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_set_rate(struct minstrel_sta_info
*mi
, struct ieee80211_sta_rates
*ratetbl
,
90 struct minstrel_rate
*r
= &mi
->r
[idx
];
92 ratetbl
->rate
[offset
].idx
= r
->rix
;
93 ratetbl
->rate
[offset
].count
= r
->adjusted_retry_count
;
94 ratetbl
->rate
[offset
].count_cts
= r
->retry_count_cts
;
95 ratetbl
->rate
[offset
].count_rts
= r
->retry_count_rtscts
;
99 minstrel_update_rates(struct minstrel_priv
*mp
, struct minstrel_sta_info
*mi
)
101 struct ieee80211_sta_rates
*ratetbl
;
104 ratetbl
= kzalloc(sizeof(*ratetbl
), GFP_ATOMIC
);
108 /* Start with max_tp_rate */
109 minstrel_set_rate(mi
, ratetbl
, i
++, mi
->max_tp_rate
[0]);
111 if (mp
->hw
->max_rates
>= 3) {
112 /* At least 3 tx rates supported, use max_tp_rate2 next */
113 minstrel_set_rate(mi
, ratetbl
, i
++, mi
->max_tp_rate
[1]);
116 if (mp
->hw
->max_rates
>= 2) {
117 /* At least 2 tx rates supported, use max_prob_rate next */
118 minstrel_set_rate(mi
, ratetbl
, i
++, mi
->max_prob_rate
);
121 /* Use lowest rate last */
122 ratetbl
->rate
[i
].idx
= mi
->lowest_rix
;
123 ratetbl
->rate
[i
].count
= mp
->max_retry
;
124 ratetbl
->rate
[i
].count_cts
= mp
->max_retry
;
125 ratetbl
->rate
[i
].count_rts
= mp
->max_retry
;
127 rate_control_set_rates(mp
->hw
, mi
->sta
, ratetbl
);
131 minstrel_update_stats(struct minstrel_priv
*mp
, struct minstrel_sta_info
*mi
)
133 u8 tmp_tp_rate
[MAX_THR_RATES
];
134 u8 tmp_prob_rate
= 0;
138 for (i
=0; i
< MAX_THR_RATES
; i
++)
141 for (i
= 0; i
< mi
->n_rates
; i
++) {
142 struct minstrel_rate
*mr
= &mi
->r
[i
];
144 usecs
= mr
->perfect_tx_time
;
148 if (unlikely(mr
->attempts
> 0)) {
149 mr
->sample_skipped
= 0;
150 mr
->cur_prob
= MINSTREL_FRAC(mr
->success
, mr
->attempts
);
151 mr
->succ_hist
+= mr
->success
;
152 mr
->att_hist
+= mr
->attempts
;
153 mr
->probability
= minstrel_ewma(mr
->probability
,
157 mr
->sample_skipped
++;
159 mr
->last_success
= mr
->success
;
160 mr
->last_attempts
= mr
->attempts
;
164 /* Update throughput per rate, reset thr. below 10% success */
165 if (mr
->probability
< MINSTREL_FRAC(10, 100))
168 mr
->cur_tp
= mr
->probability
* (1000000 / usecs
);
170 /* Sample less often below the 10% chance of success.
171 * Sample less often above the 95% chance of success. */
172 if (mr
->probability
> MINSTREL_FRAC(95, 100) ||
173 mr
->probability
< MINSTREL_FRAC(10, 100)) {
174 mr
->adjusted_retry_count
= mr
->retry_count
>> 1;
175 if (mr
->adjusted_retry_count
> 2)
176 mr
->adjusted_retry_count
= 2;
177 mr
->sample_limit
= 4;
179 mr
->sample_limit
= -1;
180 mr
->adjusted_retry_count
= mr
->retry_count
;
182 if (!mr
->adjusted_retry_count
)
183 mr
->adjusted_retry_count
= 2;
185 minstrel_sort_best_tp_rates(mi
, i
, tmp_tp_rate
);
187 /* To determine the most robust rate (max_prob_rate) used at
188 * 3rd mmr stage we distinct between two cases:
189 * (1) if any success probabilitiy >= 95%, out of those rates
190 * choose the maximum throughput rate as max_prob_rate
191 * (2) if all success probabilities < 95%, the rate with
192 * highest success probability is choosen as max_prob_rate */
193 if (mr
->probability
>= MINSTREL_FRAC(95,100)) {
194 if (mr
->cur_tp
>= mi
->r
[tmp_prob_rate
].cur_tp
)
197 if (mr
->probability
>= mi
->r
[tmp_prob_rate
].probability
)
202 /* Assign the new rate set */
203 memcpy(mi
->max_tp_rate
, tmp_tp_rate
, sizeof(mi
->max_tp_rate
));
204 mi
->max_prob_rate
= tmp_prob_rate
;
206 /* Reset update timer */
207 mi
->stats_update
= jiffies
;
209 minstrel_update_rates(mp
, mi
);
213 minstrel_tx_status(void *priv
, struct ieee80211_supported_band
*sband
,
214 struct ieee80211_sta
*sta
, void *priv_sta
,
217 struct minstrel_priv
*mp
= priv
;
218 struct minstrel_sta_info
*mi
= priv_sta
;
219 struct ieee80211_tx_info
*info
= IEEE80211_SKB_CB(skb
);
220 struct ieee80211_tx_rate
*ar
= info
->status
.rates
;
224 success
= !!(info
->flags
& IEEE80211_TX_STAT_ACK
);
226 for (i
= 0; i
< IEEE80211_TX_MAX_RATES
; i
++) {
230 ndx
= rix_to_ndx(mi
, ar
[i
].idx
);
234 mi
->r
[ndx
].attempts
+= ar
[i
].count
;
236 if ((i
!= IEEE80211_TX_MAX_RATES
- 1) && (ar
[i
+ 1].idx
< 0))
237 mi
->r
[ndx
].success
+= success
;
240 if ((info
->flags
& IEEE80211_TX_CTL_RATE_CTRL_PROBE
) && (i
>= 0))
243 if (mi
->sample_deferred
> 0)
244 mi
->sample_deferred
--;
246 if (time_after(jiffies
, mi
->stats_update
+
247 (mp
->update_interval
* HZ
) / 1000))
248 minstrel_update_stats(mp
, mi
);
252 static inline unsigned int
253 minstrel_get_retry_count(struct minstrel_rate
*mr
,
254 struct ieee80211_tx_info
*info
)
256 unsigned int retry
= mr
->adjusted_retry_count
;
258 if (info
->control
.use_rts
)
259 retry
= max(2U, min(mr
->retry_count_rtscts
, retry
));
260 else if (info
->control
.use_cts_prot
)
261 retry
= max(2U, min(mr
->retry_count_cts
, retry
));
267 minstrel_get_next_sample(struct minstrel_sta_info
*mi
)
269 unsigned int sample_ndx
;
270 sample_ndx
= SAMPLE_TBL(mi
, mi
->sample_row
, mi
->sample_column
);
272 if ((int) mi
->sample_row
>= mi
->n_rates
) {
275 if (mi
->sample_column
>= SAMPLE_COLUMNS
)
276 mi
->sample_column
= 0;
282 minstrel_get_rate(void *priv
, struct ieee80211_sta
*sta
,
283 void *priv_sta
, struct ieee80211_tx_rate_control
*txrc
)
285 struct sk_buff
*skb
= txrc
->skb
;
286 struct ieee80211_tx_info
*info
= IEEE80211_SKB_CB(skb
);
287 struct minstrel_sta_info
*mi
= priv_sta
;
288 struct minstrel_priv
*mp
= priv
;
289 struct ieee80211_tx_rate
*rate
= &info
->control
.rates
[0];
290 struct minstrel_rate
*msr
, *mr
;
293 bool prev_sample
= mi
->prev_sample
;
297 /* management/no-ack frames do not use rate control */
298 if (rate_control_send_low(sta
, priv_sta
, txrc
))
301 /* check multi-rate-retry capabilities & adjust lookaround_rate */
302 mrr_capable
= mp
->has_mrr
&&
304 !txrc
->bss_conf
->use_cts_prot
;
306 sampling_ratio
= mp
->lookaround_rate_mrr
;
308 sampling_ratio
= mp
->lookaround_rate
;
310 /* increase sum packet counter */
313 delta
= (mi
->packet_count
* sampling_ratio
/ 100) -
314 (mi
->sample_count
+ mi
->sample_deferred
/ 2);
316 /* delta < 0: no sampling required */
317 mi
->prev_sample
= false;
318 if (delta
< 0 || (!mrr_capable
&& prev_sample
))
321 if (mi
->packet_count
>= 10000) {
322 mi
->sample_deferred
= 0;
323 mi
->sample_count
= 0;
324 mi
->packet_count
= 0;
325 } else if (delta
> mi
->n_rates
* 2) {
326 /* With multi-rate retry, not every planned sample
327 * attempt actually gets used, due to the way the retry
328 * chain is set up - [max_tp,sample,prob,lowest] for
329 * sample_rate < max_tp.
331 * If there's too much sampling backlog and the link
332 * starts getting worse, minstrel would start bursting
333 * out lots of sampling frames, which would result
334 * in a large throughput loss. */
335 mi
->sample_count
+= (delta
- mi
->n_rates
* 2);
338 /* get next random rate sample */
339 ndx
= minstrel_get_next_sample(mi
);
341 mr
= &mi
->r
[mi
->max_tp_rate
[0]];
343 /* Decide if direct ( 1st mrr stage) or indirect (2nd mrr stage)
344 * rate sampling method should be used.
345 * Respect such rates that are not sampled for 20 interations.
348 msr
->perfect_tx_time
> mr
->perfect_tx_time
&&
349 msr
->sample_skipped
< 20) {
350 /* Only use IEEE80211_TX_CTL_RATE_CTRL_PROBE to mark
351 * packets that have the sampling rate deferred to the
352 * second MRR stage. Increase the sample counter only
353 * if the deferred sample rate was actually used.
354 * Use the sample_deferred counter to make sure that
355 * the sampling is not done in large bursts */
356 info
->flags
|= IEEE80211_TX_CTL_RATE_CTRL_PROBE
;
358 mi
->sample_deferred
++;
360 if (!msr
->sample_limit
!= 0)
364 if (msr
->sample_limit
> 0)
368 /* If we're not using MRR and the sampling rate already
369 * has a probability of >95%, we shouldn't be attempting
370 * to use it, as this only wastes precious airtime */
372 (mi
->r
[ndx
].probability
> MINSTREL_FRAC(95, 100)))
375 mi
->prev_sample
= true;
377 rate
->idx
= mi
->r
[ndx
].rix
;
378 rate
->count
= minstrel_get_retry_count(&mi
->r
[ndx
], info
);
383 calc_rate_durations(enum ieee80211_band band
,
384 struct minstrel_rate
*d
,
385 struct ieee80211_rate
*rate
)
387 int erp
= !!(rate
->flags
& IEEE80211_RATE_ERP_G
);
389 d
->perfect_tx_time
= ieee80211_frame_duration(band
, 1200,
390 rate
->bitrate
, erp
, 1);
391 d
->ack_time
= ieee80211_frame_duration(band
, 10,
392 rate
->bitrate
, erp
, 1);
396 init_sample_table(struct minstrel_sta_info
*mi
)
398 unsigned int i
, col
, new_idx
;
401 mi
->sample_column
= 0;
403 memset(mi
->sample_table
, 0xff, SAMPLE_COLUMNS
* mi
->n_rates
);
405 for (col
= 0; col
< SAMPLE_COLUMNS
; col
++) {
406 for (i
= 0; i
< mi
->n_rates
; i
++) {
407 get_random_bytes(rnd
, sizeof(rnd
));
408 new_idx
= (i
+ rnd
[i
& 7]) % mi
->n_rates
;
410 while (SAMPLE_TBL(mi
, new_idx
, col
) != 0xff)
411 new_idx
= (new_idx
+ 1) % mi
->n_rates
;
413 SAMPLE_TBL(mi
, new_idx
, col
) = i
;
419 minstrel_rate_init(void *priv
, struct ieee80211_supported_band
*sband
,
420 struct ieee80211_sta
*sta
, void *priv_sta
)
422 struct minstrel_sta_info
*mi
= priv_sta
;
423 struct minstrel_priv
*mp
= priv
;
424 struct ieee80211_rate
*ctl_rate
;
425 unsigned int i
, n
= 0;
426 unsigned int t_slot
= 9; /* FIXME: get real slot time */
429 mi
->lowest_rix
= rate_lowest_index(sband
, sta
);
430 ctl_rate
= &sband
->bitrates
[mi
->lowest_rix
];
431 mi
->sp_ack_dur
= ieee80211_frame_duration(sband
->band
, 10,
433 !!(ctl_rate
->flags
& IEEE80211_RATE_ERP_G
), 1);
435 memset(mi
->max_tp_rate
, 0, sizeof(mi
->max_tp_rate
));
436 mi
->max_prob_rate
= 0;
438 for (i
= 0; i
< sband
->n_bitrates
; i
++) {
439 struct minstrel_rate
*mr
= &mi
->r
[n
];
440 unsigned int tx_time
= 0, tx_time_cts
= 0, tx_time_rtscts
= 0;
441 unsigned int tx_time_single
;
442 unsigned int cw
= mp
->cw_min
;
444 if (!rate_supported(sta
, sband
->band
, i
))
447 memset(mr
, 0, sizeof(*mr
));
450 mr
->bitrate
= sband
->bitrates
[i
].bitrate
/ 5;
451 calc_rate_durations(sband
->band
, mr
, &sband
->bitrates
[i
]);
453 /* calculate maximum number of retransmissions before
454 * fallback (based on maximum segment size) */
455 mr
->sample_limit
= -1;
457 mr
->retry_count_cts
= 1;
458 mr
->retry_count_rtscts
= 1;
459 tx_time
= mr
->perfect_tx_time
+ mi
->sp_ack_dur
;
461 /* add one retransmission */
462 tx_time_single
= mr
->ack_time
+ mr
->perfect_tx_time
;
464 /* contention window */
465 tx_time_single
+= (t_slot
* cw
) >> 1;
466 cw
= min((cw
<< 1) | 1, mp
->cw_max
);
468 tx_time
+= tx_time_single
;
469 tx_time_cts
+= tx_time_single
+ mi
->sp_ack_dur
;
470 tx_time_rtscts
+= tx_time_single
+ 2 * mi
->sp_ack_dur
;
471 if ((tx_time_cts
< mp
->segment_size
) &&
472 (mr
->retry_count_cts
< mp
->max_retry
))
473 mr
->retry_count_cts
++;
474 if ((tx_time_rtscts
< mp
->segment_size
) &&
475 (mr
->retry_count_rtscts
< mp
->max_retry
))
476 mr
->retry_count_rtscts
++;
477 } while ((tx_time
< mp
->segment_size
) &&
478 (++mr
->retry_count
< mp
->max_retry
));
479 mr
->adjusted_retry_count
= mr
->retry_count
;
480 if (!(sband
->bitrates
[i
].flags
& IEEE80211_RATE_ERP_G
))
481 mr
->retry_count_cts
= mr
->retry_count
;
484 for (i
= n
; i
< sband
->n_bitrates
; i
++) {
485 struct minstrel_rate
*mr
= &mi
->r
[i
];
490 mi
->stats_update
= jiffies
;
492 init_sample_table(mi
);
493 minstrel_update_rates(mp
, mi
);
497 minstrel_alloc_sta(void *priv
, struct ieee80211_sta
*sta
, gfp_t gfp
)
499 struct ieee80211_supported_band
*sband
;
500 struct minstrel_sta_info
*mi
;
501 struct minstrel_priv
*mp
= priv
;
502 struct ieee80211_hw
*hw
= mp
->hw
;
506 mi
= kzalloc(sizeof(struct minstrel_sta_info
), gfp
);
510 for (i
= 0; i
< IEEE80211_NUM_BANDS
; i
++) {
511 sband
= hw
->wiphy
->bands
[i
];
512 if (sband
&& sband
->n_bitrates
> max_rates
)
513 max_rates
= sband
->n_bitrates
;
516 mi
->r
= kzalloc(sizeof(struct minstrel_rate
) * max_rates
, gfp
);
520 mi
->sample_table
= kmalloc(SAMPLE_COLUMNS
* max_rates
, gfp
);
521 if (!mi
->sample_table
)
524 mi
->stats_update
= jiffies
;
535 minstrel_free_sta(void *priv
, struct ieee80211_sta
*sta
, void *priv_sta
)
537 struct minstrel_sta_info
*mi
= priv_sta
;
539 kfree(mi
->sample_table
);
545 minstrel_init_cck_rates(struct minstrel_priv
*mp
)
547 static const int bitrates
[4] = { 10, 20, 55, 110 };
548 struct ieee80211_supported_band
*sband
;
551 sband
= mp
->hw
->wiphy
->bands
[IEEE80211_BAND_2GHZ
];
555 for (i
= 0, j
= 0; i
< sband
->n_bitrates
; i
++) {
556 struct ieee80211_rate
*rate
= &sband
->bitrates
[i
];
558 if (rate
->flags
& IEEE80211_RATE_ERP_G
)
561 for (j
= 0; j
< ARRAY_SIZE(bitrates
); j
++) {
562 if (rate
->bitrate
!= bitrates
[j
])
565 mp
->cck_rates
[j
] = i
;
572 minstrel_alloc(struct ieee80211_hw
*hw
, struct dentry
*debugfsdir
)
574 struct minstrel_priv
*mp
;
576 mp
= kzalloc(sizeof(struct minstrel_priv
), GFP_ATOMIC
);
580 /* contention window settings
581 * Just an approximation. Using the per-queue values would complicate
582 * the calculations and is probably unnecessary */
586 /* number of packets (in %) to use for sampling other rates
587 * sample less often for non-mrr packets, because the overhead
588 * is much higher than with mrr */
589 mp
->lookaround_rate
= 5;
590 mp
->lookaround_rate_mrr
= 10;
592 /* maximum time that the hw is allowed to stay in one MRR segment */
593 mp
->segment_size
= 6000;
595 if (hw
->max_rate_tries
> 0)
596 mp
->max_retry
= hw
->max_rate_tries
;
598 /* safe default, does not necessarily have to match hw properties */
601 if (hw
->max_rates
>= 4)
605 mp
->update_interval
= 100;
607 #ifdef CONFIG_MAC80211_DEBUGFS
608 mp
->fixed_rate_idx
= (u32
) -1;
609 mp
->dbg_fixed_rate
= debugfs_create_u32("fixed_rate_idx",
610 S_IRUGO
| S_IWUGO
, debugfsdir
, &mp
->fixed_rate_idx
);
613 minstrel_init_cck_rates(mp
);
619 minstrel_free(void *priv
)
621 #ifdef CONFIG_MAC80211_DEBUGFS
622 debugfs_remove(((struct minstrel_priv
*)priv
)->dbg_fixed_rate
);
627 struct rate_control_ops mac80211_minstrel
= {
629 .tx_status
= minstrel_tx_status
,
630 .get_rate
= minstrel_get_rate
,
631 .rate_init
= minstrel_rate_init
,
632 .alloc
= minstrel_alloc
,
633 .free
= minstrel_free
,
634 .alloc_sta
= minstrel_alloc_sta
,
635 .free_sta
= minstrel_free_sta
,
636 #ifdef CONFIG_MAC80211_DEBUGFS
637 .add_sta_debugfs
= minstrel_add_sta_debugfs
,
638 .remove_sta_debugfs
= minstrel_remove_sta_debugfs
,
643 rc80211_minstrel_init(void)
645 return ieee80211_rate_control_register(&mac80211_minstrel
);
649 rc80211_minstrel_exit(void)
651 ieee80211_rate_control_unregister(&mac80211_minstrel
);