TRACE_SYSTEM
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 3ffd91f..1d98e62 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1198,13 +1198,75 @@ 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_control control = {
+		.sta = pubsta
+	};
+	struct ieee80211_txq *pubtxq = NULL;
+	struct txq_info *txq;
+	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;
+		pubtxq = pubsta->txq[tid];
+	} else {
+		pubtxq = vif->txq;
+	}
+
+	if (!pubtxq)
+		goto tx_normal;
+
+	ac = pubtxq->ac;
+	txq = container_of(pubtxq, struct txq_info, txq);
+	atomic_inc(&sdata->txq_len[ac]);
+	if (atomic_read(&sdata->txq_len[ac]) >= local->hw.txq_ac_max_pending)
+		netif_stop_subqueue(sdata->dev, ac);
+
+	skb_queue_tail(&txq->queue, skb);
+	drv_wake_tx_queue(local, txq);
+
+	return;
+
+tx_normal:
+	drv_tx(local, &control, skb);
+}
+
+int ieee80211_tx_dequeue(struct ieee80211_hw *hw, struct ieee80211_txq *pubtxq,
+			 struct sk_buff **dest)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+	struct ieee80211_sub_if_data *sdata = vif_to_sdata(pubtxq->vif);
+	struct txq_info *txq = container_of(pubtxq, struct txq_info, txq);
+	u8 ac = pubtxq->ac;
+
+	*dest = skb_dequeue(&txq->queue);
+	if (!*dest)
+		return -EAGAIN;
+
+	atomic_dec(&sdata->txq_len[ac]);
+	if (__netif_subqueue_stopped(sdata->dev, ac))
+		ieee80211_propagate_queue_wake(local, sdata->vif.hw_queue[ac]);
+
+	return 0;
+}
+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;
 
@@ -1262,10 +1324,9 @@ 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;
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index f9319a5..90e9763 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -308,6 +308,11 @@ void ieee80211_propagate_queue_wake(struct ieee80211_local *local, int queue)
 		for (ac = 0; ac < n_acs; ac++) {
 			int ac_queue = sdata->vif.hw_queue[ac];
 
+			if (local->ops->wake_tx_queue &&
+			    (atomic_read(&sdata->txq_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 &&
@@ -3182,3 +3187,33 @@ u8 *ieee80211_add_wmm_info_ie(u8 *buf, u8 qosinfo)
 
 	return buf;
 }
+
+void ieee80211_init_tx_queue(struct ieee80211_sub_if_data *sdata,
+			     struct sta_info *sta,
+			     struct txq_info *txq, int tid)
+{
+	skb_queue_head_init(&txq->queue);
+	txq->txq.vif = &sdata->vif;
+
+	if (sta) {
+		txq->txq.sta = &sta->sta;
+		sta->sta.txq[tid] = &txq->txq;
+		txq->txq.ac = ieee802_1d_to_ac[tid & 7];
+	} else {
+		sdata->vif.txq = &txq->txq;
+		txq->txq.ac = IEEE80211_AC_BE;
+	}
+}
+
+void ieee80211_flush_tx_queue(struct ieee80211_local *local,
+			      struct ieee80211_txq *pubtxq)
+{
+	struct txq_info *txq = container_of(pubtxq, struct txq_info, txq);
+	struct ieee80211_sub_if_data *sdata = vif_to_sdata(pubtxq->vif);
+	struct sk_buff *skb;
+
+	while ((skb = skb_dequeue(&txq->queue)) != NULL) {
+		atomic_dec(&sdata->txq_len[pubtxq->ac]);
+		ieee80211_free_txskb(&local->hw, skb);
+	}
+}
-- 
2.1.2