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>

1 files changed, 65 insertions, 3 deletions

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,