Introduce TX aggregation and software TX queue management

for Atheros AR5416 and later wireless devices.

This is a very large commit - the complete history can be
found in the user/adrian/if_ath_tx branch.

Legacy (ie, pre-AR5416) devices also use the per-software
TXQ support and (in theory) can support non-aggregation
ADDBA sessions. However, the net80211 stack doesn't currently
support this.

In summary:

TX path:

* queued frames normally go onto a per-TID, per-node queue
* some special frames (eg ADDBA control frames) are thrown
  directly onto the relevant hardware queue so they can
  go out before any software queued frames are queued.
* Add methods to create, suspend, resume and tear down an
  aggregation session.
* Add in software retransmission of both normal and aggregate
  frames.
* Add in completion handling of aggregate frames, including
  parsing the block ack bitmap provided by the hardware.
* Write an aggregation function which can assemble frames into
  an aggregate based on the selected rate control and channel
  configuration.
* The per-TID queues are locked based on their target hardware
  TX queue. This matches what ath9k/atheros does, and thus
  simplified porting over some of the aggregation logic.
* When doing TX aggregation, stick the sequence number allocation
  in the TX path rather than net80211 TX path, and protect it
  by the TXQ lock.

Rate control:

* Delay rate control selection until the frame is about to
  be queued to the hardware, so retried frames can have their
  rate control choices changed. Frames with a static rate
  control selection have that applied before each TX, just
  to simplify the TX path (ie, not have "static" and "dynamic"
  rate control special cased.)
* Teach ath_rate_sample about aggregates - both completion and
  errors.
* Add an EWMA for tracking what the current "good" MCS rate is
  based on failure rates.

Misc:

* Introduce a bunch of dirty hacks and workarounds so TID mapping
  and net80211 frame inspection can be kept out of the net80211
  layer. Because of the way this code works (and it's from Atheros
  and Linux ath9k), there is a consistent, 1:1 mapping between
  TID and AC. So we need to ensure that frames going to a specific
  TID will _always_ end up on the right AC, and vice versa, or the
  completion/locking will simply get very confused. I plan on
  addressing this mess in the future.

Known issues:

* There is no BAR frame transmission just yet. A whole lot of
  tidying up needs to occur before BAR frame TX can occur in the
  "correct" place - ie, once the TID TX queue has been drained.

* Interface reset/purge/etc results in frames in the TX and RX
  queues being removed. This creates holes in the sequence numbers
  being assigned and the TX/RX AMPDU code (on either side) just
  hangs.

* There's no filtered frame support at the present moment, so
  stations going into power saving mode will simply have a number
  of frames dropped - likely resulting in a traffic "hang".

* Raw frame TX is going to just not function with 11n aggregation.
  Likely this needs to be modified to always override the sequence
  number if the frame is going into an aggregation session.
  However, general raw frame injection currently doesn't work in
  general in net80211, so let's just ignore this for now until
  this is sorted out.

* HT protection is just not implemented and won't be until the above
  is sorted out. In addition, the AR5416 has issues RTS protecting
  large aggregates (anything >8k), so the work around needs to be
  ported and tested. Thus, this will be put on hold until the above
  work is complete.

* The rate control module 'sample' is the only currently supported
  module; onoe/amrr haven't been tested and have likely bit rotted
  a little. I'll follow up with some commits to make them work again
  for non-11n rates, but they won't be updated to handle 11n and
  aggregation. If someone wishes to do so then they're welcome to
  send along patches.

* .. and "sample" doesn't really do a good job of 11n TX. Specifically,
  the metrics used (packet TX time and failure/success rates) isn't as
  useful for 11n. It's likely that it should be extended to take into
  account the aggregate throughput possible and then choose a rate
  which maximises that. Ie, it may be acceptable for a higher MCS rate
  with a higher failure to be used if it gives a more acceptable
  throughput/latency then a lower MCS rate @ a lower error rate.
  Again, patches will be gratefully accepted.

Because of this, ATH_ENABLE_11N is still not enabled by default.

Sponsored by:	Hobnob, Inc.
Obtained from:	Linux, Atheros

1 files changed, 61 insertions, 1 deletions

diff --git a/sys/dev/ath/if_ath.c b/sys/dev/ath/if_ath.c
index ef3db94..210b965 100644
--- a/sys/dev/ath/if_ath.c
+++ b/sys/dev/ath/if_ath.c
@@ -723,6 +723,19 @@ ath_attach(u_int16_t devid, struct ath_softc *sc)
 	ic->ic_scan_end = ath_scan_end;
 	ic->ic_set_channel = ath_set_channel;
 
+	/* 802.11n specific - but just override anyway */
+	sc->sc_addba_request = ic->ic_addba_request;
+	sc->sc_addba_response = ic->ic_addba_response;
+	sc->sc_addba_stop = ic->ic_addba_stop;
+	sc->sc_bar_response = ic->ic_bar_response;
+	sc->sc_addba_response_timeout = ic->ic_addba_response_timeout;
+
+	ic->ic_addba_request = ath_addba_request;
+	ic->ic_addba_response = ath_addba_response;
+	ic->ic_addba_response_timeout = ath_addba_response_timeout;
+	ic->ic_addba_stop = ath_addba_stop;
+	ic->ic_bar_response = ath_bar_response;
+
 	ieee80211_radiotap_attach(ic,
 	    &sc->sc_tx_th.wt_ihdr, sizeof(sc->sc_tx_th),
 		ATH_TX_RADIOTAP_PRESENT,
@@ -3343,6 +3356,9 @@ ath_node_alloc(struct ieee80211vap *vap, const uint8_t mac[IEEE80211_ADDR_LEN])
 	    device_get_nameunit(sc->sc_dev), an);
 	mtx_init(&an->an_mtx, an->an_name, NULL, MTX_DEF);
 
+	/* XXX setup ath_tid */
+	ath_tx_tid_init(sc, an);
+
 	DPRINTF(sc, ATH_DEBUG_NODE, "%s: an %p\n", __func__, an);
 	return &an->an_node;
 }
@@ -3354,6 +3370,7 @@ ath_node_cleanup(struct ieee80211_node *ni)
 	struct ath_softc *sc = ic->ic_ifp->if_softc;
 
 	/* Cleanup ath_tid, free unused bufs, unlink bufs in TXQ */
+	ath_tx_node_flush(sc, ATH_NODE(ni));
 	ath_rate_node_cleanup(sc, ATH_NODE(ni));
 	sc->sc_node_cleanup(ni);
 }
@@ -4364,6 +4381,29 @@ ath_tx_default_comp(struct ath_softc *sc, struct ath_buf *bf, int fail)
 }
 
 /*
+ * Update rate control with the given completion status.
+ */
+void
+ath_tx_update_ratectrl(struct ath_softc *sc, struct ieee80211_node *ni,
+    struct ath_rc_series *rc, struct ath_tx_status *ts, int frmlen,
+    int nframes, int nbad)
+{
+	struct ath_node *an;
+
+	/* Only for unicast frames */
+	if (ni == NULL)
+		return;
+
+	an = ATH_NODE(ni);
+
+	if ((ts->ts_status & HAL_TXERR_FILT) == 0) {
+		ATH_NODE_LOCK(an);
+		ath_rate_tx_complete(sc, an, rc, ts, frmlen, nframes, nbad);
+		ATH_NODE_UNLOCK(an);
+	}
+}
+
+/*
  * Update the busy status of the last frame on the free list.
  * When doing TDMA, the busy flag tracks whether the hardware
  * currently points to this buffer or not, and thus gated DMA
@@ -4396,6 +4436,8 @@ ath_tx_update_busy(struct ath_softc *sc)
 
 /*
  * Process completed xmit descriptors from the specified queue.
+ * Kick the packet scheduler if needed. This can occur from this
+ * particular task.
  */
 static int
 ath_tx_processq(struct ath_softc *sc, struct ath_txq *txq, int dosched)
@@ -4405,6 +4447,7 @@ ath_tx_processq(struct ath_softc *sc, struct ath_txq *txq, int dosched)
 	struct ath_desc *ds;
 	struct ath_tx_status *ts;
 	struct ieee80211_node *ni;
+	struct ath_node *an;
 	int nacked;
 	HAL_STATUS status;
 
@@ -4471,6 +4514,7 @@ ath_tx_processq(struct ath_softc *sc, struct ath_txq *txq, int dosched)
 
 		/* If unicast frame, update general statistics */
 		if (ni != NULL) {
+			an = ATH_NODE(ni);
 			/* update statistics */
 			ath_tx_update_stats(sc, ts, bf);
 		}
@@ -4490,7 +4534,10 @@ ath_tx_processq(struct ath_softc *sc, struct ath_txq *txq, int dosched)
 				 * XXX assume this isn't an aggregate
 				 * frame.
 				 */
-				ath_rate_tx_complete(sc, ATH_NODE(ni), bf);
+				ath_tx_update_ratectrl(sc, ni,
+				     bf->bf_state.bfs_rc, ts,
+				    bf->bf_state.bfs_pktlen, 1,
+				    (ts->ts_status == 0 ? 0 : 1));
 			}
 			ath_tx_default_comp(sc, bf, 0);
 		} else
@@ -4503,6 +4550,14 @@ ath_tx_processq(struct ath_softc *sc, struct ath_txq *txq, int dosched)
 	if (txq->axq_depth <= 1)
 		ieee80211_ff_flush(ic, txq->axq_ac);
 #endif
+
+	/* Kick the TXQ scheduler */
+	if (dosched) {
+		ATH_TXQ_LOCK(txq);
+		ath_txq_sched(sc, txq);
+		ATH_TXQ_UNLOCK(txq);
+	}
+
 	return nacked;
 }
 
@@ -4736,6 +4791,11 @@ ath_tx_draintxq(struct ath_softc *sc, struct ath_txq *txq)
 			ath_tx_default_comp(sc, bf, 1);
 	}
 
+	/*
+	 * Drain software queued frames which are on
+	 * active TIDs.
+	 */
+	ath_tx_txq_drain(sc, txq);
 }
 
 static void