mac80211: Add airtime accounting and scheduling to TXQs

This adds airtime accounting and scheduling to the mac80211 TXQ
scheduler. A new callback, ieee80211_sta_register_airtime(), is added
that drivers can call to report airtime usage for stations.

When airtime information is present, mac80211 will schedule TXQs
(through ieee80211_next_txq()) in a way that enforces airtime fairness
between active stations. This scheduling works the same way as the ath9k
in-driver airtime fairness scheduling. If no airtime usage is reported
by the driver, the scheduler will default to round-robin scheduling.

For drivers that don't control TXQ scheduling in software, a new API
function, ieee80211_txq_may_transmit(), is added which the driver can use
to check if the TXQ is eligible for transmission, or should be throttled to
enforce fairness. Calls to this function must also be enclosed in
ieee80211_txq_schedule_{start,end}() calls to ensure proper locking.

The API ieee80211_txq_may_transmit() also ensures that TXQ list will be
aligned aginst driver's own round-robin scheduler list. i.e it rotates
the TXQ list till it makes the requested node becomes the first entry
in TXQ list. Thus both the TXQ list and driver's list are in sync.

Co-developed-by: Rajkumar Manoharan <rmanohar@codeaurora.org>
Signed-off-by: Louie Lu <git@louie.lu>
[added debugfs write op to reset airtime counter]
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Rajkumar Manoharan <rmanohar@codeaurora.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

9 files changed, 223 insertions, 10 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index de65fe3ed9cc..83ee573b1804 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1447,6 +1447,9 @@ static int sta_apply_parameters(struct ieee80211_local *local,
 	if (ieee80211_vif_is_mesh(&sdata->vif))
 		sta_apply_mesh_params(local, sta, params);
 
+	if (params->airtime_weight)
+		sta->airtime_weight = params->airtime_weight;
+
 	/* set the STA state after all sta info from usermode has been set */
 	if (test_sta_flag(sta, WLAN_STA_TDLS_PEER) ||
 	    set & BIT(NL80211_STA_FLAG_ASSOCIATED)) {
diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index 3fe541e358f3..81c5fec2eae7 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -383,6 +383,9 @@ void debugfs_hw_add(struct ieee80211_local *local)
 	if (local->ops->wake_tx_queue)
 		DEBUGFS_ADD_MODE(aqm, 0600);
 
+	debugfs_create_u16("airtime_flags", 0600,
+			   phyd, &local->airtime_flags);
+
 	statsd = debugfs_create_dir("statistics", phyd);
 
 	/* if the dir failed, don't put all the other things into the root! */
diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
index b753194710ad..3aa618dcc58e 100644
--- a/net/mac80211/debugfs_sta.c
+++ b/net/mac80211/debugfs_sta.c
@@ -181,9 +181,9 @@ static ssize_t sta_aqm_read(struct file *file, char __user *userbuf,
 			       txqi->tin.tx_bytes,
 			       txqi->tin.tx_packets,
 			       txqi->flags,
-			       txqi->flags & (1<<IEEE80211_TXQ_STOP) ? "STOP" : "RUN",
-			       txqi->flags & (1<<IEEE80211_TXQ_AMPDU) ? " AMPDU" : "",
-			       txqi->flags & (1<<IEEE80211_TXQ_NO_AMSDU) ? " NO-AMSDU" : "");
+			       test_bit(IEEE80211_TXQ_STOP, &txqi->flags) ? "STOP" : "RUN",
+			       test_bit(IEEE80211_TXQ_AMPDU, &txqi->flags) ? " AMPDU" : "",
+			       test_bit(IEEE80211_TXQ_NO_AMSDU, &txqi->flags) ? " NO-AMSDU" : "");
 	}
 
 	rcu_read_unlock();
@@ -195,6 +195,64 @@ static ssize_t sta_aqm_read(struct file *file, char __user *userbuf,
 }
 STA_OPS(aqm);
 
+static ssize_t sta_airtime_read(struct file *file, char __user *userbuf,
+				size_t count, loff_t *ppos)
+{
+	struct sta_info *sta = file->private_data;
+	struct ieee80211_local *local = sta->sdata->local;
+	size_t bufsz = 200;
+	char *buf = kzalloc(bufsz, GFP_KERNEL), *p = buf;
+	u64 rx_airtime = 0, tx_airtime = 0;
+	s64 deficit[IEEE80211_NUM_ACS];
+	ssize_t rv;
+	int ac;
+
+	if (!buf)
+		return -ENOMEM;
+
+	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
+		spin_lock_bh(&local->active_txq_lock[ac]);
+		rx_airtime += sta->airtime[ac].rx_airtime;
+		tx_airtime += sta->airtime[ac].tx_airtime;
+		deficit[ac] = sta->airtime[ac].deficit;
+		spin_unlock_bh(&local->active_txq_lock[ac]);
+	}
+
+	p += scnprintf(p, bufsz + buf - p,
+		"RX: %llu us\nTX: %llu us\nWeight: %u\n"
+		"Deficit: VO: %lld us VI: %lld us BE: %lld us BK: %lld us\n",
+		rx_airtime,
+		tx_airtime,
+		sta->airtime_weight,
+		deficit[0],
+		deficit[1],
+		deficit[2],
+		deficit[3]);
+
+	rv = simple_read_from_buffer(userbuf, count, ppos, buf, p - buf);
+	kfree(buf);
+	return rv;
+}
+
+static ssize_t sta_airtime_write(struct file *file, const char __user *userbuf,
+				 size_t count, loff_t *ppos)
+{
+	struct sta_info *sta = file->private_data;
+	struct ieee80211_local *local = sta->sdata->local;
+	int ac;
+
+	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
+		spin_lock_bh(&local->active_txq_lock[ac]);
+		sta->airtime[ac].rx_airtime = 0;
+		sta->airtime[ac].tx_airtime = 0;
+		sta->airtime[ac].deficit = sta->airtime_weight;
+		spin_unlock_bh(&local->active_txq_lock[ac]);
+	}
+
+	return count;
+}
+STA_OPS_RW(airtime);
+
 static ssize_t sta_agg_status_read(struct file *file, char __user *userbuf,
 					size_t count, loff_t *ppos)
 {
@@ -906,6 +964,10 @@ void ieee80211_sta_debugfs_add(struct sta_info *sta)
 	if (local->ops->wake_tx_queue)
 		DEBUGFS_ADD(aqm);
 
+	if (wiphy_ext_feature_isset(local->hw.wiphy,
+				    NL80211_EXT_FEATURE_AIRTIME_FAIRNESS))
+		DEBUGFS_ADD(airtime);
+
 	if (sizeof(sta->driver_buffered_tids) == sizeof(u32))
 		debugfs_create_x32("driver_buffered_tids", 0400,
 				   sta->debugfs_dir,
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index d1db27b1e989..056b16bce3b0 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1138,6 +1138,8 @@ struct ieee80211_local {
 	struct list_head active_txqs[IEEE80211_NUM_ACS];
 	u16 schedule_round[IEEE80211_NUM_ACS];
 
+	u16 airtime_flags;
+
 	const struct ieee80211_ops *ops;
 
 	/*
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 9b9d6cadf56e..896f17d726d0 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -667,6 +667,7 @@ struct ieee80211_hw *ieee80211_alloc_hw_nm(size_t priv_data_len,
 		INIT_LIST_HEAD(&local->active_txqs[i]);
 		spin_lock_init(&local->active_txq_lock[i]);
 	}
+	local->airtime_flags = AIRTIME_USE_TX | AIRTIME_USE_RX;
 
 	INIT_LIST_HEAD(&local->chanctx_list);
 	mutex_init(&local->chanctx_mtx);
@@ -1153,6 +1154,9 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 	if (!local->hw.max_nan_de_entries)
 		local->hw.max_nan_de_entries = IEEE80211_MAX_NAN_INSTANCE_ID;
 
+	if (!local->hw.weight_multiplier)
+		local->hw.weight_multiplier = 1;
+
 	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 83e1c316a29e..11f058987a54 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -90,7 +90,6 @@ static void __cleanup_single_sta(struct sta_info *sta)
 	struct tid_ampdu_tx *tid_tx;
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
 	struct ieee80211_local *local = sdata->local;
-	struct fq *fq = &local->fq;
 	struct ps_data *ps;
 
 	if (test_sta_flag(sta, WLAN_STA_PS_STA) ||
@@ -120,9 +119,7 @@ static void __cleanup_single_sta(struct sta_info *sta)
 
 			txqi = to_txq_info(sta->sta.txq[i]);
 
-			spin_lock_bh(&fq->lock);
 			ieee80211_txq_purge(local, txqi);
-			spin_unlock_bh(&fq->lock);
 		}
 	}
 
@@ -387,9 +384,12 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 	if (sta_prepare_rate_control(local, sta, gfp))
 		goto free_txq;
 
+	sta->airtime_weight = IEEE80211_DEFAULT_AIRTIME_WEIGHT;
+
 	for (i = 0; i < IEEE80211_NUM_ACS; i++) {
 		skb_queue_head_init(&sta->ps_tx_buf[i]);
 		skb_queue_head_init(&sta->tx_filtered[i]);
+		sta->airtime[i].deficit = sta->airtime_weight;
 	}
 
 	for (i = 0; i < IEEE80211_NUM_TIDS; i++)
@@ -1826,6 +1826,27 @@ void ieee80211_sta_set_buffered(struct ieee80211_sta *pubsta,
 }
 EXPORT_SYMBOL(ieee80211_sta_set_buffered);
 
+void ieee80211_sta_register_airtime(struct ieee80211_sta *pubsta, u8 tid,
+				    u32 tx_airtime, u32 rx_airtime)
+{
+	struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
+	struct ieee80211_local *local = sta->sdata->local;
+	u8 ac = ieee80211_ac_from_tid(tid);
+	u32 airtime = 0;
+
+	if (sta->local->airtime_flags & AIRTIME_USE_TX)
+		airtime += tx_airtime;
+	if (sta->local->airtime_flags & AIRTIME_USE_RX)
+		airtime += rx_airtime;
+
+	spin_lock_bh(&local->active_txq_lock[ac]);
+	sta->airtime[ac].tx_airtime += tx_airtime;
+	sta->airtime[ac].rx_airtime += rx_airtime;
+	sta->airtime[ac].deficit -= airtime;
+	spin_unlock_bh(&local->active_txq_lock[ac]);
+}
+EXPORT_SYMBOL(ieee80211_sta_register_airtime);
+
 int sta_info_move_state(struct sta_info *sta,
 			enum ieee80211_sta_state new_state)
 {
@@ -2188,6 +2209,23 @@ void sta_set_sinfo(struct sta_info *sta, struct station_info *sinfo,
 		sinfo->filled |= BIT_ULL(NL80211_STA_INFO_TX_FAILED);
 	}
 
+	if (!(sinfo->filled & BIT_ULL(NL80211_STA_INFO_RX_DURATION))) {
+		for (ac = 0; ac < IEEE80211_NUM_ACS; ac++)
+			sinfo->rx_duration += sta->airtime[ac].rx_airtime;
+		sinfo->filled |= BIT_ULL(NL80211_STA_INFO_RX_DURATION);
+	}
+
+	if (!(sinfo->filled & BIT_ULL(NL80211_STA_INFO_TX_DURATION))) {
+		for (ac = 0; ac < IEEE80211_NUM_ACS; ac++)
+			sinfo->tx_duration += sta->airtime[ac].tx_airtime;
+		sinfo->filled |= BIT_ULL(NL80211_STA_INFO_TX_DURATION);
+	}
+
+	if (!(sinfo->filled & BIT_ULL(NL80211_STA_INFO_AIRTIME_WEIGHT))) {
+		sinfo->airtime_weight = sta->airtime_weight;
+		sinfo->filled |= BIT_ULL(NL80211_STA_INFO_AIRTIME_WEIGHT);
+	}
+
 	sinfo->rx_dropped_misc = sta->rx_stats.dropped;
 	if (sta->pcpu_rx_stats) {
 		for_each_possible_cpu(cpu) {
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 8eb29041be54..9a380803e597 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -127,6 +127,16 @@ enum ieee80211_agg_stop_reason {
 	AGG_STOP_DESTROY_STA,
 };
 
+/* Debugfs flags to enable/disable use of RX/TX airtime in scheduler */
+#define AIRTIME_USE_TX		BIT(0)
+#define AIRTIME_USE_RX		BIT(1)
+
+struct airtime_info {
+	u64 rx_airtime;
+	u64 tx_airtime;
+	s64 deficit;
+};
+
 struct sta_info;
 
 /**
@@ -565,6 +575,9 @@ struct sta_info {
 	} tx_stats;
 	u16 tid_seq[IEEE80211_QOS_CTL_TID_MASK + 1];
 
+	struct airtime_info airtime[IEEE80211_NUM_ACS];
+	u16 airtime_weight;
+
 	/*
 	 * Aggregation information, locked with lock.
 	 */
diff --git a/net/mac80211/status.c b/net/mac80211/status.c
index 3f0b96e1e02f..5b9952b1caf3 100644
--- a/net/mac80211/status.c
+++ b/net/mac80211/status.c
@@ -823,6 +823,12 @@ static void __ieee80211_tx_status(struct ieee80211_hw *hw,
 			ieee80211_sta_tx_notify(sta->sdata, (void *) skb->data,
 						acked, info->status.tx_time);
 
+		if (info->status.tx_time &&
+		    wiphy_ext_feature_isset(local->hw.wiphy,
+					    NL80211_EXT_FEATURE_AIRTIME_FAIRNESS))
+			ieee80211_sta_register_airtime(&sta->sta, tid,
+						       info->status.tx_time, 0);
+
 		if (ieee80211_hw_check(&local->hw, REPORTS_TX_ACK_STATUS)) {
 			if (info->flags & IEEE80211_TX_STAT_ACK) {
 				if (sta->status_stats.lost_packets)
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 544da6411620..f46d8d822f86 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1488,8 +1488,11 @@ void ieee80211_txq_purge(struct ieee80211_local *local,
 	struct fq *fq = &local->fq;
 	struct fq_tin *tin = &txqi->tin;
 
+	spin_lock_bh(&fq->lock);
 	fq_tin_reset(fq, tin, fq_skb_free_func);
 	ieee80211_purge_tx_queue(&local->hw, &txqi->frags);
+	spin_unlock_bh(&fq->lock);
+
 	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]);
@@ -3641,11 +3644,28 @@ struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
 
 	lockdep_assert_held(&local->active_txq_lock[ac]);
 
+ begin:
 	txqi = list_first_entry_or_null(&local->active_txqs[ac],
 					struct txq_info,
 					schedule_order);
+	if (!txqi)
+		return NULL;
+
+	if (txqi->txq.sta) {
+		struct sta_info *sta = container_of(txqi->txq.sta,
+						struct sta_info, sta);
+
+		if (sta->airtime[txqi->txq.ac].deficit < 0) {
+			sta->airtime[txqi->txq.ac].deficit +=
+				sta->airtime_weight;
+			list_move_tail(&txqi->schedule_order,
+				       &local->active_txqs[txqi->txq.ac]);
+			goto begin;
+		}
+	}
+
 
-	if (!txqi || txqi->schedule_round == local->schedule_round[ac])
+	if (txqi->schedule_round == local->schedule_round[ac])
 		return NULL;
 
 	list_del_init(&txqi->schedule_order);
@@ -3663,12 +3683,74 @@ void ieee80211_return_txq(struct ieee80211_hw *hw,
 	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]);
+	    (!skb_queue_empty(&txqi->frags) || txqi->tin.backlog_packets)) {
+		/* If airtime accounting is active, always enqueue STAs at the
+		 * head of the list to ensure that they only get moved to the
+		 * back by the airtime DRR scheduler once they have a negative
+		 * deficit. A station that already has a negative deficit will
+		 * get immediately moved to the back of the list on the next
+		 * call to ieee80211_next_txq().
+		 */
+		if (txqi->txq.sta &&
+		    wiphy_ext_feature_isset(local->hw.wiphy,
+					    NL80211_EXT_FEATURE_AIRTIME_FAIRNESS))
+			list_add(&txqi->schedule_order,
+				 &local->active_txqs[txq->ac]);
+		else
+			list_add_tail(&txqi->schedule_order,
+				      &local->active_txqs[txq->ac]);
+	}
 }
 EXPORT_SYMBOL(ieee80211_return_txq);
 
+bool ieee80211_txq_may_transmit(struct ieee80211_hw *hw,
+				struct ieee80211_txq *txq)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+	struct txq_info *iter, *tmp, *txqi = to_txq_info(txq);
+	struct sta_info *sta;
+	u8 ac = txq->ac;
+
+	lockdep_assert_held(&local->active_txq_lock[ac]);
+
+	if (!txqi->txq.sta)
+		goto out;
+
+	if (list_empty(&txqi->schedule_order))
+		goto out;
+
+	list_for_each_entry_safe(iter, tmp, &local->active_txqs[ac],
+				 schedule_order) {
+		if (iter == txqi)
+			break;
+
+		if (!iter->txq.sta) {
+			list_move_tail(&iter->schedule_order,
+				       &local->active_txqs[ac]);
+			continue;
+		}
+		sta = container_of(iter->txq.sta, struct sta_info, sta);
+		if (sta->airtime[ac].deficit < 0)
+			sta->airtime[ac].deficit += sta->airtime_weight;
+		list_move_tail(&iter->schedule_order, &local->active_txqs[ac]);
+	}
+
+	sta = container_of(txqi->txq.sta, struct sta_info, sta);
+	if (sta->airtime[ac].deficit >= 0)
+		goto out;
+
+	sta->airtime[ac].deficit += sta->airtime_weight;
+	list_move_tail(&txqi->schedule_order, &local->active_txqs[ac]);
+
+	return false;
+out:
+	if (!list_empty(&txqi->schedule_order))
+		list_del_init(&txqi->schedule_order);
+
+	return true;
+}
+EXPORT_SYMBOL(ieee80211_txq_may_transmit);
+
 void ieee80211_txq_schedule_start(struct ieee80211_hw *hw, u8 ac)
 	__acquires(txq_lock)
 {