ath9k: Switch to using mac80211 intermediate software queues.

This switches ath9k over to using the mac80211 intermediate software
queueing mechanism for data packets. It removes the queueing inside the
driver, except for the retry queue, and instead pulls from mac80211 when
a packet is needed. The retry queue is used to store a packet that was
pulled but can't be sent immediately.

The old code path in ath_tx_start that would queue packets has been
removed completely, as has the qlen limit tunables (since there's no
longer a queue in the driver to limit).

The mac80211 intermediate software queues offer significant latency
reductions, and this patch allows ath9k to realise them. The exact gains
from this varies with the test scenario, but in an access point scenario
we have seen latency reductions ranging from 1/3 to as much as an order
of magnitude. We also achieve slightly better aggregation.

Median latency (ping) figures with this patch applied at the access point,
with two high-rate stations and one low-rate station (HT20 5Ghz), running
a Flent rtt_fair_var_up test with one TCP flow and one ping flow going to
each station:

                                 Fast station        Slow station
Default pfifo_fast qdisc:            430.4 ms            638.7 ms
fq_codel qdisc on iface:              35.5 ms            211.8 ms
This patch set:                       22.4 ms             38.2 ms

Median aggregation sizes over the same test:

Default pfifo_fast qdisc:            9.5 pkts            1.9 pkts
fq_codel qdisc on iface:            11.2 pkts            1.9 pkts
This patch set:                     13.9 pkts            1.9 pkts

This patch is based on Tim's original patch set, but reworked quite
thoroughly.

Cc: Tim Shepard <shep@alum.mit.edu>
Cc: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index e9f32b5..59e3bd0 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -1902,9 +1902,11 @@ static int ath9k_ampdu_action(struct ieee80211_hw *hw,
 	bool flush = false;
 	int ret = 0;
 	struct ieee80211_sta *sta = params->sta;
+	struct ath_node *an = (struct ath_node *)sta->drv_priv;
 	enum ieee80211_ampdu_mlme_action action = params->action;
 	u16 tid = params->tid;
 	u16 *ssn = &params->ssn;
+	struct ath_atx_tid *atid;
 
 	mutex_lock(&sc->mutex);
 
@@ -1937,9 +1939,9 @@ static int ath9k_ampdu_action(struct ieee80211_hw *hw,
 		ath9k_ps_restore(sc);
 		break;
 	case IEEE80211_AMPDU_TX_OPERATIONAL:
-		ath9k_ps_wakeup(sc);
-		ath_tx_aggr_resume(sc, sta, tid);
-		ath9k_ps_restore(sc);
+		atid = ath_node_to_tid(an, tid);
+		atid->baw_size = IEEE80211_MIN_AMPDU_BUF <<
+			        sta->ht_cap.ampdu_factor;
 		break;
 	default:
 		ath_err(ath9k_hw_common(sc->sc_ah), "Unknown AMPDU action\n");
@@ -2701,4 +2703,5 @@ struct ieee80211_ops ath9k_ops = {
 	.sw_scan_start	    = ath9k_sw_scan_start,
 	.sw_scan_complete   = ath9k_sw_scan_complete,
 	.get_txpower        = ath9k_get_txpower,
+	.wake_tx_queue      = ath9k_wake_tx_queue,
 };