ath9k: Calculate sleep duration

Right now sleep duration is configured as beacon interval. It should be
the multiple of beacon interval by listen period which helps to
reduce station power consumption.
Signed-off-by: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -57,7 +57,7 @@ int ath9k_cmn_beacon_config_sta(struct ath_hw *ah,
 				 struct ath9k_beacon_state *bs)
 {
 	struct ath_common *common = ath9k_hw_common(ah);
-	int dtim_intval;
+	int dtim_intval, sleepduration;
 	u64 tsf;
 
 	/* No need to configure beacon if we are not associated */
@@ -75,6 +75,7 @@ int ath9k_cmn_beacon_config_sta(struct ath_hw *ah,
 	 * last beacon we received (which may be none).
 	 */
 	dtim_intval = conf->intval * conf->dtim_period;
+	sleepduration = ah->hw->conf.listen_interval * conf->intval;
 
 	/*
 	 * Pull nexttbtt forward to reflect the current
@@ -112,7 +113,7 @@ int ath9k_cmn_beacon_config_sta(struct ath_hw *ah,
 	 */
 
 	bs->bs_sleepduration = TU_TO_USEC(roundup(IEEE80211_MS_TO_TU(100),
-						 conf->intval));
+						  sleepduration));
 	if (bs->bs_sleepduration > bs->bs_dtimperiod)
 		bs->bs_sleepduration = bs->bs_dtimperiod;