mac80211: add new minstrel_ht patches to improve probing on mt76x2

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

4 files changed, 591 insertions, 0 deletions

diff --git a/package/kernel/mac80211/patches/subsys/310-mac80211-minstrel_ht-fix-per-group-max-throughput-ra.patch b/package/kernel/mac80211/patches/subsys/310-mac80211-minstrel_ht-fix-per-group-max-throughput-ra.patch
new file mode 100644
index 0000000000..d971d84178
--- /dev/null
+++ b/package/kernel/mac80211/patches/subsys/310-mac80211-minstrel_ht-fix-per-group-max-throughput-ra.patch
@@ -0,0 +1,22 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Fri, 14 Jun 2019 21:12:04 +0200
+Subject: [PATCH] mac80211: minstrel_ht: fix per-group max throughput rate
+ initialization
+
+The group number needs to be multiplied by the number of rates per group
+to get the full rate index
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/mac80211/rc80211_minstrel_ht.c
++++ b/net/mac80211/rc80211_minstrel_ht.c
+@@ -575,7 +575,7 @@ minstrel_ht_update_stats(struct minstrel
+ 
+ 		/* (re)Initialize group rate indexes */
+ 		for(j = 0; j < MAX_THR_RATES; j++)
+-			tmp_group_tp_rate[j] = group;
++			tmp_group_tp_rate[j] = MCS_GROUP_RATES * group;
+ 
+ 		for (i = 0; i < MCS_GROUP_RATES; i++) {
+ 			if (!(mi->supported[group] & BIT(i)))
diff --git a/package/kernel/mac80211/patches/subsys/311-mac80211-minstrel_ht-reduce-unnecessary-rate-probing.patch b/package/kernel/mac80211/patches/subsys/311-mac80211-minstrel_ht-reduce-unnecessary-rate-probing.patch
new file mode 100644
index 0000000000..11f6ead13d
--- /dev/null
+++ b/package/kernel/mac80211/patches/subsys/311-mac80211-minstrel_ht-reduce-unnecessary-rate-probing.patch
@@ -0,0 +1,42 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Wed, 5 Jun 2019 20:42:49 +0200
+Subject: [PATCH] mac80211: minstrel_ht: reduce unnecessary rate probing
+ attempts
+
+On hardware with static fallback tables (e.g. mt76x2), rate probing attempts
+can be very expensive.
+On such devices, avoid sampling rates slower than the per-group max throughput
+rate, based on the assumption that the fallback table will take care of probing
+lower rates within that group if the higher rates fail.
+To make this work, this also fixes a wrong initialization in the previously
+unused per-group sorted rate array.
+To further reduce unnecessary probing attempts, skip duplicate attempts on
+rates slower than the max throughput rate.
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/mac80211/rc80211_minstrel_ht.c
++++ b/net/mac80211/rc80211_minstrel_ht.c
+@@ -1059,6 +1059,21 @@ minstrel_get_sample_rate(struct minstrel
+ 	    minstrel_get_duration(mi->max_prob_rate) * 3 < sample_dur)
+ 		return -1;
+ 
++
++	/*
++	 * For devices with no configurable multi-rate retry, skip sampling
++	 * below the per-group max throughput rate, and only use one sampling
++	 * attempt per rate
++	 */
++	if (mp->hw->max_rates == 1 &&
++	    (minstrel_get_duration(mg->max_group_tp_rate[0]) < sample_dur ||
++	     mrs->attempts))
++		return -1;
++
++	/* Skip already sampled slow rates */
++	if (sample_dur >= minstrel_get_duration(tp_rate1) && mrs->attempts)
++		return -1;
++
+ 	/*
+ 	 * Make sure that lower rates get sampled only occasionally,
+ 	 * if the link is working perfectly.
diff --git a/package/kernel/mac80211/patches/subsys/312-mac80211-minstrel_ht-fix-default-max-throughput-rate.patch b/package/kernel/mac80211/patches/subsys/312-mac80211-minstrel_ht-fix-default-max-throughput-rate.patch
new file mode 100644
index 0000000000..9855c35a5d
--- /dev/null
+++ b/package/kernel/mac80211/patches/subsys/312-mac80211-minstrel_ht-fix-default-max-throughput-rate.patch
@@ -0,0 +1,46 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Fri, 14 Jun 2019 21:14:22 +0200
+Subject: [PATCH] mac80211: minstrel_ht: fix default max throughput rate
+ indexes
+
+Use the first supported rate instead of 0 (which can be invalid)
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/mac80211/rc80211_minstrel_ht.c
++++ b/net/mac80211/rc80211_minstrel_ht.c
+@@ -486,7 +486,7 @@ minstrel_ht_assign_best_tp_rates(struct
+ 	tmp_prob = mi->groups[tmp_group].rates[tmp_idx].prob_ewma;
+ 	tmp_mcs_tp = minstrel_ht_get_tp_avg(mi, tmp_group, tmp_idx, tmp_prob);
+ 
+-	if (tmp_cck_tp > tmp_mcs_tp) {
++	if (tmp_cck_tp_rate && tmp_cck_tp > tmp_mcs_tp) {
+ 		for(i = 0; i < MAX_THR_RATES; i++) {
+ 			minstrel_ht_sort_best_tp_rates(mi, tmp_cck_tp_rate[i],
+ 						       tmp_mcs_tp_rate);
+@@ -558,11 +558,19 @@ minstrel_ht_update_stats(struct minstrel
+ 	mi->sample_slow = 0;
+ 	mi->sample_count = 0;
+ 
+-	/* Initialize global rate indexes */
+-	for(j = 0; j < MAX_THR_RATES; j++){
+-		tmp_mcs_tp_rate[j] = 0;
+-		tmp_cck_tp_rate[j] = 0;
+-	}
++	memset(tmp_mcs_tp_rate, 0, sizeof(tmp_mcs_tp_rate));
++	memset(tmp_cck_tp_rate, 0, sizeof(tmp_cck_tp_rate));
++	if (mi->supported[MINSTREL_CCK_GROUP])
++		for (j = 0; j < ARRAY_SIZE(tmp_cck_tp_rate); j++)
++			tmp_cck_tp_rate[j] = MINSTREL_CCK_GROUP * MCS_GROUP_RATES;
++
++	if (mi->supported[MINSTREL_VHT_GROUP_0])
++		index = MINSTREL_VHT_GROUP_0 * MCS_GROUP_RATES;
++	else
++		index = MINSTREL_HT_GROUP_0 * MCS_GROUP_RATES;
++
++	for (j = 0; j < ARRAY_SIZE(tmp_mcs_tp_rate); j++)
++		tmp_mcs_tp_rate[j] = index;
+ 
+ 	/* Find best rate sets within all MCS groups*/
+ 	for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {
diff --git a/package/kernel/mac80211/patches/subsys/313-mac80211-minstrel_ht-improve-rate-probing-for-device.patch b/package/kernel/mac80211/patches/subsys/313-mac80211-minstrel_ht-improve-rate-probing-for-device.patch
new file mode 100644
index 0000000000..5b8e608b0a
--- /dev/null
+++ b/package/kernel/mac80211/patches/subsys/313-mac80211-minstrel_ht-improve-rate-probing-for-device.patch
@@ -0,0 +1,481 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Fri, 14 Jun 2019 21:15:47 +0200
+Subject: [PATCH] mac80211: minstrel_ht: improve rate probing for devices
+ with static fallback
+
+On some devices that only support static rate fallback tables sending rate
+control probing packets can be really expensive.
+Probing lower rates can already hurt throughput quite a bit. What hurts even
+more is the fact that on mt76x0/mt76x2, single probing packets can only be
+forced by directing packets at a different internal hardware queue, which
+causes some heavy reordering and extra latency.
+The reordering issue is mainly problematic while pushing lots of packets to
+a particular station. If there is little activity, the overhead of probing is
+neglegible.
+
+The static fallback behavior is designed to pretty much only handle rate
+control algorithms that use only a very limited set of rates on which the
+algorithm switches up/down based on packet error rate.
+
+In order to better support that kind of hardware, this patch implements a
+different approach to rate probing where it switches to a slightly higher rate,
+waits for tx status feedback, then updates the stats and switches back to
+the new max throughput rate. This only triggers above a packet rate of 100
+per stats interval (~50ms).
+For that kind of probing, the code has to reduce the set of probing rates
+a lot more compared to single packet probing, so it uses only one packet
+per MCS group which is either slightly faster, or as close as possible to
+the max throughput rate.
+This allows switching between similar rates with different numbers of
+streams. The algorithm assumes that the hardware will work its way lower
+within an MCS group in case of retransmissions, so that lower rates don't
+have to be probed by the high packets per second rate probing code.
+
+To further reduce the search space, it also does not probe rates with lower
+channel bandwidth than the max throughput rate.
+
+At the moment, these changes will only affect mt76x0/mt76x2.
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/net/mac80211/rc80211_minstrel.h
++++ b/net/mac80211/rc80211_minstrel.h
+@@ -95,6 +95,7 @@ struct minstrel_sta_info {
+ struct minstrel_priv {
+ 	struct ieee80211_hw *hw;
+ 	bool has_mrr;
++	u32 sample_switch;
+ 	unsigned int cw_min;
+ 	unsigned int cw_max;
+ 	unsigned int max_retry;
+--- a/net/mac80211/rc80211_minstrel_ht.c
++++ b/net/mac80211/rc80211_minstrel_ht.c
+@@ -18,6 +18,8 @@
+ #define AVG_AMPDU_SIZE	16
+ #define AVG_PKT_SIZE	1200
+ 
++#define SAMPLE_SWITCH_THR	100
++
+ /* Number of bits for an average sized packet */
+ #define MCS_NBITS ((AVG_PKT_SIZE * AVG_AMPDU_SIZE) << 3)
+ 
+@@ -58,6 +60,7 @@
+ 	[GROUP_IDX(_streams, _sgi, _ht40)] = {				\
+ 	.streams = _streams,						\
+ 	.shift = _s,							\
++	.bw = _ht40,							\
+ 	.flags =							\
+ 		IEEE80211_TX_RC_MCS |					\
+ 		(_sgi ? IEEE80211_TX_RC_SHORT_GI : 0) |			\
+@@ -94,6 +97,7 @@
+ 	[VHT_GROUP_IDX(_streams, _sgi, _bw)] = {			\
+ 	.streams = _streams,						\
+ 	.shift = _s,							\
++	.bw = _bw,							\
+ 	.flags =							\
+ 		IEEE80211_TX_RC_VHT_MCS |				\
+ 		(_sgi ? IEEE80211_TX_RC_SHORT_GI : 0) |			\
+@@ -526,6 +530,133 @@ minstrel_ht_prob_rate_reduce_streams(str
+ 	}
+ }
+ 
++static inline int
++minstrel_get_duration(int index)
++{
++	const struct mcs_group *group = &minstrel_mcs_groups[index / MCS_GROUP_RATES];
++	unsigned int duration = group->duration[index % MCS_GROUP_RATES];
++	return duration << group->shift;
++}
++
++static bool
++minstrel_ht_probe_group(struct minstrel_ht_sta *mi, const struct mcs_group *tp_group,
++						int tp_idx, const struct mcs_group *group)
++{
++	if (group->bw < tp_group->bw)
++		return false;
++
++	if (group->streams == tp_group->streams)
++		return true;
++
++	if (tp_idx < 4 && group->streams == tp_group->streams - 1)
++		return true;
++
++	return group->streams == tp_group->streams + 1;
++}
++
++static void
++minstrel_ht_find_probe_rates(struct minstrel_ht_sta *mi, u16 *rates, int *n_rates,
++			     bool faster_rate)
++{
++	const struct mcs_group *group, *tp_group;
++	int i, g, max_dur;
++	int tp_idx;
++
++	tp_group = &minstrel_mcs_groups[mi->max_tp_rate[0] / MCS_GROUP_RATES];
++	tp_idx = mi->max_tp_rate[0] % MCS_GROUP_RATES;
++
++	max_dur = minstrel_get_duration(mi->max_tp_rate[0]);
++	if (faster_rate)
++		max_dur -= max_dur / 16;
++
++	for (g = 0; g < MINSTREL_GROUPS_NB; g++) {
++		u16 supported = mi->supported[g];
++
++		if (!supported)
++			continue;
++
++		group = &minstrel_mcs_groups[g];
++		if (!minstrel_ht_probe_group(mi, tp_group, tp_idx, group))
++			continue;
++
++		for (i = 0; supported; supported >>= 1, i++) {
++			int idx;
++
++			if (!(supported & 1))
++				continue;
++
++			if ((group->duration[i] << group->shift) > max_dur)
++				continue;
++
++			idx = g * MCS_GROUP_RATES + i;
++			if (idx == mi->max_tp_rate[0])
++				continue;
++
++			rates[(*n_rates)++] = idx;
++			break;
++		}
++	}
++}
++
++static void
++minstrel_ht_rate_sample_switch(struct minstrel_priv *mp,
++			       struct minstrel_ht_sta *mi)
++{
++	struct minstrel_rate_stats *mrs;
++	u16 rates[MINSTREL_GROUPS_NB];
++	int n_rates = 0;
++	int probe_rate = 0;
++	bool faster_rate;
++	int i;
++	u8 random;
++
++	/*
++	 * Use rate switching instead of probing packets for devices with
++	 * little control over retry fallback behavior
++	 */
++	if (mp->hw->max_rates > 1)
++		return;
++
++	/*
++	 * If the current EWMA prob is >75%, look for a rate that's 6.25%
++	 * faster than the max tp rate.
++	 * If that fails, look again for a rate that is at least as fast
++	 */
++	mrs = minstrel_get_ratestats(mi, mi->max_tp_rate[0]);
++	faster_rate = mrs->prob_ewma > MINSTREL_FRAC(75, 100);
++	minstrel_ht_find_probe_rates(mi, rates, &n_rates, faster_rate);
++	if (!n_rates && faster_rate)
++		minstrel_ht_find_probe_rates(mi, rates, &n_rates, false);
++
++	/* If no suitable rate was found, try to pick the next one in the group */
++	if (!n_rates) {
++		int g_idx = mi->max_tp_rate[0] / MCS_GROUP_RATES;
++		u16 supported = mi->supported[g_idx];
++
++		supported >>= mi->max_tp_rate[0] % MCS_GROUP_RATES;
++		for (i = 0; supported; i++) {
++			if (!(supported & 1))
++				continue;
++
++			probe_rate = mi->max_tp_rate[0] + i;
++			goto out;
++		}
++
++		return;
++	}
++
++	i = 0;
++	if (n_rates > 1) {
++		random = prandom_u32();
++		i = random % n_rates;
++	}
++	probe_rate = rates[i];
++
++out:
++	mi->sample_rate = probe_rate;
++	mi->sample_mode = MINSTREL_SAMPLE_ACTIVE;
++}
++
+ /*
+  * Update rate statistics and select new primary rates
+  *
+@@ -536,7 +667,8 @@ minstrel_ht_prob_rate_reduce_streams(str
+  *    higher throughput rates, even if the probablity is a bit lower
+  */
+ static void
+-minstrel_ht_update_stats(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
++minstrel_ht_update_stats(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
++			 bool sample)
+ {
+ 	struct minstrel_mcs_group_data *mg;
+ 	struct minstrel_rate_stats *mrs;
+@@ -544,6 +676,18 @@ minstrel_ht_update_stats(struct minstrel
+ 	u16 tmp_mcs_tp_rate[MAX_THR_RATES], tmp_group_tp_rate[MAX_THR_RATES];
+ 	u16 tmp_cck_tp_rate[MAX_THR_RATES], index;
+ 
++	mi->sample_mode = MINSTREL_SAMPLE_IDLE;
++
++	if (sample) {
++		mi->total_packets_cur = mi->total_packets -
++					mi->total_packets_last;
++		mi->total_packets_last = mi->total_packets;
++	}
++	if (!mp->sample_switch)
++		sample = false;
++	if (mi->total_packets_cur < SAMPLE_SWITCH_THR && mp->sample_switch != 1)
++	    sample = false;
++
+ 	if (mi->ampdu_packets > 0) {
+ 		if (!ieee80211_hw_check(mp->hw, TX_STATUS_NO_AMPDU_LEN))
+ 			mi->avg_ampdu_len = minstrel_ewma(mi->avg_ampdu_len,
+@@ -630,12 +774,16 @@ minstrel_ht_update_stats(struct minstrel
+ 	/* try to sample all available rates during each interval */
+ 	mi->sample_count *= 8;
+ 
++	if (sample)
++		minstrel_ht_rate_sample_switch(mp, mi);
++
+ #ifdef CPTCFG_MAC80211_DEBUGFS
+ 	/* use fixed index if set */
+ 	if (mp->fixed_rate_idx != -1) {
+ 		for (i = 0; i < 4; i++)
+ 			mi->max_tp_rate[i] = mp->fixed_rate_idx;
+ 		mi->max_prob_rate = mp->fixed_rate_idx;
++		mi->sample_mode = MINSTREL_SAMPLE_IDLE;
+ 	}
+ #endif
+ 
+@@ -739,15 +887,17 @@ minstrel_ht_tx_status(void *priv, struct
+ 	struct minstrel_ht_sta_priv *msp = priv_sta;
+ 	struct minstrel_ht_sta *mi = &msp->ht;
+ 	struct ieee80211_tx_rate *ar = info->status.rates;
+-	struct minstrel_rate_stats *rate, *rate2;
++	struct minstrel_rate_stats *rate, *rate2, *rate_sample = NULL;
+ 	struct minstrel_priv *mp = priv;
+ 	bool last, update = false;
++	bool sample_status = false;
+ 	int i;
+ 
+ 	if (!msp->is_ht)
+ 		return mac80211_minstrel.tx_status_ext(priv, sband,
+ 						       &msp->legacy, st);
+ 
++
+ 	/* This packet was aggregated but doesn't carry status info */
+ 	if ((info->flags & IEEE80211_TX_CTL_AMPDU) &&
+ 	    !(info->flags & IEEE80211_TX_STAT_AMPDU))
+@@ -773,12 +923,17 @@ minstrel_ht_tx_status(void *priv, struct
+ 	if (info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE)
+ 		mi->sample_packets += info->status.ampdu_len;
+ 
++	if (mi->sample_mode != MINSTREL_SAMPLE_IDLE)
++		rate_sample = minstrel_get_ratestats(mi, mi->sample_rate);
++
+ 	last = !minstrel_ht_txstat_valid(mp, &ar[0]);
+ 	for (i = 0; !last; i++) {
+ 		last = (i == IEEE80211_TX_MAX_RATES - 1) ||
+ 		       !minstrel_ht_txstat_valid(mp, &ar[i + 1]);
+ 
+ 		rate = minstrel_ht_get_stats(mp, mi, &ar[i]);
++		if (rate == rate_sample)
++			sample_status = true;
+ 
+ 		if (last)
+ 			rate->success += info->status.ampdu_ack_len;
+@@ -786,44 +941,60 @@ minstrel_ht_tx_status(void *priv, struct
+ 		rate->attempts += ar[i].count * info->status.ampdu_len;
+ 	}
+ 
+-	/*
+-	 * check for sudden death of spatial multiplexing,
+-	 * downgrade to a lower number of streams if necessary.
+-	 */
+-	rate = minstrel_get_ratestats(mi, mi->max_tp_rate[0]);
+-	if (rate->attempts > 30 &&
+-	    MINSTREL_FRAC(rate->success, rate->attempts) <
+-	    MINSTREL_FRAC(20, 100)) {
+-		minstrel_downgrade_rate(mi, &mi->max_tp_rate[0], true);
++	switch (mi->sample_mode) {
++	case MINSTREL_SAMPLE_IDLE:
++		break;
++
++	case MINSTREL_SAMPLE_ACTIVE:
++		if (!sample_status)
++			break;
++
++		mi->sample_mode = MINSTREL_SAMPLE_PENDING;
+ 		update = true;
+-	}
++		break;
++
++	case MINSTREL_SAMPLE_PENDING:
++		if (sample_status)
++			break;
+ 
+-	rate2 = minstrel_get_ratestats(mi, mi->max_tp_rate[1]);
+-	if (rate2->attempts > 30 &&
+-	    MINSTREL_FRAC(rate2->success, rate2->attempts) <
+-	    MINSTREL_FRAC(20, 100)) {
+-		minstrel_downgrade_rate(mi, &mi->max_tp_rate[1], false);
+ 		update = true;
++		minstrel_ht_update_stats(mp, mi, false);
++		break;
++	}
++
++
++	if (mp->hw->max_rates > 1) {
++		/*
++		 * check for sudden death of spatial multiplexing,
++		 * downgrade to a lower number of streams if necessary.
++		 */
++		rate = minstrel_get_ratestats(mi, mi->max_tp_rate[0]);
++		if (rate->attempts > 30 &&
++		    MINSTREL_FRAC(rate->success, rate->attempts) <
++		    MINSTREL_FRAC(20, 100)) {
++			minstrel_downgrade_rate(mi, &mi->max_tp_rate[0], true);
++			update = true;
++		}
++
++		rate2 = minstrel_get_ratestats(mi, mi->max_tp_rate[1]);
++		if (rate2->attempts > 30 &&
++		    MINSTREL_FRAC(rate2->success, rate2->attempts) <
++		    MINSTREL_FRAC(20, 100)) {
++			minstrel_downgrade_rate(mi, &mi->max_tp_rate[1], false);
++			update = true;
++		}
+ 	}
+ 
+ 	if (time_after(jiffies, mi->last_stats_update +
+ 				(mp->update_interval / 2 * HZ) / 1000)) {
+ 		update = true;
+-		minstrel_ht_update_stats(mp, mi);
++		minstrel_ht_update_stats(mp, mi, true);
+ 	}
+ 
+ 	if (update)
+ 		minstrel_ht_update_rates(mp, mi);
+ }
+ 
+-static inline int
+-minstrel_get_duration(int index)
+-{
+-	const struct mcs_group *group = &minstrel_mcs_groups[index / MCS_GROUP_RATES];
+-	unsigned int duration = group->duration[index % MCS_GROUP_RATES];
+-	return duration << group->shift;
+-}
+-
+ static void
+ minstrel_calc_retransmit(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
+                          int index)
+@@ -988,14 +1159,18 @@ static void
+ minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
+ {
+ 	struct ieee80211_sta_rates *rates;
++	u16 first_rate = mi->max_tp_rate[0];
+ 	int i = 0;
+ 
++	if (mi->sample_mode == MINSTREL_SAMPLE_ACTIVE)
++		first_rate = mi->sample_rate;
++
+ 	rates = kzalloc(sizeof(*rates), GFP_ATOMIC);
+ 	if (!rates)
+ 		return;
+ 
+ 	/* Start with max_tp_rate[0] */
+-	minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_tp_rate[0]);
++	minstrel_ht_set_rate(mp, mi, rates, i++, first_rate);
+ 
+ 	if (mp->hw->max_rates >= 3) {
+ 		/* At least 3 tx rates supported, use max_tp_rate[1] next */
+@@ -1020,6 +1195,11 @@ minstrel_get_sample_rate(struct minstrel
+ 	int tp_rate1, tp_rate2;
+ 	int sample_idx = 0;
+ 
++	if (mp->hw->max_rates == 1 && mp->sample_switch &&
++	    (mi->total_packets_cur >= SAMPLE_SWITCH_THR ||
++	     mp->sample_switch == 1))
++		return -1;
++
+ 	if (mi->sample_wait > 0) {
+ 		mi->sample_wait--;
+ 		return -1;
+@@ -1341,7 +1521,7 @@ minstrel_ht_update_caps(void *priv, stru
+ 	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);
++	minstrel_ht_update_stats(mp, mi, true);
+ 	minstrel_ht_update_rates(mp, mi);
+ 
+ 	return;
+@@ -1459,6 +1639,8 @@ minstrel_ht_alloc(struct ieee80211_hw *h
+ 	if (!mp)
+ 		return NULL;
+ 
++	mp->sample_switch = -1;
++
+ 	/* contention window settings
+ 	 * Just an approximation. Using the per-queue values would complicate
+ 	 * the calculations and is probably unnecessary */
+@@ -1490,6 +1672,8 @@ minstrel_ht_alloc(struct ieee80211_hw *h
+ 	mp->fixed_rate_idx = (u32) -1;
+ 	debugfs_create_u32("fixed_rate_idx", S_IRUGO | S_IWUGO, debugfsdir,
+ 			   &mp->fixed_rate_idx);
++	debugfs_create_u32("sample_switch", S_IRUGO | S_IWUSR, debugfsdir,
++			   &mp->sample_switch);
+ #endif
+ 
+ 	minstrel_ht_init_cck_rates(mp);
+--- a/net/mac80211/rc80211_minstrel_ht.h
++++ b/net/mac80211/rc80211_minstrel_ht.h
+@@ -33,6 +33,7 @@ struct mcs_group {
+ 	u16 flags;
+ 	u8 streams;
+ 	u8 shift;
++	u8 bw;
+ 	u16 duration[MCS_GROUP_RATES];
+ };
+ 
+@@ -50,6 +51,12 @@ struct minstrel_mcs_group_data {
+ 	struct minstrel_rate_stats rates[MCS_GROUP_RATES];
+ };
+ 
++enum minstrel_sample_mode {
++	MINSTREL_SAMPLE_IDLE,
++	MINSTREL_SAMPLE_ACTIVE,
++	MINSTREL_SAMPLE_PENDING,
++};
++
+ struct minstrel_ht_sta {
+ 	struct ieee80211_sta *sta;
+ 
+@@ -71,6 +78,8 @@ struct minstrel_ht_sta {
+ 	unsigned int overhead;
+ 	unsigned int overhead_rtscts;
+ 
++	unsigned int total_packets_last;
++	unsigned int total_packets_cur;
+ 	unsigned int total_packets;
+ 	unsigned int sample_packets;
+ 
+@@ -82,6 +91,9 @@ struct minstrel_ht_sta {
+ 	u8 sample_count;
+ 	u8 sample_slow;
+ 
++	enum minstrel_sample_mode sample_mode;
++	u16 sample_rate;
++
+ 	/* current MCS group to be sampled */
+ 	u8 sample_group;
+