Don't resume a TID on each filtered frame completion - only do it if

we did suspend it.

The whole suspend/resume TID queue thing is supposed to be a matched
reference count - a subsystem (eg addba negotiation, BAR transmission,
filtered frames, etc) is supposed to call pause() once and then resume()
once.

ath_tx_tid_filt_comp_complete() is called upon the completion of any
filtered frame, regardless of whether the driver had aleady seen
a filtered frame and called pause().

So only call resume() if tid->isfiltered = 1, which indicates that
we had called pause() once.

This fixes a seemingly whacked and different problem - traffic hangs.

What was actually going on:

* There'd be some marginal link with crappy behaviour, causing filtered
  frames and BAR TXing to occur;
* A BAR TX would occur, setting the new BAW (block-ack window) to seqno n;
* .. and pause() would be called, blocking further transmission;
* A filtered frame completion would occur from the hardware, but with
  tid->isfiltered = 0 which indiciates we haven't actually marked
  the queue yet as filtered;
* ath_tx_tid_filt_comp_complete() would call resume(), continuing
  transmission;
* Some frames would be queued to the hardware, since the TID is now no
  longer paused;
* .. and if some make it out and ACked successfully, the new BAW
  may be seqno n+1 or more;
* .. then the BAR TX completes and sets the new seqno back to n.

At this point the BAW tracking would be loopy because the BAW
start was modified but the BAW ring buffer wasn't updated in lock
step.

Tested:

* Routerstation Pro + AR9220 AP

1 files changed, 8 insertions, 2 deletions

diff --git a/sys/dev/ath/if_ath_tx.c b/sys/dev/ath/if_ath_tx.c
index 0c3808c91296..acd14846ca63 100644
--- a/sys/dev/ath/if_ath_tx.c
+++ b/sys/dev/ath/if_ath_tx.c
@@ -3357,6 +3357,7 @@ static void
 ath_tx_tid_filt_comp_complete(struct ath_softc *sc, struct ath_tid *tid)
 {
 	struct ath_buf *bf;
+	int do_resume = 0;
 
 	ATH_TX_LOCK_ASSERT(sc);
 
@@ -3365,7 +3366,11 @@ ath_tx_tid_filt_comp_complete(struct ath_softc *sc, struct ath_tid *tid)
 
 	DPRINTF(sc, ATH_DEBUG_SW_TX_FILT, "%s: hwq=0, transition back\n",
 	    __func__);
-	tid->isfiltered = 0;
+	if (tid->isfiltered == 1) {
+		tid->isfiltered = 0;
+		do_resume = 1;
+	}
+
 	/* XXX ath_tx_tid_resume() also calls ath_tx_set_clrdmask()! */
 	ath_tx_set_clrdmask(sc, tid->an);
 
@@ -3375,7 +3380,8 @@ ath_tx_tid_filt_comp_complete(struct ath_softc *sc, struct ath_tid *tid)
 		ATH_TID_INSERT_HEAD(tid, bf, bf_list);
 	}
 
-	ath_tx_tid_resume(sc, tid);
+	if (do_resume)
+		ath_tx_tid_resume(sc, tid);
 }
 
 /*