ath9k: Further fix for mesh beaconing

This fix ensure the timers to be set at beacon interval boundaries.
Without this change timers can be set improperly resulting in the absence of beacons.
Signed-off-by: Fabrice Deyber <fabricedeyber@agilemesh.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/beacon.c

@@ -652,22 +652,13 @@ static void ath_beacon_config_adhoc(struct ath_softc *sc,
 {
 	struct ath_hw *ah = sc->sc_ah;
 	struct ath_common *common = ath9k_hw_common(ah);
-	u32 tsf, delta, intval, nexttbtt;
+	u32 tsf, intval, nexttbtt;
 
 	ath9k_reset_beacon_status(sc);
 
-	tsf = ath9k_hw_gettsf32(ah) + TU_TO_USEC(FUDGE);
 	intval = TU_TO_USEC(conf->beacon_interval);
-
-	if (!sc->beacon.bc_tstamp)
+	tsf = roundup(ath9k_hw_gettsf32(ah) + TU_TO_USEC(FUDGE), intval);
 	nexttbtt = tsf + intval;
-	else {
-		if (tsf > sc->beacon.bc_tstamp)
-			delta = (tsf - sc->beacon.bc_tstamp);
-		else
-			delta = (tsf + 1 + (~0U - sc->beacon.bc_tstamp));
-		nexttbtt = tsf + intval - (delta % intval);
-	}
 
 	ath_dbg(common, ATH_DBG_BEACON,
 		"IBSS nexttbtt %u intval %u (%u)\n",