/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_ENERGY_MODEL_H
#define _LINUX_ENERGY_MODEL_H
#include <linux/cpumask.h>
#include <linux/jump_label.h>
#include <linux/kobject.h>
#include <linux/rcupdate.h>
#include <linux/sched/cpufreq.h>
#include <linux/sched/topology.h>
#include <linux/types.h>

#ifdef CONFIG_ENERGY_MODEL
/**
 * em_cap_state - Capacity state of a performance domain
 * @frequency:  The CPU frequency in KHz, for consistency with CPUFreq
 * @power:      The power consumed by 1 CPU at this level, in milli-watts
 * @cost:       The cost coefficient associated with this level, used during
 *              energy calculation. Equal to: power * max_frequency / frequency
 */
struct em_cap_state {
        unsigned long frequency;
        unsigned long power;
        unsigned long cost;
};

/**
 * em_perf_domain - Performance domain
 * @table:              List of capacity states, in ascending order
 * @nr_cap_states:      Number of capacity states
 * @cpus:               Cpumask covering the CPUs of the domain
 *
 * A "performance domain" represents a group of CPUs whose performance is
 * scaled together. All CPUs of a performance domain must have the same
 * micro-architecture. Performance domains often have a 1-to-1 mapping with
 * CPUFreq policies.
 */
struct em_perf_domain {
        struct em_cap_state *table;
        int nr_cap_states;
        unsigned long cpus[0];
};

#define EM_CPU_MAX_POWER 0xFFFF

struct em_data_callback {
        /**
         * active_power() - Provide power at the next capacity state of a CPU
         * @power       : Active power at the capacity state in mW (modified)
         * @freq        : Frequency at the capacity state in kHz (modified)
         * @cpu         : CPU for which we do this operation
         *
         * active_power() must find the lowest capacity state of 'cpu' above
         * 'freq' and update 'power' and 'freq' to the matching active power
         * and frequency.
         *
         * The power is the one of a single CPU in the domain, expressed in
         * milli-watts. It is expected to fit in the [0, EM_CPU_MAX_POWER]
         * range.
         *
         * Return 0 on success.
         */
        int (*active_power)(unsigned long *power, unsigned long *freq, int cpu);
};
#define EM_DATA_CB(_active_power_cb) { .active_power = &_active_power_cb }

struct em_perf_domain *em_cpu_get(int cpu);
int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
                                                struct em_data_callback *cb);

/**
 * em_pd_energy() - Estimates the energy consumed by the CPUs of a perf. domain
 * @pd          : performance domain for which energy has to be estimated
 * @max_util    : highest utilization among CPUs of the domain
 * @sum_util    : sum of the utilization of all CPUs in the domain
 *
 * Return: the sum of the energy consumed by the CPUs of the domain assuming
 * a capacity state satisfying the max utilization of the domain.
 */
static inline unsigned long em_pd_energy(struct em_perf_domain *pd,
                                unsigned long max_util, unsigned long sum_util)
{
        unsigned long freq, scale_cpu;
        struct em_cap_state *cs;
        int i, cpu;

        /*
         * In order to predict the capacity state, map the utilization of the
         * most utilized CPU of the performance domain to a requested frequency,
         * like schedutil.
         */
        cpu = cpumask_first(to_cpumask(pd->cpus));
        scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
        cs = &pd->table[pd->nr_cap_states - 1];
        freq = map_util_freq(max_util, cs->frequency, scale_cpu);

        /*
         * Find the lowest capacity state of the Energy Model above the
         * requested frequency.
         */
        for (i = 0; i < pd->nr_cap_states; i++) {
                cs = &pd->table[i];
                if (cs->frequency >= freq)
                        break;
        }

        /*
         * The capacity of a CPU in the domain at that capacity state (cs)
         * can be computed as:
         *
         *             cs->freq * scale_cpu
         *   cs->cap = --------------------                          (1)
         *                 cpu_max_freq
         *
         * So, ignoring the costs of idle states (which are not available in
         * the EM), the energy consumed by this CPU at that capacity state is
         * estimated as:
         *
         *             cs->power * cpu_util
         *   cpu_nrg = --------------------                          (2)
         *                   cs->cap
         *
         * since 'cpu_util / cs->cap' represents its percentage of busy time.
         *
         *   NOTE: Although the result of this computation actually is in
         *         units of power, it can be manipulated as an energy value
         *         over a scheduling period, since it is assumed to be
         *         constant during that interval.
         *
         * By injecting (1) in (2), 'cpu_nrg' can be re-expressed as a product
         * of two terms:
         *
         *             cs->power * cpu_max_freq   cpu_util
         *   cpu_nrg = ------------------------ * ---------          (3)
         *                    cs->freq            scale_cpu
         *
         * The first term is static, and is stored in the em_cap_state struct
         * as 'cs->cost'.
         *
         * Since all CPUs of the domain have the same micro-architecture, they
         * share the same 'cs->cost', and the same CPU capacity. Hence, the
         * total energy of the domain (which is the simple sum of the energy of
         * all of its CPUs) can be factorized as:
         *
         *            cs->cost * \Sum cpu_util
         *   pd_nrg = ------------------------                       (4)
         *                  scale_cpu
         */
        return cs->cost * sum_util / scale_cpu;
}

/**
 * em_pd_nr_cap_states() - Get the number of capacity states of a perf. domain
 * @pd          : performance domain for which this must be done
 *
 * Return: the number of capacity states in the performance domain table
 */
static inline int em_pd_nr_cap_states(struct em_perf_domain *pd)
{
        return pd->nr_cap_states;
}

#else
struct em_perf_domain {};
struct em_data_callback {};
#define EM_DATA_CB(_active_power_cb) { }

static inline int em_register_perf_domain(cpumask_t *span,
                        unsigned int nr_states, struct em_data_callback *cb)
{
        return -EINVAL;
}
static inline struct em_perf_domain *em_cpu_get(int cpu)
{
        return NULL;
}
static inline unsigned long em_pd_energy(struct em_perf_domain *pd,
                        unsigned long max_util, unsigned long sum_util)
{
        return 0;
}
static inline int em_pd_nr_cap_states(struct em_perf_domain *pd)
{
        return 0;
}
#endif

#endif