mac80211: fix AQL issue with multicast traffic

Exclude multicast from pending AQL budget

Signed-off-by: Felix Fietkau <nbd@nbd.name>
(cherry-picked from commit 9f1d622328)

package/kernel/mac80211/patches/subsys/339-mac80211-exclude-multicast-packets-from-AQL-pending-.patch

@@ -0,0 +1,30 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Wed, 13 Jul 2022 07:32:26 +0200
+Subject: [PATCH] mac80211: exclude multicast packets from AQL pending airtime
+
+In AP mode, multicast traffic is handled very differently from normal traffic,
+especially if at least one client is in powersave mode.
+This means that multicast packets can be buffered a lot longer than normal
+unicast packets, and can eat up the AQL budget very quickly because of the low
+data rate.
+Along with the recent change to maintain a global PHY AQL limit, this can lead
+to significant latency spikes for unicast traffic.
+
+Since queueing multicast to hardware is currently not constrained by AQL limits
+anyway, let's just exclude it from the AQL pending airtime calculation entirely.
+
+Fixes: 8e4bac067105 ("wifi: mac80211: add a per-PHY AQL limit to improve fairness")
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/mac80211/tx.c
++++ b/net/mac80211/tx.c
+@@ -3792,7 +3792,7 @@ begin:
+ encap_out:
+ 	IEEE80211_SKB_CB(skb)->control.vif = vif;
+ 
+-	if (vif &&
++	if (tx.sta &&
+ 	    wiphy_ext_feature_isset(local->hw.wiphy, NL80211_EXT_FEATURE_AQL)) {
+ 		bool ampdu = txq->ac != IEEE80211_AC_VO;
+ 		u32 airtime;