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, 5 insertions, 1 deletions

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index d017ad14d7db..834d2171f344 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1565,8 +1565,12 @@ static void sta_ps_start(struct sta_info *sta)
 
 	for (tid = 0; tid < IEEE80211_NUM_TIDS; tid++) {
 		struct ieee80211_txq *txq = sta->sta.txq[tid];
+		struct txq_info *txqi = to_txq_info(txq);
 
-		ieee80211_unschedule_txq(&local->hw, txq, false);
+		spin_lock(&local->active_txq_lock[txq->ac]);
+		if (!list_empty(&txqi->schedule_order))
+			list_del_init(&txqi->schedule_order);
+		spin_unlock(&local->active_txq_lock[txq->ac]);
 
 		if (txq_has_queue(txq))
 			set_bit(tid, &sta->txq_buffered_tids);