// SPDX-License-Identifier: GPL-2.0-only
/*
 *  drivers/cpufreq/cpufreq_stats.c
 *
 *  Copyright (C) 2003-2004 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
 *  (C) 2004 Zou Nan hai <nanhai.zou@intel.com>.
 */

#include <linux/cpu.h>
#include <linux/cpufreq.h>
#include <linux/module.h>
#include <linux/sched/clock.h>
#include <linux/slab.h>

struct cpufreq_stats {
        unsigned int total_trans;
        unsigned long long last_time;
        unsigned int max_state;
        unsigned int state_num;
        unsigned int last_index;
        u64 *time_in_state;
        unsigned int *freq_table;
        unsigned int *trans_table;

        /* Deferred reset */
        unsigned int reset_pending;
        unsigned long long reset_time;
};

static void cpufreq_stats_update(struct cpufreq_stats *stats,
                                 unsigned long long time)
{
        unsigned long long cur_time = local_clock();

        stats->time_in_state[stats->last_index] += cur_time - time;
        stats->last_time = cur_time;
}

static void cpufreq_stats_reset_table(struct cpufreq_stats *stats)
{
        unsigned int count = stats->max_state;

        memset(stats->time_in_state, 0, count * sizeof(u64));
        memset(stats->trans_table, 0, count * count * sizeof(int));
        stats->last_time = local_clock();
        stats->total_trans = 0;

        /* Adjust for the time elapsed since reset was requested */
        WRITE_ONCE(stats->reset_pending, 0);
        /*
         * Prevent the reset_time read from being reordered before the
         * reset_pending accesses in cpufreq_stats_record_transition().
         */
        smp_rmb();
        cpufreq_stats_update(stats, READ_ONCE(stats->reset_time));
}

static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf)
{
        struct cpufreq_stats *stats = policy->stats;

        if (READ_ONCE(stats->reset_pending))
                return sprintf(buf, "%d\n", 0);
        else
                return sprintf(buf, "%u\n", stats->total_trans);
}
cpufreq_freq_attr_ro(total_trans);

static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf)
{
        struct cpufreq_stats *stats = policy->stats;
        bool pending = READ_ONCE(stats->reset_pending);
        unsigned long long time;
        ssize_t len = 0;
        int i;

        for (i = 0; i < stats->state_num; i++) {
                if (pending) {
                        if (i == stats->last_index) {
                                /*
                                 * Prevent the reset_time read from occurring
                                 * before the reset_pending read above.
                                 */
                                smp_rmb();
                                time = local_clock() - READ_ONCE(stats->reset_time);
                        } else {
                                time = 0;
                        }
                } else {
                        time = stats->time_in_state[i];
                        if (i == stats->last_index)
                                time += local_clock() - stats->last_time;
                }

                len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i],
                               nsec_to_clock_t(time));
        }
        return len;
}
cpufreq_freq_attr_ro(time_in_state);

/* We don't care what is written to the attribute */
static ssize_t store_reset(struct cpufreq_policy *policy, const char *buf,
                           size_t count)
{
        struct cpufreq_stats *stats = policy->stats;

        /*
         * Defer resetting of stats to cpufreq_stats_record_transition() to
         * avoid races.
         */
        WRITE_ONCE(stats->reset_time, local_clock());
        /*
         * The memory barrier below is to prevent the readers of reset_time from
         * seeing a stale or partially updated value.
         */
        smp_wmb();
        WRITE_ONCE(stats->reset_pending, 1);

        return count;
}
cpufreq_freq_attr_wo(reset);

static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
{
        struct cpufreq_stats *stats = policy->stats;
        bool pending = READ_ONCE(stats->reset_pending);
        ssize_t len = 0;
        int i, j, count;

        len += sysfs_emit_at(buf, len, "   From  :    To\n");
        len += sysfs_emit_at(buf, len, "         : ");
        for (i = 0; i < stats->state_num; i++) {
                if (len >= PAGE_SIZE - 1)
                        break;
                len += sysfs_emit_at(buf, len, "%9u ", stats->freq_table[i]);
        }
        if (len >= PAGE_SIZE - 1)
                return PAGE_SIZE - 1;

        len += sysfs_emit_at(buf, len, "\n");

        for (i = 0; i < stats->state_num; i++) {
                if (len >= PAGE_SIZE - 1)
                        break;

                len += sysfs_emit_at(buf, len, "%9u: ", stats->freq_table[i]);

                for (j = 0; j < stats->state_num; j++) {
                        if (len >= PAGE_SIZE - 1)
                                break;

                        if (pending)
                                count = 0;
                        else
                                count = stats->trans_table[i * stats->max_state + j];

                        len += sysfs_emit_at(buf, len, "%9u ", count);
                }
                if (len >= PAGE_SIZE - 1)
                        break;
                len += sysfs_emit_at(buf, len, "\n");
        }

        if (len >= PAGE_SIZE - 1) {
                pr_warn_once("cpufreq transition table exceeds PAGE_SIZE. Disabling\n");
                return -EFBIG;
        }
        return len;
}
cpufreq_freq_attr_ro(trans_table);

static struct attribute *default_attrs[] = {
        &total_trans.attr,
        &time_in_state.attr,
        &reset.attr,
        &trans_table.attr,
        NULL
};
static const struct attribute_group stats_attr_group = {
        .attrs = default_attrs,
        .name = "stats"
};

static int freq_table_get_index(struct cpufreq_stats *stats, unsigned int freq)
{
        int index;
        for (index = 0; index < stats->max_state; index++)
                if (stats->freq_table[index] == freq)
                        return index;
        return -1;
}

void cpufreq_stats_free_table(struct cpufreq_policy *policy)
{
        struct cpufreq_stats *stats = policy->stats;

        /* Already freed */
        if (!stats)
                return;

        pr_debug("%s: Free stats table\n", __func__);

        sysfs_remove_group(&policy->kobj, &stats_attr_group);
        kfree(stats->time_in_state);
        kfree(stats);
        policy->stats = NULL;
}

void cpufreq_stats_create_table(struct cpufreq_policy *policy)
{
        unsigned int i = 0, count;
        struct cpufreq_stats *stats;
        unsigned int alloc_size;
        struct cpufreq_frequency_table *pos;

        count = cpufreq_table_count_valid_entries(policy);
        if (!count)
                return;

        /* stats already initialized */
        if (policy->stats)
                return;

        stats = kzalloc_obj(*stats);
        if (!stats)
                return;

        alloc_size = count * sizeof(int) + count * sizeof(u64);

        alloc_size += count * count * sizeof(int);

        /* Allocate memory for time_in_state/freq_table/trans_table in one go */
        stats->time_in_state = kzalloc(alloc_size, GFP_KERNEL);
        if (!stats->time_in_state)
                goto free_stat;

        stats->freq_table = (unsigned int *)(stats->time_in_state + count);

        stats->trans_table = stats->freq_table + count;

        stats->max_state = count;

        /* Find valid-unique entries */
        cpufreq_for_each_valid_entry(pos, policy->freq_table)
                if (policy->freq_table_sorted != CPUFREQ_TABLE_UNSORTED ||
                    freq_table_get_index(stats, pos->frequency) == -1)
                        stats->freq_table[i++] = pos->frequency;

        stats->state_num = i;
        stats->last_time = local_clock();
        stats->last_index = freq_table_get_index(stats, policy->cur);

        policy->stats = stats;
        if (!sysfs_create_group(&policy->kobj, &stats_attr_group))
                return;

        /* We failed, release resources */
        policy->stats = NULL;
        kfree(stats->time_in_state);
free_stat:
        kfree(stats);
}

void cpufreq_stats_record_transition(struct cpufreq_policy *policy,
                                     unsigned int new_freq)
{
        struct cpufreq_stats *stats = policy->stats;
        int old_index, new_index;

        if (unlikely(!stats))
                return;

        if (unlikely(READ_ONCE(stats->reset_pending)))
                cpufreq_stats_reset_table(stats);

        old_index = stats->last_index;
        new_index = freq_table_get_index(stats, new_freq);

        /* We can't do stats->time_in_state[-1]= .. */
        if (unlikely(old_index == -1 || new_index == -1 || old_index == new_index))
                return;

        cpufreq_stats_update(stats, stats->last_time);

        stats->last_index = new_index;
        stats->trans_table[old_index * stats->max_state + new_index]++;
        stats->total_trans++;
}