diff --git a/drivers/net/wireless/ath/ath9k/beacon.c b/drivers/net/wireless/ath/ath9k/beacon.c
index 5128856d77d219a1679626b67538da8cfcb5ef70..78ffe762e26cdc8a54937ba8149012992b7b528b 100644
--- a/drivers/net/wireless/ath/ath9k/beacon.c
+++ b/drivers/net/wireless/ath/ath9k/beacon.c
@@ -431,6 +431,33 @@ static void ath9k_beacon_init(struct ath_softc *sc, u32 nexttbtt,
 	ath9k_hw_enable_interrupts(ah);
 }
 
+/* Calculate the modulo of a 64 bit TSF snapshot with a TU divisor */
+static u32 ath9k_mod_tsf64_tu(u64 tsf, u32 div_tu)
+{
+	u32 tsf_mod, tsf_hi, tsf_lo, mod_hi, mod_lo;
+
+	tsf_mod = tsf & (BIT(10) - 1);
+	tsf_hi = tsf >> 32;
+	tsf_lo = ((u32) tsf) >> 10;
+
+	mod_hi = tsf_hi % div_tu;
+	mod_lo = ((mod_hi << 22) + tsf_lo) % div_tu;
+
+	return (mod_lo << 10) | tsf_mod;
+}
+
+static u32 ath9k_get_next_tbtt(struct ath_softc *sc, u64 tsf,
+			       unsigned int interval)
+{
+	struct ath_hw *ah = sc->sc_ah;
+	unsigned int offset;
+
+	tsf += TU_TO_USEC(FUDGE + ah->config.sw_beacon_response_time);
+	offset = ath9k_mod_tsf64_tu(tsf, interval);
+
+	return (u32) tsf + TU_TO_USEC(interval) - offset;
+}
+
 /*
  * For multi-bss ap support beacons are either staggered evenly over N slots or
  * burst together.  For the former arrange for the SWBA to be delivered for each
@@ -446,7 +473,8 @@ static void ath9k_beacon_config_ap(struct ath_softc *sc,
 	/* NB: the beacon interval is kept internally in TU's */
 	intval = TU_TO_USEC(conf->beacon_interval);
 	intval /= ATH_BCBUF;
-	nexttbtt = intval;
+	nexttbtt = ath9k_get_next_tbtt(sc, ath9k_hw_gettsf64(ah),
+				       conf->beacon_interval);
 
 	if (conf->enable_beacon)
 		ah->imask |= ATH9K_INT_SWBA;
@@ -458,7 +486,7 @@ static void ath9k_beacon_config_ap(struct ath_softc *sc,
 		(conf->enable_beacon) ? "Enable" : "Disable",
 		nexttbtt, intval, conf->beacon_interval);
 
-	ath9k_beacon_init(sc, nexttbtt, intval, true);
+	ath9k_beacon_init(sc, nexttbtt, intval, false);
 }
 
 /*
@@ -475,10 +503,9 @@ static void ath9k_beacon_config_sta(struct ath_softc *sc,
 	struct ath_hw *ah = sc->sc_ah;
 	struct ath_common *common = ath9k_hw_common(ah);
 	struct ath9k_beacon_state bs;
-	int dtimperiod, dtimcount, sleepduration;
-	u32 nexttbtt = 0, intval, tsftu;
+	int dtim_intval, sleepduration;
+	u32 nexttbtt = 0, intval;
 	u64 tsf;
-	int num_beacons, offset, dtim_dec_count;
 
 	/* No need to configure beacon if we are not associated */
 	if (!test_bit(SC_OP_PRIM_STA_VIF, &sc->sc_flags)) {
@@ -494,11 +521,7 @@ static void ath9k_beacon_config_sta(struct ath_softc *sc,
 	 * Setup dtim parameters according to
 	 * last beacon we received (which may be none).
 	 */
-	dtimperiod = conf->dtim_period;
-	dtimcount = conf->dtim_count;
-	if (dtimcount >= dtimperiod)	/* NB: sanity check */
-		dtimcount = 0;
-
+	dtim_intval = intval * conf->dtim_period;
 	sleepduration = conf->listen_interval * intval;
 
 	/*
@@ -506,24 +529,14 @@ static void ath9k_beacon_config_sta(struct ath_softc *sc,
 	 * TSF and calculate dtim state for the result.
 	 */
 	tsf = ath9k_hw_gettsf64(ah);
-	tsftu = TSF_TO_TU(tsf>>32, tsf) + FUDGE;
-
-	num_beacons = tsftu / intval + 1;
-	offset = tsftu % intval;
-	nexttbtt = tsftu - offset;
-	if (offset)
-		nexttbtt += intval;
-
-	/* DTIM Beacon every dtimperiod Beacon */
-	dtim_dec_count = num_beacons % dtimperiod;
-	dtimcount -= dtim_dec_count;
-	if (dtimcount < 0)
-		dtimcount += dtimperiod;
+	nexttbtt = ath9k_get_next_tbtt(sc, tsf, intval);
 
 	bs.bs_intval = TU_TO_USEC(intval);
-	bs.bs_nexttbtt = TU_TO_USEC(nexttbtt);
-	bs.bs_dtimperiod = dtimperiod * bs.bs_intval;
-	bs.bs_nextdtim = bs.bs_nexttbtt + dtimcount * bs.bs_intval;
+	bs.bs_dtimperiod = conf->dtim_period * bs.bs_intval;
+	bs.bs_nexttbtt = nexttbtt;
+	bs.bs_nextdtim = nexttbtt;
+	if (conf->dtim_period > 1)
+		bs.bs_nextdtim = ath9k_get_next_tbtt(sc, tsf, dtim_intval);
 
 	/*
 	 * Calculate the number of consecutive beacons to miss* before taking
@@ -559,7 +572,6 @@ static void ath9k_beacon_config_sta(struct ath_softc *sc,
 	/* TSF out of range threshold fixed at 1 second */
 	bs.bs_tsfoor_threshold = ATH9K_TSFOOR_THRESHOLD;
 
-	ath_dbg(common, BEACON, "tsf: %llu tsftu: %u\n", tsf, tsftu);
 	ath_dbg(common, BEACON, "bmiss: %u sleep: %u\n",
 		bs.bs_bmissthreshold, bs.bs_sleepduration);
 
@@ -584,25 +596,11 @@ static void ath9k_beacon_config_adhoc(struct ath_softc *sc,
 
 	intval = TU_TO_USEC(conf->beacon_interval);
 
-	if (conf->ibss_creator) {
+	if (conf->ibss_creator)
 		nexttbtt = intval;
-	} else {
-		u32 tbtt, offset, tsftu;
-		u64 tsf;
-
-		/*
-		 * Pull nexttbtt forward to reflect the current
-		 * sync'd TSF.
-		 */
-		tsf = ath9k_hw_gettsf64(ah);
-		tsftu = TSF_TO_TU(tsf >> 32, tsf) + FUDGE;
-		offset = tsftu % conf->beacon_interval;
-		tbtt = tsftu - offset;
-		if (offset)
-			tbtt += conf->beacon_interval;
-
-		nexttbtt = TU_TO_USEC(tbtt);
-	}
+	else
+		nexttbtt = ath9k_get_next_tbtt(sc, ath9k_hw_gettsf64(ah),
+					       conf->beacon_interval);
 
 	if (conf->enable_beacon)
 		ah->imask |= ATH9K_INT_SWBA;
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index 4798f6ae061e5a94b587d92bbee7375caabb7473..6a231201c7dcffeb89cdafa512ecc0a97e1a63f5 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -760,6 +760,8 @@ static int ath9k_start(struct ieee80211_hw *hw)
 	 */
 	ath9k_cmn_init_crypto(sc->sc_ah);
 
+	ath9k_hw_reset_tsf(ah);
+
 	spin_unlock_bh(&sc->sc_pcu_lock);
 
 	mutex_unlock(&sc->mutex);