mac80211: Fix dynamic power save for scanning.

Not only ps_sdata but also IEEE80211_CONF_PS is to be considered
before restoring PS in scan_ps_disable(). For instance, when ps_sdata
is set but CONF_PS is not set just because the dynamic timer is still
running, a sw scan leads to setting of CONF_PS in scan_ps_disable
instead of restarting the dynamic PS timer.
Also for the above case, a null data frame is to be sent after
returning to operating channel which was not happening with the
current implementation. This patch fixes this too.

Signed-off-by: Vivek Natarajan <vnatarajan@atheros.com>
Reviewed-by: Kalle Valo <kalle.valo@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/ieee80211_i.h

@@ -746,6 +746,7 @@ struct ieee80211_local {
 	unsigned int wmm_acm; /* bit field of ACM bits (BIT(802.1D tag)) */
 
 	bool pspolling;
+	bool scan_ps_enabled;
 	/*
 	 * PS can only be enabled when we have exactly one managed
 	 * interface (and monitors) in PS, this then points there.

net/mac80211/scan.c

@@ -227,20 +227,22 @@ static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
 static void ieee80211_scan_ps_enable(struct ieee80211_sub_if_data *sdata)
 {
 	struct ieee80211_local *local = sdata->local;
-	bool ps = false;
+
+	local->scan_ps_enabled = false;
 
 	/* FIXME: what to do when local->pspolling is true? */
 
 	del_timer_sync(&local->dynamic_ps_timer);
 	cancel_work_sync(&local->dynamic_ps_enable_work);
 
 	if (local->hw.conf.flags & IEEE80211_CONF_PS) {
-		ps = true;
+		local->scan_ps_enabled = true;
 		local->hw.conf.flags &= ~IEEE80211_CONF_PS;
 		ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
 	}
 
-	if (!ps || !(local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK))
+	if (!(local->scan_ps_enabled) ||
+	    !(local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK))
 		/*
 		 * If power save was enabled, no need to send a nullfunc
 		 * frame because AP knows that we are sleeping. But if the
@@ -261,7 +263,7 @@ static void ieee80211_scan_ps_disable(struct ieee80211_sub_if_data *sdata)
 
 	if (!local->ps_sdata)
 		ieee80211_send_nullfunc(local, sdata, 0);
-	else {
+	else if (local->scan_ps_enabled) {
 		/*
 		 * In !IEEE80211_HW_PS_NULLFUNC_STACK case the hardware
 		 * will send a nullfunc frame with the powersave bit set
@@ -277,6 +279,16 @@ static void ieee80211_scan_ps_disable(struct ieee80211_sub_if_data *sdata)
 		 */
 		local->hw.conf.flags |= IEEE80211_CONF_PS;
 		ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
+	} else if (local->hw.conf.dynamic_ps_timeout > 0) {
+		/*
+		 * If IEEE80211_CONF_PS was not set and the dynamic_ps_timer
+		 * had been running before leaving the operating channel,
+		 * restart the timer now and send a nullfunc frame to inform
+		 * the AP that we are awake.
+		 */
+		ieee80211_send_nullfunc(local, sdata, 0);
+		mod_timer(&local->dynamic_ps_timer, jiffies +
+			  msecs_to_jiffies(local->hw.conf.dynamic_ps_timeout));
 	}
 }