mac80211: replace legacy minstrel with minstrel_ht, improve rate selection

Legacy minstrel is essentially unmaintained and was showing poor performance
Replace it with minstrel_ht and improve rate selection and sampling behavior

Signed-off-by: Felix Fietkau <nbd@nbd.name>

1 files changed, 166 insertions, 0 deletions

diff --git a/package/kernel/mac80211/patches/subsys/337-mac80211-minstrel_ht-clean-up-CCK-code.patch b/package/kernel/mac80211/patches/subsys/337-mac80211-minstrel_ht-clean-up-CCK-code.patch
new file mode 100644
index 0000000000..f667d2c94e
--- /dev/null
+++ b/package/kernel/mac80211/patches/subsys/337-mac80211-minstrel_ht-clean-up-CCK-code.patch
@@ -0,0 +1,166 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Fri, 25 Dec 2020 16:22:52 +0100
+Subject: [PATCH] mac80211: minstrel_ht: clean up CCK code
+
+- move ack overhead out of rate duration table
+- remove cck_supported, cck_supported_short
+
+Preparation for adding OFDM legacy rates support
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/mac80211/rc80211_minstrel_ht.c
++++ b/net/mac80211/rc80211_minstrel_ht.c
+@@ -136,20 +136,16 @@
+ 	__VHT_GROUP(_streams, _sgi, _bw,				\
+ 		    VHT_GROUP_SHIFT(_streams, _sgi, _bw))
+ 
+-#define CCK_DURATION(_bitrate, _short, _len)		\
++#define CCK_DURATION(_bitrate, _short)			\
+ 	(1000 * (10 /* SIFS */ +			\
+ 	 (_short ? 72 + 24 : 144 + 48) +		\
+-	 (8 * (_len + 4) * 10) / (_bitrate)))
+-
+-#define CCK_ACK_DURATION(_bitrate, _short)			\
+-	(CCK_DURATION((_bitrate > 10 ? 20 : 10), false, 60) +	\
+-	 CCK_DURATION(_bitrate, _short, AVG_PKT_SIZE))
++	 (8 * (AVG_PKT_SIZE + 4) * 10) / (_bitrate)))
+ 
+ #define CCK_DURATION_LIST(_short, _s)			\
+-	CCK_ACK_DURATION(10, _short) >> _s,		\
+-	CCK_ACK_DURATION(20, _short) >> _s,		\
+-	CCK_ACK_DURATION(55, _short) >> _s,		\
+-	CCK_ACK_DURATION(110, _short) >> _s
++	CCK_DURATION(10, _short) >> _s,			\
++	CCK_DURATION(20, _short) >> _s,			\
++	CCK_DURATION(55, _short) >> _s,			\
++	CCK_DURATION(110, _short) >> _s
+ 
+ #define __CCK_GROUP(_s)					\
+ 	[MINSTREL_CCK_GROUP] = {			\
+@@ -163,7 +159,7 @@
+ 	}
+ 
+ #define CCK_GROUP_SHIFT					\
+-	GROUP_SHIFT(CCK_ACK_DURATION(10, false))
++	GROUP_SHIFT(CCK_DURATION(10, false))
+ 
+ #define CCK_GROUP __CCK_GROUP(CCK_GROUP_SHIFT)
+ 
+@@ -349,15 +345,19 @@ int
+ minstrel_ht_get_tp_avg(struct minstrel_ht_sta *mi, int group, int rate,
+ 		       int prob_avg)
+ {
+-	unsigned int nsecs = 0;
++	unsigned int nsecs = 0, overhead = mi->overhead;
++	unsigned int ampdu_len = 1;
+ 
+ 	/* do not account throughput if sucess prob is below 10% */
+ 	if (prob_avg < MINSTREL_FRAC(10, 100))
+ 		return 0;
+ 
+-	if (group != MINSTREL_CCK_GROUP)
+-		nsecs = 1000 * mi->overhead / minstrel_ht_avg_ampdu_len(mi);
++	if (group == MINSTREL_CCK_GROUP)
++		overhead = mi->overhead_legacy;
++	else
++		ampdu_len = minstrel_ht_avg_ampdu_len(mi);
+ 
++	nsecs = 1000 * overhead / ampdu_len;
+ 	nsecs += minstrel_mcs_groups[group].duration[rate] <<
+ 		 minstrel_mcs_groups[group].shift;
+ 
+@@ -1031,7 +1031,10 @@ minstrel_calc_retransmit(struct minstrel
+ 	ctime += (t_slot * cw) >> 1;
+ 	cw = min((cw << 1) | 1, mp->cw_max);
+ 
+-	if (index / MCS_GROUP_RATES != MINSTREL_CCK_GROUP) {
++	if (index / MCS_GROUP_RATES == MINSTREL_CCK_GROUP) {
++		overhead = mi->overhead_legacy;
++		overhead_rtscts = mi->overhead_legacy_rtscts;
++	} else {
+ 		overhead = mi->overhead;
+ 		overhead_rtscts = mi->overhead_rtscts;
+ 	}
+@@ -1369,18 +1372,14 @@ minstrel_ht_update_cck(struct minstrel_p
+ 	if (!ieee80211_hw_check(mp->hw, SUPPORTS_HT_CCK_RATES))
+ 		return;
+ 
+-	mi->cck_supported = 0;
+-	mi->cck_supported_short = 0;
+ 	for (i = 0; i < 4; i++) {
+ 		if (!rate_supported(sta, sband->band, mp->cck_rates[i]))
+ 			continue;
+ 
+-		mi->cck_supported |= BIT(i);
++		mi->supported[MINSTREL_CCK_GROUP] |= BIT(i);
+ 		if (sband->bitrates[i].flags & IEEE80211_RATE_SHORT_PREAMBLE)
+-			mi->cck_supported_short |= BIT(i);
++			mi->supported[MINSTREL_CCK_GROUP] |= BIT(i + 4);
+ 	}
+-
+-	mi->supported[MINSTREL_CCK_GROUP] = mi->cck_supported;
+ }
+ 
+ static void
+@@ -1394,12 +1393,13 @@ minstrel_ht_update_caps(void *priv, stru
+ 	struct ieee80211_mcs_info *mcs = &sta->ht_cap.mcs;
+ 	u16 ht_cap = sta->ht_cap.cap;
+ 	struct ieee80211_sta_vht_cap *vht_cap = &sta->vht_cap;
++	const struct ieee80211_rate *ctl_rate;
++	bool ldpc, erp;
+ 	int use_vht;
+ 	int n_supported = 0;
+ 	int ack_dur;
+ 	int stbc;
+ 	int i;
+-	bool ldpc;
+ 
+ 	/* fall back to the old minstrel for legacy stations */
+ 	if (!sta->ht_cap.ht_supported)
+@@ -1423,6 +1423,14 @@ minstrel_ht_update_caps(void *priv, stru
+ 	mi->overhead += ack_dur;
+ 	mi->overhead_rtscts = mi->overhead + 2 * ack_dur;
+ 
++	ctl_rate = &sband->bitrates[rate_lowest_index(sband, sta)];
++	erp = ctl_rate->flags & IEEE80211_RATE_ERP_G;
++	ack_dur = ieee80211_frame_duration(sband->band, 10,
++					   ctl_rate->bitrate, erp, 1,
++					   ieee80211_chandef_get_shift(chandef));
++	mi->overhead_legacy = ack_dur;
++	mi->overhead_legacy_rtscts = mi->overhead_legacy + 2 * ack_dur;
++
+ 	mi->avg_ampdu_len = MINSTREL_FRAC(1, 1);
+ 
+ 	/* When using MRR, sample more on the first attempt, without delay */
+@@ -1523,8 +1531,6 @@ minstrel_ht_update_caps(void *priv, stru
+ 	if (!n_supported)
+ 		goto use_legacy;
+ 
+-	mi->supported[MINSTREL_CCK_GROUP] |= mi->cck_supported_short << 4;
+-
+ 	/* create an initial rate table with the lowest supported rates */
+ 	minstrel_ht_update_stats(mp, mi, true);
+ 	minstrel_ht_update_rates(mp, mi);
+--- a/net/mac80211/rc80211_minstrel_ht.h
++++ b/net/mac80211/rc80211_minstrel_ht.h
+@@ -77,6 +77,8 @@ struct minstrel_ht_sta {
+ 	/* overhead time in usec for each frame */
+ 	unsigned int overhead;
+ 	unsigned int overhead_rtscts;
++	unsigned int overhead_legacy;
++	unsigned int overhead_legacy_rtscts;
+ 
+ 	unsigned int total_packets_last;
+ 	unsigned int total_packets_cur;
+@@ -97,9 +99,6 @@ struct minstrel_ht_sta {
+ 	/* current MCS group to be sampled */
+ 	u8 sample_group;
+ 
+-	u8 cck_supported;
+-	u8 cck_supported_short;
+-
+ 	/* Bitfield of supported MCS rates of all groups */
+ 	u16 supported[MINSTREL_GROUPS_NB];
+