linux/drivers/cpufreq/cpufreq_stats.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  drivers/cpufreq/cpufreq_stats.c
   4 *
   5 *  Copyright (C) 2003-2004 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
   6 *  (C) 2004 Zou Nan hai <nanhai.zou@intel.com>.
   7 */
   8
   9#include <linux/cpu.h>
  10#include <linux/cpufreq.h>
  11#include <linux/module.h>
  12#include <linux/sched/clock.h>
  13#include <linux/slab.h>
  14
  15struct cpufreq_stats {
  16        unsigned int total_trans;
  17        unsigned long long last_time;
  18        unsigned int max_state;
  19        unsigned int state_num;
  20        unsigned int last_index;
  21        u64 *time_in_state;
  22        unsigned int *freq_table;
  23        unsigned int *trans_table;
  24
  25        /* Deferred reset */
  26        unsigned int reset_pending;
  27        unsigned long long reset_time;
  28};
  29
  30static void cpufreq_stats_update(struct cpufreq_stats *stats,
  31                                 unsigned long long time)
  32{
  33        unsigned long long cur_time = local_clock();
  34
  35        stats->time_in_state[stats->last_index] += cur_time - time;
  36        stats->last_time = cur_time;
  37}
  38
  39static void cpufreq_stats_reset_table(struct cpufreq_stats *stats)
  40{
  41        unsigned int count = stats->max_state;
  42
  43        memset(stats->time_in_state, 0, count * sizeof(u64));
  44        memset(stats->trans_table, 0, count * count * sizeof(int));
  45        stats->last_time = local_clock();
  46        stats->total_trans = 0;
  47
  48        /* Adjust for the time elapsed since reset was requested */
  49        WRITE_ONCE(stats->reset_pending, 0);
  50        /*
  51         * Prevent the reset_time read from being reordered before the
  52         * reset_pending accesses in cpufreq_stats_record_transition().
  53         */
  54        smp_rmb();
  55        cpufreq_stats_update(stats, READ_ONCE(stats->reset_time));
  56}
  57
  58static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf)
  59{
  60        struct cpufreq_stats *stats = policy->stats;
  61
  62        if (READ_ONCE(stats->reset_pending))
  63                return sprintf(buf, "%d\n", 0);
  64        else
  65                return sprintf(buf, "%u\n", stats->total_trans);
  66}
  67cpufreq_freq_attr_ro(total_trans);
  68
  69static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf)
  70{
  71        struct cpufreq_stats *stats = policy->stats;
  72        bool pending = READ_ONCE(stats->reset_pending);
  73        unsigned long long time;
  74        ssize_t len = 0;
  75        int i;
  76
  77        for (i = 0; i < stats->state_num; i++) {
  78                if (pending) {
  79                        if (i == stats->last_index) {
  80                                /*
  81                                 * Prevent the reset_time read from occurring
  82                                 * before the reset_pending read above.
  83                                 */
  84                                smp_rmb();
  85                                time = local_clock() - READ_ONCE(stats->reset_time);
  86                        } else {
  87                                time = 0;
  88                        }
  89                } else {
  90                        time = stats->time_in_state[i];
  91                        if (i == stats->last_index)
  92                                time += local_clock() - stats->last_time;
  93                }
  94
  95                len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i],
  96                               nsec_to_clock_t(time));
  97        }
  98        return len;
  99}
 100cpufreq_freq_attr_ro(time_in_state);
 101
 102/* We don't care what is written to the attribute */
 103static ssize_t store_reset(struct cpufreq_policy *policy, const char *buf,
 104                           size_t count)
 105{
 106        struct cpufreq_stats *stats = policy->stats;
 107
 108        /*
 109         * Defer resetting of stats to cpufreq_stats_record_transition() to
 110         * avoid races.
 111         */
 112        WRITE_ONCE(stats->reset_time, local_clock());
 113        /*
 114         * The memory barrier below is to prevent the readers of reset_time from
 115         * seeing a stale or partially updated value.
 116         */
 117        smp_wmb();
 118        WRITE_ONCE(stats->reset_pending, 1);
 119
 120        return count;
 121}
 122cpufreq_freq_attr_wo(reset);
 123
 124static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
 125{
 126        struct cpufreq_stats *stats = policy->stats;
 127        bool pending = READ_ONCE(stats->reset_pending);
 128        ssize_t len = 0;
 129        int i, j, count;
 130
 131        len += scnprintf(buf + len, PAGE_SIZE - len, "   From  :    To\n");
 132        len += scnprintf(buf + len, PAGE_SIZE - len, "         : ");
 133        for (i = 0; i < stats->state_num; i++) {
 134                if (len >= PAGE_SIZE)
 135                        break;
 136                len += scnprintf(buf + len, PAGE_SIZE - len, "%9u ",
 137                                stats->freq_table[i]);
 138        }
 139        if (len >= PAGE_SIZE)
 140                return PAGE_SIZE;
 141
 142        len += scnprintf(buf + len, PAGE_SIZE - len, "\n");
 143
 144        for (i = 0; i < stats->state_num; i++) {
 145                if (len >= PAGE_SIZE)
 146                        break;
 147
 148                len += scnprintf(buf + len, PAGE_SIZE - len, "%9u: ",
 149                                stats->freq_table[i]);
 150
 151                for (j = 0; j < stats->state_num; j++) {
 152                        if (len >= PAGE_SIZE)
 153                                break;
 154
 155                        if (pending)
 156                                count = 0;
 157                        else
 158                                count = stats->trans_table[i * stats->max_state + j];
 159
 160                        len += scnprintf(buf + len, PAGE_SIZE - len, "%9u ", count);
 161                }
 162                if (len >= PAGE_SIZE)
 163                        break;
 164                len += scnprintf(buf + len, PAGE_SIZE - len, "\n");
 165        }
 166
 167        if (len >= PAGE_SIZE) {
 168                pr_warn_once("cpufreq transition table exceeds PAGE_SIZE. Disabling\n");
 169                return -EFBIG;
 170        }
 171        return len;
 172}
 173cpufreq_freq_attr_ro(trans_table);
 174
 175static struct attribute *default_attrs[] = {
 176        &total_trans.attr,
 177        &time_in_state.attr,
 178        &reset.attr,
 179        &trans_table.attr,
 180        NULL
 181};
 182static const struct attribute_group stats_attr_group = {
 183        .attrs = default_attrs,
 184        .name = "stats"
 185};
 186
 187static int freq_table_get_index(struct cpufreq_stats *stats, unsigned int freq)
 188{
 189        int index;
 190        for (index = 0; index < stats->max_state; index++)
 191                if (stats->freq_table[index] == freq)
 192                        return index;
 193        return -1;
 194}
 195
 196void cpufreq_stats_free_table(struct cpufreq_policy *policy)
 197{
 198        struct cpufreq_stats *stats = policy->stats;
 199
 200        /* Already freed */
 201        if (!stats)
 202                return;
 203
 204        pr_debug("%s: Free stats table\n", __func__);
 205
 206        sysfs_remove_group(&policy->kobj, &stats_attr_group);
 207        kfree(stats->time_in_state);
 208        kfree(stats);
 209        policy->stats = NULL;
 210}
 211
 212void cpufreq_stats_create_table(struct cpufreq_policy *policy)
 213{
 214        unsigned int i = 0, count;
 215        struct cpufreq_stats *stats;
 216        unsigned int alloc_size;
 217        struct cpufreq_frequency_table *pos;
 218
 219        count = cpufreq_table_count_valid_entries(policy);
 220        if (!count)
 221                return;
 222
 223        /* stats already initialized */
 224        if (policy->stats)
 225                return;
 226
 227        stats = kzalloc(sizeof(*stats), GFP_KERNEL);
 228        if (!stats)
 229                return;
 230
 231        alloc_size = count * sizeof(int) + count * sizeof(u64);
 232
 233        alloc_size += count * count * sizeof(int);
 234
 235        /* Allocate memory for time_in_state/freq_table/trans_table in one go */
 236        stats->time_in_state = kzalloc(alloc_size, GFP_KERNEL);
 237        if (!stats->time_in_state)
 238                goto free_stat;
 239
 240        stats->freq_table = (unsigned int *)(stats->time_in_state + count);
 241
 242        stats->trans_table = stats->freq_table + count;
 243
 244        stats->max_state = count;
 245
 246        /* Find valid-unique entries */
 247        cpufreq_for_each_valid_entry(pos, policy->freq_table)
 248                if (freq_table_get_index(stats, pos->frequency) == -1)
 249                        stats->freq_table[i++] = pos->frequency;
 250
 251        stats->state_num = i;
 252        stats->last_time = local_clock();
 253        stats->last_index = freq_table_get_index(stats, policy->cur);
 254
 255        policy->stats = stats;
 256        if (!sysfs_create_group(&policy->kobj, &stats_attr_group))
 257                return;
 258
 259        /* We failed, release resources */
 260        policy->stats = NULL;
 261        kfree(stats->time_in_state);
 262free_stat:
 263        kfree(stats);
 264}
 265
 266void cpufreq_stats_record_transition(struct cpufreq_policy *policy,
 267                                     unsigned int new_freq)
 268{
 269        struct cpufreq_stats *stats = policy->stats;
 270        int old_index, new_index;
 271
 272        if (unlikely(!stats))
 273                return;
 274
 275        if (unlikely(READ_ONCE(stats->reset_pending)))
 276                cpufreq_stats_reset_table(stats);
 277
 278        old_index = stats->last_index;
 279        new_index = freq_table_get_index(stats, new_freq);
 280
 281        /* We can't do stats->time_in_state[-1]= .. */
 282        if (unlikely(old_index == -1 || new_index == -1 || old_index == new_index))
 283                return;
 284
 285        cpufreq_stats_update(stats, stats->last_time);
 286
 287        stats->last_index = new_index;
 288        stats->trans_table[old_index * stats->max_state + new_index]++;
 289        stats->total_trans++;
 290}
 291
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