/*
* 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 <linux/slab.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(i < 0);
return i;
}
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;
mr->sample_limit = 4;
} else {
mr->sample_limit = -1;
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_rate *ar = info->status.rates;
int i, ndx;
int success;
success = !!(info->flags & IEEE80211_TX_STAT_ACK);
for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
if (ar[i].idx < 0)
break;
ndx = rix_to_ndx(mi, ar[i].idx);
if (ndx < 0)
continue;
mi->r[ndx].attempts += ar[i].count;
if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].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->control.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS)
retry = max(2U, min(mr->retry_count_rtscts, retry));
else if (info->control.rates[0].flags & IEEE80211_TX_RC_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 ((int) 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;
}
static void
minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
void *priv_sta, struct ieee80211_tx_rate_control *txrc)
{
struct sk_buff *skb = txrc->skb;
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
struct minstrel_sta_info *mi = priv_sta;
struct minstrel_priv *mp = priv;
struct ieee80211_tx_rate *ar = info->control.rates;
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 (rate_control_send_low(sta, priv_sta, txrc))
return;
mrr = mp->has_mrr && !txrc->rts && !txrc->bss_conf->use_cts_prot;
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) && (mrr || !mi->prev_sample)) {
struct minstrel_rate *msr;
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);
msr = &mi->r[sample_ndx];
sample = true;
sample_slower = mrr && (msr->perfect_tx_time >
mi->r[ndx].perfect_tx_time);
if (!sample_slower) {
if (msr->sample_limit != 0) {
ndx = sample_ndx;
mi->sample_count++;
if (msr->sample_limit > 0)
msr->sample_limit--;
} else {
sample = false;
}
} 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++;
}
}
mi->prev_sample = sample;
/* If we're not using MRR and the sampling rate already
* has a probability of >95%, we shouldn't be attempting
* to use it, as this only wastes precious airtime */
if (!mrr && sample && (mi->r[ndx].probability > 17100))
ndx = mi->max_tp_rate;
ar[0].idx = mi->r[ndx].rix;
ar[0].count = minstrel_get_retry_count(&mi->r[ndx], info);
if (!mrr) {
if (!sample)
ar[0].count = mp->max_retry;
ar[1].idx = mi->lowest_rix;
ar[1].count = mp->max_retry;
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 = 1; i < 4; i++) {
ar[i].idx = mi->r[mrr_ndx[i - 1]].rix;
ar[i].count = mi->r[mrr_ndx[i - 1]].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 ieee80211_local *local = hw_to_local(mp->hw);
struct ieee80211_rate *ctl_rate;
unsigned int i, n = 0;
unsigned int t_slot = 9; /* FIXME: get real slot time */
mi->lowest_rix = rate_lowest_index(sband, sta);
ctl_rate = &sband->bitrates[mi->lowest_rix];
mi->sp_ack_dur = ieee80211_frame_duration(local, 10, ctl_rate->bitrate,
!!(ctl_rate->flags & IEEE80211_RATE_ERP_G), 1);
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, local, mr,
&sband->bitrates[i]);
/* calculate maximum number of retransmissions before
* fallback (based on maximum segment size) */
mr->sample_limit = -1;
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[i];
if (sband && 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_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_rate_tries > 0)
mp->max_retry = hw->max_rate_tries;
else
/* safe default, does not necessarily have to match hw properties */
mp->max_retry = 7;
if (hw->max_rates >= 4)
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,
.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);
}
