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mac80211/minstrel_ht: add support for using CCK rates
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When MCS rates start to get bad in 2.4 GHz because of long range or
strong interference, CCK rates can be a lot more robust.

This patch adds a pseudo MCS group containing CCK rates (long preamble
in the lower 4 slots, short preamble in the upper slots).

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
[make minstrel_ht_get_stats static]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Felix Fietkau authored and Johannes Berg committed Feb 13, 2013
1 parent 6719429 commit a0497f9
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Showing 5 changed files with 237 additions and 60 deletions.
29 changes: 29 additions & 0 deletions net/mac80211/rc80211_minstrel.c
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Original file line number Diff line number Diff line change
Expand Up @@ -494,6 +494,33 @@ minstrel_free_sta(void *priv, struct ieee80211_sta *sta, void *priv_sta)
kfree(mi);
}

static void
minstrel_init_cck_rates(struct minstrel_priv *mp)
{
static const int bitrates[4] = { 10, 20, 55, 110 };
struct ieee80211_supported_band *sband;
int i, j;

sband = mp->hw->wiphy->bands[IEEE80211_BAND_2GHZ];
if (!sband)
return;

for (i = 0, j = 0; i < sband->n_bitrates; i++) {
struct ieee80211_rate *rate = &sband->bitrates[i];

if (rate->flags & IEEE80211_RATE_ERP_G)
continue;

for (j = 0; j < ARRAY_SIZE(bitrates); j++) {
if (rate->bitrate != bitrates[j])
continue;

mp->cck_rates[j] = i;
break;
}
}
}

static void *
minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
{
Expand Down Expand Up @@ -539,6 +566,8 @@ minstrel_alloc(struct ieee80211_hw *hw, struct dentry *debugfsdir)
S_IRUGO | S_IWUGO, debugfsdir, &mp->fixed_rate_idx);
#endif

minstrel_init_cck_rates(mp);

return mp;
}

Expand Down
2 changes: 2 additions & 0 deletions net/mac80211/rc80211_minstrel.h
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,8 @@ struct minstrel_priv {
unsigned int lookaround_rate;
unsigned int lookaround_rate_mrr;

u8 cck_rates[4];

#ifdef CONFIG_MAC80211_DEBUGFS
/*
* enable fixed rate processing per RC
Expand Down
152 changes: 135 additions & 17 deletions net/mac80211/rc80211_minstrel_ht.c
View file
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Copyright (C) 2010 Felix Fietkau <nbd@openwrt.org>
* Copyright (C) 2010-2013 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
Expand Down Expand Up @@ -63,6 +63,30 @@
} \
}

#define CCK_DURATION(_bitrate, _short, _len) \
(10 /* SIFS */ + \
(_short ? 72 + 24 : 144 + 48 ) + \
(8 * (_len + 4) * 10) / (_bitrate))

#define CCK_ACK_DURATION(_bitrate, _short) \
(CCK_DURATION((_bitrate > 10 ? 20 : 10), false, 60) + \
CCK_DURATION(_bitrate, _short, AVG_PKT_SIZE))

#define CCK_DURATION_LIST(_short) \
CCK_ACK_DURATION(10, _short), \
CCK_ACK_DURATION(20, _short), \
CCK_ACK_DURATION(55, _short), \
CCK_ACK_DURATION(110, _short)

#define CCK_GROUP \
[MINSTREL_MAX_STREAMS * MINSTREL_STREAM_GROUPS] = { \
.streams = 0, \
.duration = { \
CCK_DURATION_LIST(false), \
CCK_DURATION_LIST(true) \
} \
}

/*
* To enable sufficiently targeted rate sampling, MCS rates are divided into
* groups, based on the number of streams and flags (HT40, SGI) that they
Expand Down Expand Up @@ -95,8 +119,13 @@ const struct mcs_group minstrel_mcs_groups[] = {
#if MINSTREL_MAX_STREAMS >= 3
MCS_GROUP(3, 1, 1),
#endif

/* must be last */
CCK_GROUP
};

#define MINSTREL_CCK_GROUP (ARRAY_SIZE(minstrel_mcs_groups) - 1)

static u8 sample_table[SAMPLE_COLUMNS][MCS_GROUP_RATES];

/*
Expand All @@ -119,6 +148,29 @@ minstrel_ht_get_group_idx(struct ieee80211_tx_rate *rate)
!!(rate->flags & IEEE80211_TX_RC_40_MHZ_WIDTH));
}

static struct minstrel_rate_stats *
minstrel_ht_get_stats(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
struct ieee80211_tx_rate *rate)
{
int group, idx;

if (rate->flags & IEEE80211_TX_RC_MCS) {
group = minstrel_ht_get_group_idx(rate);
idx = rate->idx % MCS_GROUP_RATES;
} else {
group = MINSTREL_CCK_GROUP;

for (idx = 0; idx < ARRAY_SIZE(mp->cck_rates); idx++)
if (rate->idx == mp->cck_rates[idx])
break;

/* short preamble */
if (!(mi->groups[group].supported & BIT(idx)))
idx += 4;
}
return &mi->groups[group].rates[idx];
}

static inline struct minstrel_rate_stats *
minstrel_get_ratestats(struct minstrel_ht_sta *mi, int index)
{
Expand Down Expand Up @@ -159,7 +211,7 @@ static void
minstrel_ht_calc_tp(struct minstrel_ht_sta *mi, int group, int rate)
{
struct minstrel_rate_stats *mr;
unsigned int usecs;
unsigned int usecs = 0;

mr = &mi->groups[group].rates[rate];

Expand All @@ -168,7 +220,9 @@ minstrel_ht_calc_tp(struct minstrel_ht_sta *mi, int group, int rate)
return;
}

usecs = mi->overhead / MINSTREL_TRUNC(mi->avg_ampdu_len);
if (group != MINSTREL_CCK_GROUP)
usecs = mi->overhead / MINSTREL_TRUNC(mi->avg_ampdu_len);

usecs += minstrel_mcs_groups[group].duration[rate];
mr->cur_tp = MINSTREL_TRUNC((1000000 / usecs) * mr->probability);
}
Expand Down Expand Up @@ -293,15 +347,21 @@ minstrel_ht_update_stats(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
}

static bool
minstrel_ht_txstat_valid(struct ieee80211_tx_rate *rate)
minstrel_ht_txstat_valid(struct minstrel_priv *mp, struct ieee80211_tx_rate *rate)
{
if (rate->idx < 0)
return false;

if (!rate->count)
return false;

return !!(rate->flags & IEEE80211_TX_RC_MCS);
if (rate->flags & IEEE80211_TX_RC_MCS)
return true;

return rate->idx == mp->cck_rates[0] ||
rate->idx == mp->cck_rates[1] ||
rate->idx == mp->cck_rates[2] ||
rate->idx == mp->cck_rates[3];
}

static void
Expand Down Expand Up @@ -386,7 +446,6 @@ minstrel_ht_tx_status(void *priv, struct ieee80211_supported_band *sband,
struct minstrel_rate_stats *rate, *rate2;
struct minstrel_priv *mp = priv;
bool last;
int group;
int i;

if (!msp->is_ht)
Expand Down Expand Up @@ -415,13 +474,12 @@ minstrel_ht_tx_status(void *priv, struct ieee80211_supported_band *sband,
if (info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE)
mi->sample_packets += info->status.ampdu_len;

last = !minstrel_ht_txstat_valid(&ar[0]);
last = !minstrel_ht_txstat_valid(mp, &ar[0]);
for (i = 0; !last; i++) {
last = (i == IEEE80211_TX_MAX_RATES - 1) ||
!minstrel_ht_txstat_valid(&ar[i + 1]);
!minstrel_ht_txstat_valid(mp, &ar[i + 1]);

group = minstrel_ht_get_group_idx(&ar[i]);
rate = &mi->groups[group].rates[ar[i].idx % 8];
rate = minstrel_ht_get_stats(mp, mi, &ar[i]);

if (last)
rate->success += info->status.ampdu_ack_len;
Expand All @@ -447,7 +505,8 @@ minstrel_ht_tx_status(void *priv, struct ieee80211_supported_band *sband,

if (time_after(jiffies, mi->stats_update + (mp->update_interval / 2 * HZ) / 1000)) {
minstrel_ht_update_stats(mp, mi);
if (!(info->flags & IEEE80211_TX_CTL_AMPDU))
if (!(info->flags & IEEE80211_TX_CTL_AMPDU) &&
mi->max_prob_rate / MCS_GROUP_RATES != MINSTREL_CCK_GROUP)
minstrel_aggr_check(sta, skb);
}
}
Expand All @@ -463,6 +522,7 @@ minstrel_calc_retransmit(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
unsigned int ctime = 0;
unsigned int t_slot = 9; /* FIXME */
unsigned int ampdu_len = MINSTREL_TRUNC(mi->avg_ampdu_len);
unsigned int overhead = 0, overhead_rtscts = 0;

mr = minstrel_get_ratestats(mi, index);
if (mr->probability < MINSTREL_FRAC(1, 10)) {
Expand All @@ -484,9 +544,14 @@ minstrel_calc_retransmit(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
ctime += (t_slot * cw) >> 1;
cw = min((cw << 1) | 1, mp->cw_max);

if (index / MCS_GROUP_RATES != MINSTREL_CCK_GROUP) {
overhead = mi->overhead;
overhead_rtscts = mi->overhead_rtscts;
}

/* Total TX time for data and Contention after first 2 tries */
tx_time = ctime + 2 * (mi->overhead + tx_time_data);
tx_time_rtscts = ctime + 2 * (mi->overhead_rtscts + tx_time_data);
tx_time = ctime + 2 * (overhead + tx_time_data);
tx_time_rtscts = ctime + 2 * (overhead_rtscts + tx_time_data);

/* See how many more tries we can fit inside segment size */
do {
Expand All @@ -495,8 +560,8 @@ minstrel_calc_retransmit(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
cw = min((cw << 1) | 1, mp->cw_max);

/* Total TX time after this try */
tx_time += ctime + mi->overhead + tx_time_data;
tx_time_rtscts += ctime + mi->overhead_rtscts + tx_time_data;
tx_time += ctime + overhead + tx_time_data;
tx_time_rtscts += ctime + overhead_rtscts + tx_time_data;

if (tx_time_rtscts < mp->segment_size)
mr->retry_count_rtscts++;
Expand Down Expand Up @@ -526,9 +591,16 @@ minstrel_ht_set_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
else
rate->count = mr->retry_count;

rate->flags = IEEE80211_TX_RC_MCS | group->flags;
rate->flags = 0;
if (rtscts)
rate->flags |= IEEE80211_TX_RC_USE_RTS_CTS;

if (index / MCS_GROUP_RATES == MINSTREL_CCK_GROUP) {
rate->idx = mp->cck_rates[index % ARRAY_SIZE(mp->cck_rates)];
return;
}

rate->flags |= IEEE80211_TX_RC_MCS | group->flags;
rate->idx = index % MCS_GROUP_RATES + (group->streams - 1) * MCS_GROUP_RATES;
}

Expand Down Expand Up @@ -591,6 +663,22 @@ minstrel_get_sample_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
return sample_idx;
}

static void
minstrel_ht_check_cck_shortpreamble(struct minstrel_priv *mp,
struct minstrel_ht_sta *mi, bool val)
{
u8 supported = mi->groups[MINSTREL_CCK_GROUP].supported;

if (!supported || !mi->cck_supported_short)
return;

if (supported & (mi->cck_supported_short << (val * 4)))
return;

supported ^= mi->cck_supported_short | (mi->cck_supported_short << 4);
mi->groups[MINSTREL_CCK_GROUP].supported = supported;
}

static void
minstrel_ht_get_rate(void *priv, struct ieee80211_sta *sta, void *priv_sta,
struct ieee80211_tx_rate_control *txrc)
Expand All @@ -610,6 +698,7 @@ minstrel_ht_get_rate(void *priv, struct ieee80211_sta *sta, void *priv_sta,
return mac80211_minstrel.get_rate(priv, sta, &msp->legacy, txrc);

info->flags |= mi->tx_flags;
minstrel_ht_check_cck_shortpreamble(mp, mi, txrc->short_preamble);

/* Don't use EAPOL frames for sampling on non-mrr hw */
if (mp->hw->max_rates == 1 &&
Expand Down Expand Up @@ -682,6 +771,30 @@ minstrel_ht_get_rate(void *priv, struct ieee80211_sta *sta, void *priv_sta,
}
}

static void
minstrel_ht_update_cck(struct minstrel_priv *mp, struct minstrel_ht_sta *mi,
struct ieee80211_supported_band *sband,
struct ieee80211_sta *sta)
{
int i;

if (sband->band != IEEE80211_BAND_2GHZ)
return;

mi->cck_supported = 0;
mi->cck_supported_short = 0;
for (i = 0; i < 4; i++) {
if (!rate_supported(sta, sband->band, mp->cck_rates[i]))
continue;

mi->cck_supported |= BIT(i);
if (sband->bitrates[i].flags & IEEE80211_RATE_SHORT_PREAMBLE)
mi->cck_supported_short |= BIT(i);
}

mi->groups[MINSTREL_CCK_GROUP].supported = mi->cck_supported;
}

static void
minstrel_ht_update_caps(void *priv, struct ieee80211_supported_band *sband,
struct ieee80211_sta *sta, void *priv_sta)
Expand All @@ -702,7 +815,7 @@ minstrel_ht_update_caps(void *priv, struct ieee80211_supported_band *sband,
goto use_legacy;

BUILD_BUG_ON(ARRAY_SIZE(minstrel_mcs_groups) !=
MINSTREL_MAX_STREAMS * MINSTREL_STREAM_GROUPS);
MINSTREL_MAX_STREAMS * MINSTREL_STREAM_GROUPS + 1);

msp->is_ht = true;
memset(mi, 0, sizeof(*mi));
Expand Down Expand Up @@ -738,6 +851,11 @@ minstrel_ht_update_caps(void *priv, struct ieee80211_supported_band *sband,
u16 req = 0;

mi->groups[i].supported = 0;
if (i == MINSTREL_CCK_GROUP) {
minstrel_ht_update_cck(mp, mi, sband, sta);
continue;
}

if (minstrel_mcs_groups[i].flags & IEEE80211_TX_RC_SHORT_GI) {
if (minstrel_mcs_groups[i].flags & IEEE80211_TX_RC_40_MHZ_WIDTH)
req |= IEEE80211_HT_CAP_SGI_40;
Expand Down
5 changes: 4 additions & 1 deletion net/mac80211/rc80211_minstrel_ht.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -107,8 +107,11 @@ struct minstrel_ht_sta {
/* current MCS group to be sampled */
u8 sample_group;

u8 cck_supported;
u8 cck_supported_short;

/* MCS rate group info and statistics */
struct minstrel_mcs_group_data groups[MINSTREL_MAX_STREAMS * MINSTREL_STREAM_GROUPS];
struct minstrel_mcs_group_data groups[MINSTREL_MAX_STREAMS * MINSTREL_STREAM_GROUPS + 1];
};

struct minstrel_ht_sta_priv {
Expand Down
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