mac80211: remove legacy minstrel rate control

CFLAGS_trace.o := -I$(src)

rc80211_minstrel-y := \

	rc80211_minstrel.o \

	rc80211_minstrel_ht.o

rc80211_minstrel-$(CONFIG_MAC80211_DEBUGFS) += \

	rc80211_minstrel_debugfs.o \

	rc80211_minstrel_ht_debugfs.o

mac80211-$(CONFIG_MAC80211_RC_MINSTREL) += $(rc80211_minstrel-y)

/*

 * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>

 *

 * 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.

 *

 * Based on minstrel.c:

 *   Copyright (C) 2005-2007 Derek Smithies <derek@indranet.co.nz>

 *   Sponsored by Indranet Technologies Ltd

 *

 * Based on sample.c:

 *   Copyright (c) 2005 John Bicket

 *   All rights reserved.

 *

 *   Redistribution and use in source and binary forms, with or without

 *   modification, are permitted provided that the following conditions

 *   are met:

 *   1. Redistributions of source code must retain the above copyright

 *      notice, this list of conditions and the following disclaimer,

 *      without modification.

 *   2. Redistributions in binary form must reproduce at minimum a disclaimer

 *      similar to the "NO WARRANTY" disclaimer below ("Disclaimer") and any

 *      redistribution must be conditioned upon including a substantially

 *      similar Disclaimer requirement for further binary redistribution.

 *   3. Neither the names of the above-listed copyright holders nor the names

 *      of any contributors may be used to endorse or promote products derived

 *      from this software without specific prior written permission.

 *

 *   Alternatively, this software may be distributed under the terms of the

 *   GNU General Public License ("GPL") version 2 as published by the Free

 *   Software Foundation.

 *

 *   NO WARRANTY

 *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 *   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 *   LIMITED TO, THE IMPLIED WARRANTIES OF NONINFRINGEMENT, MERCHANTIBILITY

 *   AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL

 *   THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY,

 *   OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

 *   SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

 *   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER

 *   IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 *   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF

 *   THE POSSIBILITY OF SUCH DAMAGES.

 */

#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 <linux/slab.h>

#include <net/mac80211.h>

#include "rate.h"

#include "rc80211_minstrel.h"

#define SAMPLE_TBL(_mi, _idx, _col) \

		_mi->sample_table[(_idx * SAMPLE_COLUMNS) + _col]

/* convert mac80211 rate index to local array index */

static inline int

rix_to_ndx(struct minstrel_sta_info *mi, int rix)

{

	int i = rix;

	for (i = rix; i >= 0; i--)

		if (mi->r[i].rix == rix)

			break;

	return i;

}

/* return current EMWA throughput */

int minstrel_get_tp_avg(struct minstrel_rate *mr, int prob_avg)

{

	int usecs;

	usecs = mr->perfect_tx_time;

	if (!usecs)

		usecs = 1000000;

	/* reset thr. below 10% success */

	if (mr->stats.prob_avg < MINSTREL_FRAC(10, 100))

		return 0;

	if (prob_avg > MINSTREL_FRAC(90, 100))

		return MINSTREL_TRUNC(100000 * (MINSTREL_FRAC(90, 100) / usecs));

	else

		return MINSTREL_TRUNC(100000 * (prob_avg / usecs));

}

/* find & sort topmost throughput rates */

static inline void

minstrel_sort_best_tp_rates(struct minstrel_sta_info *mi, int i, u8 *tp_list)

{

	int j;

	struct minstrel_rate_stats *tmp_mrs;

	struct minstrel_rate_stats *cur_mrs = &mi->r[i].stats;

	for (j = MAX_THR_RATES; j > 0; --j) {

		tmp_mrs = &mi->r[tp_list[j - 1]].stats;

		if (minstrel_get_tp_avg(&mi->r[i], cur_mrs->prob_avg) <=

		    minstrel_get_tp_avg(&mi->r[tp_list[j - 1]], tmp_mrs->prob_avg))

			break;

	}

	if (j < MAX_THR_RATES - 1)

		memmove(&tp_list[j + 1], &tp_list[j], MAX_THR_RATES - (j + 1));

	if (j < MAX_THR_RATES)

		tp_list[j] = i;

}

static void

minstrel_set_rate(struct minstrel_sta_info *mi, struct ieee80211_sta_rates *ratetbl,

		  int offset, int idx)

{

	struct minstrel_rate *r = &mi->r[idx];

	ratetbl->rate[offset].idx = r->rix;

	ratetbl->rate[offset].count = r->adjusted_retry_count;

	ratetbl->rate[offset].count_cts = r->retry_count_cts;

	ratetbl->rate[offset].count_rts = r->stats.retry_count_rtscts;

}

static void

minstrel_update_rates(struct minstrel_priv *mp, struct minstrel_sta_info *mi)

{

	struct ieee80211_sta_rates *ratetbl;

	int i = 0;

	ratetbl = kzalloc(sizeof(*ratetbl), GFP_ATOMIC);

	if (!ratetbl)

		return;

	/* Start with max_tp_rate */

	minstrel_set_rate(mi, ratetbl, i++, mi->max_tp_rate[0]);

	if (mp->hw->max_rates >= 3) {

		/* At least 3 tx rates supported, use max_tp_rate2 next */

		minstrel_set_rate(mi, ratetbl, i++, mi->max_tp_rate[1]);

	}

	if (mp->hw->max_rates >= 2) {

		/* At least 2 tx rates supported, use max_prob_rate next */

		minstrel_set_rate(mi, ratetbl, i++, mi->max_prob_rate);

	}

	/* Use lowest rate last */

	ratetbl->rate[i].idx = mi->lowest_rix;

	ratetbl->rate[i].count = mp->max_retry;

	ratetbl->rate[i].count_cts = mp->max_retry;

	ratetbl->rate[i].count_rts = mp->max_retry;

	rate_control_set_rates(mp->hw, mi->sta, ratetbl);

}

/*

* Recalculate statistics and counters of a given rate

*/

void

minstrel_calc_rate_stats(struct minstrel_priv *mp,

			 struct minstrel_rate_stats *mrs)

{

	unsigned int cur_prob;

	if (unlikely(mrs->attempts > 0)) {

		mrs->sample_skipped = 0;

		cur_prob = MINSTREL_FRAC(mrs->success, mrs->attempts);

		if (mp->new_avg) {

			minstrel_filter_avg_add(&mrs->prob_avg,

						&mrs->prob_avg_1, cur_prob);

		} else if (unlikely(!mrs->att_hist)) {

			mrs->prob_avg = cur_prob;

		} else {

			/*update exponential weighted moving avarage */

			mrs->prob_avg = minstrel_ewma(mrs->prob_avg,

						      cur_prob,

						      EWMA_LEVEL);

		}

		mrs->att_hist += mrs->attempts;

		mrs->succ_hist += mrs->success;

	} else {

		mrs->sample_skipped++;

	}

	mrs->last_success = mrs->success;

	mrs->last_attempts = mrs->attempts;

	mrs->success = 0;

	mrs->attempts = 0;

}

static void

minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)

{

	u8 tmp_tp_rate[MAX_THR_RATES];

	u8 tmp_prob_rate = 0;

	int i, tmp_cur_tp, tmp_prob_tp;

	for (i = 0; i < MAX_THR_RATES; i++)

	    tmp_tp_rate[i] = 0;

	for (i = 0; i < mi->n_rates; i++) {

		struct minstrel_rate *mr = &mi->r[i];

		struct minstrel_rate_stats *mrs = &mi->r[i].stats;

		struct minstrel_rate_stats *tmp_mrs = &mi->r[tmp_prob_rate].stats;

		/* Update statistics of success probability per rate */

		minstrel_calc_rate_stats(mp, mrs);

		/* Sample less often below the 10% chance of success.

		 * Sample less often above the 95% chance of success. */

		if (mrs->prob_avg > MINSTREL_FRAC(95, 100) ||

		    mrs->prob_avg < MINSTREL_FRAC(10, 100)) {

			mr->adjusted_retry_count = mrs->retry_count >> 1;

			if (mr->adjusted_retry_count > 2)

				mr->adjusted_retry_count = 2;

			mr->sample_limit = 4;

		} else {

			mr->sample_limit = -1;

			mr->adjusted_retry_count = mrs->retry_count;

		}

		if (!mr->adjusted_retry_count)

			mr->adjusted_retry_count = 2;

		minstrel_sort_best_tp_rates(mi, i, tmp_tp_rate);

		/* To determine the most robust rate (max_prob_rate) used at

		 * 3rd mmr stage we distinct between two cases:

		 * (1) if any success probabilitiy >= 95%, out of those rates

		 * choose the maximum throughput rate as max_prob_rate

		 * (2) if all success probabilities < 95%, the rate with

		 * highest success probability is chosen as max_prob_rate */

		if (mrs->prob_avg >= MINSTREL_FRAC(95, 100)) {

			tmp_cur_tp = minstrel_get_tp_avg(mr, mrs->prob_avg);

			tmp_prob_tp = minstrel_get_tp_avg(&mi->r[tmp_prob_rate],

							  tmp_mrs->prob_avg);

			if (tmp_cur_tp >= tmp_prob_tp)

				tmp_prob_rate = i;

		} else {

			if (mrs->prob_avg >= tmp_mrs->prob_avg)

				tmp_prob_rate = i;

		}

	}

	/* Assign the new rate set */

	memcpy(mi->max_tp_rate, tmp_tp_rate, sizeof(mi->max_tp_rate));

	mi->max_prob_rate = tmp_prob_rate;

#ifdef CONFIG_MAC80211_DEBUGFS

	/* use fixed index if set */

	if (mp->fixed_rate_idx != -1) {

		mi->max_tp_rate[0] = mp->fixed_rate_idx;

		mi->max_tp_rate[1] = mp->fixed_rate_idx;

		mi->max_prob_rate = mp->fixed_rate_idx;

	}

#endif

	/* Reset update timer */

	mi->last_stats_update = jiffies;

	minstrel_update_rates(mp, mi);

}

static void

minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,

		   void *priv_sta, struct ieee80211_tx_status *st)

{

	struct ieee80211_tx_info *info = st->info;

	struct minstrel_priv *mp = priv;

	struct minstrel_sta_info *mi = priv_sta;

	struct ieee80211_tx_rate *ar = info->status.rates;

	int i, ndx;

	int success;

	success = !!(info->flags & IEEE80211_TX_STAT_ACK);

	for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {

		if (ar[i].idx < 0 || !ar[i].count)

			break;

		ndx = rix_to_ndx(mi, ar[i].idx);

		if (ndx < 0)

			continue;

		mi->r[ndx].stats.attempts += ar[i].count;

		if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))

			mi->r[ndx].stats.success += success;

	}

	if (time_after(jiffies, mi->last_stats_update +

				mp->update_interval / (mp->new_avg ? 2 : 1)))

		minstrel_update_stats(mp, mi);

}

static inline unsigned int

minstrel_get_retry_count(struct minstrel_rate *mr,

			 struct ieee80211_tx_info *info)

{

	u8 retry = mr->adjusted_retry_count;

	if (info->control.use_rts)

		retry = max_t(u8, 2, min(mr->stats.retry_count_rtscts, retry));

	else if (info->control.use_cts_prot)

		retry = max_t(u8, 2, min(mr->retry_count_cts, retry));

	return retry;

}

static int

minstrel_get_next_sample(struct minstrel_sta_info *mi)

{

	unsigned int sample_ndx;

	sample_ndx = SAMPLE_TBL(mi, mi->sample_row, mi->sample_column);

	mi->sample_row++;

	if ((int) mi->sample_row >= mi->n_rates) {

		mi->sample_row = 0;

		mi->sample_column++;

		if (mi->sample_column >= SAMPLE_COLUMNS)

			mi->sample_column = 0;

	}

	return sample_ndx;

}

static void

minstrel_get_rate(void *priv, struct ieee80211_sta *sta,

		  void *priv_sta, struct ieee80211_tx_rate_control *txrc)

{

	struct sk_buff *skb = txrc->skb;

	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

	struct minstrel_sta_info *mi = priv_sta;

	struct minstrel_priv *mp = priv;

	struct ieee80211_tx_rate *rate = &info->control.rates[0];

	struct minstrel_rate *msr, *mr;

	unsigned int ndx;

	bool mrr_capable;

	bool prev_sample;

	int delta;

	int sampling_ratio;

	/* check multi-rate-retry capabilities & adjust lookaround_rate */

	mrr_capable = mp->has_mrr &&

		      !txrc->rts &&

		      !txrc->bss_conf->use_cts_prot;

	if (mrr_capable)

		sampling_ratio = mp->lookaround_rate_mrr;

	else

		sampling_ratio = mp->lookaround_rate;

	/* increase sum packet counter */

	mi->total_packets++;

#ifdef CONFIG_MAC80211_DEBUGFS

	if (mp->fixed_rate_idx != -1)

		return;

#endif

	/* Don't use EAPOL frames for sampling on non-mrr hw */

	if (mp->hw->max_rates == 1 &&

	    (info->control.flags & IEEE80211_TX_CTRL_PORT_CTRL_PROTO))

		return;

	delta = (mi->total_packets * sampling_ratio / 100) -

			mi->sample_packets;

	/* delta < 0: no sampling required */

	prev_sample = mi->prev_sample;

	mi->prev_sample = false;

	if (delta < 0 || (!mrr_capable && prev_sample))

		return;

	if (mi->total_packets >= 10000) {

		mi->sample_packets = 0;

		mi->total_packets = 0;

	} else if (delta > mi->n_rates * 2) {

		/* With multi-rate retry, not every planned sample

		 * attempt actually gets used, due to the way the retry

		 * chain is set up - [max_tp,sample,prob,lowest] for

		 * sample_rate < max_tp.

		 *

		 * If there's too much sampling backlog and the link

		 * starts getting worse, minstrel would start bursting

		 * out lots of sampling frames, which would result

		 * in a large throughput loss. */

		mi->sample_packets += (delta - mi->n_rates * 2);

	}

	/* get next random rate sample */

	ndx = minstrel_get_next_sample(mi);

	msr = &mi->r[ndx];

	mr = &mi->r[mi->max_tp_rate[0]];

	/* Decide if direct ( 1st mrr stage) or indirect (2nd mrr stage)

	 * rate sampling method should be used.

	 * Respect such rates that are not sampled for 20 interations.

	 */

	if (msr->perfect_tx_time < mr->perfect_tx_time ||

	    msr->stats.sample_skipped >= 20) {

		if (!msr->sample_limit)

			return;

		mi->sample_packets++;

		if (msr->sample_limit > 0)

			msr->sample_limit--;

	}

	/* If we're not using MRR and the sampling rate already

	 * has a probability of >95%, we shouldn't be attempting

	 * to use it, as this only wastes precious airtime */

	if (!mrr_capable &&

	   (mi->r[ndx].stats.prob_avg > MINSTREL_FRAC(95, 100)))

		return;

	mi->prev_sample = true;

	rate->idx = mi->r[ndx].rix;

	rate->count = minstrel_get_retry_count(&mi->r[ndx], info);

	info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;

}

static void

calc_rate_durations(enum nl80211_band band,

		    struct minstrel_rate *d,

		    struct ieee80211_rate *rate,

		    struct cfg80211_chan_def *chandef)

{

	int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);

	int shift = ieee80211_chandef_get_shift(chandef);

	d->perfect_tx_time = ieee80211_frame_duration(band, 1200,

			DIV_ROUND_UP(rate->bitrate, 1 << shift), erp, 1,

			shift);

	d->ack_time = ieee80211_frame_duration(band, 10,

			DIV_ROUND_UP(rate->bitrate, 1 << shift), erp, 1,

			shift);

}

static void

init_sample_table(struct minstrel_sta_info *mi)

{

	unsigned int i, col, new_idx;

	u8 rnd[8];

	mi->sample_column = 0;

	mi->sample_row = 0;

	memset(mi->sample_table, 0xff, SAMPLE_COLUMNS * mi->n_rates);

	for (col = 0; col < SAMPLE_COLUMNS; col++) {

		prandom_bytes(rnd, sizeof(rnd));

		for (i = 0; i < mi->n_rates; i++) {

			new_idx = (i + rnd[i & 7]) % mi->n_rates;

			while (SAMPLE_TBL(mi, new_idx, col) != 0xff)

				new_idx = (new_idx + 1) % mi->n_rates;

			SAMPLE_TBL(mi, new_idx, col) = i;

		}

	}

}

static void

minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,

		   struct cfg80211_chan_def *chandef,

		   struct ieee80211_sta *sta, void *priv_sta)

{

	struct minstrel_sta_info *mi = priv_sta;

	struct minstrel_priv *mp = priv;

	struct ieee80211_rate *ctl_rate;

	unsigned int i, n = 0;

	unsigned int t_slot = 9; /* FIXME: get real slot time */

	u32 rate_flags;

	mi->sta = sta;

	mi->lowest_rix = rate_lowest_index(sband, sta);

	ctl_rate = &sband->bitrates[mi->lowest_rix];

	mi->sp_ack_dur = ieee80211_frame_duration(sband->band, 10,

				ctl_rate->bitrate,

				!!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1,

				ieee80211_chandef_get_shift(chandef));

	rate_flags = ieee80211_chandef_rate_flags(&mp->hw->conf.chandef);

	memset(mi->max_tp_rate, 0, sizeof(mi->max_tp_rate));

	mi->max_prob_rate = 0;

	for (i = 0; i < sband->n_bitrates; i++) {

		struct minstrel_rate *mr = &mi->r[n];

		struct minstrel_rate_stats *mrs = &mi->r[n].stats;

		unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;

		unsigned int tx_time_single;

		unsigned int cw = mp->cw_min;

		int shift;

		if (!rate_supported(sta, sband->band, i))

			continue;

		if ((rate_flags & sband->bitrates[i].flags) != rate_flags)

			continue;

		n++;

		memset(mr, 0, sizeof(*mr));

		memset(mrs, 0, sizeof(*mrs));

		mr->rix = i;

		shift = ieee80211_chandef_get_shift(chandef);

		mr->bitrate = DIV_ROUND_UP(sband->bitrates[i].bitrate,

					   (1 << shift) * 5);

		calc_rate_durations(sband->band, mr, &sband->bitrates[i],

				    chandef);

		/* calculate maximum number of retransmissions before

		 * fallback (based on maximum segment size) */

		mr->sample_limit = -1;

		mrs->retry_count = 1;

		mr->retry_count_cts = 1;

		mrs->retry_count_rtscts = 1;

		tx_time = mr->perfect_tx_time + mi->sp_ack_dur;

		do {

			/* add one retransmission */

			tx_time_single = mr->ack_time + mr->perfect_tx_time;

			/* contention window */

			tx_time_single += (t_slot * cw) >> 1;

			cw = min((cw << 1) | 1, mp->cw_max);

			tx_time += tx_time_single;

			tx_time_cts += tx_time_single + mi->sp_ack_dur;

			tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;

			if ((tx_time_cts < mp->segment_size) &&

				(mr->retry_count_cts < mp->max_retry))

				mr->retry_count_cts++;

			if ((tx_time_rtscts < mp->segment_size) &&

				(mrs->retry_count_rtscts < mp->max_retry))

				mrs->retry_count_rtscts++;

		} while ((tx_time < mp->segment_size) &&

				(++mr->stats.retry_count < mp->max_retry));

		mr->adjusted_retry_count = mrs->retry_count;

		if (!(sband->bitrates[i].flags & IEEE80211_RATE_ERP_G))

			mr->retry_count_cts = mrs->retry_count;

	}

	for (i = n; i < sband->n_bitrates; i++) {

		struct minstrel_rate *mr = &mi->r[i];

		mr->rix = -1;

	}

	mi->n_rates = n;

	mi->last_stats_update = jiffies;

	init_sample_table(mi);

	minstrel_update_rates(mp, mi);

}

static u32 minstrel_get_expected_throughput(void *priv_sta)

{

	struct minstrel_sta_info *mi = priv_sta;

	struct minstrel_rate_stats *tmp_mrs;

	int idx = mi->max_tp_rate[0];

	int tmp_cur_tp;

	/* convert pkt per sec in kbps (1200 is the average pkt size used for

	 * computing cur_tp

	 */

	tmp_mrs = &mi->r[idx].stats;

	tmp_cur_tp = minstrel_get_tp_avg(&mi->r[idx], tmp_mrs->prob_avg) * 10;

	tmp_cur_tp = tmp_cur_tp * 1200 * 8 / 1024;

	return tmp_cur_tp;

}

const struct rate_control_ops mac80211_minstrel = {

	.tx_status_ext = minstrel_tx_status,

	.get_rate = minstrel_get_rate,

	.rate_init = minstrel_rate_init,

	.get_expected_throughput = minstrel_get_expected_throughput,

};

/* SPDX-License-Identifier: GPL-2.0-only */

/*

 * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>

 */

#ifndef __RC_MINSTREL_H

#define __RC_MINSTREL_H

#define EWMA_LEVEL	96	/* ewma weighting factor [/EWMA_DIV] */

#define EWMA_DIV	128

#define SAMPLE_COLUMNS	10	/* number of columns in sample table */

/* scaled fraction values */

#define MINSTREL_SCALE  12

#define MINSTREL_FRAC(val, div) (((val) << MINSTREL_SCALE) / div)

#define MINSTREL_TRUNC(val) ((val) >> MINSTREL_SCALE)

/* number of highest throughput rates to consider*/

#define MAX_THR_RATES 4

/*

 * Coefficients for moving average with noise filter (period=16),

 * scaled by 10 bits

 *

 * a1 = exp(-pi * sqrt(2) / period)

 * coeff2 = 2 * a1 * cos(sqrt(2) * 2 * pi / period)

 * coeff3 = -sqr(a1)

 * coeff1 = 1 - coeff2 - coeff3

 */

#define MINSTREL_AVG_COEFF1		(MINSTREL_FRAC(1, 1) - \

					 MINSTREL_AVG_COEFF2 - \

					 MINSTREL_AVG_COEFF3)

#define MINSTREL_AVG_COEFF2		0x00001499

#define MINSTREL_AVG_COEFF3		-0x0000092e

/*

 * Perform EWMA (Exponentially Weighted Moving Average) calculation

 */

static inline int

minstrel_ewma(int old, int new, int weight)

{

	int diff, incr;

	diff = new - old;

	incr = (EWMA_DIV - weight) * diff / EWMA_DIV;

	return old + incr;

}

static inline int minstrel_filter_avg_add(u16 *prev_1, u16 *prev_2, s32 in)

{

	s32 out_1 = *prev_1;

	s32 out_2 = *prev_2;

	s32 val;

	if (!in)

		in += 1;

	if (!out_1) {

		val = out_1 = in;

		goto out;

	}

	val = MINSTREL_AVG_COEFF1 * in;

	val += MINSTREL_AVG_COEFF2 * out_1;

	val += MINSTREL_AVG_COEFF3 * out_2;

	val >>= MINSTREL_SCALE;

	if (val > 1 << MINSTREL_SCALE)

		val = 1 << MINSTREL_SCALE;

	if (val < 0)

		val = 1;

out:

	*prev_2 = out_1;

	*prev_1 = val;

	return val;

}

struct minstrel_rate_stats {

	/* current / last sampling period attempts/success counters */

	u16 attempts, last_attempts;

	u16 success, last_success;