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)
73 minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
75 u32 max_tp = 0, index_max_tp = 0, index_max_tp2 = 0;
76 u32 max_prob = 0, index_max_prob = 0;
80 for (i = 0; i < mi->n_rates; i++) {
81 struct minstrel_rate *mr = &mi->r[i];
83 usecs = mr->perfect_tx_time;
87 if (unlikely(mr->attempts > 0)) {
88 mr->sample_skipped = 0;
89 mr->cur_prob = MINSTREL_FRAC(mr->success, mr->attempts);
90 mr->succ_hist += mr->success;
91 mr->att_hist += mr->attempts;
92 mr->probability = minstrel_ewma(mr->probability,
95 mr->cur_tp = mr->probability * (1000000 / usecs);
99 mr->last_success = mr->success;
100 mr->last_attempts = mr->attempts;
104 /* Sample less often below the 10% chance of success.
105 * Sample less often above the 95% chance of success. */
106 if (mr->probability > MINSTREL_FRAC(95, 100) ||
107 mr->probability < MINSTREL_FRAC(10, 100)) {
108 mr->adjusted_retry_count = mr->retry_count >> 1;
109 if (mr->adjusted_retry_count > 2)
110 mr->adjusted_retry_count = 2;
111 mr->sample_limit = 4;
113 mr->sample_limit = -1;
114 mr->adjusted_retry_count = mr->retry_count;
116 if (!mr->adjusted_retry_count)
117 mr->adjusted_retry_count = 2;
120 for (i = 0; i < mi->n_rates; i++) {
121 struct minstrel_rate *mr = &mi->r[i];
122 if (max_tp < mr->cur_tp) {
126 if (max_prob < mr->probability) {
128 max_prob = mr->probability;
133 for (i = 0; i < mi->n_rates; i++) {
134 struct minstrel_rate *mr = &mi->r[i];
136 if (i == index_max_tp)
139 if (max_tp < mr->cur_tp) {
144 mi->max_tp_rate = index_max_tp;
145 mi->max_tp_rate2 = index_max_tp2;
146 mi->max_prob_rate = index_max_prob;
148 /* Reset update timer */
149 mi->stats_update = jiffies;
153 minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
154 struct ieee80211_sta *sta, void *priv_sta,
157 struct minstrel_priv *mp = priv;
158 struct minstrel_sta_info *mi = priv_sta;
159 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
160 struct ieee80211_tx_rate *ar = info->status.rates;
164 success = !!(info->flags & IEEE80211_TX_STAT_ACK);
166 for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
170 ndx = rix_to_ndx(mi, ar[i].idx);
174 mi->r[ndx].attempts += ar[i].count;
176 if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
177 mi->r[ndx].success += success;
180 if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
183 if (mi->sample_deferred > 0)
184 mi->sample_deferred--;
186 if (time_after(jiffies, mi->stats_update +
187 (mp->update_interval * HZ) / 1000))
188 minstrel_update_stats(mp, mi);
192 static inline unsigned int
193 minstrel_get_retry_count(struct minstrel_rate *mr,
194 struct ieee80211_tx_info *info)
196 unsigned int retry = mr->adjusted_retry_count;
198 if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS)
199 retry = max(2U, min(mr->retry_count_rtscts, retry));
200 else if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT)
201 retry = max(2U, min(mr->retry_count_cts, retry));
207 minstrel_get_next_sample(struct minstrel_sta_info *mi)
209 unsigned int sample_ndx;
210 sample_ndx = SAMPLE_TBL(mi, mi->sample_row, mi->sample_column);
212 if ((int) mi->sample_row >= mi->n_rates) {
215 if (mi->sample_column >= SAMPLE_COLUMNS)
216 mi->sample_column = 0;
222 minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
223 void *priv_sta, struct ieee80211_tx_rate_control *txrc)
225 struct sk_buff *skb = txrc->skb;
226 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
227 struct minstrel_sta_info *mi = priv_sta;
228 struct minstrel_priv *mp = priv;
229 struct ieee80211_tx_rate *ar = info->control.rates;
230 unsigned int ndx, sample_ndx = 0;
232 bool indirect_rate_sampling = false;
233 bool rate_sampling = false;
238 /* management/no-ack frames do not use rate control */
239 if (rate_control_send_low(sta, priv_sta, txrc))
242 /* check multi-rate-retry capabilities & adjust lookaround_rate */
243 mrr_capable = mp->has_mrr &&
245 !txrc->bss_conf->use_cts_prot;
247 sampling_ratio = mp->lookaround_rate_mrr;
249 sampling_ratio = mp->lookaround_rate;
251 /* init rateindex [ndx] with max throughput rate */
252 ndx = mi->max_tp_rate;
254 /* increase sum packet counter */
257 delta = (mi->packet_count * sampling_ratio / 100) -
258 (mi->sample_count + mi->sample_deferred / 2);
260 /* delta > 0: sampling required */
261 if ((delta > 0) && (mrr_capable || !mi->prev_sample)) {
262 struct minstrel_rate *msr;
263 if (mi->packet_count >= 10000) {
264 mi->sample_deferred = 0;
265 mi->sample_count = 0;
266 mi->packet_count = 0;
267 } else if (delta > mi->n_rates * 2) {
268 /* With multi-rate retry, not every planned sample
269 * attempt actually gets used, due to the way the retry
270 * chain is set up - [max_tp,sample,prob,lowest] for
271 * sample_rate < max_tp.
273 * If there's too much sampling backlog and the link
274 * starts getting worse, minstrel would start bursting
275 * out lots of sampling frames, which would result
276 * in a large throughput loss. */
277 mi->sample_count += (delta - mi->n_rates * 2);
280 /* get next random rate sample */
281 sample_ndx = minstrel_get_next_sample(mi);
282 msr = &mi->r[sample_ndx];
283 rate_sampling = true;
285 /* Decide if direct ( 1st mrr stage) or indirect (2nd mrr stage)
286 * rate sampling method should be used.
287 * Respect such rates that are not sampled for 20 interations.
290 msr->perfect_tx_time > mi->r[ndx].perfect_tx_time &&
291 msr->sample_skipped < 20)
292 indirect_rate_sampling = true;
294 if (!indirect_rate_sampling) {
295 if (msr->sample_limit != 0) {
298 if (msr->sample_limit > 0)
301 rate_sampling = false;
303 /* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
304 * packets that have the sampling rate deferred to the
305 * second MRR stage. Increase the sample counter only
306 * if the deferred sample rate was actually used.
307 * Use the sample_deferred counter to make sure that
308 * the sampling is not done in large bursts */
309 info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
310 mi->sample_deferred++;
313 mi->prev_sample = rate_sampling;
315 /* If we're not using MRR and the sampling rate already
316 * has a probability of >95%, we shouldn't be attempting
317 * to use it, as this only wastes precious airtime */
318 if (!mrr_capable && rate_sampling &&
319 (mi->r[ndx].probability > MINSTREL_FRAC(95, 100)))
320 ndx = mi->max_tp_rate;
322 /* mrr setup for 1st stage */
323 ar[0].idx = mi->r[ndx].rix;
324 ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
326 /* non mrr setup for 2nd stage */
329 ar[0].count = mp->max_retry;
330 ar[1].idx = mi->lowest_rix;
331 ar[1].count = mp->max_retry;
335 /* mrr setup for 2nd stage */
337 if (indirect_rate_sampling)
338 mrr_ndx[0] = sample_ndx;
340 mrr_ndx[0] = mi->max_tp_rate;
342 mrr_ndx[0] = mi->max_tp_rate2;
345 /* mrr setup for 3rd & 4th stage */
346 mrr_ndx[1] = mi->max_prob_rate;
348 for (i = 1; i < 4; i++) {
349 ar[i].idx = mi->r[mrr_ndx[i - 1]].rix;
350 ar[i].count = mi->r[mrr_ndx[i - 1]].adjusted_retry_count;
356 calc_rate_durations(enum ieee80211_band band,
357 struct minstrel_rate *d,
358 struct ieee80211_rate *rate)
360 int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
362 d->perfect_tx_time = ieee80211_frame_duration(band, 1200,
363 rate->bitrate, erp, 1);
364 d->ack_time = ieee80211_frame_duration(band, 10,
365 rate->bitrate, erp, 1);
369 init_sample_table(struct minstrel_sta_info *mi)
371 unsigned int i, col, new_idx;
374 mi->sample_column = 0;
376 memset(mi->sample_table, 0xff, SAMPLE_COLUMNS * mi->n_rates);
378 for (col = 0; col < SAMPLE_COLUMNS; col++) {
379 for (i = 0; i < mi->n_rates; i++) {
380 get_random_bytes(rnd, sizeof(rnd));
381 new_idx = (i + rnd[i & 7]) % mi->n_rates;
383 while (SAMPLE_TBL(mi, new_idx, col) != 0xff)
384 new_idx = (new_idx + 1) % mi->n_rates;
386 SAMPLE_TBL(mi, new_idx, col) = i;
392 minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
393 struct ieee80211_sta *sta, void *priv_sta)
395 struct minstrel_sta_info *mi = priv_sta;
396 struct minstrel_priv *mp = priv;
397 struct ieee80211_rate *ctl_rate;
398 unsigned int i, n = 0;
399 unsigned int t_slot = 9; /* FIXME: get real slot time */
401 mi->lowest_rix = rate_lowest_index(sband, sta);
402 ctl_rate = &sband->bitrates[mi->lowest_rix];
403 mi->sp_ack_dur = ieee80211_frame_duration(sband->band, 10,
405 !!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1);
407 for (i = 0; i < sband->n_bitrates; i++) {
408 struct minstrel_rate *mr = &mi->r[n];
409 unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
410 unsigned int tx_time_single;
411 unsigned int cw = mp->cw_min;
413 if (!rate_supported(sta, sband->band, i))
416 memset(mr, 0, sizeof(*mr));
419 mr->bitrate = sband->bitrates[i].bitrate / 5;
420 calc_rate_durations(sband->band, mr, &sband->bitrates[i]);
422 /* calculate maximum number of retransmissions before
423 * fallback (based on maximum segment size) */
424 mr->sample_limit = -1;
426 mr->retry_count_cts = 1;
427 mr->retry_count_rtscts = 1;
428 tx_time = mr->perfect_tx_time + mi->sp_ack_dur;
430 /* add one retransmission */
431 tx_time_single = mr->ack_time + mr->perfect_tx_time;
433 /* contention window */
434 tx_time_single += (t_slot * cw) >> 1;
435 cw = min((cw << 1) | 1, mp->cw_max);
437 tx_time += tx_time_single;
438 tx_time_cts += tx_time_single + mi->sp_ack_dur;
439 tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;
440 if ((tx_time_cts < mp->segment_size) &&
441 (mr->retry_count_cts < mp->max_retry))
442 mr->retry_count_cts++;
443 if ((tx_time_rtscts < mp->segment_size) &&
444 (mr->retry_count_rtscts < mp->max_retry))
445 mr->retry_count_rtscts++;
446 } while ((tx_time < mp->segment_size) &&
447 (++mr->retry_count < mp->max_retry));
448 mr->adjusted_retry_count = mr->retry_count;
451 for (i = n; i < sband->n_bitrates; i++) {
452 struct minstrel_rate *mr = &mi->r[i];
457 mi->stats_update = jiffies;
459 init_sample_table(mi);
463 minstrel_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
465 struct ieee80211_supported_band *sband;
466 struct minstrel_sta_info *mi;
467 struct minstrel_priv *mp = priv;
468 struct ieee80211_hw *hw = mp->hw;
472 mi = kzalloc(sizeof(struct minstrel_sta_info), gfp);
476 for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
477 sband = hw->wiphy->bands[i];
478 if (sband && sband->n_bitrates > max_rates)
479 max_rates = sband->n_bitrates;
482 mi->r = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
486 mi->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
487 if (!mi->sample_table)
490 mi->stats_update = jiffies;
501 minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
503 struct minstrel_sta_info *mi = priv_sta;
505 kfree(mi->sample_table);
511 minstrel_init_cck_rates(struct minstrel_priv *mp)
513 static const int bitrates[4] = { 10, 20, 55, 110 };
514 struct ieee80211_supported_band *sband;
517 sband = mp->hw->wiphy->bands[IEEE80211_BAND_2GHZ];
521 for (i = 0, j = 0; i < sband->n_bitrates; i++) {
522 struct ieee80211_rate *rate = &sband->bitrates[i];
524 if (rate->flags & IEEE80211_RATE_ERP_G)
527 for (j = 0; j < ARRAY_SIZE(bitrates); j++) {
528 if (rate->bitrate != bitrates[j])
531 mp->cck_rates[j] = i;
538 minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
540 struct minstrel_priv *mp;
542 mp = kzalloc(sizeof(struct minstrel_priv), GFP_ATOMIC);
546 /* contention window settings
547 * Just an approximation. Using the per-queue values would complicate
548 * the calculations and is probably unnecessary */
552 /* number of packets (in %) to use for sampling other rates
553 * sample less often for non-mrr packets, because the overhead
554 * is much higher than with mrr */
555 mp->lookaround_rate = 5;
556 mp->lookaround_rate_mrr = 10;
558 /* maximum time that the hw is allowed to stay in one MRR segment */
559 mp->segment_size = 6000;
561 if (hw->max_rate_tries > 0)
562 mp->max_retry = hw->max_rate_tries;
564 /* safe default, does not necessarily have to match hw properties */
567 if (hw->max_rates >= 4)
571 mp->update_interval = 100;
573 #ifdef CONFIG_MAC80211_DEBUGFS
574 mp->fixed_rate_idx = (u32) -1;
575 mp->dbg_fixed_rate = debugfs_create_u32("fixed_rate_idx",
576 S_IRUGO | S_IWUGO, debugfsdir, &mp->fixed_rate_idx);
579 minstrel_init_cck_rates(mp);
585 minstrel_free(void *priv)
587 #ifdef CONFIG_MAC80211_DEBUGFS
588 debugfs_remove(((struct minstrel_priv *)priv)->dbg_fixed_rate);
593 struct rate_control_ops mac80211_minstrel = {
595 .tx_status = minstrel_tx_status,
596 .get_rate = minstrel_get_rate,
597 .rate_init = minstrel_rate_init,
598 .alloc = minstrel_alloc,
599 .free = minstrel_free,
600 .alloc_sta = minstrel_alloc_sta,
601 .free_sta = minstrel_free_sta,
602 #ifdef CONFIG_MAC80211_DEBUGFS
603 .add_sta_debugfs = minstrel_add_sta_debugfs,
604 .remove_sta_debugfs = minstrel_remove_sta_debugfs,
609 rc80211_minstrel_init(void)
611 return ieee80211_rate_control_register(&mac80211_minstrel);
615 rc80211_minstrel_exit(void)
617 ieee80211_rate_control_unregister(&mac80211_minstrel);