mac80211: add min required channel definition field

Add a new field to ieee80211_chanctx_conf to indicate
the min required channel configuration.

Tuning to a narrower channel might help reducing
the noise level and saving some power.

The min required channel definition is the max of
all min required channel definitions of the interfaces
bound to this channel context.

In AP mode, use 20MHz when there are no connected station.
When a new station is added/removed, calculate the new max
bandwidth supported by any of the stations (e.g. 80MHz when
80MHz and 40MHz stations are connected).

In other cases, simply use bss_conf.chandef as the
min required chandef.

Notify drivers about changes to this field by calling
drv_change_chanctx with a new CHANGE_MIN_WIDTH notification.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 139 insertions, 0 deletions

diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
index cefee2be0b8..a57d5d9466b 100644
--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -9,6 +9,140 @@
 #include "ieee80211_i.h"
 #include "driver-ops.h"
 
+static enum nl80211_chan_width ieee80211_get_sta_bw(struct ieee80211_sta *sta)
+{
+	switch (sta->bandwidth) {
+	case IEEE80211_STA_RX_BW_20:
+		if (sta->ht_cap.ht_supported)
+			return NL80211_CHAN_WIDTH_20;
+		else
+			return NL80211_CHAN_WIDTH_20_NOHT;
+	case IEEE80211_STA_RX_BW_40:
+		return NL80211_CHAN_WIDTH_40;
+	case IEEE80211_STA_RX_BW_80:
+		return NL80211_CHAN_WIDTH_80;
+	case IEEE80211_STA_RX_BW_160:
+		/*
+		 * This applied for both 160 and 80+80. since we use
+		 * the returned value to consider degradation of
+		 * ctx->conf.min_def, we have to make sure to take
+		 * the bigger one (NL80211_CHAN_WIDTH_160).
+		 * Otherwise we might try degrading even when not
+		 * needed, as the max required sta_bw returned (80+80)
+		 * might be smaller than the configured bw (160).
+		 */
+		return NL80211_CHAN_WIDTH_160;
+	default:
+		WARN_ON(1);
+		return NL80211_CHAN_WIDTH_20;
+	}
+}
+
+static enum nl80211_chan_width
+ieee80211_get_max_required_bw(struct ieee80211_sub_if_data *sdata)
+{
+	enum nl80211_chan_width max_bw = NL80211_CHAN_WIDTH_20_NOHT;
+	struct sta_info *sta;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(sta, &sdata->local->sta_list, list) {
+		if (sdata != sta->sdata &&
+		    !(sta->sdata->bss && sta->sdata->bss == sdata->bss))
+			continue;
+
+		if (!sta->uploaded)
+			continue;
+
+		max_bw = max(max_bw, ieee80211_get_sta_bw(&sta->sta));
+	}
+	rcu_read_unlock();
+
+	return max_bw;
+}
+
+static enum nl80211_chan_width
+ieee80211_get_chanctx_max_required_bw(struct ieee80211_local *local,
+				      struct ieee80211_chanctx_conf *conf)
+{
+	struct ieee80211_sub_if_data *sdata;
+	enum nl80211_chan_width max_bw = NL80211_CHAN_WIDTH_20_NOHT;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
+		struct ieee80211_vif *vif = &sdata->vif;
+		enum nl80211_chan_width width = NL80211_CHAN_WIDTH_20_NOHT;
+
+		if (!ieee80211_sdata_running(sdata))
+			continue;
+
+		if (rcu_access_pointer(sdata->vif.chanctx_conf) != conf)
+			continue;
+
+		switch (vif->type) {
+		case NL80211_IFTYPE_AP:
+		case NL80211_IFTYPE_AP_VLAN:
+			width = ieee80211_get_max_required_bw(sdata);
+			break;
+		case NL80211_IFTYPE_P2P_DEVICE:
+			continue;
+		case NL80211_IFTYPE_STATION:
+		case NL80211_IFTYPE_ADHOC:
+		case NL80211_IFTYPE_WDS:
+		case NL80211_IFTYPE_MESH_POINT:
+			width = vif->bss_conf.chandef.width;
+			break;
+		case NL80211_IFTYPE_UNSPECIFIED:
+		case NUM_NL80211_IFTYPES:
+		case NL80211_IFTYPE_MONITOR:
+		case NL80211_IFTYPE_P2P_CLIENT:
+		case NL80211_IFTYPE_P2P_GO:
+			WARN_ON_ONCE(1);
+		}
+		max_bw = max(max_bw, width);
+	}
+	rcu_read_unlock();
+
+	return max_bw;
+}
+
+/*
+ * recalc the min required chan width of the channel context, which is
+ * the max of min required widths of all the interfaces bound to this
+ * channel context.
+ */
+void ieee80211_recalc_chanctx_min_def(struct ieee80211_local *local,
+				      struct ieee80211_chanctx *ctx)
+{
+	enum nl80211_chan_width max_bw;
+	struct cfg80211_chan_def min_def;
+
+	lockdep_assert_held(&local->chanctx_mtx);
+
+	/* don't optimize 5MHz, 10MHz, and radar_enabled confs */
+	if (ctx->conf.def.width == NL80211_CHAN_WIDTH_5 ||
+	    ctx->conf.def.width == NL80211_CHAN_WIDTH_10 ||
+	    ctx->conf.radar_enabled) {
+		ctx->conf.min_def = ctx->conf.def;
+		return;
+	}
+
+	max_bw = ieee80211_get_chanctx_max_required_bw(local, &ctx->conf);
+
+	/* downgrade chandef up to max_bw */
+	min_def = ctx->conf.def;
+	while (min_def.width > max_bw)
+		ieee80211_chandef_downgrade(&min_def);
+
+	if (cfg80211_chandef_identical(&ctx->conf.min_def, &min_def))
+		return;
+
+	ctx->conf.min_def = min_def;
+	if (!ctx->driver_present)
+		return;
+
+	drv_change_chanctx(local, ctx, IEEE80211_CHANCTX_CHANGE_MIN_WIDTH);
+}
+
 static void ieee80211_change_chanctx(struct ieee80211_local *local,
 				     struct ieee80211_chanctx *ctx,
 				     const struct cfg80211_chan_def *chandef)
@@ -20,6 +154,7 @@ static void ieee80211_change_chanctx(struct ieee80211_local *local,
 
 	ctx->conf.def = *chandef;
 	drv_change_chanctx(local, ctx, IEEE80211_CHANCTX_CHANGE_WIDTH);
+	ieee80211_recalc_chanctx_min_def(local, ctx);
 
 	if (!local->use_chanctx) {
 		local->_oper_chandef = *chandef;
@@ -93,6 +228,7 @@ ieee80211_new_chanctx(struct ieee80211_local *local,
 	ctx->conf.rx_chains_dynamic = 1;
 	ctx->mode = mode;
 	ctx->conf.radar_enabled = ieee80211_is_radar_required(local);
+	ieee80211_recalc_chanctx_min_def(local, ctx);
 	if (!local->use_chanctx)
 		local->hw.conf.radar_enabled = ctx->conf.radar_enabled;
 
@@ -179,6 +315,7 @@ static int ieee80211_assign_vif_chanctx(struct ieee80211_sub_if_data *sdata,
 	ctx->refcount++;
 
 	ieee80211_recalc_txpower(sdata);
+	ieee80211_recalc_chanctx_min_def(local, ctx);
 	sdata->vif.bss_conf.idle = false;
 
 	if (sdata->vif.type != NL80211_IFTYPE_P2P_DEVICE &&
@@ -243,6 +380,7 @@ static void ieee80211_unassign_vif_chanctx(struct ieee80211_sub_if_data *sdata,
 		ieee80211_recalc_chanctx_chantype(sdata->local, ctx);
 		ieee80211_recalc_smps_chanctx(local, ctx);
 		ieee80211_recalc_radar_chanctx(local, ctx);
+		ieee80211_recalc_chanctx_min_def(local, ctx);
 	}
 }
 
@@ -456,6 +594,7 @@ int ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
 	ieee80211_recalc_chanctx_chantype(local, ctx);
 	ieee80211_recalc_smps_chanctx(local, ctx);
 	ieee80211_recalc_radar_chanctx(local, ctx);
+	ieee80211_recalc_chanctx_min_def(local, ctx);
 
 	ret = 0;
  out: