1 /*
2 * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>
3 *
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.
7 *
8 * Based on minstrel.c:
9 * Copyright (C) 2005-2007 Derek Smithies <derek@indranet.co.nz>
10 * Sponsored by Indranet Technologies Ltd
11 *
12 * Based on sample.c:
13 * Copyright (c) 2005 John Bicket
14 * All rights reserved.
15 *
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
18 * are met:
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.
29 *
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.
33 *
34 * NO WARRANTY
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.
46 */
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>
55 #include "rate.h"
56 #include "rc80211_minstrel.h"
57
58 #define SAMPLE_COLUMNS 10
59 #define SAMPLE_TBL(_mi, _idx, _col) \
60 _mi->sample_table[(_idx * SAMPLE_COLUMNS) + _col]
61
62 /* convert mac80211 rate index to local array index */
63 static inline int
rix_to_ndx(struct minstrel_sta_info * mi,int rix)64 rix_to_ndx(struct minstrel_sta_info *mi, int rix)
65 {
66 int i = rix;
67 for (i = rix; i >= 0; i--)
68 if (mi->r[i].rix == rix)
69 break;
70 return i;
71 }
72
73 static void
minstrel_update_stats(struct minstrel_priv * mp,struct minstrel_sta_info * mi)74 minstrel_update_stats(struct minstrel_priv *mp, struct minstrel_sta_info *mi)
75 {
76 u32 max_tp = 0, index_max_tp = 0, index_max_tp2 = 0;
77 u32 max_prob = 0, index_max_prob = 0;
78 u32 usecs;
79 u32 p;
80 int i;
81
82 mi->stats_update = jiffies;
83 for (i = 0; i < mi->n_rates; i++) {
84 struct minstrel_rate *mr = &mi->r[i];
85
86 usecs = mr->perfect_tx_time;
87 if (!usecs)
88 usecs = 1000000;
89
90 /* To avoid rounding issues, probabilities scale from 0 (0%)
91 * to 18000 (100%) */
92 if (mr->attempts) {
93 p = (mr->success * 18000) / mr->attempts;
94 mr->succ_hist += mr->success;
95 mr->att_hist += mr->attempts;
96 mr->cur_prob = p;
97 p = ((p * (100 - mp->ewma_level)) + (mr->probability *
98 mp->ewma_level)) / 100;
99 mr->probability = p;
100 mr->cur_tp = p * (1000000 / usecs);
101 }
102
103 mr->last_success = mr->success;
104 mr->last_attempts = mr->attempts;
105 mr->success = 0;
106 mr->attempts = 0;
107
108 /* Sample less often below the 10% chance of success.
109 * Sample less often above the 95% chance of success. */
110 if ((mr->probability > 17100) || (mr->probability < 1800)) {
111 mr->adjusted_retry_count = mr->retry_count >> 1;
112 if (mr->adjusted_retry_count > 2)
113 mr->adjusted_retry_count = 2;
114 mr->sample_limit = 4;
115 } else {
116 mr->sample_limit = -1;
117 mr->adjusted_retry_count = mr->retry_count;
118 }
119 if (!mr->adjusted_retry_count)
120 mr->adjusted_retry_count = 2;
121 }
122
123 for (i = 0; i < mi->n_rates; i++) {
124 struct minstrel_rate *mr = &mi->r[i];
125 if (max_tp < mr->cur_tp) {
126 index_max_tp = i;
127 max_tp = mr->cur_tp;
128 }
129 if (max_prob < mr->probability) {
130 index_max_prob = i;
131 max_prob = mr->probability;
132 }
133 }
134
135 max_tp = 0;
136 for (i = 0; i < mi->n_rates; i++) {
137 struct minstrel_rate *mr = &mi->r[i];
138
139 if (i == index_max_tp)
140 continue;
141
142 if (max_tp < mr->cur_tp) {
143 index_max_tp2 = i;
144 max_tp = mr->cur_tp;
145 }
146 }
147 mi->max_tp_rate = index_max_tp;
148 mi->max_tp_rate2 = index_max_tp2;
149 mi->max_prob_rate = index_max_prob;
150 }
151
152 static void
minstrel_tx_status(void * priv,struct ieee80211_supported_band * sband,struct ieee80211_sta * sta,void * priv_sta,struct sk_buff * skb)153 minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
154 struct ieee80211_sta *sta, void *priv_sta,
155 struct sk_buff *skb)
156 {
157 struct minstrel_sta_info *mi = priv_sta;
158 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
159 struct ieee80211_tx_rate *ar = info->status.rates;
160 int i, ndx;
161 int success;
162
163 success = !!(info->flags & IEEE80211_TX_STAT_ACK);
164
165 for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
166 if (ar[i].idx < 0)
167 break;
168
169 ndx = rix_to_ndx(mi, ar[i].idx);
170 if (ndx < 0)
171 continue;
172
173 mi->r[ndx].attempts += ar[i].count;
174
175 if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
176 mi->r[ndx].success += success;
177 }
178
179 if ((info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE) && (i >= 0))
180 mi->sample_count++;
181
182 if (mi->sample_deferred > 0)
183 mi->sample_deferred--;
184 }
185
186
187 static inline unsigned int
minstrel_get_retry_count(struct minstrel_rate * mr,struct ieee80211_tx_info * info)188 minstrel_get_retry_count(struct minstrel_rate *mr,
189 struct ieee80211_tx_info *info)
190 {
191 unsigned int retry = mr->adjusted_retry_count;
192
193 if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS)
194 retry = max(2U, min(mr->retry_count_rtscts, retry));
195 else if (info->control.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT)
196 retry = max(2U, min(mr->retry_count_cts, retry));
197 return retry;
198 }
199
200
201 static int
minstrel_get_next_sample(struct minstrel_sta_info * mi)202 minstrel_get_next_sample(struct minstrel_sta_info *mi)
203 {
204 unsigned int sample_ndx;
205 sample_ndx = SAMPLE_TBL(mi, mi->sample_idx, mi->sample_column);
206 mi->sample_idx++;
207 if ((int) mi->sample_idx > (mi->n_rates - 2)) {
208 mi->sample_idx = 0;
209 mi->sample_column++;
210 if (mi->sample_column >= SAMPLE_COLUMNS)
211 mi->sample_column = 0;
212 }
213 return sample_ndx;
214 }
215
216 static void
minstrel_get_rate(void * priv,struct ieee80211_sta * sta,void * priv_sta,struct ieee80211_tx_rate_control * txrc)217 minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
218 void *priv_sta, struct ieee80211_tx_rate_control *txrc)
219 {
220 struct sk_buff *skb = txrc->skb;
221 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
222 struct minstrel_sta_info *mi = priv_sta;
223 struct minstrel_priv *mp = priv;
224 struct ieee80211_tx_rate *ar = info->control.rates;
225 unsigned int ndx, sample_ndx = 0;
226 bool mrr;
227 bool sample_slower = false;
228 bool sample = false;
229 int i, delta;
230 int mrr_ndx[3];
231 int sample_rate;
232
233 if (rate_control_send_low(sta, priv_sta, txrc))
234 return;
235
236 mrr = mp->has_mrr && !txrc->rts && !txrc->bss_conf->use_cts_prot;
237
238 if (time_after(jiffies, mi->stats_update + (mp->update_interval *
239 HZ) / 1000))
240 minstrel_update_stats(mp, mi);
241
242 ndx = mi->max_tp_rate;
243
244 if (mrr)
245 sample_rate = mp->lookaround_rate_mrr;
246 else
247 sample_rate = mp->lookaround_rate;
248
249 mi->packet_count++;
250 delta = (mi->packet_count * sample_rate / 100) -
251 (mi->sample_count + mi->sample_deferred / 2);
252
253 /* delta > 0: sampling required */
254 if ((delta > 0) && (mrr || !mi->prev_sample)) {
255 struct minstrel_rate *msr;
256 if (mi->packet_count >= 10000) {
257 mi->sample_deferred = 0;
258 mi->sample_count = 0;
259 mi->packet_count = 0;
260 } else if (delta > mi->n_rates * 2) {
261 /* With multi-rate retry, not every planned sample
262 * attempt actually gets used, due to the way the retry
263 * chain is set up - [max_tp,sample,prob,lowest] for
264 * sample_rate < max_tp.
265 *
266 * If there's too much sampling backlog and the link
267 * starts getting worse, minstrel would start bursting
268 * out lots of sampling frames, which would result
269 * in a large throughput loss. */
270 mi->sample_count += (delta - mi->n_rates * 2);
271 }
272
273 sample_ndx = minstrel_get_next_sample(mi);
274 msr = &mi->r[sample_ndx];
275 sample = true;
276 sample_slower = mrr && (msr->perfect_tx_time >
277 mi->r[ndx].perfect_tx_time);
278
279 if (!sample_slower) {
280 if (msr->sample_limit != 0) {
281 ndx = sample_ndx;
282 mi->sample_count++;
283 if (msr->sample_limit > 0)
284 msr->sample_limit--;
285 } else {
286 sample = false;
287 }
288 } else {
289 /* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
290 * packets that have the sampling rate deferred to the
291 * second MRR stage. Increase the sample counter only
292 * if the deferred sample rate was actually used.
293 * Use the sample_deferred counter to make sure that
294 * the sampling is not done in large bursts */
295 info->flags |= IEEE80211_TX_CTL_RATE_CTRL_PROBE;
296 mi->sample_deferred++;
297 }
298 }
299 mi->prev_sample = sample;
300
301 /* If we're not using MRR and the sampling rate already
302 * has a probability of >95%, we shouldn't be attempting
303 * to use it, as this only wastes precious airtime */
304 if (!mrr && sample && (mi->r[ndx].probability > 17100))
305 ndx = mi->max_tp_rate;
306
307 ar[0].idx = mi->r[ndx].rix;
308 ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
309
310 if (!mrr) {
311 if (!sample)
312 ar[0].count = mp->max_retry;
313 ar[1].idx = mi->lowest_rix;
314 ar[1].count = mp->max_retry;
315 return;
316 }
317
318 /* MRR setup */
319 if (sample) {
320 if (sample_slower)
321 mrr_ndx[0] = sample_ndx;
322 else
323 mrr_ndx[0] = mi->max_tp_rate;
324 } else {
325 mrr_ndx[0] = mi->max_tp_rate2;
326 }
327 mrr_ndx[1] = mi->max_prob_rate;
328 mrr_ndx[2] = 0;
329 for (i = 1; i < 4; i++) {
330 ar[i].idx = mi->r[mrr_ndx[i - 1]].rix;
331 ar[i].count = mi->r[mrr_ndx[i - 1]].adjusted_retry_count;
332 }
333 }
334
335
336 static void
calc_rate_durations(struct minstrel_sta_info * mi,struct ieee80211_local * local,struct minstrel_rate * d,struct ieee80211_rate * rate)337 calc_rate_durations(struct minstrel_sta_info *mi, struct ieee80211_local *local,
338 struct minstrel_rate *d, struct ieee80211_rate *rate)
339 {
340 int erp = !!(rate->flags & IEEE80211_RATE_ERP_G);
341
342 d->perfect_tx_time = ieee80211_frame_duration(local, 1200,
343 rate->bitrate, erp, 1);
344 d->ack_time = ieee80211_frame_duration(local, 10,
345 rate->bitrate, erp, 1);
346 }
347
348 static void
init_sample_table(struct minstrel_sta_info * mi)349 init_sample_table(struct minstrel_sta_info *mi)
350 {
351 unsigned int i, col, new_idx;
352 unsigned int n_srates = mi->n_rates - 1;
353 u8 rnd[8];
354
355 mi->sample_column = 0;
356 mi->sample_idx = 0;
357 memset(mi->sample_table, 0, SAMPLE_COLUMNS * mi->n_rates);
358
359 for (col = 0; col < SAMPLE_COLUMNS; col++) {
360 for (i = 0; i < n_srates; i++) {
361 get_random_bytes(rnd, sizeof(rnd));
362 new_idx = (i + rnd[i & 7]) % n_srates;
363
364 while (SAMPLE_TBL(mi, new_idx, col) != 0)
365 new_idx = (new_idx + 1) % n_srates;
366
367 /* Don't sample the slowest rate (i.e. slowest base
368 * rate). We must presume that the slowest rate works
369 * fine, or else other management frames will also be
370 * failing and the link will break */
371 SAMPLE_TBL(mi, new_idx, col) = i + 1;
372 }
373 }
374 }
375
376 static void
minstrel_rate_init(void * priv,struct ieee80211_supported_band * sband,struct ieee80211_sta * sta,void * priv_sta)377 minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
378 struct ieee80211_sta *sta, void *priv_sta)
379 {
380 struct minstrel_sta_info *mi = priv_sta;
381 struct minstrel_priv *mp = priv;
382 struct ieee80211_local *local = hw_to_local(mp->hw);
383 struct ieee80211_rate *ctl_rate;
384 unsigned int i, n = 0;
385 unsigned int t_slot = 9; /* FIXME: get real slot time */
386
387 mi->lowest_rix = rate_lowest_index(sband, sta);
388 ctl_rate = &sband->bitrates[mi->lowest_rix];
389 mi->sp_ack_dur = ieee80211_frame_duration(local, 10, ctl_rate->bitrate,
390 !!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1);
391
392 for (i = 0; i < sband->n_bitrates; i++) {
393 struct minstrel_rate *mr = &mi->r[n];
394 unsigned int tx_time = 0, tx_time_cts = 0, tx_time_rtscts = 0;
395 unsigned int tx_time_single;
396 unsigned int cw = mp->cw_min;
397
398 if (!rate_supported(sta, sband->band, i))
399 continue;
400 n++;
401 memset(mr, 0, sizeof(*mr));
402
403 mr->rix = i;
404 mr->bitrate = sband->bitrates[i].bitrate / 5;
405 calc_rate_durations(mi, local, mr,
406 &sband->bitrates[i]);
407
408 /* calculate maximum number of retransmissions before
409 * fallback (based on maximum segment size) */
410 mr->sample_limit = -1;
411 mr->retry_count = 1;
412 mr->retry_count_cts = 1;
413 mr->retry_count_rtscts = 1;
414 tx_time = mr->perfect_tx_time + mi->sp_ack_dur;
415 do {
416 /* add one retransmission */
417 tx_time_single = mr->ack_time + mr->perfect_tx_time;
418
419 /* contention window */
420 tx_time_single += t_slot + min(cw, mp->cw_max);
421 cw = (cw << 1) | 1;
422
423 tx_time += tx_time_single;
424 tx_time_cts += tx_time_single + mi->sp_ack_dur;
425 tx_time_rtscts += tx_time_single + 2 * mi->sp_ack_dur;
426 if ((tx_time_cts < mp->segment_size) &&
427 (mr->retry_count_cts < mp->max_retry))
428 mr->retry_count_cts++;
429 if ((tx_time_rtscts < mp->segment_size) &&
430 (mr->retry_count_rtscts < mp->max_retry))
431 mr->retry_count_rtscts++;
432 } while ((tx_time < mp->segment_size) &&
433 (++mr->retry_count < mp->max_retry));
434 mr->adjusted_retry_count = mr->retry_count;
435 }
436
437 for (i = n; i < sband->n_bitrates; i++) {
438 struct minstrel_rate *mr = &mi->r[i];
439 mr->rix = -1;
440 }
441
442 mi->n_rates = n;
443 mi->stats_update = jiffies;
444
445 init_sample_table(mi);
446 }
447
448 static void *
minstrel_alloc_sta(void * priv,struct ieee80211_sta * sta,gfp_t gfp)449 minstrel_alloc_sta(void *priv, struct ieee80211_sta *sta, gfp_t gfp)
450 {
451 struct ieee80211_supported_band *sband;
452 struct minstrel_sta_info *mi;
453 struct minstrel_priv *mp = priv;
454 struct ieee80211_hw *hw = mp->hw;
455 int max_rates = 0;
456 int i;
457
458 mi = kzalloc(sizeof(struct minstrel_sta_info), gfp);
459 if (!mi)
460 return NULL;
461
462 for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
463 sband = hw->wiphy->bands[i];
464 if (sband && sband->n_bitrates > max_rates)
465 max_rates = sband->n_bitrates;
466 }
467
468 mi->r = kzalloc(sizeof(struct minstrel_rate) * max_rates, gfp);
469 if (!mi->r)
470 goto error;
471
472 mi->sample_table = kmalloc(SAMPLE_COLUMNS * max_rates, gfp);
473 if (!mi->sample_table)
474 goto error1;
475
476 mi->stats_update = jiffies;
477 return mi;
478
479 error1:
480 kfree(mi->r);
481 error:
482 kfree(mi);
483 return NULL;
484 }
485
486 static void
minstrel_free_sta(void * priv,struct ieee80211_sta * sta,void * priv_sta)487 minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
488 {
489 struct minstrel_sta_info *mi = priv_sta;
490
491 kfree(mi->sample_table);
492 kfree(mi->r);
493 kfree(mi);
494 }
495
496 static void *
minstrel_alloc(struct ieee80211_hw * hw,struct dentry * debugfsdir)497 minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
498 {
499 struct minstrel_priv *mp;
500
501 mp = kzalloc(sizeof(struct minstrel_priv), GFP_ATOMIC);
502 if (!mp)
503 return NULL;
504
505 /* contention window settings
506 * Just an approximation. Using the per-queue values would complicate
507 * the calculations and is probably unnecessary */
508 mp->cw_min = 15;
509 mp->cw_max = 1023;
510
511 /* number of packets (in %) to use for sampling other rates
512 * sample less often for non-mrr packets, because the overhead
513 * is much higher than with mrr */
514 mp->lookaround_rate = 5;
515 mp->lookaround_rate_mrr = 10;
516
517 /* moving average weight for EWMA */
518 mp->ewma_level = 75;
519
520 /* maximum time that the hw is allowed to stay in one MRR segment */
521 mp->segment_size = 6000;
522
523 if (hw->max_rate_tries > 0)
524 mp->max_retry = hw->max_rate_tries;
525 else
526 /* safe default, does not necessarily have to match hw properties */
527 mp->max_retry = 7;
528
529 if (hw->max_rates >= 4)
530 mp->has_mrr = true;
531
532 mp->hw = hw;
533 mp->update_interval = 100;
534
535 return mp;
536 }
537
538 static void
minstrel_free(void * priv)539 minstrel_free(void *priv)
540 {
541 kfree(priv);
542 }
543
544 struct rate_control_ops mac80211_minstrel = {
545 .name = "minstrel",
546 .tx_status = minstrel_tx_status,
547 .get_rate = minstrel_get_rate,
548 .rate_init = minstrel_rate_init,
549 .alloc = minstrel_alloc,
550 .free = minstrel_free,
551 .alloc_sta = minstrel_alloc_sta,
552 .free_sta = minstrel_free_sta,
553 #ifdef CONFIG_MAC80211_DEBUGFS
554 .add_sta_debugfs = minstrel_add_sta_debugfs,
555 .remove_sta_debugfs = minstrel_remove_sta_debugfs,
556 #endif
557 };
558
559 int __init
rc80211_minstrel_init(void)560 rc80211_minstrel_init(void)
561 {
562 return ieee80211_rate_control_register(&mac80211_minstrel);
563 }
564
565 void
rc80211_minstrel_exit(void)566 rc80211_minstrel_exit(void)
567 {
568 ieee80211_rate_control_unregister(&mac80211_minstrel);
569 }
570
571