drivers/cpufreq/cpufreq_stats.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  *  drivers/cpufreq/cpufreq_stats.c
0004  *
0005  *  Copyright (C) 2003-2004 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
0006  *  (C) 2004 Zou Nan hai <nanhai.zou@intel.com>.
0007  */
0008
0009 #include <linux/cpu.h>
0010 #include <linux/cpufreq.h>
0011 #include <linux/module.h>
0012 #include <linux/sched/clock.h>
0013 #include <linux/slab.h>
0014
0015 struct cpufreq_stats {
0016     unsigned int total_trans;
0017     unsigned long long last_time;
0018     unsigned int max_state;
0019     unsigned int state_num;
0020     unsigned int last_index;
0021     u64 *time_in_state;
0022     unsigned int *freq_table;
0023     unsigned int *trans_table;
0024
0025     /* Deferred reset */
0026     unsigned int reset_pending;
0027     unsigned long long reset_time;
0028 };
0029
0030 static void cpufreq_stats_update(struct cpufreq_stats *stats,
0031                  unsigned long long time)
0032 {
0033     unsigned long long cur_time = local_clock();
0034
0035     stats->time_in_state[stats->last_index] += cur_time - time;
0036     stats->last_time = cur_time;
0037 }
0038
0039 static void cpufreq_stats_reset_table(struct cpufreq_stats *stats)
0040 {
0041     unsigned int count = stats->max_state;
0042
0043     memset(stats->time_in_state, 0, count * sizeof(u64));
0044     memset(stats->trans_table, 0, count * count * sizeof(int));
0045     stats->last_time = local_clock();
0046     stats->total_trans = 0;
0047
0048     /* Adjust for the time elapsed since reset was requested */
0049     WRITE_ONCE(stats->reset_pending, 0);
0050     /*
0051      * Prevent the reset_time read from being reordered before the
0052      * reset_pending accesses in cpufreq_stats_record_transition().
0053      */
0054     smp_rmb();
0055     cpufreq_stats_update(stats, READ_ONCE(stats->reset_time));
0056 }
0057
0058 static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf)
0059 {
0060     struct cpufreq_stats *stats = policy->stats;
0061
0062     if (READ_ONCE(stats->reset_pending))
0063         return sprintf(buf, "%d\n", 0);
0064     else
0065         return sprintf(buf, "%u\n", stats->total_trans);
0066 }
0067 cpufreq_freq_attr_ro(total_trans);
0068
0069 static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf)
0070 {
0071     struct cpufreq_stats *stats = policy->stats;
0072     bool pending = READ_ONCE(stats->reset_pending);
0073     unsigned long long time;
0074     ssize_t len = 0;
0075     int i;
0076
0077     for (i = 0; i < stats->state_num; i++) {
0078         if (pending) {
0079             if (i == stats->last_index) {
0080                 /*
0081                  * Prevent the reset_time read from occurring
0082                  * before the reset_pending read above.
0083                  */
0084                 smp_rmb();
0085                 time = local_clock() - READ_ONCE(stats->reset_time);
0086             } else {
0087                 time = 0;
0088             }
0089         } else {
0090             time = stats->time_in_state[i];
0091             if (i == stats->last_index)
0092                 time += local_clock() - stats->last_time;
0093         }
0094
0095         len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i],
0096                    nsec_to_clock_t(time));
0097     }
0098     return len;
0099 }
0100 cpufreq_freq_attr_ro(time_in_state);
0101
0102 /* We don't care what is written to the attribute */
0103 static ssize_t store_reset(struct cpufreq_policy *policy, const char *buf,
0104                size_t count)
0105 {
0106     struct cpufreq_stats *stats = policy->stats;
0107
0108     /*
0109      * Defer resetting of stats to cpufreq_stats_record_transition() to
0110      * avoid races.
0111      */
0112     WRITE_ONCE(stats->reset_time, local_clock());
0113     /*
0114      * The memory barrier below is to prevent the readers of reset_time from
0115      * seeing a stale or partially updated value.
0116      */
0117     smp_wmb();
0118     WRITE_ONCE(stats->reset_pending, 1);
0119
0120     return count;
0121 }
0122 cpufreq_freq_attr_wo(reset);
0123
0124 static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
0125 {
0126     struct cpufreq_stats *stats = policy->stats;
0127     bool pending = READ_ONCE(stats->reset_pending);
0128     ssize_t len = 0;
0129     int i, j, count;
0130
0131     len += scnprintf(buf + len, PAGE_SIZE - len, "   From  :    To\n");
0132     len += scnprintf(buf + len, PAGE_SIZE - len, "         : ");
0133     for (i = 0; i < stats->state_num; i++) {
0134         if (len >= PAGE_SIZE)
0135             break;
0136         len += scnprintf(buf + len, PAGE_SIZE - len, "%9u ",
0137                 stats->freq_table[i]);
0138     }
0139     if (len >= PAGE_SIZE)
0140         return PAGE_SIZE;
0141
0142     len += scnprintf(buf + len, PAGE_SIZE - len, "\n");
0143
0144     for (i = 0; i < stats->state_num; i++) {
0145         if (len >= PAGE_SIZE)
0146             break;
0147
0148         len += scnprintf(buf + len, PAGE_SIZE - len, "%9u: ",
0149                 stats->freq_table[i]);
0150
0151         for (j = 0; j < stats->state_num; j++) {
0152             if (len >= PAGE_SIZE)
0153                 break;
0154
0155             if (pending)
0156                 count = 0;
0157             else
0158                 count = stats->trans_table[i * stats->max_state + j];
0159
0160             len += scnprintf(buf + len, PAGE_SIZE - len, "%9u ", count);
0161         }
0162         if (len >= PAGE_SIZE)
0163             break;
0164         len += scnprintf(buf + len, PAGE_SIZE - len, "\n");
0165     }
0166
0167     if (len >= PAGE_SIZE) {
0168         pr_warn_once("cpufreq transition table exceeds PAGE_SIZE. Disabling\n");
0169         return -EFBIG;
0170     }
0171     return len;
0172 }
0173 cpufreq_freq_attr_ro(trans_table);
0174
0175 static struct attribute *default_attrs[] = {
0176     &total_trans.attr,
0177     &time_in_state.attr,
0178     &reset.attr,
0179     &trans_table.attr,
0180     NULL
0181 };
0182 static const struct attribute_group stats_attr_group = {
0183     .attrs = default_attrs,
0184     .name = "stats"
0185 };
0186
0187 static int freq_table_get_index(struct cpufreq_stats *stats, unsigned int freq)
0188 {
0189     int index;
0190     for (index = 0; index < stats->max_state; index++)
0191         if (stats->freq_table[index] == freq)
0192             return index;
0193     return -1;
0194 }
0195
0196 void cpufreq_stats_free_table(struct cpufreq_policy *policy)
0197 {
0198     struct cpufreq_stats *stats = policy->stats;
0199
0200     /* Already freed */
0201     if (!stats)
0202         return;
0203
0204     pr_debug("%s: Free stats table\n", __func__);
0205
0206     sysfs_remove_group(&policy->kobj, &stats_attr_group);
0207     kfree(stats->time_in_state);
0208     kfree(stats);
0209     policy->stats = NULL;
0210 }
0211
0212 void cpufreq_stats_create_table(struct cpufreq_policy *policy)
0213 {
0214     unsigned int i = 0, count;
0215     struct cpufreq_stats *stats;
0216     unsigned int alloc_size;
0217     struct cpufreq_frequency_table *pos;
0218
0219     count = cpufreq_table_count_valid_entries(policy);
0220     if (!count)
0221         return;
0222
0223     /* stats already initialized */
0224     if (policy->stats)
0225         return;
0226
0227     stats = kzalloc(sizeof(*stats), GFP_KERNEL);
0228     if (!stats)
0229         return;
0230
0231     alloc_size = count * sizeof(int) + count * sizeof(u64);
0232
0233     alloc_size += count * count * sizeof(int);
0234
0235     /* Allocate memory for time_in_state/freq_table/trans_table in one go */
0236     stats->time_in_state = kzalloc(alloc_size, GFP_KERNEL);
0237     if (!stats->time_in_state)
0238         goto free_stat;
0239
0240     stats->freq_table = (unsigned int *)(stats->time_in_state + count);
0241
0242     stats->trans_table = stats->freq_table + count;
0243
0244     stats->max_state = count;
0245
0246     /* Find valid-unique entries */
0247     cpufreq_for_each_valid_entry(pos, policy->freq_table)
0248         if (freq_table_get_index(stats, pos->frequency) == -1)
0249             stats->freq_table[i++] = pos->frequency;
0250
0251     stats->state_num = i;
0252     stats->last_time = local_clock();
0253     stats->last_index = freq_table_get_index(stats, policy->cur);
0254
0255     policy->stats = stats;
0256     if (!sysfs_create_group(&policy->kobj, &stats_attr_group))
0257         return;
0258
0259     /* We failed, release resources */
0260     policy->stats = NULL;
0261     kfree(stats->time_in_state);
0262 free_stat:
0263     kfree(stats);
0264 }
0265
0266 void cpufreq_stats_record_transition(struct cpufreq_policy *policy,
0267                      unsigned int new_freq)
0268 {
0269     struct cpufreq_stats *stats = policy->stats;
0270     int old_index, new_index;
0271
0272     if (unlikely(!stats))
0273         return;
0274
0275     if (unlikely(READ_ONCE(stats->reset_pending)))
0276         cpufreq_stats_reset_table(stats);
0277
0278     old_index = stats->last_index;
0279     new_index = freq_table_get_index(stats, new_freq);
0280
0281     /* We can't do stats->time_in_state[-1]= .. */
0282     if (unlikely(old_index == -1 || new_index == -1 || old_index == new_index))
0283         return;
0284
0285     cpufreq_stats_update(stats, stats->last_time);
0286
0287     stats->last_index = new_index;
0288     stats->trans_table[old_index * stats->max_state + new_index]++;
0289     stats->total_trans++;
0290 }