rc80211_minstrel_ht.c 27.4 KB
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/*
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 * Copyright (C) 2010-2013 Felix Fietkau <nbd@openwrt.org>
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 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/netdevice.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/debugfs.h>
#include <linux/random.h>
#include <linux/ieee80211.h>
#include <net/mac80211.h>
#include "rate.h"
#include "rc80211_minstrel.h"
#include "rc80211_minstrel_ht.h"

#define AVG_PKT_SIZE	1200

/* Number of bits for an average sized packet */
#define MCS_NBITS (AVG_PKT_SIZE << 3)

/* Number of symbols for a packet with (bps) bits per symbol */
#define MCS_NSYMS(bps) ((MCS_NBITS + (bps) - 1) / (bps))

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/* Transmission time (nanoseconds) for a packet containing (syms) symbols */
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#define MCS_SYMBOL_TIME(sgi, syms)					\
	(sgi ?								\
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	  ((syms) * 18000 + 4000) / 5 :	/* syms * 3.6 us */		\
	  ((syms) * 1000) << 2		/* syms * 4 us */		\
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	)

/* Transmit duration for the raw data part of an average sized packet */
#define MCS_DURATION(streams, sgi, bps) MCS_SYMBOL_TIME(sgi, MCS_NSYMS((streams) * (bps)))

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/*
 * Define group sort order: HT40 -> SGI -> #streams
 */
#define GROUP_IDX(_streams, _sgi, _ht40)	\
	MINSTREL_MAX_STREAMS * 2 * _ht40 +	\
	MINSTREL_MAX_STREAMS * _sgi +		\
	_streams - 1

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/* MCS rate information for an MCS group */
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#define MCS_GROUP(_streams, _sgi, _ht40)				\
	[GROUP_IDX(_streams, _sgi, _ht40)] = {				\
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	.streams = _streams,						\
	.flags =							\
		(_sgi ? IEEE80211_TX_RC_SHORT_GI : 0) |			\
		(_ht40 ? IEEE80211_TX_RC_40_MHZ_WIDTH : 0),		\
	.duration = {							\
		MCS_DURATION(_streams, _sgi, _ht40 ? 54 : 26),		\
		MCS_DURATION(_streams, _sgi, _ht40 ? 108 : 52),		\
		MCS_DURATION(_streams, _sgi, _ht40 ? 162 : 78),		\
		MCS_DURATION(_streams, _sgi, _ht40 ? 216 : 104),	\
		MCS_DURATION(_streams, _sgi, _ht40 ? 324 : 156),	\
		MCS_DURATION(_streams, _sgi, _ht40 ? 432 : 208),	\
		MCS_DURATION(_streams, _sgi, _ht40 ? 486 : 234),	\
		MCS_DURATION(_streams, _sgi, _ht40 ? 540 : 260)		\
	}								\
}

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#define CCK_DURATION(_bitrate, _short, _len)		\
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	(1000 * (10 /* SIFS */ +			\
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	 (_short ? 72 + 24 : 144 + 48 ) +		\
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	 (8 * (_len + 4) * 10) / (_bitrate)))
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#define CCK_ACK_DURATION(_bitrate, _short)			\
	(CCK_DURATION((_bitrate > 10 ? 20 : 10), false, 60) +	\
	 CCK_DURATION(_bitrate, _short, AVG_PKT_SIZE))

#define CCK_DURATION_LIST(_short)			\
	CCK_ACK_DURATION(10, _short),			\
	CCK_ACK_DURATION(20, _short),			\
	CCK_ACK_DURATION(55, _short),			\
	CCK_ACK_DURATION(110, _short)

#define CCK_GROUP						\
	[MINSTREL_MAX_STREAMS * MINSTREL_STREAM_GROUPS] = {	\
		.streams = 0,					\
		.duration = {					\
			CCK_DURATION_LIST(false),		\
			CCK_DURATION_LIST(true)			\
		}						\
	}

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/*
 * To enable sufficiently targeted rate sampling, MCS rates are divided into
 * groups, based on the number of streams and flags (HT40, SGI) that they
 * use.
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 *
 * Sortorder has to be fixed for GROUP_IDX macro to be applicable:
 * HT40 -> SGI -> #streams
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 */
const struct mcs_group minstrel_mcs_groups[] = {
	MCS_GROUP(1, 0, 0),
	MCS_GROUP(2, 0, 0),
#if MINSTREL_MAX_STREAMS >= 3
	MCS_GROUP(3, 0, 0),
#endif

	MCS_GROUP(1, 1, 0),
	MCS_GROUP(2, 1, 0),
#if MINSTREL_MAX_STREAMS >= 3
	MCS_GROUP(3, 1, 0),
#endif

	MCS_GROUP(1, 0, 1),
	MCS_GROUP(2, 0, 1),
#if MINSTREL_MAX_STREAMS >= 3
	MCS_GROUP(3, 0, 1),
#endif

	MCS_GROUP(1, 1, 1),
	MCS_GROUP(2, 1, 1),
#if MINSTREL_MAX_STREAMS >= 3
	MCS_GROUP(3, 1, 1),
#endif
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	/* must be last */
	CCK_GROUP
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};

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#define MINSTREL_CCK_GROUP	(ARRAY_SIZE(minstrel_mcs_groups) - 1)

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static u8 sample_table[SAMPLE_COLUMNS][MCS_GROUP_RATES];

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static void
minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi);

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/*
 * Look up an MCS group index based on mac80211 rate information
 */
static int
minstrel_ht_get_group_idx(struct ieee80211_tx_rate *rate)
{
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	return GROUP_IDX((rate->idx / MCS_GROUP_RATES) + 1,
			 !!(rate->flags & IEEE80211_TX_RC_SHORT_GI),
			 !!(rate->flags & IEEE80211_TX_RC_40_MHZ_WIDTH));
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}

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static struct minstrel_rate_stats *
minstrel_ht_get_stats(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
		      struct ieee80211_tx_rate *rate)
{
	int group, idx;

	if (rate->flags & IEEE80211_TX_RC_MCS) {
		group = minstrel_ht_get_group_idx(rate);
		idx = rate->idx % MCS_GROUP_RATES;
	} else {
		group = MINSTREL_CCK_GROUP;

		for (idx = 0; idx < ARRAY_SIZE(mp->cck_rates); idx++)
			if (rate->idx == mp->cck_rates[idx])
				break;

		/* short preamble */
		if (!(mi->groups[group].supported & BIT(idx)))
			idx += 4;
	}
	return &mi->groups[group].rates[idx];
}

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static inline struct minstrel_rate_stats *
minstrel_get_ratestats(struct minstrel_ht_sta *mi, int index)
{
	return &mi->groups[index / MCS_GROUP_RATES].rates[index % MCS_GROUP_RATES];
}


/*
 * Recalculate success probabilities and counters for a rate using EWMA
 */
static void
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minstrel_calc_rate_ewma(struct minstrel_rate_stats *mr)
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{
	if (unlikely(mr->attempts > 0)) {
		mr->sample_skipped = 0;
		mr->cur_prob = MINSTREL_FRAC(mr->success, mr->attempts);
		if (!mr->att_hist)
			mr->probability = mr->cur_prob;
		else
			mr->probability = minstrel_ewma(mr->probability,
				mr->cur_prob, EWMA_LEVEL);
		mr->att_hist += mr->attempts;
		mr->succ_hist += mr->success;
	} else {
		mr->sample_skipped++;
	}
	mr->last_success = mr->success;
	mr->last_attempts = mr->attempts;
	mr->success = 0;
	mr->attempts = 0;
}

/*
 * Calculate throughput based on the average A-MPDU length, taking into account
 * the expected number of retransmissions and their expected length
 */
static void
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minstrel_ht_calc_tp(struct minstrel_ht_sta *mi, int group, int rate)
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{
	struct minstrel_rate_stats *mr;
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	unsigned int nsecs = 0;
	unsigned int tp;
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	unsigned int prob;
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	mr = &mi->groups[group].rates[rate];
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	prob = mr->probability;
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	if (prob < MINSTREL_FRAC(1, 10)) {
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		mr->cur_tp = 0;
		return;
	}

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	/*
	 * For the throughput calculation, limit the probability value to 90% to
	 * account for collision related packet error rate fluctuation
	 */
	if (prob > MINSTREL_FRAC(9, 10))
		prob = MINSTREL_FRAC(9, 10);

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	if (group != MINSTREL_CCK_GROUP)
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		nsecs = 1000 * mi->overhead / MINSTREL_TRUNC(mi->avg_ampdu_len);
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	nsecs += minstrel_mcs_groups[group].duration[rate];
	tp = 1000000 * ((mr->probability * 1000) / nsecs);

	mr->cur_tp = MINSTREL_TRUNC(tp);
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}

/*
 * Update rate statistics and select new primary rates
 *
 * Rules for rate selection:
 *  - max_prob_rate must use only one stream, as a tradeoff between delivery
 *    probability and throughput during strong fluctuations
 *  - as long as the max prob rate has a probability of more than 3/4, pick
 *    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)
{
	struct minstrel_mcs_group_data *mg;
	struct minstrel_rate_stats *mr;
	int cur_prob, cur_prob_tp, cur_tp, cur_tp2;
	int group, i, index;
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	bool mi_rates_valid = false;
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	if (mi->ampdu_packets > 0) {
		mi->avg_ampdu_len = minstrel_ewma(mi->avg_ampdu_len,
			MINSTREL_FRAC(mi->ampdu_len, mi->ampdu_packets), EWMA_LEVEL);
		mi->ampdu_len = 0;
		mi->ampdu_packets = 0;
	}

	mi->sample_slow = 0;
	mi->sample_count = 0;

	for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {
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		bool mg_rates_valid = false;

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		cur_prob = 0;
		cur_prob_tp = 0;
		cur_tp = 0;
		cur_tp2 = 0;

		mg = &mi->groups[group];
		if (!mg->supported)
			continue;

		mi->sample_count++;

		for (i = 0; i < MCS_GROUP_RATES; i++) {
			if (!(mg->supported & BIT(i)))
				continue;

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			/* initialize rates selections starting indexes */
			if (!mg_rates_valid) {
				mg->max_tp_rate = mg->max_tp_rate2 =
					mg->max_prob_rate = i;
				if (!mi_rates_valid) {
					mi->max_tp_rate = mi->max_tp_rate2 =
						mi->max_prob_rate = i;
					mi_rates_valid = true;
				}
				mg_rates_valid = true;
			}

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			mr = &mg->rates[i];
			mr->retry_updated = false;
			index = MCS_GROUP_RATES * group + i;
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			minstrel_calc_rate_ewma(mr);
			minstrel_ht_calc_tp(mi, group, i);
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			if (!mr->cur_tp)
				continue;

			if ((mr->cur_tp > cur_prob_tp && mr->probability >
			     MINSTREL_FRAC(3, 4)) || mr->probability > cur_prob) {
				mg->max_prob_rate = index;
				cur_prob = mr->probability;
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				cur_prob_tp = mr->cur_tp;
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			}

			if (mr->cur_tp > cur_tp) {
				swap(index, mg->max_tp_rate);
				cur_tp = mr->cur_tp;
				mr = minstrel_get_ratestats(mi, index);
			}

			if (index >= mg->max_tp_rate)
				continue;

			if (mr->cur_tp > cur_tp2) {
				mg->max_tp_rate2 = index;
				cur_tp2 = mr->cur_tp;
			}
		}
	}

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	/* try to sample all available rates during each interval */
	mi->sample_count *= 8;
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	cur_prob = 0;
	cur_prob_tp = 0;
	cur_tp = 0;
	cur_tp2 = 0;
	for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {
		mg = &mi->groups[group];
		if (!mg->supported)
			continue;

		mr = minstrel_get_ratestats(mi, mg->max_tp_rate);
		if (cur_tp < mr->cur_tp) {
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			mi->max_tp_rate2 = mi->max_tp_rate;
			cur_tp2 = cur_tp;
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			mi->max_tp_rate = mg->max_tp_rate;
			cur_tp = mr->cur_tp;
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			mi->max_prob_streams = minstrel_mcs_groups[group].streams - 1;
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		}

		mr = minstrel_get_ratestats(mi, mg->max_tp_rate2);
		if (cur_tp2 < mr->cur_tp) {
			mi->max_tp_rate2 = mg->max_tp_rate2;
			cur_tp2 = mr->cur_tp;
		}
	}

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	if (mi->max_prob_streams < 1)
		mi->max_prob_streams = 1;
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	for (group = 0; group < ARRAY_SIZE(minstrel_mcs_groups); group++) {
		mg = &mi->groups[group];
		if (!mg->supported)
			continue;
		mr = minstrel_get_ratestats(mi, mg->max_prob_rate);
		if (cur_prob_tp < mr->cur_tp &&
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		    minstrel_mcs_groups[group].streams <= mi->max_prob_streams) {
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			mi->max_prob_rate = mg->max_prob_rate;
			cur_prob = mr->cur_prob;
			cur_prob_tp = mr->cur_tp;
		}
	}


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	mi->stats_update = jiffies;
}

static bool
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minstrel_ht_txstat_valid(struct minstrel_priv *mp, struct ieee80211_tx_rate *rate)
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{
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	if (rate->idx < 0)
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		return false;

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	if (!rate->count)
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		return false;

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	if (rate->flags & IEEE80211_TX_RC_MCS)
		return true;

	return rate->idx == mp->cck_rates[0] ||
	       rate->idx == mp->cck_rates[1] ||
	       rate->idx == mp->cck_rates[2] ||
	       rate->idx == mp->cck_rates[3];
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}

static void
minstrel_next_sample_idx(struct minstrel_ht_sta *mi)
{
	struct minstrel_mcs_group_data *mg;

	for (;;) {
		mi->sample_group++;
		mi->sample_group %= ARRAY_SIZE(minstrel_mcs_groups);
		mg = &mi->groups[mi->sample_group];

		if (!mg->supported)
			continue;

		if (++mg->index >= MCS_GROUP_RATES) {
			mg->index = 0;
			if (++mg->column >= ARRAY_SIZE(sample_table))
				mg->column = 0;
		}
		break;
	}
}

static void
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minstrel_downgrade_rate(struct minstrel_ht_sta *mi, unsigned int *idx,
			bool primary)
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{
	int group, orig_group;

	orig_group = group = *idx / MCS_GROUP_RATES;
	while (group > 0) {
		group--;

		if (!mi->groups[group].supported)
			continue;

		if (minstrel_mcs_groups[group].streams >
		    minstrel_mcs_groups[orig_group].streams)
			continue;

		if (primary)
			*idx = mi->groups[group].max_tp_rate;
		else
			*idx = mi->groups[group].max_tp_rate2;
		break;
	}
}

static void
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minstrel_aggr_check(struct ieee80211_sta *pubsta, struct sk_buff *skb)
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{
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
	struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
	u16 tid;

	if (unlikely(!ieee80211_is_data_qos(hdr->frame_control)))
		return;

	if (unlikely(skb->protocol == cpu_to_be16(ETH_P_PAE)))
		return;

	tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
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	if (likely(sta->ampdu_mlme.tid_tx[tid]))
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		return;

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	if (skb_get_queue_mapping(skb) == IEEE80211_AC_VO)
		return;

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	ieee80211_start_tx_ba_session(pubsta, tid, 5000);
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}

static void
minstrel_ht_tx_status(void *priv, struct ieee80211_supported_band *sband,
                      struct ieee80211_sta *sta, void *priv_sta,
                      struct sk_buff *skb)
{
	struct minstrel_ht_sta_priv *msp = priv_sta;
	struct minstrel_ht_sta *mi = &msp->ht;
	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
	struct ieee80211_tx_rate *ar = info->status.rates;
	struct minstrel_rate_stats *rate, *rate2;
	struct minstrel_priv *mp = priv;
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	bool last, update = false;
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	int i;
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	if (!msp->is_ht)
		return mac80211_minstrel.tx_status(priv, sband, sta, &msp->legacy, skb);

	/* This packet was aggregated but doesn't carry status info */
	if ((info->flags & IEEE80211_TX_CTL_AMPDU) &&
	    !(info->flags & IEEE80211_TX_STAT_AMPDU))
		return;

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	if (!(info->flags & IEEE80211_TX_STAT_AMPDU)) {
		info->status.ampdu_ack_len =
			(info->flags & IEEE80211_TX_STAT_ACK ? 1 : 0);
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		info->status.ampdu_len = 1;
	}

	mi->ampdu_packets++;
	mi->ampdu_len += info->status.ampdu_len;

	if (!mi->sample_wait && !mi->sample_tries && mi->sample_count > 0) {
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		mi->sample_wait = 16 + 2 * MINSTREL_TRUNC(mi->avg_ampdu_len);
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		mi->sample_tries = 1;
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		mi->sample_count--;
	}

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	if (info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE)
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		mi->sample_packets += info->status.ampdu_len;

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	last = !minstrel_ht_txstat_valid(mp, &ar[0]);
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	for (i = 0; !last; i++) {
		last = (i == IEEE80211_TX_MAX_RATES - 1) ||
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		       !minstrel_ht_txstat_valid(mp, &ar[i + 1]);
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		rate = minstrel_ht_get_stats(mp, mi, &ar[i]);
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		if (last)
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			rate->success += info->status.ampdu_ack_len;

		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);
	if (rate->attempts > 30 &&
	    MINSTREL_FRAC(rate->success, rate->attempts) <
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	    MINSTREL_FRAC(20, 100)) {
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		minstrel_downgrade_rate(mi, &mi->max_tp_rate, true);
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		update = true;
	}
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	rate2 = minstrel_get_ratestats(mi, mi->max_tp_rate2);
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	if (rate2->attempts > 30 &&
	    MINSTREL_FRAC(rate2->success, rate2->attempts) <
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	    MINSTREL_FRAC(20, 100)) {
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		minstrel_downgrade_rate(mi, &mi->max_tp_rate2, false);
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		update = true;
	}
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	if (time_after(jiffies, mi->stats_update + (mp->update_interval / 2 * HZ) / 1000)) {
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		update = true;
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		minstrel_ht_update_stats(mp, mi);
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		if (!(info->flags & IEEE80211_TX_CTL_AMPDU) &&
		    mi->max_prob_rate / MCS_GROUP_RATES != MINSTREL_CCK_GROUP)
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			minstrel_aggr_check(sta, skb);
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	}
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	if (update)
		minstrel_ht_update_rates(mp, mi);
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}

static void
minstrel_calc_retransmit(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
                         int index)
{
	struct minstrel_rate_stats *mr;
	const struct mcs_group *group;
	unsigned int tx_time, tx_time_rtscts, tx_time_data;
	unsigned int cw = mp->cw_min;
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	unsigned int ctime = 0;
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	unsigned int t_slot = 9; /* FIXME */
	unsigned int ampdu_len = MINSTREL_TRUNC(mi->avg_ampdu_len);
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	unsigned int overhead = 0, overhead_rtscts = 0;
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	mr = minstrel_get_ratestats(mi, index);
	if (mr->probability < MINSTREL_FRAC(1, 10)) {
		mr->retry_count = 1;
		mr->retry_count_rtscts = 1;
		return;
	}

	mr->retry_count = 2;
	mr->retry_count_rtscts = 2;
	mr->retry_updated = true;

	group = &minstrel_mcs_groups[index / MCS_GROUP_RATES];
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	tx_time_data = group->duration[index % MCS_GROUP_RATES] * ampdu_len / 1000;
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	/* Contention time for first 2 tries */
	ctime = (t_slot * cw) >> 1;
	cw = min((cw << 1) | 1, mp->cw_max);
	ctime += (t_slot * cw) >> 1;
	cw = min((cw << 1) | 1, mp->cw_max);

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	if (index / MCS_GROUP_RATES != MINSTREL_CCK_GROUP) {
		overhead = mi->overhead;
		overhead_rtscts = mi->overhead_rtscts;
	}

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	/* Total TX time for data and Contention after first 2 tries */
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	tx_time = ctime + 2 * (overhead + tx_time_data);
	tx_time_rtscts = ctime + 2 * (overhead_rtscts + tx_time_data);
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	/* See how many more tries we can fit inside segment size */
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	do {
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		/* Contention time for this try */
		ctime = (t_slot * cw) >> 1;
		cw = min((cw << 1) | 1, mp->cw_max);

		/* Total TX time after this try */
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		tx_time += ctime + overhead + tx_time_data;
		tx_time_rtscts += ctime + overhead_rtscts + tx_time_data;
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		if (tx_time_rtscts < mp->segment_size)
			mr->retry_count_rtscts++;
	} while ((tx_time < mp->segment_size) &&
	         (++mr->retry_count < mp->max_retry));
}


static void
minstrel_ht_set_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
606
                     struct ieee80211_sta_rates *ratetbl, int offset, int index)
607 608 609
{
	const struct mcs_group *group = &minstrel_mcs_groups[index / MCS_GROUP_RATES];
	struct minstrel_rate_stats *mr;
610 611
	u8 idx;
	u16 flags;
612 613 614 615 616

	mr = minstrel_get_ratestats(mi, index);
	if (!mr->retry_updated)
		minstrel_calc_retransmit(mp, mi, index);

617 618 619 620 621 622 623 624 625
	if (mr->probability < MINSTREL_FRAC(20, 100) || !mr->retry_count) {
		ratetbl->rate[offset].count = 2;
		ratetbl->rate[offset].count_rts = 2;
		ratetbl->rate[offset].count_cts = 2;
	} else {
		ratetbl->rate[offset].count = mr->retry_count;
		ratetbl->rate[offset].count_cts = mr->retry_count;
		ratetbl->rate[offset].count_rts = mr->retry_count_rtscts;
	}
626 627

	if (index / MCS_GROUP_RATES == MINSTREL_CCK_GROUP) {
628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652
		idx = mp->cck_rates[index % ARRAY_SIZE(mp->cck_rates)];
		flags = 0;
	} else {
		idx = index % MCS_GROUP_RATES +
		      (group->streams - 1) * MCS_GROUP_RATES;
		flags = IEEE80211_TX_RC_MCS | group->flags;
	}

	if (offset > 0) {
		ratetbl->rate[offset].count = ratetbl->rate[offset].count_rts;
		flags |= IEEE80211_TX_RC_USE_RTS_CTS;
	}

	ratetbl->rate[offset].idx = idx;
	ratetbl->rate[offset].flags = flags;
}

static void
minstrel_ht_update_rates(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
{
	struct ieee80211_sta_rates *rates;
	int i = 0;

	rates = kzalloc(sizeof(*rates), GFP_ATOMIC);
	if (!rates)
653
		return;
654 655 656 657 658 659 660 661 662 663 664 665 666

	/* Start with max_tp_rate */
	minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_tp_rate);

	if (mp->hw->max_rates >= 3) {
		/* At least 3 tx rates supported, use max_tp_rate2 next */
		minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_tp_rate2);
	}

	if (mp->hw->max_rates >= 2) {
		/*
		 * At least 2 tx rates supported, use max_prob_rate next */
		minstrel_ht_set_rate(mp, mi, rates, i++, mi->max_prob_rate);
667 668
	}

669 670
	rates->rate[i].idx = -1;
	rate_control_set_rates(mp->hw, mi->sta, rates);
671 672 673 674 675 676 677 678 679 680 681 682 683 684
}

static inline int
minstrel_get_duration(int index)
{
	const struct mcs_group *group = &minstrel_mcs_groups[index / MCS_GROUP_RATES];
	return group->duration[index % MCS_GROUP_RATES];
}

static int
minstrel_get_sample_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
{
	struct minstrel_rate_stats *mr;
	struct minstrel_mcs_group_data *mg;
685
	unsigned int sample_dur, sample_group;
686 687 688 689 690 691 692 693 694 695 696 697 698
	int sample_idx = 0;

	if (mi->sample_wait > 0) {
		mi->sample_wait--;
		return -1;
	}

	if (!mi->sample_tries)
		return -1;

	mg = &mi->groups[mi->sample_group];
	sample_idx = sample_table[mg->column][mg->index];
	mr = &mg->rates[sample_idx];
699 700
	sample_group = mi->sample_group;
	sample_idx += sample_group * MCS_GROUP_RATES;
701
	minstrel_next_sample_idx(mi);
702

703 704 705
	/*
	 * Sampling might add some overhead (RTS, no aggregation)
	 * to the frame. Hence, don't use sampling for the currently
706
	 * used rates.
707
	 */
708 709 710
	if (sample_idx == mi->max_tp_rate ||
	    sample_idx == mi->max_tp_rate2 ||
	    sample_idx == mi->max_prob_rate)
711
		return -1;
712

713
	/*
714 715
	 * Do not sample if the probability is already higher than 95%
	 * to avoid wasting airtime.
716
	 */
717
	if (mr->probability > MINSTREL_FRAC(95, 100))
718
		return -1;
719 720 721 722 723

	/*
	 * Make sure that lower rates get sampled only occasionally,
	 * if the link is working perfectly.
	 */
724 725 726 727 728
	sample_dur = minstrel_get_duration(sample_idx);
	if (sample_dur >= minstrel_get_duration(mi->max_tp_rate2) &&
	    (mi->max_prob_streams <
	     minstrel_mcs_groups[sample_group].streams ||
	     sample_dur >= minstrel_get_duration(mi->max_prob_rate))) {
729
		if (mr->sample_skipped < 20)
730
			return -1;
731 732

		if (mi->sample_slow++ > 2)
733
			return -1;
734
	}
735
	mi->sample_tries--;
736 737 738 739

	return sample_idx;
}

740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755
static void
minstrel_ht_check_cck_shortpreamble(struct minstrel_priv *mp,
				    struct minstrel_ht_sta *mi, bool val)
{
	u8 supported = mi->groups[MINSTREL_CCK_GROUP].supported;

	if (!supported || !mi->cck_supported_short)
		return;

	if (supported & (mi->cck_supported_short << (val * 4)))
		return;

	supported ^= mi->cck_supported_short | (mi->cck_supported_short << 4);
	mi->groups[MINSTREL_CCK_GROUP].supported = supported;
}

756 757 758 759
static void
minstrel_ht_get_rate(void *priv, struct ieee80211_sta *sta, void *priv_sta,
                     struct ieee80211_tx_rate_control *txrc)
{
760
	const struct mcs_group *sample_group;
761
	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(txrc->skb);
762
	struct ieee80211_tx_rate *rate = &info->status.rates[0];
763 764 765 766 767 768 769 770 771 772 773 774
	struct minstrel_ht_sta_priv *msp = priv_sta;
	struct minstrel_ht_sta *mi = &msp->ht;
	struct minstrel_priv *mp = priv;
	int sample_idx;

	if (rate_control_send_low(sta, priv_sta, txrc))
		return;

	if (!msp->is_ht)
		return mac80211_minstrel.get_rate(priv, sta, &msp->legacy, txrc);

	info->flags |= mi->tx_flags;
775
	minstrel_ht_check_cck_shortpreamble(mp, mi, txrc->short_preamble);
776 777 778 779 780 781 782

	/* Don't use EAPOL frames for sampling on non-mrr hw */
	if (mp->hw->max_rates == 1 &&
	    txrc->skb->protocol == cpu_to_be16(ETH_P_PAE))
		sample_idx = -1;
	else
		sample_idx = minstrel_get_sample_rate(mp, mi);
783 784 785

#ifdef CONFIG_MAC80211_DEBUGFS
	/* use fixed index if set */
786 787 788 789 790 791
	if (mp->fixed_rate_idx != -1) {
		mi->max_tp_rate = mp->fixed_rate_idx;
		mi->max_tp_rate2 = mp->fixed_rate_idx;
		mi->max_prob_rate = mp->fixed_rate_idx;
		sample_idx = -1;
	}
792 793
#endif

794 795 796 797 798 799 800
	mi->total_packets++;

	/* wraparound */
	if (mi->total_packets == ~0) {
		mi->total_packets = 0;
		mi->sample_packets = 0;
	}
801 802 803 804 805 806 807 808 809 810

	if (sample_idx < 0)
		return;

	sample_group = &minstrel_mcs_groups[sample_idx / MCS_GROUP_RATES];
	info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
	rate->idx = sample_idx % MCS_GROUP_RATES +
		    (sample_group->streams - 1) * MCS_GROUP_RATES;
	rate->flags = IEEE80211_TX_RC_MCS | sample_group->flags;
	rate->count = 1;
811 812
}

813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836
static void
minstrel_ht_update_cck(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
		       struct ieee80211_supported_band *sband,
		       struct ieee80211_sta *sta)
{
	int i;

	if (sband->band != IEEE80211_BAND_2GHZ)
		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);
		if (sband->bitrates[i].flags & IEEE80211_RATE_SHORT_PREAMBLE)
			mi->cck_supported_short |= BIT(i);
	}

	mi->groups[MINSTREL_CCK_GROUP].supported = mi->cck_supported;
}

837 838
static void
minstrel_ht_update_caps(void *priv, struct ieee80211_supported_band *sband,
839
			struct cfg80211_chan_def *chandef,
840
                        struct ieee80211_sta *sta, void *priv_sta)
841 842 843 844 845 846
{
	struct minstrel_priv *mp = priv;
	struct minstrel_ht_sta_priv *msp = priv_sta;
	struct minstrel_ht_sta *mi = &msp->ht;
	struct ieee80211_mcs_info *mcs = &sta->ht_cap.mcs;
	u16 sta_cap = sta->ht_cap.cap;
847
	int n_supported = 0;
848 849 850 851 852
	int ack_dur;
	int stbc;
	int i;

	/* fall back to the old minstrel for legacy stations */
853 854
	if (!sta->ht_cap.ht_supported)
		goto use_legacy;
855 856

	BUILD_BUG_ON(ARRAY_SIZE(minstrel_mcs_groups) !=
857
		MINSTREL_MAX_STREAMS * MINSTREL_STREAM_GROUPS + 1);
858 859 860

	msp->is_ht = true;
	memset(mi, 0, sizeof(*mi));
861 862

	mi->sta = sta;
863 864
	mi->stats_update = jiffies;

865 866 867
	ack_dur = ieee80211_frame_duration(sband->band, 10, 60, 1, 1, 0);
	mi->overhead = ieee80211_frame_duration(sband->band, 0, 60, 1, 1, 0);
	mi->overhead += ack_dur;
868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890
	mi->overhead_rtscts = mi->overhead + 2 * ack_dur;

	mi->avg_ampdu_len = MINSTREL_FRAC(1, 1);

	/* When using MRR, sample more on the first attempt, without delay */
	if (mp->has_mrr) {
		mi->sample_count = 16;
		mi->sample_wait = 0;
	} else {
		mi->sample_count = 8;
		mi->sample_wait = 8;
	}
	mi->sample_tries = 4;

	stbc = (sta_cap & IEEE80211_HT_CAP_RX_STBC) >>
		IEEE80211_HT_CAP_RX_STBC_SHIFT;
	mi->tx_flags |= stbc << IEEE80211_TX_CTL_STBC_SHIFT;

	if (sta_cap & IEEE80211_HT_CAP_LDPC_CODING)
		mi->tx_flags |= IEEE80211_TX_CTL_LDPC;

	for (i = 0; i < ARRAY_SIZE(mi->groups); i++) {
		mi->groups[i].supported = 0;
891 892 893 894 895
		if (i == MINSTREL_CCK_GROUP) {
			minstrel_ht_update_cck(mp, mi, sband, sta);
			continue;
		}

896
		if (minstrel_mcs_groups[i].flags & IEEE80211_TX_RC_SHORT_GI) {
897 898 899 900 901 902 903
			if (minstrel_mcs_groups[i].flags & IEEE80211_TX_RC_40_MHZ_WIDTH) {
				if (!(sta_cap & IEEE80211_HT_CAP_SGI_40))
					continue;
			} else {
				if (!(sta_cap & IEEE80211_HT_CAP_SGI_20))
					continue;
			}
904 905
		}

906 907
		if (minstrel_mcs_groups[i].flags & IEEE80211_TX_RC_40_MHZ_WIDTH &&
		    sta->bandwidth < IEEE80211_STA_RX_BW_40)
908 909
			continue;

910
		/* Mark MCS > 7 as unsupported if STA is in static SMPS mode */
911
		if (sta->smps_mode == IEEE80211_SMPS_STATIC &&
912 913 914
		    minstrel_mcs_groups[i].streams > 1)
			continue;

915 916
		mi->groups[i].supported =
			mcs->rx_mask[minstrel_mcs_groups[i].streams - 1];
917 918 919

		if (mi->groups[i].supported)
			n_supported++;
920
	}
921 922 923 924

	if (!n_supported)
		goto use_legacy;

925
	/* create an initial rate table with the lowest supported rates */
926
	minstrel_ht_update_stats(mp, mi);
927
	minstrel_ht_update_rates(mp, mi);
928

929 930 931 932 933 934 935
	return;

use_legacy:
	msp->is_ht = false;
	memset(&msp->legacy, 0, sizeof(msp->legacy));
	msp->legacy.r = msp->ratelist;
	msp->legacy.sample_table = msp->sample_table;
936 937
	return mac80211_minstrel.rate_init(priv, sband, chandef, sta,
					   &msp->legacy);
938 939 940 941
}

static void
minstrel_ht_rate_init(void *priv, struct ieee80211_supported_band *sband,
942
		      struct cfg80211_chan_def *chandef,
943 944
                      struct ieee80211_sta *sta, void *priv_sta)
{
945
	minstrel_ht_update_caps(priv, sband, chandef, sta, priv_sta);
946 947 948 949
}

static void
minstrel_ht_rate_update(void *priv, struct ieee80211_supported_band *sband,
950
			struct cfg80211_chan_def *chandef,
951
                        struct ieee80211_sta *sta, void *priv_sta,
952
                        u32 changed)
953
{
954
	minstrel_ht_update_caps(priv, sband, chandef, sta, priv_sta);
955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972
}

static void *
minstrel_ht_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
{
	struct ieee80211_supported_band *sband;
	struct minstrel_ht_sta_priv *msp;
	struct minstrel_priv *mp = priv;
	struct ieee80211_hw *hw = mp->hw;
	int max_rates = 0;
	int i;

	for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
		sband = hw->wiphy->bands[i];
		if (sband && sband->n_bitrates > max_rates)
			max_rates = sband->n_bitrates;
	}

973
	msp = kzalloc(sizeof(*msp), gfp);
974 975 976 977 978 979 980 981 982 983 984 985 986 987
	if (!msp)
		return NULL;

	msp->ratelist = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
	if (!msp->ratelist)
		goto error;

	msp->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
	if (!msp->sample_table)
		goto error1;

	return msp;

error1:
988
	kfree(msp->ratelist);
989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064
error:
	kfree(msp);
	return NULL;
}

static void
minstrel_ht_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
{
	struct minstrel_ht_sta_priv *msp = priv_sta;

	kfree(msp->sample_table);
	kfree(msp->ratelist);
	kfree(msp);
}

static void *
minstrel_ht_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
{
	return mac80211_minstrel.alloc(hw, debugfsdir);
}

static void
minstrel_ht_free(void *priv)
{
	mac80211_minstrel.free(priv);
}

static struct rate_control_ops mac80211_minstrel_ht = {
	.name = "minstrel_ht",
	.tx_status = minstrel_ht_tx_status,
	.get_rate = minstrel_ht_get_rate,
	.rate_init = minstrel_ht_rate_init,
	.rate_update = minstrel_ht_rate_update,
	.alloc_sta = minstrel_ht_alloc_sta,
	.free_sta = minstrel_ht_free_sta,
	.alloc = minstrel_ht_alloc,
	.free = minstrel_ht_free,
#ifdef CONFIG_MAC80211_DEBUGFS
	.add_sta_debugfs = minstrel_ht_add_sta_debugfs,
	.remove_sta_debugfs = minstrel_ht_remove_sta_debugfs,
#endif
};


static void
init_sample_table(void)
{
	int col, i, new_idx;
	u8 rnd[MCS_GROUP_RATES];

	memset(sample_table, 0xff, sizeof(sample_table));
	for (col = 0; col < SAMPLE_COLUMNS; col++) {
		for (i = 0; i < MCS_GROUP_RATES; i++) {
			get_random_bytes(rnd, sizeof(rnd));
			new_idx = (i + rnd[i]) % MCS_GROUP_RATES;

			while (sample_table[col][new_idx] != 0xff)
				new_idx = (new_idx + 1) % MCS_GROUP_RATES;

			sample_table[col][new_idx] = i;
		}
	}
}

int __init
rc80211_minstrel_ht_init(void)
{
	init_sample_table();
	return ieee80211_rate_control_register(&mac80211_minstrel_ht);
}

void
rc80211_minstrel_ht_exit(void)
{
	ieee80211_rate_control_unregister(&mac80211_minstrel_ht);
}