kernel/power/energy_model.c

// 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>

#define FILE_PROPERTY 0444

/*
 * 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", FILE_PROPERTY, d, &ps->frequency);
    debugfs_create_ulong("power", FILE_PROPERTY, d, &ps->power);
    debugfs_create_ulong("cost", FILE_PROPERTY, 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 int em_debug_units_show(struct seq_file *s, void *unused)
{
    struct em_perf_domain *pd = s->private;
    char *units = pd->milliwatts ? "milliWatts" : "bogoWatts";

    seq_printf(s, "%s\n", units);

    return 0;
}
DEFINE_SHOW_ATTRIBUTE(em_debug_units);

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", FILE_PROPERTY, d, dev->em_pd->cpus, &em_debug_cpus_fops);
    }

    debugfs_create_file("units", FILE_PROPERTY, d, dev->em_pd, &em_debug_units_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;
}
fs_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 power, freq, prev_freq = 0, prev_cost = ULONG_MAX;
    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;
        }

    /* Compute the cost of each performance state. */
    fmax = (u64)table[nr_states - 1].frequency;
    for (i = nr_states - 1; i >= 0; i--) {
        unsigned long power_res = em_scale_power(table[i].power);

        table[i].cost = div64_u64(fmax * power_res, table[i].frequency);
        if (table[i].cost >= prev_cost) {
            dev_dbg(dev, "EM: OPP:%lu is inefficient\n",
                table[i].frequency);
        } else {
            prev_cost = table[i].cost;
        }
    }

    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.
 * @milliwatts    : Flag indicating that the power values are in milliWatts or
 *        in some other scale. It must be set properly.
 *
 * Create Energy Model tables for a performance domain using the callbacks
 * defined in cb.
 *
 * The @milliwatts is important to set with correct value. Some kernel
 * sub-systems might rely on this flag and check if all devices in the EM are
 * using the same scale.
 *
 * 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, bool milliwatts)
{
    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;
    }

    dev->em_pd->milliwatts = milliwatts;

    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);