--- a/ath/if_ath.c
+++ b/ath/if_ath.c
@@ -384,6 +384,7 @@ static u_int32_t ath_get_real_maxtxpower
 
 static void ath_poll_disable(struct net_device *dev);
 static void ath_poll_enable(struct net_device *dev);
+static void ath_fetch_idle_time(struct ath_softc *sc);
 
 /* calibrate every 30 secs in steady state but check every second at first. */
 static int ath_calinterval = ATH_SHORT_CALINTERVAL;
@@ -2581,6 +2582,7 @@ ath_init(struct net_device *dev)
 	 * be followed by initialization of the appropriate bits
 	 * and then setup of the interrupt mask.
 	 */
+	ath_fetch_idle_time(sc);
 	sc->sc_curchan.channel = ic->ic_curchan->ic_freq;
 	sc->sc_curchan.channelFlags = ath_chan2flags(ic->ic_curchan);
 	if (!ath_hal_reset(ah, sc->sc_opmode, &sc->sc_curchan, AH_FALSE, &status)) {
@@ -2914,6 +2916,48 @@ ath_hw_check_atim(struct ath_softc *sc, 
 	return 0;
 }
 
+#define AR5K_MIBC       0x0040
+#define AR5K_MIBC_FREEZE   (1 << 1)
+#define AR5K_TXFC       0x80ec
+#define AR5K_RXFC       0x80f0
+#define AR5K_RXCLEAR	0x80f4
+#define AR5K_CYCLES		0x80f8
+static void
+ath_fetch_idle_time(struct ath_softc *sc)
+{
+	struct ieee80211com *ic = &sc->sc_ic;
+	struct ath_hal *ah = sc->sc_ah;
+	u_int32_t cc, rx;
+	u_int32_t time = 0;
+
+	if (sc->sc_ah->ah_macType < 5212)
+		return;
+
+	if (!ic->ic_curchan || (ic->ic_curchan == IEEE80211_CHAN_ANYC))
+		return;
+
+	OS_REG_WRITE(ah, AR5K_MIBC, AR5K_MIBC_FREEZE);
+	rx = OS_REG_READ(ah, AR5K_RXCLEAR);
+	cc = OS_REG_READ(ah, AR5K_CYCLES);
+
+	if (!cc)
+		return;
+
+	if (rx > cc)
+		return; /* should not happen */
+
+	if (sc->sc_last_chan)
+		sc->sc_last_chan->ic_idletime = 100 * (cc - rx) / cc;
+	sc->sc_last_chan = ic->ic_curchan;
+
+	OS_REG_WRITE(ah, AR5K_RXCLEAR, 0);
+	OS_REG_WRITE(ah, AR5K_CYCLES, 0);
+	OS_REG_WRITE(ah, AR5K_TXFC, 0);
+	OS_REG_WRITE(ah, AR5K_RXFC, 0);
+	OS_REG_WRITE(ah, AR5K_MIBC, 0);
+}
+#undef AR5K_RXCLEAR
+#undef AR5K_CYCLES
 
 /*
  * Reset the hardware w/o losing operational state.  This is
@@ -2941,6 +2985,7 @@ ath_reset(struct net_device *dev)
 	 * Convert to a HAL channel description with the flags
 	 * constrained to reflect the current operating mode.
 	 */
+	ath_fetch_idle_time(sc);
 	c = ic->ic_curchan;
 	sc->sc_curchan.channel = c->ic_freq;
 	sc->sc_curchan.channelFlags = ath_chan2flags(c);
@@ -9023,6 +9068,7 @@ ath_chan_set(struct ath_softc *sc, struc
 	u_int8_t channel_change_required = 0;
 	struct timeval tv;
 
+
 	/*
 	 * Convert to a HAL channel description with
 	 * the flags constrained to reflect the current
@@ -9031,6 +9077,14 @@ ath_chan_set(struct ath_softc *sc, struc
 	memset(&hchan, 0, sizeof(HAL_CHANNEL));
 	hchan.channel = chan->ic_freq;
 	hchan.channelFlags = ath_chan2flags(chan);
+
+	/* don't do duplicate channel changes, but do
+	 * store the available idle time */
+	ath_fetch_idle_time(sc);
+	if ((sc->sc_curchan.channel == hchan.channel) &&
+		(sc->sc_curchan.channelFlags == hchan.channelFlags))
+		return 0;
+
 	KASSERT(hchan.channel != 0,
 		("bogus channel %u/0x%x", hchan.channel, hchan.channelFlags));
 	do_gettimeofday(&tv);
--- a/ath/if_athvar.h
+++ b/ath/if_athvar.h
@@ -774,6 +774,7 @@ struct ath_softc {
 	struct ieee80211vap **sc_bslot;		/* beacon xmit slots */
 	int sc_bnext;				/* next slot for beacon xmit */
 
+	struct ieee80211_channel *sc_last_chan;
 	int sc_beacon_cal;			/* use beacon timer for calibration */
 	u_int64_t sc_lastcal;			/* last time the calibration was performed */
 	struct timer_list sc_cal_ch;		/* calibration timer */
--- a/net80211/_ieee80211.h
+++ b/net80211/_ieee80211.h
@@ -148,6 +148,7 @@ struct ieee80211_channel {
 	int8_t ic_maxpower;	/* maximum tx power in dBm */
 	int8_t ic_minpower;	/* minimum tx power in dBm */
 	u_int8_t ic_scanflags;
+	u_int8_t ic_idletime; /* phy idle time in % */
 };
 
 #define	IEEE80211_CHAN_MAX	255
--- a/net80211/ieee80211_scan_ap.c
+++ b/net80211/ieee80211_scan_ap.c
@@ -417,6 +417,19 @@ pc_cmp_rssi(struct ap_state *as, struct 
 
 /* This function must be invoked with locks acquired */
 static int
+pc_cmp_idletime(struct ieee80211_channel *a,
+		struct ieee80211_channel *b)
+{
+	if (!a->ic_idletime || !b->ic_idletime)
+		return 0;
+
+	/* a is better than b (return < 0) when a has more idle time than b */
+	return b->ic_idletime - a->ic_idletime;
+}
+
+
+/* This function must be invoked with locks acquired */
+static int
 pc_cmp_samechan(struct ieee80211com *ic, struct ieee80211_channel *a,
 		struct ieee80211_channel *b)
 {
@@ -451,6 +464,7 @@ pc_cmp(const void *_a, const void *_b)
 
 	EVALUATE_CRITERION(radar, a, b);
 	EVALUATE_CRITERION(keepmode, params, a, b);
+	EVALUATE_CRITERION(idletime, a, b);
 	EVALUATE_CRITERION(sc, ic, a, b);
 	/* XXX: rssi useless? pick_channel evaluates it anyway */
 	EVALUATE_CRITERION(rssi, params->ss->ss_priv, a, b);
@@ -519,16 +533,9 @@ pick_channel(struct ieee80211_scan_state
 #endif
 
 	best = NULL;
-	best_rssi = 0xff; /* If signal is bigger than 0xff, we'd be melting. */
 
 	for (i = 0; i < ss_last; i++) {
 		c = &chans[i];
-		benefit = best_rssi - as->as_maxrssi[c->chan->ic_ieee];
-		sta_assoc = ic->ic_sta_assoc;
-
-		/* Don't switch... */
-		if (benefit <= 0)
-			continue;
 
 		/* Verify channel is not marked for non-occupancy */
 		if (IEEE80211_IS_CHAN_RADAR(c->chan))
@@ -546,31 +553,8 @@ pick_channel(struct ieee80211_scan_state
 				break;
 		}
 
-		if (sta_assoc != 0) {
-			int sl = ic->ic_cn_total - 
-				ic->ic_chan_nodes[c->chan->ic_ieee]; /* count */
-			if (ic->ic_sc_algorithm == IEEE80211_SC_LOOSE) {
-				int sl_max = ic->ic_sc_sldg * benefit;
-				sl = 1000 * sl / sta_assoc; /* permil */
-				IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
-						"%s: chan %d, dB gained: %d, "
-						"STAs lost: %d permil (max %d)\n",
-						__func__, c->chan->ic_ieee, 
-						benefit, sl, sl_max);
-				if (sl > sl_max)
-					continue;
-			} else if (((ic->ic_sc_algorithm == 
-						 IEEE80211_SC_TIGHT) ||
-					(ic->ic_sc_algorithm == 
-						 IEEE80211_SC_STRICT)) && 
-					(sl > 0)) {
-				/* Break the loop as the subsequent chans 
-				 * won't be better. */
-				break;
-			}
-		}
 		best = c->chan;
-		best_rssi = as->as_maxrssi[best->ic_ieee];
+		break;
 	}
 
 	if (best != NULL) {
@@ -599,6 +583,9 @@ ap_end(struct ieee80211_scan_state *ss, 
 		("wrong opmode %u", vap->iv_opmode));
 
 	ic = vap->iv_ic;
+
+	/* record stats for the channel that was scanned last */
+	ic->ic_set_channel(ic);
 	bestchan = pick_channel(ss, vap, flags);
 	if (bestchan == NULL) {
 		if (ss->ss_last > 0) {
--- a/net80211/ieee80211_scan.c
+++ b/net80211/ieee80211_scan.c
@@ -1002,20 +1002,34 @@ ieee80211_scan_add_channels(struct ieee8
 {
 	struct ieee80211_channel *c, *cg;
 	u_int modeflags;
+	int has_non_turbo = 0;
 	int i;
 
 	KASSERT(mode < ARRAY_SIZE(chanflags), ("Unexpected mode %u", mode));
 	modeflags = chanflags[mode];
 	for (i = 0; i < ic->ic_nchans; i++) {
 		c = &ic->ic_channels[i];
+		if (c->ic_flags & (IEEE80211_CHAN_TURBO | IEEE80211_CHAN_STURBO))
+			continue;
+
+		has_non_turbo = 1;
+		break;
+	}
+	for (i = 0; i < ic->ic_nchans; i++) {
+		c = &ic->ic_channels[i];
 		if (c == NULL || isclr(ic->ic_chan_active, c->ic_ieee))
 			continue;
 		if (c->ic_scanflags & IEEE80211_NOSCAN_SET)
 			continue;
-		if (modeflags &&
-			((c->ic_flags & IEEE80211_CHAN_ALLTURBO) !=
-			 (modeflags & IEEE80211_CHAN_ALLTURBO)))
-			continue;
+		if (modeflags) {
+			if ((c->ic_flags & IEEE80211_CHAN_ALLTURBO) !=
+				 (modeflags & IEEE80211_CHAN_ALLTURBO))
+				continue;
+		} else if (has_non_turbo) {
+			if ((ss->ss_vap->iv_opmode == IEEE80211_M_HOSTAP) &&
+				(c->ic_flags & (IEEE80211_CHAN_TURBO | IEEE80211_CHAN_STURBO)))
+				continue;
+		}
 		if (mode == IEEE80211_MODE_AUTO) {
 			/*
 			 * XXX special-case 11b/g channels so we select