mac80211: Optimize scans on current operating channel.

This should decrease un-necessary flushes, on/off channel work,
and channel changes in cases where the only scanned channel is
the current operating channel.

* Removes SCAN_OFF_CHANNEL flag, uses SDATA_STATE_OFFCHANNEL
  and is-scanning flags instead.

* Add helper method to determine if we are currently configured
  for the operating channel.

* Do no blindly go off/on channel in work.c  Instead, only call
  appropriate on/off code when we really need to change channels.
  Always enable offchannel-ps mode when starting work,
  and disable it when we are done.

* Consolidate ieee80211_offchannel_stop_station and
  ieee80211_offchannel_stop_beaconing, call it
  ieee80211_offchannel_stop_vifs instead.

* Accept non-beacon frames when scanning on operating channel.

* Scan state machine optimized to minimize on/off channel
  transitions.  Also, when going on-channel, go ahead and
  re-enable beaconing.  We're going to be there for 200ms,
  so seems like some useful beaconing could happen.
  Always enable offchannel-ps mode when starting software
  scan, and disable it when we are done.

* Grab local->mtx earlier in __ieee80211_scan_completed_finish
  so that we are protected when calling hw_config(), etc.

* Pass probe-responses up the stack if scanning on local
  channel, so that mlme can take a look.

Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 63 insertions, 25 deletions

diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 1ef73be76b25..0ea6adae3e06 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -212,6 +212,14 @@ ieee80211_scan_rx(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
 	if (bss)
 		ieee80211_rx_bss_put(sdata->local, bss);
 
+	/* If we are on-operating-channel, and this packet is for the
+	 * current channel, pass the pkt on up the stack so that
+	 * the rest of the stack can make use of it.
+	 */
+	if (ieee80211_cfg_on_oper_channel(sdata->local)
+	    && (channel == sdata->local->oper_channel))
+		return RX_CONTINUE;
+
 	dev_kfree_skb(skb);
 	return RX_QUEUED;
 }
@@ -293,15 +301,31 @@ static void __ieee80211_scan_completed_finish(struct ieee80211_hw *hw,
 					      bool was_hw_scan)
 {
 	struct ieee80211_local *local = hw_to_local(hw);
+	bool on_oper_chan;
+	bool enable_beacons = false;
+
+	mutex_lock(&local->mtx);
+	on_oper_chan = ieee80211_cfg_on_oper_channel(local);
+
+	if (was_hw_scan || !on_oper_chan) {
+		if (WARN_ON(local->scan_channel))
+			local->scan_channel = NULL;
+		ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
+	}
 
-	ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
 	if (!was_hw_scan) {
+		bool on_oper_chan2;
 		ieee80211_configure_filter(local);
 		drv_sw_scan_complete(local);
-		ieee80211_offchannel_return(local, true);
+		on_oper_chan2 = ieee80211_cfg_on_oper_channel(local);
+		/* We should always be on-channel at this point. */
+		WARN_ON(!on_oper_chan2);
+		if (on_oper_chan2 && (on_oper_chan != on_oper_chan2))
+			enable_beacons = true;
+
+		ieee80211_offchannel_return(local, enable_beacons, true);
 	}
 
-	mutex_lock(&local->mtx);
 	ieee80211_recalc_idle(local);
 	mutex_unlock(&local->mtx);
 
@@ -341,13 +365,15 @@ static int ieee80211_start_sw_scan(struct ieee80211_local *local)
 	 */
 	drv_sw_scan_start(local);
 
-	ieee80211_offchannel_stop_beaconing(local);
-
 	local->leave_oper_channel_time = 0;
 	local->next_scan_state = SCAN_DECISION;
 	local->scan_channel_idx = 0;
 
-	drv_flush(local, false);
+	/* We always want to use off-channel PS, even if we
+	 * are not really leaving oper-channel.  Don't
+	 * tell the AP though, as long as we are on-channel.
+	 */
+	ieee80211_offchannel_enable_all_ps(local, false);
 
 	ieee80211_configure_filter(local);
 
@@ -487,7 +513,21 @@ static void ieee80211_scan_state_decision(struct ieee80211_local *local,
 	}
 	mutex_unlock(&local->iflist_mtx);
 
-	if (local->scan_channel) {
+	next_chan = local->scan_req->channels[local->scan_channel_idx];
+
+	if (ieee80211_cfg_on_oper_channel(local)) {
+		/* We're currently on operating channel. */
+		if ((next_chan == local->oper_channel) &&
+		    (local->_oper_channel_type == NL80211_CHAN_NO_HT))
+			/* We don't need to move off of operating channel. */
+			local->next_scan_state = SCAN_SET_CHANNEL;
+		else
+			/*
+			 * We do need to leave operating channel, as next
+			 * scan is somewhere else.
+			 */
+			local->next_scan_state = SCAN_LEAVE_OPER_CHANNEL;
+	} else {
 		/*
 		 * we're currently scanning a different channel, let's
 		 * see if we can scan another channel without interfering
@@ -503,7 +543,6 @@ static void ieee80211_scan_state_decision(struct ieee80211_local *local,
 		 *
 		 * Otherwise switch back to the operating channel.
 		 */
-		next_chan = local->scan_req->channels[local->scan_channel_idx];
 
 		bad_latency = time_after(jiffies +
 				ieee80211_scan_get_channel_time(next_chan),
@@ -521,12 +560,6 @@ static void ieee80211_scan_state_decision(struct ieee80211_local *local,
 			local->next_scan_state = SCAN_ENTER_OPER_CHANNEL;
 		else
 			local->next_scan_state = SCAN_SET_CHANNEL;
-	} else {
-		/*
-		 * we're on the operating channel currently, let's
-		 * leave that channel now to scan another one
-		 */
-		local->next_scan_state = SCAN_LEAVE_OPER_CHANNEL;
 	}
 
 	*next_delay = 0;
@@ -535,9 +568,10 @@ static void ieee80211_scan_state_decision(struct ieee80211_local *local,
 static void ieee80211_scan_state_leave_oper_channel(struct ieee80211_local *local,
 						    unsigned long *next_delay)
 {
-	ieee80211_offchannel_stop_station(local);
-
-	__set_bit(SCAN_OFF_CHANNEL, &local->scanning);
+	/* PS will already be in off-channel mode,
+	 * we do that once at the beginning of scanning.
+	 */
+	ieee80211_offchannel_stop_vifs(local, false);
 
 	/*
 	 * What if the nullfunc frames didn't arrive?
@@ -560,15 +594,15 @@ static void ieee80211_scan_state_enter_oper_channel(struct ieee80211_local *loca
 {
 	/* switch back to the operating channel */
 	local->scan_channel = NULL;
-	ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
+	if (!ieee80211_cfg_on_oper_channel(local))
+		ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
 
 	/*
-	 * Only re-enable station mode interface now; beaconing will be
-	 * re-enabled once the full scan has been completed.
+	 * Re-enable vifs and beaconing.  Leave PS
+	 * in off-channel state..will put that back
+	 * on-channel at the end of scanning.
 	 */
-	ieee80211_offchannel_return(local, false);
-
-	__clear_bit(SCAN_OFF_CHANNEL, &local->scanning);
+	ieee80211_offchannel_return(local, true, false);
 
 	*next_delay = HZ / 5;
 	local->next_scan_state = SCAN_DECISION;
@@ -584,8 +618,12 @@ static void ieee80211_scan_state_set_channel(struct ieee80211_local *local,
 	chan = local->scan_req->channels[local->scan_channel_idx];
 
 	local->scan_channel = chan;
-	if (ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL))
-		skip = 1;
+
+	/* Only call hw-config if we really need to change channels. */
+	if ((chan != local->hw.conf.channel) ||
+	    (local->hw.conf.channel_type != NL80211_CHAN_NO_HT))
+		if (ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL))
+			skip = 1;
 
 	/* advance state machine to next channel/band */
 	local->scan_channel_idx++;