// SPDX-License-Identifier: GPL-2.0
/*
 * Energy Model of CPUs
 *
 * Copyright (c) 2018, Arm ltd.
 * Written by: Quentin Perret, Arm ltd.
 */

#define pr_fmt(fmt) "energy_model: " fmt

#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/debugfs.h>
#include <linux/energy_model.h>
#include <linux/sched/topology.h>
#include <linux/slab.h>

/* Mapping of each CPU to the performance domain to which it belongs. */
static DEFINE_PER_CPU(struct em_perf_domain *, em_data);

/*
 * Mutex serializing the registrations of performance domains and letting
 * callbacks defined by drivers sleep.
 */
static DEFINE_MUTEX(em_pd_mutex);

#ifdef CONFIG_DEBUG_FS
static struct dentry *rootdir;

static void em_debug_create_cs(struct em_cap_state *cs, struct dentry *pd)
{
        struct dentry *d;
        char name[24];

        snprintf(name, sizeof(name), "cs:%lu", cs->frequency);

        /* Create per-cs directory */
        d = debugfs_create_dir(name, pd);
        debugfs_create_ulong("frequency", 0444, d, &cs->frequency);
        debugfs_create_ulong("power", 0444, d, &cs->power);
        debugfs_create_ulong("cost", 0444, d, &cs->cost);
}

static int em_debug_cpus_show(struct seq_file *s, void *unused)
{
        seq_printf(s, "%*pbl\n", cpumask_pr_args(to_cpumask(s->private)));

        return 0;
}
DEFINE_SHOW_ATTRIBUTE(em_debug_cpus);

static void em_debug_create_pd(struct em_perf_domain *pd, int cpu)
{
        struct dentry *d;
        char name[8];
        int i;

        snprintf(name, sizeof(name), "pd%d", cpu);

        /* Create the directory of the performance domain */
        d = debugfs_create_dir(name, rootdir);

        debugfs_create_file("cpus", 0444, d, pd->cpus, &em_debug_cpus_fops);

        /* Create a sub-directory for each capacity state */
        for (i = 0; i < pd->nr_cap_states; i++)
                em_debug_create_cs(&pd->table[i], d);
}

static int __init em_debug_init(void)
{
        /* Create /sys/kernel/debug/energy_model directory */
        rootdir = debugfs_create_dir("energy_model", NULL);

        return 0;
}
core_initcall(em_debug_init);
#else /* CONFIG_DEBUG_FS */
static void em_debug_create_pd(struct em_perf_domain *pd, int cpu) {}
#endif
static struct em_perf_domain *em_create_pd(cpumask_t *span, int nr_states,
                                                struct em_data_callback *cb)
{
        unsigned long opp_eff, prev_opp_eff = ULONG_MAX;
        unsigned long power, freq, prev_freq = 0;
        int i, ret, cpu = cpumask_first(span);
        struct em_cap_state *table;
        struct em_perf_domain *pd;
        u64 fmax;

        if (!cb->active_power)
                return NULL;

        pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
        if (!pd)
                return NULL;

        table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
        if (!table)
                goto free_pd;

        /* Build the list of capacity states for this performance domain */
        for (i = 0, freq = 0; i < nr_states; i++, freq++) {
                /*
                 * active_power() is a driver callback which ceils 'freq' to
                 * lowest capacity state of 'cpu' above 'freq' and updates
                 * 'power' and 'freq' accordingly.
                 */
                ret = cb->active_power(&power, &freq, cpu);
                if (ret) {
                        pr_err("pd%d: invalid cap. state: %d\n", cpu, ret);
                        goto free_cs_table;
                }

                /*
                 * We expect the driver callback to increase the frequency for
                 * higher capacity states.
                 */
                if (freq <= prev_freq) {
                        pr_err("pd%d: non-increasing freq: %lu\n", cpu, freq);
                        goto free_cs_table;
                }

                /*
                 * The power returned by active_state() is expected to be
                 * positive, in milli-watts and to fit into 16 bits.
                 */
                if (!power || power > EM_CPU_MAX_POWER) {
                        pr_err("pd%d: invalid power: %lu\n", cpu, power);
                        goto free_cs_table;
                }

                table[i].power = power;
                table[i].frequency = prev_freq = freq;

                /*
                 * The hertz/watts efficiency ratio should decrease as the
                 * frequency grows on sane platforms. But this isn't always
                 * true in practice so warn the user if a higher OPP is more
                 * power efficient than a lower one.
                 */
                opp_eff = freq / power;
                if (opp_eff >= prev_opp_eff)
                        pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_cap_state %d >= em_cap_state%d\n",
                                        cpu, i, i - 1);
                prev_opp_eff = opp_eff;
        }

        /* Compute the cost of each capacity_state. */
        fmax = (u64) table[nr_states - 1].frequency;
        for (i = 0; i < nr_states; i++) {
                table[i].cost = div64_u64(fmax * table[i].power,
                                          table[i].frequency);
        }

        pd->table = table;
        pd->nr_cap_states = nr_states;
        cpumask_copy(to_cpumask(pd->cpus), span);

        em_debug_create_pd(pd, cpu);

        return pd;

free_cs_table:
        kfree(table);
free_pd:
        kfree(pd);

        return NULL;
}

/**
 * em_cpu_get() - Return the performance domain for a CPU
 * @cpu : CPU to find the performance domain for
 *
 * Return: the performance domain to which 'cpu' belongs, or NULL if it doesn't
 * exist.
 */
struct em_perf_domain *em_cpu_get(int cpu)
{
        return READ_ONCE(per_cpu(em_data, cpu));
}
EXPORT_SYMBOL_GPL(em_cpu_get);

/**
 * em_register_perf_domain() - Register the Energy Model of a performance domain
 * @span        : Mask of CPUs in the performance domain
 * @nr_states   : Number of capacity states to register
 * @cb          : Callback functions providing the data of the Energy Model
 *
 * Create Energy Model tables for a performance domain using the callbacks
 * defined in cb.
 *
 * If multiple clients register the same performance domain, all but the first
 * registration will be ignored.
 *
 * Return 0 on success
 */
int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
                                                struct em_data_callback *cb)
{
        unsigned long cap, prev_cap = 0;
        struct em_perf_domain *pd;
        int cpu, ret = 0;

        if (!span || !nr_states || !cb)
                return -EINVAL;

        /*
         * Use a mutex to serialize the registration of performance domains and
         * let the driver-defined callback functions sleep.
         */
        mutex_lock(&em_pd_mutex);

        for_each_cpu(cpu, span) {
                /* Make sure we don't register again an existing domain. */
                if (READ_ONCE(per_cpu(em_data, cpu))) {
                        ret = -EEXIST;
                        goto unlock;
                }

                /*
                 * All CPUs of a domain must have the same micro-architecture
                 * since they all share the same table.
                 */
                cap = arch_scale_cpu_capacity(NULL, cpu);
                if (prev_cap && prev_cap != cap) {
                        pr_err("CPUs of %*pbl must have the same capacity\n",
                                                        cpumask_pr_args(span));
                        ret = -EINVAL;
                        goto unlock;
                }
                prev_cap = cap;
        }

        /* Create the performance domain and add it to the Energy Model. */
        pd = em_create_pd(span, nr_states, cb);
        if (!pd) {
                ret = -EINVAL;
                goto unlock;
        }

        for_each_cpu(cpu, span) {
                /*
                 * The per-cpu array can be read concurrently from em_cpu_get().
                 * The barrier enforces the ordering needed to make sure readers
                 * can only access well formed em_perf_domain structs.
                 */
                smp_store_release(per_cpu_ptr(&em_data, cpu), pd);
        }

        pr_debug("Created perf domain %*pbl\n", cpumask_pr_args(span));
unlock:
        mutex_unlock(&em_pd_mutex);

        return ret;
}
EXPORT_SYMBOL_GPL(em_register_perf_domain);