drivers/cpufreq/cpufreq_stats.c

   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
  15 struct 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
  30 static 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
  39 static 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
  58 static 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 }
  67 cpufreq_freq_attr_ro(total_trans);
  68
  69 static 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 }
 100 cpufreq_freq_attr_ro(time_in_state);
 101
 102 /* We don't care what is written to the attribute */
 103 static 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 }
 122 cpufreq_freq_attr_wo(reset);
 123
 124 static 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 }
 173 cpufreq_freq_attr_ro(trans_table);
 174
 175 static struct attribute *default_attrs[] = {
 176         &total_trans.attr,
 177         &time_in_state.attr,
 178         &reset.attr,
 179         &trans_table.attr,
 180         NULL
 181 };
 182 static const struct attribute_group stats_attr_group = {
 183         .attrs = default_attrs,
 184         .name = "stats"
 185 };
 186
 187 static 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
 196 void 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
 212 void cpufreq_stats_create_table(struct cpufreq_policy *policy)
 213 {
 214         unsigned int i = 0, count = 0, ret = -ENOMEM;
 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         ret = sysfs_create_group(&policy->kobj, &stats_attr_group);
 257         if (!ret)
 258                 return;
 259
 260         /* We failed, release resources */
 261         policy->stats = NULL;
 262         kfree(stats->time_in_state);
 263 free_stat:
 264         kfree(stats);
 265 }
 266
 267 void cpufreq_stats_record_transition(struct cpufreq_policy *policy,
 268                                      unsigned int new_freq)
 269 {
 270         struct cpufreq_stats *stats = policy->stats;
 271         int old_index, new_index;
 272
 273         if (unlikely(!stats))
 274                 return;
 275
 276         if (unlikely(READ_ONCE(stats->reset_pending)))
 277                 cpufreq_stats_reset_table(stats);
 278
 279         old_index = stats->last_index;
 280         new_index = freq_table_get_index(stats, new_freq);
 281
 282         /* We can't do stats->time_in_state[-1]= .. */
 283         if (unlikely(old_index == -1 || new_index == -1 || old_index == new_index))
 284                 return;
 285
 286         cpufreq_stats_update(stats, stats->last_time);
 287
 288         stats->last_index = new_index;
 289         stats->trans_table[old_index * stats->max_state + new_index]++;
 290         stats->total_trans++;
 291 }