Implement my first cut at "correct" node power-save and

PS-POLL support.

This implements PS-POLL awareness i nthe

* Implement frame "leaking", which allows for a software queue
  to be scheduled even though it's asleep
* Track whether a frame has been leaked or not
* Leak out a single non-AMPDU frame when transmitting aggregates
* Queue BAR frames if the node is asleep
* Direct-dispatch the rest of control and management frames.
  This allows for things like re-association to occur (which involves
  sending probe req/resp as well as assoc request/response) when
  the node is asleep and then tries reassociating.
* Limit how many frames can set in the software node queue whilst
  the node is asleep.  net80211 is already buffering frames for us
  so this is mostly just paranoia.
* Add a PS-POLL method which leaks out a frame if there's something
  in the software queue, else it calls net80211's ps-poll routine.
  Since the ath PS-POLL routine marks the node as having a single frame
  to leak, either a software queued frame would leak, OR the next queued
  frame would leak. The next queued frame could be something from the
  net80211 power save queue, OR it could be a NULL frame from net80211.

TODO:

* Don't transmit further BAR frames (eg via a timeout) if the node is
  currently asleep.  Otherwise we may end up exhausting management frames
  due to the lots of queued BAR frames.

  I may just undo this bit later on and direct-dispatch BAR frames
  even if the node is asleep.

* It would be nice to burst out a single A-MPDU frame if both ends
  support this.  I may end adding a FreeBSD IE soon to negotiate
  this power save behaviour.

* I should make STAs timeout of power save mode if they've been in power
  save for more than a handful of seconds.  This way cards that get
  "stuck" in power save mode don't stay there for the "inactivity" timeout
  in net80211.

* Move the queue depth check into the driver layer (ath_start / ath_transmit)
  rather than doing it in the TX path.

* There could be some naughty corner cases with ps-poll leaking.
  Specifically, if net80211 generates a NULL data frame whilst another
  transmitter sends a normal data frame out net80211 output / transmit,
  we need to ensure that the NULL data frame goes out first.
  This is one of those things that should occur inside the VAP/ic TX lock.
  Grr, more investigations to do..

Tested:

* STA: AR5416, AR9280
* AP: AR5416, AR9280, AR9160

1 files changed, 159 insertions, 3 deletions

diff --git a/sys/dev/ath/if_ath.c b/sys/dev/ath/if_ath.c
index 961a8b7..04d723a 100644
--- a/sys/dev/ath/if_ath.c
+++ b/sys/dev/ath/if_ath.c
@@ -125,7 +125,7 @@ __FBSDID("$FreeBSD$");
 /*
  * Only enable this if you're working on PS-POLL support.
  */
-#undef	ATH_SW_PSQ
+#define	ATH_SW_PSQ
 
 /*
  * ATH_BCBUF determines the number of vap's that can transmit
@@ -212,6 +212,7 @@ static void	ath_announce(struct ath_softc *);
 static void	ath_dfs_tasklet(void *, int);
 static void	ath_node_powersave(struct ieee80211_node *, int);
 static int	ath_node_set_tim(struct ieee80211_node *, int);
+static void	ath_node_recv_pspoll(struct ieee80211_node *, struct mbuf *);
 
 #ifdef IEEE80211_SUPPORT_TDMA
 #include <dev/ath/if_ath_tdma.h>
@@ -695,6 +696,11 @@ ath_attach(u_int16_t devid, struct ath_softc *sc)
 	sc->sc_txq_mcastq_maxdepth = ath_txbuf;
 
 	/*
+	 * How deep can the node software TX queue get whilst it's asleep.
+	 */
+	sc->sc_txq_node_psq_maxdepth = 16;
+
+	/*
 	 * Default the maximum queue depth for a given node
 	 * to 1/4'th the TX buffers, or 64, whichever
 	 * is larger.
@@ -1248,6 +1254,9 @@ ath_vap_create(struct ieee80211com *ic, const char name[IFNAMSIZ], int unit,
 	avp->av_set_tim = vap->iv_set_tim;
 	vap->iv_set_tim = ath_node_set_tim;
 
+	avp->av_recv_pspoll = vap->iv_recv_pspoll;
+	vap->iv_recv_pspoll = ath_node_recv_pspoll;
+
 	/* Set default parameters */
 
 	/*
@@ -6169,9 +6178,11 @@ ath_tx_update_tim(struct ath_softc *sc, struct ieee80211_node *ni,
 		    an->an_tim_set == 1 &&
 		    an->an_swq_depth == 0) {
 			DPRINTF(sc, ATH_DEBUG_NODE_PWRSAVE,
-			    "%s: an=%p, swq_depth=0, tim_set=1, psq_set=0,"
+			    "%s: %6D: swq_depth=0, tim_set=1, psq_set=0,"
 			    " clear!\n",
-			    __func__, an);
+			    __func__,
+			    ni->ni_macaddr,
+			    ":");
 			an->an_tim_set = 0;
 			(void) avp->av_set_tim(ni, 0);
 		}
@@ -6181,6 +6192,151 @@ ath_tx_update_tim(struct ath_softc *sc, struct ieee80211_node *ni,
 #endif	/* ATH_SW_PSQ */
 }
 
+/*
+ * Received a ps-poll frame from net80211.
+ *
+ * Here we get a chance to serve out a software-queued frame ourselves
+ * before we punt it to net80211 to transmit us one itself - either
+ * because there's traffic in the net80211 psq, or a NULL frame to
+ * indicate there's nothing else.
+ */
+static void
+ath_node_recv_pspoll(struct ieee80211_node *ni, struct mbuf *m)
+{
+#ifdef	ATH_SW_PSQ
+	struct ath_node *an;
+	struct ath_vap *avp;
+	struct ieee80211com *ic = ni->ni_ic;
+	struct ath_softc *sc = ic->ic_ifp->if_softc;
+	int tid;
+
+	/* Just paranoia */
+	if (ni == NULL)
+		return;
+
+	/*
+	 * Unassociated (temporary node) station.
+	 */
+	if (ni->ni_associd == 0)
+		return;
+
+	/*
+	 * We do have an active node, so let's begin looking into it.
+	 */
+	an = ATH_NODE(ni);
+	avp = ATH_VAP(ni->ni_vap);
+
+	/*
+	 * For now, we just call the original ps-poll method.
+	 * Once we're ready to flip this on:
+	 *
+	 * + Set leak to 1, as no matter what we're going to have
+	 *   to send a frame;
+	 * + Check the software queue and if there's something in it,
+	 *   schedule the highest TID thas has traffic from this node.
+	 *   Then make sure we schedule the software scheduler to
+	 *   run so it picks up said frame.
+	 *
+	 * That way whatever happens, we'll at least send _a_ frame
+	 * to the given node.
+	 *
+	 * Again, yes, it's crappy QoS if the node has multiple
+	 * TIDs worth of traffic - but let's get it working first
+	 * before we optimise it.
+	 *
+	 * Also yes, there's definitely latency here - we're not
+	 * direct dispatching to the hardware in this path (and
+	 * we're likely being called from the packet receive path,
+	 * so going back into TX may be a little hairy!) but again
+	 * I'd like to get this working first before optimising
+	 * turn-around time.
+	 */
+
+	ATH_TX_LOCK(sc);
+
+	/*
+	 * Legacy - we're called and the node isn't asleep.
+	 * Immediately punt.
+	 */
+	if (! an->an_is_powersave) {
+		device_printf(sc->sc_dev,
+		    "%s: %6D: not in powersave?\n",
+		    __func__,
+		    ni->ni_macaddr,
+		    ":");
+		ATH_TX_UNLOCK(sc);
+		avp->av_recv_pspoll(ni, m);
+		return;
+	}
+
+	/*
+	 * We're in powersave.
+	 *
+	 * Leak a frame.
+	 */
+	an->an_leak_count = 1;
+
+	/*
+	 * Now, if there's no frames in the node, just punt to
+	 * recv_pspoll.
+	 *
+	 * Don't bother checking if the TIM bit is set, we really
+	 * only care if there are any frames here!
+	 */
+	if (an->an_swq_depth == 0) {
+		ATH_TX_UNLOCK(sc);
+		DPRINTF(sc, ATH_DEBUG_NODE_PWRSAVE,
+		    "%s: %6D: SWQ empty; punting to net80211\n",
+		    __func__,
+		    ni->ni_macaddr,
+		    ":");
+		avp->av_recv_pspoll(ni, m);
+		return;
+	}
+
+	/*
+	 * Ok, let's schedule the highest TID that has traffic
+	 * and then schedule something.
+	 */
+	for (tid = IEEE80211_TID_SIZE - 1; tid >= 0; tid--) {
+		struct ath_tid *atid = &an->an_tid[tid];
+		/*
+		 * No frames? Skip.
+		 */
+		if (atid->axq_depth == 0)
+			continue;
+		ath_tx_tid_sched(sc, atid);
+		/*
+		 * XXX we could do a direct call to the TXQ
+		 * scheduler code here to optimise latency
+		 * at the expense of a REALLY deep callstack.
+		 */
+		ATH_TX_UNLOCK(sc);
+		taskqueue_enqueue(sc->sc_tq, &sc->sc_txqtask);
+		DPRINTF(sc, ATH_DEBUG_NODE_PWRSAVE,
+		    "%s: %6D: leaking frame to TID %d\n",
+		    __func__,
+		    ni->ni_macaddr,
+		    ":",
+		    tid);
+		return;
+	}
+
+	ATH_TX_UNLOCK(sc);
+
+	/*
+	 * XXX nothing in the TIDs at this point? Eek.
+	 */
+	device_printf(sc->sc_dev, "%s: %6D: TIDs empty, but ath_node showed traffic?!\n",
+	    __func__,
+	    ni->ni_macaddr,
+	    ":");
+	avp->av_recv_pspoll(ni, m);
+#else
+	avp->av_recv_pspoll(ni, m);
+#endif	/* ATH_SW_PSQ */
+}
+
 MODULE_VERSION(if_ath, 1);
 MODULE_DEPEND(if_ath, wlan, 1, 1, 1);          /* 802.11 media layer */
 #if	defined(IEEE80211_ALQ) || defined(AH_DEBUG_ALQ)