// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2017-2026 Morse Micro
*/
#include "mmrc.h"
/*
* The default packet size in bits used for calculated throughput of a given
* rate
*/
#define DEFAULT_PACKET_SIZE_BITS 9600
/*
* The default packet size in bytes used for calculating retries for a given
* rate
*/
#define DEFAULT_PACKET_SIZE_BYTES 1200
/* The sample frequencies at different stages */
#define LOOKAROUND_RATE_INIT 5
#define LOOKAROUND_RATE_NORMAL 50
#define LOOKAROUND_RATE_STABLE 100
/* The thresholds for stability stages */
#define STABILITY_CNT_THRESHOLD_INIT 20
#define STABILITY_CNT_THRESHOLD_NORMAL 50
#define STABILITY_CNT_THRESHOLD_STABLE 100
/* The backoff step size for the counter */
#define STABILITY_BACKOFF_STEP 2
/*
* The packet success threshold for attempting slower lookaround rates
*/
/*
* Force a look around if there haven't been any for this number of cycles
*/
#define LOOKAROUND_MAX_RC_CYCLES 5
/*
* Number of attempts for each lookaround rate within at most two RC cycles
* if there are enough packets
*/
#define LOOKAROUND_RATE_ATTEMPTS 4
/*
* Limit the number of times we try to pick a theoretically better rate to
* sample. Necessary so we don't stall the CPU, due to constantly picking worse
* rates.
*/
#define LOOKAROUND_FAIL_MAX 200
/*
* Initial and reset probability per rate in the table
* Changing this value will have a severe implication on the current heuristic
* It could mean that some rates will have better probability throughput even
* with no edivence and so will cause unexpected changes in the rate table
*/
#define RATE_INIT_PROBABILITY 0
/*
* The lowest number of MPDUs within acknowledged AMPDUs that can be used for
* rate stats
*/
#define AMPDU_STATS_MIN 2
/*
* The lowest number of stats to be used for processing in NORMAL lookaround
* mode
*/
#define STATS_MIN_NORMAL 2
/*
* The lowest number of stats to be used for processing in INIT lookaround
* mode
*/
#define STATS_MIN_INIT 1
/* The lowest probability value considered for recognising a dip */
#define PROBABILITY_DIP_MIN 20
/* The lowest probability value for recovering from a dip */
#define PROBABILITY_DIP_RECOVERY_MIN 40
/*
* The time cap on rate allocation for multiple attempts. If a single attempt
* exceeds this window, no additional attempts will be generated
*/
#define MAX_WINDOW_ATTEMPT_TIME 4000
/* The time window for all rates in rate table */
#define RATE_WINDOW_MICROSECONDS 24000
/*
* EWMA is the alpha coefficient in the exponential weighting moving average
* filter used for probability updates.
*
* Y[n] = X[n] * (100 - EWMA) + (Y[n-1] * EWMA)
* -------------------------------------
* 100
*
*/
#define EWMA 75
/*
* Evidence scaling to allow for one decimal place. Needed for low
* throughput, otherwise the history decays in a single cycle.
*/
#define EVIDENCE_SCALE 5
/*
* Evidence maximum to ensure history doesn't decay too slowly when
* there is a lot of historical data.
*/
#define EVIDENCE_MAX 100
/*
* This fixed point conversion multiplies a value by one and shifts it
* accordingly to account for the fixed point shifting at the return of a
* function
*/
#define FP_8_MULT_1 256
/* Fixed point conversion for 2.1 * 2^8 used for 4MHz symbol multiplication */
#define FP_8_4MHZ 537
/* Fixed point conversion for 4.5 * 2^8 used for 8MHz symbol multiplication */
#define FP_8_8MHZ 1152
/* Fixed point conversion for 9.0 * 2^8 used for 16MHz symbol multiplication */
#define FP_8_16MHZ 2301
/*
* Fixed point conversion for 3.6 * 2^8 used for long guard symbol tx time
* multiplication
*/
#define FP_8_LONG_GUARD_SYMBOL_TIME 1024
/*
* Fixed point conversion for 4.0 * 2^8 used for short guard symbol tx time
* multiplication
*/
#define FP_8_SHORT_GUARD_SYMBOL_TIME 921
/*
* Shift value to shift back our FP conversions
*/
#define FP_8_SHIFT 8
/*
* Limit to count of consecutive variations in one direction
*/
#define MAX_VARIATION_DIRECTION 5
/*
* Threshold for considering consecutive variation direction as variation
* or not
*/
#define VARIATION_DIRECTION_THRESHOLD 3
/* EWMA percentage value for averaging the best rate probability variation */
#define VARIATION_EWMA 95
/* Percentage variation regarded as minor */
#define MINOR_VARIATION_THRESHOLD 1
/* Percentage variation regarded as moderate */
#define MODERATE_VARIATION_THRESHOLD 3
/* Percentage variation regarded as significant */
#define SIGNIFICANT_VARIATION_THRESHOLD 5
/* If the best rate changes twice in this number of cycles, it is unstable */
#define BEST_RATE_UNSTABLE_THRESHOLD 4
/*
* Once the best rate is unchanged for this number of cycles it has
* converged
*/
#define BEST_RATE_CONVERGED_THRESHOLD 10
/* RSSI threshold for short range */
#define MMRC_SHORT_RANGE_RSSI_LIMIT -70
/* RSSI threshold for mid range */
#define MMRC_MID_RANGE_RSSI_LIMIT -85
#define MMRC_MAX_BW(bw_caps) \
(((bw_caps) & BIT(MMRC_BW_16MHZ)) ? MMRC_BW_16MHZ : \
((bw_caps) & BIT(MMRC_BW_8MHZ)) ? MMRC_BW_8MHZ : \
((bw_caps) & BIT(MMRC_BW_4MHZ)) ? MMRC_BW_4MHZ : \
((bw_caps) & BIT(MMRC_BW_2MHZ)) ? MMRC_BW_2MHZ : \
MMRC_BW_1MHZ)
/*
* This table stores the number of bits per symbols used for MCS0-MCS9 based
* on 20MHz and 1SS
*/
static const u32 sym_table[10] = { 24, 36, 48, 72, 96, 144, 192, 216, 256, 288 };
/*
* Calculate which bit is the nth bit set in an integer based flag.
*/
static u8 nth_bit(u16 in, u16 index)
{
u32 i;
u8 count = 0;
for (i = 0; count != index + 1; i++) {
if (((1u << i) & in) != 0)
count++;
}
return i - 1;
}
/*
* Calculate the input bit's index among all the set bits in an integer
* based flag.
*/
static u16 bit_index(u16 in, u32 bit_pos)
{
u16 i;
u16 index = 0;
for (i = 0; i != bit_pos + 1; i++) {
if (((1u << i) & in) != 0)
index++;
}
if (index == 0) {
/* Could not match bit pos to caps */
return 0;
}
return index - 1;
}
static u16 rows_from_sta_caps(struct mmrc_sta_capabilities *caps)
{
u16 rows = 0;
u8 n_rates = hweight_long(caps->rates);
/* Taking MCS10 into account as it is relevant for 1 MHz entries */
if (caps->rates & BIT(MMRC_MCS10)) {
n_rates -= 1;
rows = 2;
}
rows += (hweight_long(caps->bandwidth) * n_rates *
hweight_long(caps->guard) *
hweight_long(caps->spatial_streams));
return rows;
}
static void rate_update_index(struct mmrc_table *tb, struct mmrc_rate *rate)
{
u16 index = 0;
/* Information about our rates */
u16 bw = hweight_long(tb->caps.bandwidth);
u16 streams = hweight_long(tb->caps.spatial_streams);
u16 guard = hweight_long(tb->caps.guard);
u16 rows = rows_from_sta_caps(&tb->caps);
index = bit_index(tb->caps.guard, rate->guard) +
bit_index(tb->caps.bandwidth, rate->bw) * guard +
bit_index(tb->caps.spatial_streams, rate->ss) * guard * bw +
bit_index(tb->caps.rates, rate->rate) * bw * streams * guard;
if (index >= rows)
index = 0;
rate->index = index;
}
static struct mmrc_rate get_rate_row(struct mmrc_table *tb, u16 index)
{
struct mmrc_rate rate;
u16 ss_index;
/* Information about our rates */
u16 mcs = hweight_long(tb->caps.rates);
u16 bw = hweight_long(tb->caps.bandwidth);
u16 streams = hweight_long(tb->caps.spatial_streams);
u16 guard = hweight_long(tb->caps.guard);
u16 total_caps = mcs * bw * streams * guard;
/* Find our MCS */
u16 rows = total_caps / mcs;
u16 mcs_index = index / rows;
u16 mcs_modulo = index % rows;
mcs = nth_bit(tb->caps.rates, mcs_index);
/* Find our spatial stream */
rows = rows / streams;
streams = nth_bit(tb->caps.spatial_streams, mcs_modulo / rows);
/* Find our bandwidth */
ss_index = index % rows;
rows = rows / bw;
bw = nth_bit(tb->caps.bandwidth, ss_index / rows);
/* Find our guard */
guard = nth_bit(tb->caps.guard, index % guard);
/* Add range checks to keep scan-build happy */
if (bw >= MMRC_BW_MAX)
bw = MMRC_BW_1MHZ;
if (guard >= MMRC_GUARD_MAX)
guard = MMRC_GUARD_LONG;
/* Validate guard against capability */
if (guard == MMRC_GUARD_SHORT &&
!(tb->caps.sgi_per_bw & SGI_PER_BW(bw)))
guard = MMRC_GUARD_LONG;
/* Create our rate row and send it */
rate.bw = MMRC_BW_TO_BITFIELD(bw);
rate.ss = MMRC_SS_TO_BITFIELD(streams);
rate.rate = MMRC_RATE_TO_BITFIELD(mcs);
rate.guard = MMRC_GUARD_TO_BITFIELD(guard);
rate.attempts = 0;
rate.flags = 0;
/* Update index as bw or guard may have changed */
rate_update_index(tb, &rate);
return rate;
}
size_t mmrc_memory_required_for_caps(struct mmrc_sta_capabilities *caps)
{
return sizeof(struct mmrc_table) +
rows_from_sta_caps(caps) * sizeof(struct mmrc_stats_table);
}
static u32 calculate_bits_per_symbol(struct mmrc_rate *rate)
{
u32 bps;
/* If MCS10 is selected we return 2*MCS0 Symbols */
if (rate->rate == MMRC_MCS10)
return 6;
/* Confirm that the rate is valid for the sym_table lookup */
if (rate->rate >= MMRC_MCS_UNUSED) {
pr_err("%s: Invalid MCS rate %d for sym_table lookup\n",
__func__, rate->rate);
return 1;
}
/*
* Coversion from 20MHz as in sym_table to:
* 40MHz == x 2.1
* 80MHz == x 4.5
* 160MHz == x 9.0
*/
bps = sym_table[rate->rate];
switch (rate->bw) {
case (MMRC_BW_4MHZ):
bps *= FP_8_4MHZ;
break;
case (MMRC_BW_8MHZ):
bps *= FP_8_8MHZ;
break;
case (MMRC_BW_16MHZ):
bps *= FP_8_16MHZ;
break;
case (MMRC_BW_1MHZ):
bps = sym_table[rate->rate] * 24 / 52;
bps *= FP_8_MULT_1;
break;
case (MMRC_BW_2MHZ):
case (MMRC_BW_MAX):
default:
bps *= FP_8_MULT_1;
break;
}
/* SS + 1 because mmrc_spatial_stream starts at 0 */
return ((rate->ss + 1) * bps) >> FP_8_SHIFT;
}
static u32 get_tx_time(struct mmrc_rate *rate)
{
u32 tx = 0;
u32 n_sym;
u32 avg_bits;
/* Calculate tx time based on a default packet size */
avg_bits = DEFAULT_PACKET_SIZE_BITS;
/* Number of bits per symbol for this rate */
n_sym = calculate_bits_per_symbol(rate);
/* In case of bad calcuation/parameter use lowest value */
n_sym = n_sym == 0 ? sym_table[0] : n_sym;
/* number of symbols in default packet size */
n_sym = avg_bits / n_sym;
/* tx is time to transmit average packet in us */
switch (rate->guard) {
case (MMRC_GUARD_LONG):
tx = n_sym * FP_8_LONG_GUARD_SYMBOL_TIME;
break;
case (MMRC_GUARD_SHORT):
tx = n_sym * FP_8_SHORT_GUARD_SYMBOL_TIME;
break;
default:
return 0;
}
return (tx * 10) >> FP_8_SHIFT;
}
u32 mmrc_calculate_theoretical_throughput(struct mmrc_rate rate)
{
static const u32 s1g_tpt_lgi[4][11] = {
{ 300, 600, 900, 1200, 1800, 2400, 2700, 3000, 3600, 4000,
150 },
{ 650, 1300, 1950, 2600, 3900, 5200, 5850, 6500, 7800, 0, 0 },
{ 1350, 2700, 4050, 5400, 8100, 10800, 12150, 13500, 16200,
18000, 0 },
{ 2925, 5850, 8775, 11700, 17550, 23400, 26325, 29250, 35100,
39000, 0 },
};
static const u32 s1g_tpt_sgi[4][11] = {
{ 333, 666, 1000, 1333, 2000, 2666, 3000, 3333, 4000, 4444,
166 },
{ 722, 1444, 2166, 2888, 4333, 5777, 6500, 7222, 8666, 0, 0 },
{ 1500, 3000, 4500, 6000, 9000, 12000, 13500, 15000, 18000,
20000, 0 },
{ 3250, 6500, 9750, 13000, 19500, 26000, 29250, 32500, 39000,
43333, 0 },
};
if (rate.guard)
return s1g_tpt_sgi[rate.bw][rate.rate] * 1000 * (rate.ss + 1);
return s1g_tpt_lgi[rate.bw][rate.rate] * 1000 * (rate.ss + 1);
}
static u32 calculate_throughput(struct mmrc_table *tb, u8 index)
{
struct mmrc_rate rate = get_rate_row(tb, index);
/*
* Avoid the overflow (observed for 8MHz MCS9 rate: 43333) by dividing
* first before multiplying. Should not experience any loss of
* precision as the throughput is already multiplied by 1000 in
* mmrc_calculate_theoretical_throughput (returned as bits/sec)
*/
if (tb->table[rate.index].prob < 10)
return 0;
else if (rate.index == tb->best_tp.index && tb->interference_likely)
/*
* Assist the best rate by increasing the probability by the
* averaged variation
*/
return (mmrc_calculate_theoretical_throughput(rate) / 100) *
(tb->table[rate.index].prob + tb->probability_variation);
else
return (mmrc_calculate_theoretical_throughput(rate) / 100) *
tb->table[rate.index].prob;
}
static bool validate_rate(struct mmrc_table *tb, struct mmrc_rate *rate)
{
if (rate->rate == MMRC_MCS10 &&
(rate->bw != MMRC_BW_1MHZ || rate->ss != MMRC_SPATIAL_STREAM_1)) {
/*
* 802.11ah does not support MCS10 with BW that is not 1MHz or
* not 1 spatial stream.
*/
return false;
}
if (rate->rate == MMRC_MCS9 && rate->bw == MMRC_BW_2MHZ &&
rate->ss != MMRC_SPATIAL_STREAM_3) {
/*
* 802.11ah does not support MCS9 at 2MHz for 1, 2 or 4 spatial
* streams
*/
return false;
}
if (rate->guard == MMRC_GUARD_SHORT &&
!(tb->caps.sgi_per_bw & SGI_PER_BW(rate->bw)))
return false;
return true;
}
static u16 find_baseline_index(struct mmrc_table *tb)
{
u32 i, theoretical_tp, min_theoretical_tp;
u16 row_count = rows_from_sta_caps(&tb->caps);
u16 min_theoretical_tp_index = 0;
struct mmrc_rate rate;
if (tb->caps.rates & BIT(MMRC_MCS10))
return 0;
min_theoretical_tp =
mmrc_calculate_theoretical_throughput(get_rate_row(tb, 0));
for (i = 0; i < row_count; i++) {
rate = get_rate_row(tb, i);
if (!validate_rate(tb, &rate))
continue;
theoretical_tp = mmrc_calculate_theoretical_throughput(rate);
if (min_theoretical_tp > theoretical_tp) {
min_theoretical_tp = theoretical_tp;
min_theoretical_tp_index = rate.index;
}
}
return min_theoretical_tp_index;
}
/*
* Fill out the remaining rates to be used once the best rate is selected.
* Normally the retry rates are one MCS lower than the previous, however in
* unconverged mode we limit the 3 respective retry rates to MCS 4, 2 and 0
* respectively. The last retry rate is always MCS 0
*/
static void mmrc_fill_retry_rates(struct mmrc_table *tb)
{
tb->second_tp = tb->best_tp;
if (tb->second_tp.rate != MMRC_MCS0) {
tb->second_tp.rate--;
if (tb->unconverged && tb->second_tp.rate > MMRC_MCS4)
tb->second_tp.rate = MMRC_MCS4;
rate_update_index(tb, &tb->second_tp);
} else if (tb->second_tp.bw > MMRC_BW_1MHZ) {
tb->second_tp.bw--;
rate_update_index(tb, &tb->second_tp);
}
tb->best_prob = tb->second_tp;
if (tb->best_prob.rate != MMRC_MCS0) {
tb->best_prob.rate--;
if (tb->unconverged && tb->best_prob.rate > MMRC_MCS2)
tb->best_prob.rate = MMRC_MCS2;
rate_update_index(tb, &tb->best_prob);
} else if (tb->best_prob.bw > MMRC_BW_1MHZ) {
tb->best_prob.bw--;
rate_update_index(tb, &tb->best_prob);
}
tb->baseline = tb->best_prob;
if (tb->baseline.rate != MMRC_MCS0) {
tb->baseline.rate = MMRC_MCS0;
rate_update_index(tb, &tb->baseline);
} else if (tb->baseline.bw > MMRC_BW_1MHZ) {
tb->baseline.bw--;
rate_update_index(tb, &tb->baseline);
}
}
/*
* Updates the mmrc_table with the appropriate rate priority based on the
* latest update statistics
*/
static void generate_table_priority(struct mmrc_table *tb, u32 new_stats)
{
u16 i;
u16 best_row = tb->best_tp.index;
u16 prev_best_row = best_row;
u8 prev_best_rate = tb->best_tp.rate;
u16 second_best_row = tb->second_tp.index;
u32 best_tp = calculate_throughput(tb, best_row);
u32 second_best_tp = calculate_throughput(tb, second_best_row);
u32 last_nonzero_prob = 0;
struct mmrc_rate tmp;
u32 tmp_tp;
/* Use fixed rate if set */
if (tb->fixed_rate.rate != MMRC_MCS_UNUSED) {
tb->best_tp = tb->fixed_rate;
tb->second_tp = tb->fixed_rate;
tb->best_prob = tb->fixed_rate;
return;
}
for (i = 0; i < rows_from_sta_caps(&tb->caps); i++) {
tmp = get_rate_row(tb, i);
if (!validate_rate(tb, &tmp))
continue;
if (tb->table[tmp.index].evidence == 0)
continue;
/*
* Besides better throughput, also consider this rate better if
* lower rates had worse probability. That indicates the rate
* itself is not the problem. Only do the probability check for
* rates up to the previous best rate.
*/
tmp_tp = calculate_throughput(tb, tmp.index);
if (tmp_tp > best_tp ||
(tb->table[tmp.index].max_throughput <=
tb->table[prev_best_row].max_throughput &&
tb->table[tmp.index].prob >=
PROBABILITY_DIP_RECOVERY_MIN &&
tb->table[tmp.index].prob >
tb->table[last_nonzero_prob].prob)) {
second_best_row = best_row;
second_best_tp = best_tp;
best_tp = tmp_tp;
best_row = tmp.index;
} else if (tmp_tp > second_best_tp && best_row != tmp.index) {
second_best_tp = tmp_tp;
second_best_row = tmp.index;
}
if (tb->table[tmp.index].prob >= PROBABILITY_DIP_MIN &&
tb->table[tmp.index].max_throughput >=
tb->table[last_nonzero_prob].max_throughput)
last_nonzero_prob = tmp.index;
}
/* Only update rates and stability when there are new statistics */
if (!new_stats)
return;
tb->best_tp = get_rate_row(tb, best_row);
if (best_tp == 0 && tb->best_tp.rate > MMRC_MCS0) {
/* Drop one rate, as the best throughput is zero */
tb->best_tp.rate--;
rate_update_index(tb, &tb->best_tp);
}
tb->second_tp = get_rate_row(tb, second_best_row);
mmrc_fill_retry_rates(tb);
if (tb->best_tp.rate > MMRC_MCS1 && prev_best_row == best_row) {
/* Increase the counter when the best rate is not changed */
tb->stability_cnt++;
} else if (tb->stability_cnt > STABILITY_BACKOFF_STEP) {
/* Back off the counter when there is a new best rate */
tb->stability_cnt -= STABILITY_BACKOFF_STEP;
} else {
tb->stability_cnt = 0;
}
if (prev_best_row != best_row) {
s8 latest_best_rate_diff = prev_best_rate - tb->best_tp.rate;
u8 total_abs_best_rate_diff =
abs(tb->best_rate_diff[0] + tb->best_rate_diff[1] +
latest_best_rate_diff);
if (!tb->interference_likely) {
tb->probability_variation = 0;
if (!tb->unconverged &&
tb->best_rate_cycle_count <=
BEST_RATE_UNSTABLE_THRESHOLD &&
total_abs_best_rate_diff >= 2) {
/*
* Best rate has changed twice in a few cycles
* and moved at least 2 MCSs from where it was
* 3 best rate changes ago
*/
tb->unconverged = true;
tb->newly_unconverged = true;
}
}
if (tb->unconverged && !tb->newly_unconverged &&
total_abs_best_rate_diff < 2) {
/*
* Best rate has been relatively stable (not moved more
* than 1 MCS after the last 3 rate changes), go back
* to converged
*/
tb->unconverged = false;
}
tb->probability_variation_direction = 0;
tb->best_rate_cycle_count = 0;
tb->best_rate_diff[0] = tb->best_rate_diff[1];
tb->best_rate_diff[1] = latest_best_rate_diff;
} else {
tb->best_rate_cycle_count++;
if (tb->unconverged && !tb->newly_unconverged &&
tb->best_rate_cycle_count >=
BEST_RATE_CONVERGED_THRESHOLD) {
/*
* Best rate has been stable for a while, go back to
* converged
*/
tb->unconverged = false;
}
}
if (tb->newly_unconverged)
tb->newly_unconverged = false;
}
static u32 calculate_attempt_time(struct mmrc_rate *rate, size_t size)
{
u32 time;
time = get_tx_time(rate);
if (size > DEFAULT_PACKET_SIZE_BYTES)
time = (time * ((size * 1000) / DEFAULT_PACKET_SIZE_BYTES)) /
1000;
else
time = (time * 1000) /
((DEFAULT_PACKET_SIZE_BYTES * 1000) / size);
return time;
}
u32 mmrc_calculate_rate_tx_time(struct mmrc_rate *rate, size_t size)
{
u8 i;
u32 total_time = 0;
for (i = 0; i < rate->attempts; i++)
total_time += calculate_attempt_time(rate, size);
return total_time;
}
/*
* Calculates the appropriate amount of additional attempts to make based on
* packet size and theoretical throughput.
*/
static void calculate_remaining_attempts(struct mmrc_table *tb,
struct mmrc_rate_table *rate,
s32 *rem_time, size_t size)
{
size_t i;
if (*rem_time <= 0)
return;
for (i = 0; i < MMRC_MAX_CHAIN_LENGTH; i++) {
u32 attempt_time;
u32 attempt;
if (rate->rates[i].rate == MMRC_MCS_UNUSED)
break;
/*
* The attempts for these rates were calculated in the initial
* attempt allocation
*/
if (tb->table[rate->rates[i].index].prob < 20)
continue;
if (i == 0 && (calculate_throughput(tb, rate->rates[i].index) <
calculate_throughput(tb, tb->best_prob.index)))
continue;
attempt_time = calculate_attempt_time(&rate->rates[i], size);
if (!attempt_time)
continue;
attempt = (*rem_time / tb->caps.max_rates) / attempt_time;
attempt += rate->rates[i].attempts;
rate->rates[i].attempts = MMRC_ATTEMPTS_TO_BITFIELD(
attempt > MMRC_MAX_CHAIN_ATTEMPTS ?
MMRC_MAX_CHAIN_ATTEMPTS :
attempt);
}
}
/* Allocate initial attempts to all rates in a rate table */
static void allocate_initial_attempts(struct mmrc_rate_table *rate,
s32 *rem_time, size_t size)
{
u32 i;
for (i = 0; i < MMRC_MAX_CHAIN_LENGTH; i++) {
u32 attempt_time;
if (rate->rates[i].rate == MMRC_MCS_UNUSED)
break;
attempt_time = calculate_attempt_time(&rate->rates[i], size);
/*
* if the time for a single attempt is very long, lets just
* try once
*/
if (attempt_time > MAX_WINDOW_ATTEMPT_TIME) {
*rem_time -= attempt_time;
rate->rates[i].attempts = MMRC_ATTEMPTS_TO_BITFIELD(1);
} else {
*rem_time -= attempt_time * 2;
rate->rates[i].attempts = MMRC_ATTEMPTS_TO_BITFIELD(2);
}
}
}
void mmrc_get_rates(struct mmrc_table *tb, struct mmrc_rate_table *out,
size_t size)
{
u8 i;
u16 random_index;
struct mmrc_rate random;
struct mmrc_rate lookaround0 = tb->best_tp;
struct mmrc_rate lookaround1 = tb->second_tp;
bool is_lookaround;
int lookaround_index = -1;
int best_index = 0;
int random_tp = 0;
int best_tp;
int lookaround_fail_count;
bool try_current_lookaround = false;
s32 rem_time = RATE_WINDOW_MICROSECONDS;
memset(out, 0, sizeof(*out));
tb->lookaround_cnt = (tb->lookaround_cnt + 1) % tb->lookaround_wrap;
/*
* Look around if the counter wraps or there has been no look around
* for a number of rate control cycles.
*/
is_lookaround = (tb->fixed_rate.rate == MMRC_MCS_UNUSED) &&
((tb->lookaround_cnt == 0) ||
((tb->last_lookaround_cycle +
LOOKAROUND_MAX_RC_CYCLES) <= tb->cycle_cnt));
/* Also skip sampling if we don't yet have data for our best rate */
if (tb->table[tb->best_tp.index].evidence == 0)
is_lookaround = false;
if (tb->lookaround_wrap != LOOKAROUND_RATE_STABLE) {
if (tb->stability_cnt >= tb->stability_cnt_threshold) {
tb->lookaround_wrap = LOOKAROUND_RATE_STABLE;
tb->stability_cnt_threshold =
STABILITY_CNT_THRESHOLD_STABLE;
tb->stability_cnt = STABILITY_CNT_THRESHOLD_STABLE * 2;
is_lookaround = false;
}
} else if (tb->stability_cnt < tb->stability_cnt_threshold) {
tb->stability_cnt_threshold = STABILITY_CNT_THRESHOLD_NORMAL;
tb->lookaround_wrap = LOOKAROUND_RATE_NORMAL;
tb->stability_cnt = 0;
}
/* Look around only when the fixed rate is not set */
if (is_lookaround) {
tb->total_lookaround++;
tb->forced_lookaround =
(tb->forced_lookaround + 1) % LOOKAROUND_RATE_NORMAL;
tb->last_lookaround_cycle = tb->cycle_cnt;
if (tb->current_lookaround_rate_attempts <
LOOKAROUND_RATE_ATTEMPTS)
try_current_lookaround = true;
best_tp = calculate_throughput(tb, tb->best_tp.index);
for (lookaround_fail_count = 0;
lookaround_fail_count < LOOKAROUND_FAIL_MAX;
lookaround_fail_count++) {
if (try_current_lookaround) {
random_index =
tb->current_lookaround_rate_index;
try_current_lookaround = false;
} else {
random_index = get_random_u32_below(
rows_from_sta_caps(&tb->caps));
}
random = get_rate_row(tb, random_index);
if (!validate_rate(tb, &random))
continue;
if (random.rate == MMRC_MCS10)
continue;
if (tb->table[random_index].evidence > 0)
random_tp =
calculate_throughput(tb, random_index);
else
random_tp =
mmrc_calculate_theoretical_throughput(
random);
/*
* Skip rates that can only be worse than the current
* best
*/
if (random_tp <= best_tp)
continue;
/*
* Force looking up the rate no more that one MCS.
* It will avoid looking for rates with very low
* success rate. In case of better environment
* conditions MMRC will collect enough statistics to
* climb up the rates one by one.
*/
if (random.rate > tb->best_tp.rate + 1 ||
random.bw > tb->best_tp.bw + 1 ||
(random.rate > tb->best_tp.rate &&
random.bw > tb->best_tp.bw))
continue;
if (tb->current_lookaround_rate_index == random_index) {
tb->current_lookaround_rate_attempts++;
} else {
tb->current_lookaround_rate_attempts = 0;
tb->current_lookaround_rate_index =
random_index;
}
break;
}
if (lookaround_fail_count >= LOOKAROUND_FAIL_MAX) {
is_lookaround = false;
tb->current_lookaround_rate_index = tb->best_tp.index;
} else {
lookaround0 = random;
lookaround1 = tb->best_tp;
lookaround_index = 0;
best_index = 1;
}
}
if (tb->caps.max_rates == 1) {
out->rates[0] = (is_lookaround) ? lookaround0 : tb->best_tp;
out->rates[1].rate = MMRC_MCS_UNUSED;
out->rates[2].rate = MMRC_MCS_UNUSED;
out->rates[3].rate = MMRC_MCS_UNUSED;
} else if (tb->caps.max_rates == 2) {
out->rates[0] = (is_lookaround) ? lookaround0 : tb->best_tp;
out->rates[1] = (is_lookaround) ? lookaround1 : tb->best_prob;
out->rates[2].rate = MMRC_MCS_UNUSED;
out->rates[3].rate = MMRC_MCS_UNUSED;
} else if (tb->caps.max_rates == 3) {
out->rates[0] = (is_lookaround) ? lookaround0 : tb->best_tp;
out->rates[1] = (is_lookaround) ? lookaround1 : tb->second_tp;
out->rates[2] = tb->best_prob;
out->rates[3].rate = MMRC_MCS_UNUSED;
} else {
out->rates[0] = (is_lookaround) ? lookaround0 : tb->best_tp;
out->rates[1] = (is_lookaround) ? lookaround1 : tb->second_tp;
out->rates[2] = tb->best_prob;
out->rates[3] = tb->baseline;
}
/* For fallback rates, set RTS/CTS */
for (i = 1; i < MMRC_MAX_CHAIN_LENGTH; i++)
out->rates[i].flags |= BIT(MMRC_FLAGS_CTS_RTS);
/* Allocate initial attempts for rate */
allocate_initial_attempts(out, &rem_time, size);
/* Calculate and allocate remaining attempts */
calculate_remaining_attempts(tb, out, &rem_time, size);
/* Enforce limits on each attempts */
for (i = 0; i < MMRC_MAX_CHAIN_LENGTH; i++) {
if (out->rates[i].rate != MMRC_MCS_UNUSED) {
out->rates[i].attempts =
out->rates[i].attempts == 0 ?
MMRC_ATTEMPTS_TO_BITFIELD(
MMRC_MIN_CHAIN_ATTEMPTS) :
out->rates[i].attempts;
out->rates[i].attempts =
out->rates[i].attempts >
MMRC_MAX_CHAIN_ATTEMPTS ?
MMRC_ATTEMPTS_TO_BITFIELD(
MMRC_MAX_CHAIN_ATTEMPTS) :
out->rates[i].attempts;
if (i == lookaround_index &&
tb->lookaround_wrap != LOOKAROUND_RATE_INIT)
out->rates[i].attempts =
MMRC_ATTEMPTS_TO_BITFIELD(1);
}
}
/*
* Give the best rate at least 2 attempts to keep peak throughput
* unless it is too low
*/
if (out->rates[best_index].attempts == 1 &&
out->rates[best_index].rate > MMRC_MCS1)
out->rates[best_index].attempts = MMRC_ATTEMPTS_TO_BITFIELD(2);
else if (out->rates[best_index].rate <= MMRC_MCS1)
out->rates[best_index].attempts = 1;
}
static u32 calc_ewma_average(u32 avg, u32 latest, u32 weight)
{
WARN_ON_ONCE(!(weight <= 100));
if (avg == 0)
return latest;
return ((latest * (100 - weight)) + (avg * weight)) / 100;
}
static void mmrc_process_variation(struct mmrc_table *tb, u16 current_success,
u32 index)
{
u32 current_variation;
/*
* Only process probability variation for the best rate. It is likely
* the only rate to have enough data to see the variation and its
* statistics are more affected because they are usually collected over
* the full period.
*/
if (index != tb->best_tp.index)
return;
if (current_success == 0) {
if (!tb->unconverged) {
/*
* Best rate is failing completely, go to unconverged
* mode
*/
tb->unconverged = true;
tb->newly_unconverged = true;
}
return;
}
if (tb->table[index].prob == 0)
return;
/* Don't process variation while converging after association */
if (tb->lookaround_wrap == LOOKAROUND_RATE_INIT)
return;
current_variation = abs(current_success - tb->table[index].prob);
/* Calculate the EWMA of the probability variation */
tb->probability_variation = calc_ewma_average(
tb->probability_variation, current_variation, VARIATION_EWMA);
/*
* Process the variation direction to distinguish converged and
* unconverged scenarios
*/
if (tb->probability_variation >= MODERATE_VARIATION_THRESHOLD ||
tb->interference_likely) {
if ((current_success - tb->table[index].prob) *
tb->probability_variation_direction <
0)
tb->probability_variation_direction = 0;
else if (current_success > tb->table[index].prob)
tb->probability_variation_direction =
min(tb->probability_variation_direction + 1,
MAX_VARIATION_DIRECTION);
else if (current_success < tb->table[index].prob)
tb->probability_variation_direction =
max(tb->probability_variation_direction - 1,
-MAX_VARIATION_DIRECTION);
}
if (tb->best_rate_cycle_count > VARIATION_DIRECTION_THRESHOLD &&
tb->probability_variation >= SIGNIFICANT_VARIATION_THRESHOLD) {
/*
* Only enter interference mode if the best rate is stable for
* enough cycles to determine the direction is random and not
* in one direction only
*/
if (abs(tb->probability_variation_direction) <=
VARIATION_DIRECTION_THRESHOLD &&
!tb->interference_likely) {
tb->interference_likely = true;
}
} else if (tb->interference_likely &&
(tb->probability_variation <= MINOR_VARIATION_THRESHOLD ||
abs(tb->probability_variation_direction) ==
MAX_VARIATION_DIRECTION)) {
/*
* Exit interference mode if the variability drops or the
* direction stops being random
*/
tb->interference_likely = false;
}
}
void mmrc_update(struct mmrc_table *tb)
{
u32 i;
u16 this_success;
u32 scale;
u32 scaled_ewma;
u32 new_stats = 0;
u32 attempts_for_stats;
u32 success_for_stats;
u32 min_stats;
u32 throughput;
u32 evidence_sent;
tb->cycle_cnt++;
/* Allow less minimum stats when converging */
if (tb->lookaround_wrap != LOOKAROUND_RATE_INIT)
min_stats = STATS_MIN_NORMAL;
else
min_stats = STATS_MIN_INIT;
for (i = 0; i < rows_from_sta_caps(&tb->caps); i++) {
/* This algorithm is keeping track of the amount of evidence,
* being packets that have been recently sent at this rate.
* This value is smoothed with an EWMA function over time and
* used to update the probability of a rate succeeding
* dynamically. This method allows MMRC to react timely if a
* new rate is used that hasn't been used recently
*/
/* Necessary to prevent a divide by 0 */
if (tb->table[i].evidence == 0)
scale = 0;
else
scale = ((tb->table[i].evidence * 2) * 100) /
((tb->table[i].sent * EVIDENCE_SCALE) +
tb->table[i].evidence);
/* Restrict scale to appropriate values */
if (scale > 100)
scale = 100;
scaled_ewma = scale * EWMA / 100;
/*
* Only count new packets for evidence if we will process
* them
*/
evidence_sent =
tb->table[i].sent >= min_stats ? tb->table[i].sent : 0;
tb->table[i].evidence = calc_ewma_average(
tb->table[i].evidence, evidence_sent * EVIDENCE_SCALE,
scaled_ewma);
if (tb->table[i].evidence > EVIDENCE_MAX)
tb->table[i].evidence = EVIDENCE_MAX;
/* Try to use statistics from acknowledged AMPDUs first */
attempts_for_stats = tb->table[i].back_mpdu_success +
tb->table[i].back_mpdu_failure;
success_for_stats = tb->table[i].back_mpdu_success;
/*
* Use the full statistics if rates are not converged or there
* were no AMPDUs for this rate or the remaining attempts are
* less than half of what we have from AMPDUs.
*/
if (!tb->table[i].have_sent_ampdus || tb->unconverged ||
attempts_for_stats < AMPDU_STATS_MIN ||
(tb->table[i].sent - attempts_for_stats <
attempts_for_stats / 2)) {
attempts_for_stats = tb->table[i].sent;
success_for_stats = tb->table[i].sent_success;
}
if (attempts_for_stats >= min_stats ||
(attempts_for_stats > 0 && tb->table[i].prob > 0)) {
new_stats = 1;
this_success =
(100 * success_for_stats) / attempts_for_stats;
if (scaled_ewma)
mmrc_process_variation(tb, this_success, i);
tb->table[i].prob = calc_ewma_average(
tb->table[i].prob, this_success, scaled_ewma);
/* Clear our sent statistics and update totals */
tb->table[i].total_sent += tb->table[i].sent;
tb->table[i].sent = 0;
tb->table[i].total_success += tb->table[i].sent_success;
tb->table[i].sent_success = 0;
tb->table[i].back_mpdu_failure = 0;
tb->table[i].back_mpdu_success = 0;
tb->table[i].have_sent_ampdus = false;
}
throughput = calculate_throughput(tb, i);
if (tb->table[i].max_throughput < throughput)
tb->table[i].max_throughput = throughput;
/*
* Reset the running average windows if reached collector
* limits
*/
if (tb->table[i].sum_throughput > (0xFFFFFFFF - throughput)) {
tb->table[i].sum_throughput /=
tb->table[i].avg_throughput_counter;
tb->table[i].avg_throughput_counter = 1;
}
/* Update the sum and counter so it will be possible later to
* calculate the running average throughput
*/
tb->table[i].sum_throughput += throughput;
tb->table[i].avg_throughput_counter++;
}
generate_table_priority(tb, new_stats);
/*
* Switch to faster lookaround mode if rates drop low at very low
* bandwidth or we are in unconverged mode. Switching at low bandwidth
* and rate is to help recover quickly from rates where we would need
* to fragment standard MTU size packets.
*/
if (tb->lookaround_wrap != LOOKAROUND_RATE_INIT &&
(tb->unconverged || (tb->best_tp.bw == MMRC_BW_1MHZ &&
tb->best_tp.rate <= MMRC_MCS2))) {
tb->lookaround_cnt = 0;
tb->lookaround_wrap = LOOKAROUND_RATE_INIT;
tb->stability_cnt_threshold = STABILITY_CNT_THRESHOLD_INIT;
}
/*
* If it is unlikely we can do the lookaround attempts in two RC cycles
* choose a new rate
*/
if (tb->current_lookaround_rate_attempts <=
(LOOKAROUND_RATE_ATTEMPTS / 2))
tb->current_lookaround_rate_attempts = LOOKAROUND_RATE_ATTEMPTS;
}
void mmrc_feedback(struct mmrc_table *tb, struct mmrc_rate_table *rates,
s32 retry_count, bool was_aggregated)
{
s32 ind = retry_count;
u32 i;
for (i = 0; i < MMRC_MAX_CHAIN_LENGTH; i++) {
rate_update_index(tb, &rates->rates[i]);
tb->table[rates->rates[i].index].have_sent_ampdus |=
was_aggregated;
if ((s32)rates->rates[i].attempts < ind) {
ind = ind - rates->rates[i].attempts;
tb->table[rates->rates[i].index].sent +=
rates->rates[i].attempts;
if (was_aggregated) {
tb->table[rates->rates[i].index]
.back_mpdu_failure +=
rates->rates[i].attempts;
}
} else {
tb->table[rates->rates[i].index].sent += ind;
tb->table[rates->rates[i].index].sent_success += 1;
if (was_aggregated) {
tb->table[rates->rates[i].index]
.back_mpdu_success += 1;
tb->table[rates->rates[i].index]
.back_mpdu_failure +=
ind > 1 ? ind - 1 : 0;
}
return;
}
}
}
/*
* Chooses a reasonable starting rate based on range (gathered from
* RSSI measurements) or bandwidth. Then fills out the 3 retry rates
* so a full set of rates is available.
*/
static void mmrc_init_rates(struct mmrc_table *tb, s8 rssi)
{
tb->best_tp.bw = MMRC_MAX_BW(tb->caps.bandwidth);
if (tb->caps.sgi_per_bw & SGI_PER_BW(tb->best_tp.bw))
tb->best_tp.guard = MMRC_GUARD_TO_BITFIELD(MMRC_GUARD_SHORT);
else
tb->best_tp.guard = MMRC_GUARD_TO_BITFIELD(MMRC_GUARD_LONG);
tb->best_tp.rate = MMRC_RATE_TO_BITFIELD(MMRC_MCS0);
if (rssi >= MMRC_SHORT_RANGE_RSSI_LIMIT)
tb->best_tp.rate = MMRC_RATE_TO_BITFIELD(MMRC_MCS7);
else if (rssi < MMRC_SHORT_RANGE_RSSI_LIMIT &&
rssi >= MMRC_MID_RANGE_RSSI_LIMIT)
tb->best_tp.rate = MMRC_RATE_TO_BITFIELD(MMRC_MCS3);
else if (tb->best_tp.bw == MMRC_BW_1MHZ ||
tb->best_tp.bw == MMRC_BW_2MHZ)
/*
* To compensate for slow feedback when running with 1 and 2
* MHz bandwidth, we start from MCS3 which will correspond to
* reasonable feedback and will avoid resetting the rate table
* evidence.
*/
tb->best_tp.rate = MMRC_RATE_TO_BITFIELD(MMRC_MCS3);
tb->best_tp.ss = MMRC_SS_TO_BITFIELD(MMRC_SPATIAL_STREAM_1);
rate_update_index(tb, &tb->best_tp);
/* Init every rate in case they are needed to set the retry rates */
tb->second_tp = tb->best_tp;
tb->best_prob = tb->best_tp;
tb->baseline = tb->best_tp;
mmrc_fill_retry_rates(tb);
}
void mmrc_sta_init(struct mmrc_table *tb, struct mmrc_sta_capabilities *caps,
s8 rssi)
{
u32 i;
u16 row_count = rows_from_sta_caps(caps);
memset(tb, 0, mmrc_memory_required_for_caps(caps));
memcpy(&tb->caps, caps, sizeof(tb->caps));
for (i = 0; i < row_count; i++) {
tb->table[i].prob = RATE_INIT_PROBABILITY;
tb->table[i].evidence = 0;
tb->table[i].sum_throughput = 0;
tb->table[i].avg_throughput_counter = 0;
tb->table[i].max_throughput = 0;
}
tb->fixed_rate.rate = MMRC_MCS_UNUSED;
tb->cycle_cnt = 0;
tb->last_lookaround_cycle = 0;
tb->lookaround_cnt = 0;
tb->lookaround_wrap = LOOKAROUND_RATE_INIT;
tb->unconverged = true;
tb->newly_unconverged = true;
tb->stability_cnt_threshold = STABILITY_CNT_THRESHOLD_INIT;
tb->baseline = get_rate_row(tb, find_baseline_index(tb));
mmrc_init_rates(tb, rssi);
}
bool mmrc_set_fixed_rate(struct mmrc_table *tb, struct mmrc_rate fixed_rate)
{
bool caps_support_rate = true;
/* Do not accept rate which does not support the STA capabilities */
if ((BIT(fixed_rate.rate) & tb->caps.rates) == 0 ||
(BIT(fixed_rate.bw) & tb->caps.bandwidth) == 0 ||
(BIT(fixed_rate.ss) & tb->caps.spatial_streams) == 0 ||
(BIT(fixed_rate.guard) & tb->caps.guard) == 0)
caps_support_rate = false;
if (validate_rate(tb, &fixed_rate) && caps_support_rate) {
tb->fixed_rate = fixed_rate;
rate_update_index(tb, &tb->fixed_rate);
return true;
}
return false;
}
