2 * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
9 * Copyright (C) 2005-2007 Derek Smithies <derek@indranet.co.nz>
10 * Sponsored by Indranet Technologies Ltd
13 * Copyright (c) 2005 John Bicket
14 * All rights reserved.
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
19 * 1. Redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer,
21 * without modification.
22 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
23 * similar to the "NO WARRANTY" disclaimer below ("Disclaimer") and any
24 * redistribution must be conditioned upon including a substantially
25 * similar Disclaimer requirement for further binary redistribution.
26 * 3. Neither the names of the above-listed copyright holders nor the names
27 * of any contributors may be used to endorse or promote products derived
28 * from this software without specific prior written permission.
30 * Alternatively, this software may be distributed under the terms of the
31 * GNU General Public License ("GPL") version 2 as published by the Free
32 * Software Foundation.
35 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
36 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
37 * LIMITED TO, THE IMPLIED WARRANTIES OF NONINFRINGEMENT, MERCHANTIBILITY
38 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
39 * THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY,
40 * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
41 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
42 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
43 * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
44 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
45 * THE POSSIBILITY OF SUCH DAMAGES.
47 #include <linux/netdevice.h>
48 #include <linux/types.h>
49 #include <linux/skbuff.h>
50 #include <linux/debugfs.h>
51 #include <linux/random.h>
52 #include <linux/ieee80211.h>
53 #include <linux/slab.h>
54 #include <net/mac80211.h>
56 #include "rc80211_minstrel.h"
58 #define SAMPLE_TBL(_mi, _idx, _col) \
59 _mi->sample_table[(_idx * SAMPLE_COLUMNS) + _col]
61 /* convert mac80211 rate index to local array index */
63 rix_to_ndx(struct minstrel_sta_info *mi, int rix)
66 for (i = rix; i >= 0; i--)
67 if (mi->r[i].rix == rix)
72 /* find & sort topmost throughput rates */
74 minstrel_sort_best_tp_rates(struct minstrel_sta_info *mi, int i, u8 *tp_list)
76 int j = MAX_THR_RATES;
78 while (j > 0 && mi->r[i].cur_tp > mi->r[tp_list[j - 1]].cur_tp)
80 if (j < MAX_THR_RATES - 1)
81 memmove(&tp_list[j + 1], &tp_list[j], MAX_THR_RATES - (j + 1));
82 if (j < MAX_THR_RATES)
87 minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
89 u8 tmp_tp_rate[MAX_THR_RATES];
94 for (i=0; i < MAX_THR_RATES; i++)
97 for (i = 0; i < mi->n_rates; i++) {
98 struct minstrel_rate *mr = &mi->r[i];
100 usecs = mr->perfect_tx_time;
104 if (unlikely(mr->attempts > 0)) {
105 mr->sample_skipped = 0;
106 mr->cur_prob = MINSTREL_FRAC(mr->success, mr->attempts);
107 mr->succ_hist += mr->success;
108 mr->att_hist += mr->attempts;
109 mr->probability = minstrel_ewma(mr->probability,
113 mr->sample_skipped++;
115 mr->last_success = mr->success;
116 mr->last_attempts = mr->attempts;
120 /* Update throughput per rate, reset thr. below 10% success */
121 if (mr->probability < MINSTREL_FRAC(10, 100))
124 mr->cur_tp = mr->probability * (1000000 / usecs);
126 /* Sample less often below the 10% chance of success.
127 * Sample less often above the 95% chance of success. */
128 if (mr->probability > MINSTREL_FRAC(95, 100) ||
129 mr->probability < MINSTREL_FRAC(10, 100)) {
130 mr->adjusted_retry_count = mr->retry_count >> 1;
131 if (mr->adjusted_retry_count > 2)
132 mr->adjusted_retry_count = 2;
133 mr->sample_limit = 4;
135 mr->sample_limit = -1;
136 mr->adjusted_retry_count = mr->retry_count;
138 if (!mr->adjusted_retry_count)
139 mr->adjusted_retry_count = 2;
141 minstrel_sort_best_tp_rates(mi, i, tmp_tp_rate);
143 /* To determine the most robust rate (max_prob_rate) used at
144 * 3rd mmr stage we distinct between two cases:
145 * (1) if any success probabilitiy >= 95%, out of those rates
146 * choose the maximum throughput rate as max_prob_rate
147 * (2) if all success probabilities < 95%, the rate with
148 * highest success probability is choosen as max_prob_rate */
149 if (mr->probability >= MINSTREL_FRAC(95,100)) {
150 if (mr->cur_tp >= mi->r[tmp_prob_rate].cur_tp)
153 if (mr->probability >= mi->r[tmp_prob_rate].probability)
158 /* Assign the new rate set */
159 memcpy(mi->max_tp_rate, tmp_tp_rate, sizeof(mi->max_tp_rate));
160 mi->max_prob_rate = tmp_prob_rate;
162 /* Reset update timer */
163 mi->stats_update = jiffies;
167 minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
168 struct ieee80211_sta *sta, void *priv_sta,
171 struct minstrel_priv *mp = priv;
172 struct minstrel_sta_info *mi = priv_sta;
173 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
174 struct ieee80211_tx_rate *ar = info->status.rates;
178 success = !!(info->flags & IEEE80211_TX_STAT_ACK);
180 for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
184 ndx = rix_to_ndx(mi, ar[i].idx);
188 mi->r[ndx].attempts += ar[i].count;
190 if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
191 mi->r[ndx].success += success;
194 if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
197 if (mi->sample_deferred > 0)
198 mi->sample_deferred--;
200 if (time_after(jiffies, mi->stats_update +
201 (mp->update_interval * HZ) / 1000))
202 minstrel_update_stats(mp, mi);
206 static inline unsigned int
207 minstrel_get_retry_count(struct minstrel_rate *mr,
208 struct ieee80211_tx_info *info)
210 unsigned int retry = mr->adjusted_retry_count;
212 if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS)
213 retry = max(2U, min(mr->retry_count_rtscts, retry));
214 else if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT)
215 retry = max(2U, min(mr->retry_count_cts, retry));
221 minstrel_get_next_sample(struct minstrel_sta_info *mi)
223 unsigned int sample_ndx;
224 sample_ndx = SAMPLE_TBL(mi, mi->sample_row, mi->sample_column);
226 if ((int) mi->sample_row >= mi->n_rates) {
229 if (mi->sample_column >= SAMPLE_COLUMNS)
230 mi->sample_column = 0;
236 minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
237 void *priv_sta, struct ieee80211_tx_rate_control *txrc)
239 struct sk_buff *skb = txrc->skb;
240 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
241 struct minstrel_sta_info *mi = priv_sta;
242 struct minstrel_priv *mp = priv;
243 struct ieee80211_tx_rate *ar = info->control.rates;
244 unsigned int ndx, sample_ndx = 0;
246 bool indirect_rate_sampling = false;
247 bool rate_sampling = false;
252 /* management/no-ack frames do not use rate control */
253 if (rate_control_send_low(sta, priv_sta, txrc))
256 /* check multi-rate-retry capabilities & adjust lookaround_rate */
257 mrr_capable = mp->has_mrr &&
259 !txrc->bss_conf->use_cts_prot;
261 sampling_ratio = mp->lookaround_rate_mrr;
263 sampling_ratio = mp->lookaround_rate;
265 /* init rateindex [ndx] with max throughput rate */
266 ndx = mi->max_tp_rate[0];
268 /* increase sum packet counter */
271 delta = (mi->packet_count * sampling_ratio / 100) -
272 (mi->sample_count + mi->sample_deferred / 2);
274 /* delta > 0: sampling required */
275 if ((delta > 0) && (mrr_capable || !mi->prev_sample)) {
276 struct minstrel_rate *msr;
277 if (mi->packet_count >= 10000) {
278 mi->sample_deferred = 0;
279 mi->sample_count = 0;
280 mi->packet_count = 0;
281 } else if (delta > mi->n_rates * 2) {
282 /* With multi-rate retry, not every planned sample
283 * attempt actually gets used, due to the way the retry
284 * chain is set up - [max_tp,sample,prob,lowest] for
285 * sample_rate < max_tp.
287 * If there's too much sampling backlog and the link
288 * starts getting worse, minstrel would start bursting
289 * out lots of sampling frames, which would result
290 * in a large throughput loss. */
291 mi->sample_count += (delta - mi->n_rates * 2);
294 /* get next random rate sample */
295 sample_ndx = minstrel_get_next_sample(mi);
296 msr = &mi->r[sample_ndx];
297 rate_sampling = true;
299 /* Decide if direct ( 1st mrr stage) or indirect (2nd mrr stage)
300 * rate sampling method should be used.
301 * Respect such rates that are not sampled for 20 interations.
304 msr->perfect_tx_time > mi->r[ndx].perfect_tx_time &&
305 msr->sample_skipped < 20)
306 indirect_rate_sampling = true;
308 if (!indirect_rate_sampling) {
309 if (msr->sample_limit != 0) {
312 if (msr->sample_limit > 0)
315 rate_sampling = false;
317 /* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
318 * packets that have the sampling rate deferred to the
319 * second MRR stage. Increase the sample counter only
320 * if the deferred sample rate was actually used.
321 * Use the sample_deferred counter to make sure that
322 * the sampling is not done in large bursts */
323 info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
324 mi->sample_deferred++;
327 mi->prev_sample = rate_sampling;
329 /* If we're not using MRR and the sampling rate already
330 * has a probability of >95%, we shouldn't be attempting
331 * to use it, as this only wastes precious airtime */
332 if (!mrr_capable && rate_sampling &&
333 (mi->r[ndx].probability > MINSTREL_FRAC(95, 100)))
334 ndx = mi->max_tp_rate[0];
336 /* mrr setup for 1st stage */
337 ar[0].idx = mi->r[ndx].rix;
338 ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
340 /* non mrr setup for 2nd stage */
343 ar[0].count = mp->max_retry;
344 ar[1].idx = mi->lowest_rix;
345 ar[1].count = mp->max_retry;
349 /* mrr setup for 2nd stage */
351 if (indirect_rate_sampling)
352 mrr_ndx[0] = sample_ndx;
354 mrr_ndx[0] = mi->max_tp_rate[0];
356 mrr_ndx[0] = mi->max_tp_rate[1];
359 /* mrr setup for 3rd & 4th stage */
360 mrr_ndx[1] = mi->max_prob_rate;
362 for (i = 1; i < 4; i++) {
363 ar[i].idx = mi->r[mrr_ndx[i - 1]].rix;
364 ar[i].count = mi->r[mrr_ndx[i - 1]].adjusted_retry_count;
370 calc_rate_durations(enum ieee80211_band band,
371 struct minstrel_rate *d,
372 struct ieee80211_rate *rate)
374 int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
376 d->perfect_tx_time = ieee80211_frame_duration(band, 1200,
377 rate->bitrate, erp, 1);
378 d->ack_time = ieee80211_frame_duration(band, 10,
379 rate->bitrate, erp, 1);
383 init_sample_table(struct minstrel_sta_info *mi)
385 unsigned int i, col, new_idx;
388 mi->sample_column = 0;
390 memset(mi->sample_table, 0xff, SAMPLE_COLUMNS * mi->n_rates);
392 for (col = 0; col < SAMPLE_COLUMNS; col++) {
393 for (i = 0; i < mi->n_rates; i++) {
394 get_random_bytes(rnd, sizeof(rnd));
395 new_idx = (i + rnd[i & 7]) % mi->n_rates;
397 while (SAMPLE_TBL(mi, new_idx, col) != 0xff)
398 new_idx = (new_idx + 1) % mi->n_rates;
400 SAMPLE_TBL(mi, new_idx, col) = i;
406 minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
407 struct ieee80211_sta *sta, void *priv_sta)
409 struct minstrel_sta_info *mi = priv_sta;
410 struct minstrel_priv *mp = priv;
411 struct ieee80211_rate *ctl_rate;
412 unsigned int i, n = 0;
413 unsigned int t_slot = 9; /* FIXME: get real slot time */
415 mi->lowest_rix = rate_lowest_index(sband, sta);
416 ctl_rate = &sband->bitrates[mi->lowest_rix];
417 mi->sp_ack_dur = ieee80211_frame_duration(sband->band, 10,
419 !!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1);
421 for (i = 0; i < sband->n_bitrates; i++) {
422 struct minstrel_rate *mr = &mi->r[n];
423 unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
424 unsigned int tx_time_single;
425 unsigned int cw = mp->cw_min;
427 if (!rate_supported(sta, sband->band, i))
430 memset(mr, 0, sizeof(*mr));
433 mr->bitrate = sband->bitrates[i].bitrate / 5;
434 calc_rate_durations(sband->band, mr, &sband->bitrates[i]);
436 /* calculate maximum number of retransmissions before
437 * fallback (based on maximum segment size) */
438 mr->sample_limit = -1;
440 mr->retry_count_cts = 1;
441 mr->retry_count_rtscts = 1;
442 tx_time = mr->perfect_tx_time + mi->sp_ack_dur;
444 /* add one retransmission */
445 tx_time_single = mr->ack_time + mr->perfect_tx_time;
447 /* contention window */
448 tx_time_single += (t_slot * cw) >> 1;
449 cw = min((cw << 1) | 1, mp->cw_max);
451 tx_time += tx_time_single;
452 tx_time_cts += tx_time_single + mi->sp_ack_dur;
453 tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;
454 if ((tx_time_cts < mp->segment_size) &&
455 (mr->retry_count_cts < mp->max_retry))
456 mr->retry_count_cts++;
457 if ((tx_time_rtscts < mp->segment_size) &&
458 (mr->retry_count_rtscts < mp->max_retry))
459 mr->retry_count_rtscts++;
460 } while ((tx_time < mp->segment_size) &&
461 (++mr->retry_count < mp->max_retry));
462 mr->adjusted_retry_count = mr->retry_count;
465 for (i = n; i < sband->n_bitrates; i++) {
466 struct minstrel_rate *mr = &mi->r[i];
471 mi->stats_update = jiffies;
473 init_sample_table(mi);
477 minstrel_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
479 struct ieee80211_supported_band *sband;
480 struct minstrel_sta_info *mi;
481 struct minstrel_priv *mp = priv;
482 struct ieee80211_hw *hw = mp->hw;
486 mi = kzalloc(sizeof(struct minstrel_sta_info), gfp);
490 for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
491 sband = hw->wiphy->bands[i];
492 if (sband && sband->n_bitrates > max_rates)
493 max_rates = sband->n_bitrates;
496 mi->r = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
500 mi->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
501 if (!mi->sample_table)
504 mi->stats_update = jiffies;
515 minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
517 struct minstrel_sta_info *mi = priv_sta;
519 kfree(mi->sample_table);
525 minstrel_init_cck_rates(struct minstrel_priv *mp)
527 static const int bitrates[4] = { 10, 20, 55, 110 };
528 struct ieee80211_supported_band *sband;
531 sband = mp->hw->wiphy->bands[IEEE80211_BAND_2GHZ];
535 for (i = 0, j = 0; i < sband->n_bitrates; i++) {
536 struct ieee80211_rate *rate = &sband->bitrates[i];
538 if (rate->flags & IEEE80211_RATE_ERP_G)
541 for (j = 0; j < ARRAY_SIZE(bitrates); j++) {
542 if (rate->bitrate != bitrates[j])
545 mp->cck_rates[j] = i;
552 minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
554 struct minstrel_priv *mp;
556 mp = kzalloc(sizeof(struct minstrel_priv), GFP_ATOMIC);
560 /* contention window settings
561 * Just an approximation. Using the per-queue values would complicate
562 * the calculations and is probably unnecessary */
566 /* number of packets (in %) to use for sampling other rates
567 * sample less often for non-mrr packets, because the overhead
568 * is much higher than with mrr */
569 mp->lookaround_rate = 5;
570 mp->lookaround_rate_mrr = 10;
572 /* maximum time that the hw is allowed to stay in one MRR segment */
573 mp->segment_size = 6000;
575 if (hw->max_rate_tries > 0)
576 mp->max_retry = hw->max_rate_tries;
578 /* safe default, does not necessarily have to match hw properties */
581 if (hw->max_rates >= 4)
585 mp->update_interval = 100;
587 #ifdef CONFIG_MAC80211_DEBUGFS
588 mp->fixed_rate_idx = (u32) -1;
589 mp->dbg_fixed_rate = debugfs_create_u32("fixed_rate_idx",
590 S_IRUGO | S_IWUGO, debugfsdir, &mp->fixed_rate_idx);
593 minstrel_init_cck_rates(mp);
599 minstrel_free(void *priv)
601 #ifdef CONFIG_MAC80211_DEBUGFS
602 debugfs_remove(((struct minstrel_priv *)priv)->dbg_fixed_rate);
607 struct rate_control_ops mac80211_minstrel = {
609 .tx_status = minstrel_tx_status,
610 .get_rate = minstrel_get_rate,
611 .rate_init = minstrel_rate_init,
612 .alloc = minstrel_alloc,
613 .free = minstrel_free,
614 .alloc_sta = minstrel_alloc_sta,
615 .free_sta = minstrel_free_sta,
616 #ifdef CONFIG_MAC80211_DEBUGFS
617 .add_sta_debugfs = minstrel_add_sta_debugfs,
618 .remove_sta_debugfs = minstrel_remove_sta_debugfs,
623 rc80211_minstrel_init(void)
625 return ieee80211_rate_control_register(&mac80211_minstrel);
629 rc80211_minstrel_exit(void)
631 ieee80211_rate_control_unregister(&mac80211_minstrel);