wifi: mac80211: switch airtime fairness back to deficit round-robin scheduling

This reverts commits 6a789ba679d652587532cec2a0e0274fda172f3b and
2433647bc8d983a543e7d31b41ca2de1c7e2c198.

The virtual time scheduler code has a number of issues:
- queues slowed down by hardware/firmware powersave handling were not properly
  handled.
- on ath10k in push-pull mode, tx queues that the driver tries to pull from
  were starved, causing excessive latency
- delay between tx enqueue and reported airtime use were causing excessively
  bursty tx behavior

The bursty behavior may also be present on the round-robin scheduler, but there
it is much easier to fix without introducing additional regressions

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Link: https://lore.kernel.org/r/20220625212411.36675-1-nbd@nbd.name
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 13 insertions, 57 deletions

diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index 1fe43b264d75..0c748b1eb023 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -216,14 +216,14 @@ static ssize_t aql_txq_limit_read(struct file *file,
 			"VI	%u		%u\n"
 			"BE	%u		%u\n"
 			"BK	%u		%u\n",
-			local->airtime[IEEE80211_AC_VO].aql_txq_limit_low,
-			local->airtime[IEEE80211_AC_VO].aql_txq_limit_high,
-			local->airtime[IEEE80211_AC_VI].aql_txq_limit_low,
-			local->airtime[IEEE80211_AC_VI].aql_txq_limit_high,
-			local->airtime[IEEE80211_AC_BE].aql_txq_limit_low,
-			local->airtime[IEEE80211_AC_BE].aql_txq_limit_high,
-			local->airtime[IEEE80211_AC_BK].aql_txq_limit_low,
-			local->airtime[IEEE80211_AC_BK].aql_txq_limit_high);
+			local->aql_txq_limit_low[IEEE80211_AC_VO],
+			local->aql_txq_limit_high[IEEE80211_AC_VO],
+			local->aql_txq_limit_low[IEEE80211_AC_VI],
+			local->aql_txq_limit_high[IEEE80211_AC_VI],
+			local->aql_txq_limit_low[IEEE80211_AC_BE],
+			local->aql_txq_limit_high[IEEE80211_AC_BE],
+			local->aql_txq_limit_low[IEEE80211_AC_BK],
+			local->aql_txq_limit_high[IEEE80211_AC_BK]);
 	return simple_read_from_buffer(user_buf, count, ppos,
 				       buf, len);
 }
@@ -255,11 +255,11 @@ static ssize_t aql_txq_limit_write(struct file *file,
 	if (ac >= IEEE80211_NUM_ACS)
 		return -EINVAL;
 
-	q_limit_low_old = local->airtime[ac].aql_txq_limit_low;
-	q_limit_high_old = local->airtime[ac].aql_txq_limit_high;
+	q_limit_low_old = local->aql_txq_limit_low[ac];
+	q_limit_high_old = local->aql_txq_limit_high[ac];
 
-	local->airtime[ac].aql_txq_limit_low = q_limit_low;
-	local->airtime[ac].aql_txq_limit_high = q_limit_high;
+	local->aql_txq_limit_low[ac] = q_limit_low;
+	local->aql_txq_limit_high[ac] = q_limit_high;
 
 	mutex_lock(&local->sta_mtx);
 	list_for_each_entry(sta, &local->sta_list, list) {
@@ -382,46 +382,6 @@ static const struct file_operations force_tx_status_ops = {
 	.llseek = default_llseek,
 };
 
-static ssize_t airtime_read(struct file *file,
-			    char __user *user_buf,
-			    size_t count,
-			    loff_t *ppos)
-{
-	struct ieee80211_local *local = file->private_data;
-	char buf[200];
-	u64 v_t[IEEE80211_NUM_ACS];
-	u64 wt[IEEE80211_NUM_ACS];
-	int len = 0, ac;
-
-	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
-		spin_lock_bh(&local->airtime[ac].lock);
-		v_t[ac] = local->airtime[ac].v_t;
-		wt[ac] = local->airtime[ac].weight_sum;
-		spin_unlock_bh(&local->airtime[ac].lock);
-	}
-	len = scnprintf(buf, sizeof(buf),
-			"\tVO         VI         BE         BK\n"
-			"Virt-t\t%-10llu %-10llu %-10llu %-10llu\n"
-			"Weight\t%-10llu %-10llu %-10llu %-10llu\n",
-			v_t[0],
-			v_t[1],
-			v_t[2],
-			v_t[3],
-			wt[0],
-			wt[1],
-			wt[2],
-			wt[3]);
-
-	return simple_read_from_buffer(user_buf, count, ppos,
-				       buf, len);
-}
-
-static const struct file_operations airtime_ops = {
-	.read = airtime_read,
-	.open = simple_open,
-	.llseek = default_llseek,
-};
-
 #ifdef CONFIG_PM
 static ssize_t reset_write(struct file *file, const char __user *user_buf,
 			   size_t count, loff_t *ppos)
@@ -675,11 +635,7 @@ void debugfs_hw_add(struct ieee80211_local *local)
 	if (local->ops->wake_tx_queue)
 		DEBUGFS_ADD_MODE(aqm, 0600);
 
-	if (wiphy_ext_feature_isset(local->hw.wiphy,
-				    NL80211_EXT_FEATURE_AIRTIME_FAIRNESS)) {
-		DEBUGFS_ADD_MODE(airtime, 0600);
-		DEBUGFS_ADD_MODE(airtime_flags, 0600);
-	}
+	DEBUGFS_ADD_MODE(airtime_flags, 0600);
 
 	DEBUGFS_ADD(aql_txq_limit);
 	debugfs_create_u32("aql_threshold", 0600,