// SPDX-License-Identifier: GPL-2.0
/*
 * Energy Model of devices
 *
 * Copyright (c) 2018-2020, Arm ltd.
 * Written by: Quentin Perret, Arm ltd.
 * Improvements provided by: Lukasz Luba, 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>

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

static bool _is_cpu_device(struct device *dev)
{
        return (dev->bus == &cpu_subsys);
}

#ifdef CONFIG_DEBUG_FS
static struct dentry *rootdir;

static void em_debug_create_ps(struct em_perf_state *ps, struct dentry *pd)
{
        struct dentry *d;
        char name[24];

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

        /* Create per-ps directory */
        d = debugfs_create_dir(name, pd);
        debugfs_create_ulong("frequency", 0444, d, &ps->frequency);
        debugfs_create_ulong("power", 0444, d, &ps->power);
        debugfs_create_ulong("cost", 0444, d, &ps->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 device *dev)
{
        struct dentry *d;
        int i;

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

        if (_is_cpu_device(dev))
                debugfs_create_file("cpus", 0444, d, dev->em_pd->cpus,
                                    &em_debug_cpus_fops);

        /* Create a sub-directory for each performance state */
        for (i = 0; i < dev->em_pd->nr_perf_states; i++)
                em_debug_create_ps(&dev->em_pd->table[i], d);

}

static void em_debug_remove_pd(struct device *dev)
{
        struct dentry *debug_dir;

        debug_dir = debugfs_lookup(dev_name(dev), rootdir);
        debugfs_remove_recursive(debug_dir);
}

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 device *dev) {}
static void em_debug_remove_pd(struct device *dev) {}
#endif

static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd,
                                int nr_states, struct em_data_callback *cb)
{
        unsigned long opp_eff, prev_opp_eff = ULONG_MAX;
        unsigned long power, freq, prev_freq = 0;
        struct em_perf_state *table;
        int i, ret;
        u64 fmax;

        table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
        if (!table)
                return -ENOMEM;

        /* Build the list of performance 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 performance state of 'dev' above 'freq' and updates
                 * 'power' and 'freq' accordingly.
                 */
                ret = cb->active_power(&power, &freq, dev);
                if (ret) {
                        dev_err(dev, "EM: invalid perf. state: %d\n",
                                ret);
                        goto free_ps_table;
                }

                /*
                 * We expect the driver callback to increase the frequency for
                 * higher performance states.
                 */
                if (freq <= prev_freq) {
                        dev_err(dev, "EM: non-increasing freq: %lu\n",
                                freq);
                        goto free_ps_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_MAX_POWER) {
                        dev_err(dev, "EM: invalid power: %lu\n",
                                power);
                        goto free_ps_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)
                        dev_dbg(dev, "EM: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
                                        i, i - 1);
                prev_opp_eff = opp_eff;
        }

        /* Compute the cost of each performance 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_perf_states = nr_states;

        return 0;

free_ps_table:
        kfree(table);
        return -EINVAL;
}

static int em_create_pd(struct device *dev, int nr_states,
                        struct em_data_callback *cb, cpumask_t *cpus)
{
        struct em_perf_domain *pd;
        struct device *cpu_dev;
        int cpu, ret;

        if (_is_cpu_device(dev)) {
                pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
                if (!pd)
                        return -ENOMEM;

                cpumask_copy(em_span_cpus(pd), cpus);
        } else {
                pd = kzalloc(sizeof(*pd), GFP_KERNEL);
                if (!pd)
                        return -ENOMEM;
        }

        ret = em_create_perf_table(dev, pd, nr_states, cb);
        if (ret) {
                kfree(pd);
                return ret;
        }

        if (_is_cpu_device(dev))
                for_each_cpu(cpu, cpus) {
                        cpu_dev = get_cpu_device(cpu);
                        cpu_dev->em_pd = pd;
                }

        dev->em_pd = pd;

        return 0;
}

/**
 * em_pd_get() - Return the performance domain for a device
 * @dev : Device to find the performance domain for
 *
 * Returns the performance domain to which @dev belongs, or NULL if it doesn't
 * exist.
 */
struct em_perf_domain *em_pd_get(struct device *dev)
{
        if (IS_ERR_OR_NULL(dev))
                return NULL;

        return dev->em_pd;
}
EXPORT_SYMBOL_GPL(em_pd_get);

/**
 * em_cpu_get() - Return the performance domain for a CPU
 * @cpu : CPU to find the performance domain for
 *
 * Returns the performance domain to which @cpu belongs, or NULL if it doesn't
 * exist.
 */
struct em_perf_domain *em_cpu_get(int cpu)
{
        struct device *cpu_dev;

        cpu_dev = get_cpu_device(cpu);
        if (!cpu_dev)
                return NULL;

        return em_pd_get(cpu_dev);
}
EXPORT_SYMBOL_GPL(em_cpu_get);

/**
 * em_dev_register_perf_domain() - Register the Energy Model (EM) for a device
 * @dev         : Device for which the EM is to register
 * @nr_states   : Number of performance states to register
 * @cb          : Callback functions providing the data of the Energy Model
 * @cpus        : Pointer to cpumask_t, which in case of a CPU device is
 *              obligatory. It can be taken from i.e. 'policy->cpus'. For other
 *              type of devices this should be set to NULL.
 *
 * 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_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
                                struct em_data_callback *cb, cpumask_t *cpus)
{
        unsigned long cap, prev_cap = 0;
        int cpu, ret;

        if (!dev || !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);

        if (dev->em_pd) {
                ret = -EEXIST;
                goto unlock;
        }

        if (_is_cpu_device(dev)) {
                if (!cpus) {
                        dev_err(dev, "EM: invalid CPU mask\n");
                        ret = -EINVAL;
                        goto unlock;
                }

                for_each_cpu(cpu, cpus) {
                        if (em_cpu_get(cpu)) {
                                dev_err(dev, "EM: exists for CPU%d\n", 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(cpu);
                        if (prev_cap && prev_cap != cap) {
                                dev_err(dev, "EM: CPUs of %*pbl must have the same capacity\n",
                                        cpumask_pr_args(cpus));

                                ret = -EINVAL;
                                goto unlock;
                        }
                        prev_cap = cap;
                }
        }

        ret = em_create_pd(dev, nr_states, cb, cpus);
        if (ret)
                goto unlock;

        em_debug_create_pd(dev);
        dev_info(dev, "EM: created perf domain\n");

unlock:
        mutex_unlock(&em_pd_mutex);
        return ret;
}
EXPORT_SYMBOL_GPL(em_dev_register_perf_domain);

/**
 * em_dev_unregister_perf_domain() - Unregister Energy Model (EM) for a device
 * @dev         : Device for which the EM is registered
 *
 * Unregister the EM for the specified @dev (but not a CPU device).
 */
void em_dev_unregister_perf_domain(struct device *dev)
{
        if (IS_ERR_OR_NULL(dev) || !dev->em_pd)
                return;

        if (_is_cpu_device(dev))
                return;

        /*
         * The mutex separates all register/unregister requests and protects
         * from potential clean-up/setup issues in the debugfs directories.
         * The debugfs directory name is the same as device's name.
         */
        mutex_lock(&em_pd_mutex);
        em_debug_remove_pd(dev);

        kfree(dev->em_pd->table);
        kfree(dev->em_pd);
        dev->em_pd = NULL;
        mutex_unlock(&em_pd_mutex);
}
EXPORT_SYMBOL_GPL(em_dev_unregister_perf_domain);