mac80211: wowlan: enable powersave if suspend while ps-polling

If for any reason we're in the middle of PS-polling or awake after
TX due to dynamic powersave while going to suspend, go back to save
power. This might cause a response frame to get lost, but since we
can't really wait for it while going to suspend that's still better
than not enabling powersave which would cause higher power usage
during (and possibly even after) suspend.

Note that this really only affects the very few drivers that use
the powersave implementation in mac80211.
Signed-off-by: Chaitanya T K <chaitanya.mgit@gmail.com>
[rewrite misleading commit log]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/pm.c

@@ -76,6 +76,22 @@ int __ieee80211_suspend(struct ieee80211_hw *hw, struct cfg80211_wowlan *wowlan)
 			if (sdata->vif.type != NL80211_IFTYPE_STATION)
 				continue;
 			ieee80211_mgd_quiesce(sdata);
+			/* If suspended during TX in progress, and wowlan
+			 * is enabled (connection will be active) there
+			 * can be a race where the driver is put out
+			 * of power-save due to TX and during suspend
+			 * dynamic_ps_timer is cancelled and TX packet
+			 * is flushed, leaving the driver in ACTIVE even
+			 * after resuming until dynamic_ps_timer puts
+			 * driver back in DOZE.
+			 */
+			if (sdata->u.mgd.associated &&
+			    sdata->u.mgd.powersave &&
+			     !(local->hw.conf.flags & IEEE80211_CONF_PS)) {
+				local->hw.conf.flags |= IEEE80211_CONF_PS;
+				ieee80211_hw_config(local,
+						    IEEE80211_CONF_CHANGE_PS);
+			}
 		}
 
 		err = drv_suspend(local, wowlan);