mac80211: fix aggregation for hardware with ampdu queues

Hardware with AMPDU queues currently has broken aggregation.

This patch fixes it by making all A-MPDUs go over the regular AC queues,
but keeping track of the hardware queues in mac80211. As a first rough
version, it actually stops the AC queue for extended periods of time,
which can be removed by adding buffering internal to mac80211, but is
currently not a huge problem because people rarely use multiple TIDs
that are in the same AC (and iwlwifi currently doesn't operate as AP).

This is a short-term fix, my current medium-term plan, which I hope to
execute soon as well, but am not sure can finish before .30, looks like
this:
 1) rework the internal queuing layer in mac80211 that we use for
    fragments if the driver stopped queue in the middle of a fragmented
    frame to be able to queue more frames at once (rather than just a
    single frame with its fragments)
 2) instead of stopping the entire AC queue, queue up the frames in a
    per-station/per-TID queue during aggregation session initiation,
    when the session has come up take all those frames and put them
    onto the queue from 1)
 3) push the ampdu queue layer abstraction this patch introduces in
    mac80211 into the driver, and remove the virtual queue stuff from
    mac80211 again

This plan will probably also affect ath9k in that mac80211 queues the
frames instead of passing them down, even when there are no ampdu queues.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 634f65c0130..4ba3c540fcf 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -202,6 +202,18 @@ void sta_info_destroy(struct sta_info *sta)
 		/* Make sure timer won't free the tid_rx struct, see below */
 		if (tid_rx)
 			tid_rx->shutdown = true;
+
+		/*
+		 * The stop callback cannot find this station any more, but
+		 * it didn't complete its work -- start the queue if necessary
+		 */
+		if (sta->ampdu_mlme.tid_state_tx[i] & HT_AGG_STATE_INITIATOR_MSK &&
+		    sta->ampdu_mlme.tid_state_tx[i] & HT_AGG_STATE_REQ_STOP_BA_MSK &&
+		    local->hw.ampdu_queues)
+			ieee80211_wake_queue_by_reason(&local->hw,
+				local->hw.queues + sta->tid_to_tx_q[i],
+				IEEE80211_QUEUE_STOP_REASON_AGGREGATION);
+
 		spin_unlock_bh(&sta->lock);
 
 		/*
@@ -275,8 +287,7 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 		 * enable session_timer's data differentiation. refer to
 		 * sta_rx_agg_session_timer_expired for useage */
 		sta->timer_to_tid[i] = i;
-		/* tid to tx queue: initialize according to HW (0 is valid) */
-		sta->tid_to_tx_q[i] = ieee80211_num_queues(&local->hw);
+		sta->tid_to_tx_q[i] = -1;
 		/* rx */
 		sta->ampdu_mlme.tid_state_rx[i] = HT_AGG_STATE_IDLE;
 		sta->ampdu_mlme.tid_rx[i] = NULL;