mac80211: add the 'minstrel' rate control algorithm

	  mac80211 that uses a PID controller to select the TX

	  rate.

config MAC80211_RC_MINSTREL

	bool "Minstrel"

	---help---

	  This option enables the 'minstrel' TX rate control algorithm

choice

	prompt "Default rate control algorithm"

	default MAC80211_RC_DEFAULT_PID

	  default rate control algorithm. You should choose

	  this unless you know what you are doing.

config MAC80211_RC_DEFAULT_MINSTREL

	bool "Minstrel"

	depends on MAC80211_RC_MINSTREL

	---help---

	  Select Minstrel as the default rate control algorithm.

endchoice

config MAC80211_RC_DEFAULT

	string

	default "pid" if MAC80211_RC_DEFAULT_PID

	default "minstrel" if MAC80211_RC_DEFAULT_MINSTREL

	default ""

endmenu

rc80211_pid-y := rc80211_pid_algo.o

rc80211_pid-$(CONFIG_MAC80211_DEBUGFS) += rc80211_pid_debugfs.o

rc80211_minstrel-y := rc80211_minstrel.o

rc80211_minstrel-$(CONFIG_MAC80211_DEBUGFS) += rc80211_minstrel_debugfs.o

mac80211-$(CONFIG_MAC80211_RC_PID) += $(rc80211_pid-y)

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

	BUILD_BUG_ON(offsetof(struct ieee80211_tx_info, driver_data) +

	             IEEE80211_TX_INFO_DRIVER_DATA_SIZE > sizeof(skb->cb));

	ret = rc80211_minstrel_init();

	if (ret)

		return ret;

	ret = rc80211_pid_init();

	if (ret)

		return ret;

static void __exit ieee80211_exit(void)

{

	rc80211_pid_exit();

	rc80211_minstrel_exit();

	/*

	 * For key todo, it'll be empty by now but the work

}

#endif

#ifdef CONFIG_MAC80211_RC_MINSTREL

extern int rc80211_minstrel_init(void);

extern void rc80211_minstrel_exit(void);

#else

static inline int rc80211_minstrel_init(void)

{

	return 0;

}

static inline void rc80211_minstrel_exit(void)

{

}

#endif

#endif /* IEEE80211_RATE_H */

/*

 * 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 <net/mac80211.h>

#include "rate.h"

#include "rc80211_minstrel.h"

#define SAMPLE_COLUMNS	10

#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;

	WARN_ON(mi->r[i].rix != rix);

	return i;

}

static inline bool

use_low_rate(struct sk_buff *skb)

{

	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;

	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

	u16 fc;

	fc = le16_to_cpu(hdr->frame_control);

	return ((info->flags & IEEE80211_TX_CTL_NO_ACK) ||

		(fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA ||

		is_multicast_ether_addr(hdr->addr1));

}

static void

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

{

	u32 max_tp = 0, index_max_tp = 0, index_max_tp2 = 0;

	u32 max_prob = 0, index_max_prob = 0;

	u32 usecs;

	u32 p;

	int i;

	mi->stats_update = jiffies;

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

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

		usecs = mr->perfect_tx_time;

		if (!usecs)

			usecs = 1000000;

		/* To avoid rounding issues, probabilities scale from 0 (0%)

		 * to 18000 (100%) */

		if (mr->attempts) {

			p = (mr->success * 18000) / mr->attempts;

			mr->succ_hist += mr->success;

			mr->att_hist += mr->attempts;

			mr->cur_prob = p;

			p = ((p * (100 - mp->ewma_level)) + (mr->probability *

				mp->ewma_level)) / 100;

			mr->probability = p;

			mr->cur_tp = p * (1000000 / usecs);

		}

		mr->last_success = mr->success;

		mr->last_attempts = mr->attempts;

		mr->success = 0;

		mr->attempts = 0;

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

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

		if ((mr->probability > 17100) || (mr->probability < 1800)) {

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

			if (mr->adjusted_retry_count > 2)

				mr->adjusted_retry_count = 2;

		} else {

			mr->adjusted_retry_count = mr->retry_count;

		}

		if (!mr->adjusted_retry_count)

			mr->adjusted_retry_count = 2;

	}

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

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

		if (max_tp < mr->cur_tp) {

			index_max_tp = i;

			max_tp = mr->cur_tp;

		}

		if (max_prob < mr->probability) {

			index_max_prob = i;

			max_prob = mr->probability;

		}

	}

	max_tp = 0;

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

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

		if (i == index_max_tp)

			continue;

		if (max_tp < mr->cur_tp) {

			index_max_tp2 = i;

			max_tp = mr->cur_tp;

		}

	}

	mi->max_tp_rate = index_max_tp;

	mi->max_tp_rate2 = index_max_tp2;

	mi->max_prob_rate = index_max_prob;

}

static void

minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,

                   struct ieee80211_sta *sta, void *priv_sta,

		   struct sk_buff *skb)

{

	struct minstrel_sta_info *mi = priv_sta;

	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

	struct ieee80211_tx_altrate *ar = info->status.retries;

	struct minstrel_priv *mp = priv;

	int i, ndx, tries;

	int success = 0;

	if (!info->status.excessive_retries)

		success = 1;

	if (!mp->has_mrr || (ar[0].rate_idx < 0)) {

		ndx = rix_to_ndx(mi, info->tx_rate_idx);

		tries = info->status.retry_count + 1;

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

		mi->r[ndx].attempts += tries;

		return;

	}

	for (i = 0; i < 4; i++) {

		if (ar[i].rate_idx < 0)

			break;

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

		mi->r[ndx].attempts += ar[i].limit + 1;

		if ((i != 3) && (ar[i + 1].rate_idx < 0))

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

	}

	if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))

		mi->sample_count++;

	if (mi->sample_deferred > 0)

		mi->sample_deferred--;

}

static inline unsigned int

minstrel_get_retry_count(struct minstrel_rate *mr,

                         struct ieee80211_tx_info *info)

{

	unsigned int retry = mr->adjusted_retry_count;

	if (info->flags & IEEE80211_TX_CTL_USE_RTS_CTS)

		retry = max(2U, min(mr->retry_count_rtscts, retry));

	else if (info->flags & IEEE80211_TX_CTL_USE_CTS_PROTECT)

		retry = max(2U, 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_idx, mi->sample_column);

	mi->sample_idx++;

	if (mi->sample_idx > (mi->n_rates - 2)) {

		mi->sample_idx = 0;

		mi->sample_column++;

		if (mi->sample_column >= SAMPLE_COLUMNS)

			mi->sample_column = 0;

	}

	return sample_ndx;

}

void

minstrel_get_rate(void *priv, struct ieee80211_supported_band *sband,

                  struct ieee80211_sta *sta, void *priv_sta,

                  struct sk_buff *skb, struct rate_selection *sel)

{

	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);

	struct minstrel_sta_info *mi = priv_sta;

	struct minstrel_priv *mp = priv;

	struct ieee80211_tx_altrate *ar = info->control.retries;

	unsigned int ndx, sample_ndx = 0;

	bool mrr;

	bool sample_slower = false;

	bool sample = false;

	int i, delta;

	int mrr_ndx[3];

	int sample_rate;

	if (!sta || !mi || use_low_rate(skb)) {

		sel->rate_idx = rate_lowest_index(sband, sta);

		return;

	}

	mrr = mp->has_mrr;

	/* mac80211 does not allow mrr for RTS/CTS */

	if ((info->flags & IEEE80211_TX_CTL_USE_RTS_CTS) ||

	    (info->flags & IEEE80211_TX_CTL_USE_CTS_PROTECT))

		mrr = false;

	if (time_after(jiffies, mi->stats_update + (mp->update_interval *

			HZ) / 1000))

		minstrel_update_stats(mp, mi);

	ndx = mi->max_tp_rate;

	if (mrr)

		sample_rate = mp->lookaround_rate_mrr;

	else

		sample_rate = mp->lookaround_rate;

	mi->packet_count++;

	delta = (mi->packet_count * sample_rate / 100) -

			(mi->sample_count + mi->sample_deferred / 2);

	/* delta > 0: sampling required */

	if (delta > 0) {

		if (mi->packet_count >= 10000) {

			mi->sample_deferred = 0;

			mi->sample_count = 0;

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

		}

		sample_ndx = minstrel_get_next_sample(mi);

		sample = true;

		sample_slower = mrr && (mi->r[sample_ndx].perfect_tx_time >

			mi->r[ndx].perfect_tx_time);

		if (!sample_slower) {

			ndx = sample_ndx;

			mi->sample_count++;

		} else {

			/* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark

			 * packets that have the sampling rate deferred to the

			 * second MRR stage. Increase the sample counter only

			 * if the deferred sample rate was actually used.

			 * Use the sample_deferred counter to make sure that

			 * the sampling is not done in large bursts */

			info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;

			mi->sample_deferred++;

		}

	}

	sel->rate_idx = mi->r[ndx].rix;

	info->control.retry_limit = minstrel_get_retry_count(&mi->r[ndx], info);

	if (!mrr) {

		ar[0].rate_idx = mi->lowest_rix;

		ar[0].limit = mp->max_retry;

		ar[1].rate_idx = -1;

		return;

	}

	/* MRR setup */

	if (sample) {

		if (sample_slower)

			mrr_ndx[0] = sample_ndx;

		else

			mrr_ndx[0] = mi->max_tp_rate;

	} else {

		mrr_ndx[0] = mi->max_tp_rate2;

	}

	mrr_ndx[1] = mi->max_prob_rate;

	mrr_ndx[2] = 0;

	for (i = 0; i < 3; i++) {

		ar[i].rate_idx = mi->r[mrr_ndx[i]].rix;

		ar[i].limit = mi->r[mrr_ndx[i]].adjusted_retry_count;

	}

}

static void

calc_rate_durations(struct minstrel_sta_info *mi, struct ieee80211_local *local,

                    struct minstrel_rate *d, struct ieee80211_rate *rate)

{

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

	d->perfect_tx_time = ieee80211_frame_duration(local, 1200,

			rate->bitrate, erp, 1);

	d->ack_time = ieee80211_frame_duration(local, 10,

			rate->bitrate, erp, 1);

}

static void

init_sample_table(struct minstrel_sta_info *mi)

{

	unsigned int i, col, new_idx;

	unsigned int n_srates = mi->n_rates - 1;

	u8 rnd[8];

	mi->sample_column = 0;

	mi->sample_idx = 0;

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

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

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

			get_random_bytes(rnd, sizeof(rnd));

			new_idx = (i + rnd[i & 7]) % n_srates;

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

				new_idx = (new_idx + 1) % n_srates;

			/* Don't sample the slowest rate (i.e. slowest base

			 * rate). We must presume that the slowest rate works

			 * fine, or else other management frames will also be

			 * failing and the link will break */

			SAMPLE_TBL(mi, new_idx, col) = i + 1;

		}

	}

}

static void

minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,

               struct ieee80211_sta *sta, void *priv_sta)

{

	struct minstrel_sta_info *mi = priv_sta;

	struct minstrel_priv *mp = priv;

	struct minstrel_rate *mr_ctl;

	unsigned int i, n = 0;

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

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

	mr_ctl = &mi->r[rix_to_ndx(mi, mi->lowest_rix)];

	mi->sp_ack_dur = mr_ctl->ack_time;

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

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

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

		unsigned int tx_time_single;

		unsigned int cw = mp->cw_min;

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

			continue;

		n++;

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

		mr->rix = i;

		mr->bitrate = sband->bitrates[i].bitrate / 5;

		calc_rate_durations(mi, hw_to_local(mp->hw), mr,

				&sband->bitrates[i]);

		/* calculate maximum number of retransmissions before

		 * fallback (based on maximum segment size) */

		mr->retry_count = 1;

		mr->retry_count_cts = 1;

		mr->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 + min(cw, mp->cw_max);

			cw = (cw + 1) << 1;

			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) &&

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

				mr->retry_count_rtscts++;

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

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

		mr->adjusted_retry_count = mr->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->stats_update = jiffies;

	init_sample_table(mi);

}

static void *

minstrel_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)

{

	struct ieee80211_supported_band *sband;

	struct minstrel_sta_info *mi;

	struct minstrel_priv *mp = priv;

	struct ieee80211_hw *hw = mp->hw;

	int max_rates = 0;

	int i;

	mi = kzalloc(sizeof(struct minstrel_sta_info), gfp);

	if (!mi)

		return NULL;

	for (i = 0; i < IEEE80211_NUM_BANDS; i++) {

		sband = hw->wiphy->bands[hw->conf.channel->band];

		if (sband->n_bitrates > max_rates)

			max_rates = sband->n_bitrates;

	}

	mi->r = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);

	if (!mi->r)

		goto error;

	mi->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);

	if (!mi->sample_table)

		goto error1;

	mi->stats_update = jiffies;

	return mi;

error1:

	kfree(mi->r);

error:

	kfree(mi);

	return NULL;

}

static void

minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)

{

	struct minstrel_sta_info *mi = priv_sta;

	kfree(mi->sample_table);

	kfree(mi->r);

	kfree(mi);

}

static void

minstrel_clear(void *priv)

{

}

static void *

minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)

{

	struct minstrel_priv *mp;

	mp = kzalloc(sizeof(struct minstrel_priv), GFP_ATOMIC);

	if (!mp)

		return NULL;

	/* contention window settings

	 * Just an approximation. Using the per-queue values would complicate

	 * the calculations and is probably unnecessary */

	mp->cw_min = 15;

	mp->cw_max = 1023;

	/* number of packets (in %) to use for sampling other rates

	 * sample less often for non-mrr packets, because the overhead

	 * is much higher than with mrr */

	mp->lookaround_rate = 5;

	mp->lookaround_rate_mrr = 10;

	/* moving average weight for EWMA */

	mp->ewma_level = 75;

	/* maximum time that the hw is allowed to stay in one MRR segment */

	mp->segment_size = 6000;

	if (hw->max_altrate_tries > 0)

		mp->max_retry = hw->max_altrate_tries;

	else

		/* safe default, does not necessarily have to match hw properties */

		mp->max_retry = 7;

	if (hw->max_altrates >= 3)

		mp->has_mrr = true;

	mp->hw = hw;

	mp->update_interval = 100;

	return mp;

}

static void

minstrel_free(void *priv)

{

	kfree(priv);

}

static struct rate_control_ops mac80211_minstrel = {

	.name = "minstrel",

	.tx_status = minstrel_tx_status,

	.get_rate = minstrel_get_rate,

	.rate_init = minstrel_rate_init,

	.clear = minstrel_clear,

	.alloc = minstrel_alloc,

	.free = minstrel_free,

	.alloc_sta = minstrel_alloc_sta,

	.free_sta = minstrel_free_sta,

#ifdef CONFIG_MAC80211_DEBUGFS

	.add_sta_debugfs = minstrel_add_sta_debugfs,

	.remove_sta_debugfs = minstrel_remove_sta_debugfs,

#endif

};

int __init

rc80211_minstrel_init(void)

{

	return ieee80211_rate_control_register(&mac80211_minstrel);

}

void

rc80211_minstrel_exit(void)

{

	ieee80211_rate_control_unregister(&mac80211_minstrel);

}