xref: /device/soc/rockchip/common/sdk_linux/include/linux/energy_model.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_ENERGY_MODEL_H
#define _LINUX_ENERGY_MODEL_H
#include <linux/cpumask.h>
#include <linux/device.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>

/**
 * em_perf_state - Performance state of a performance domain
 * @frequency:    The frequency in KHz, for consistency with CPUFreq
 * @power:    The power consumed at this level, in milli-watts (by 1 CPU or
        by a registered device). It can be a total power: static and
        dynamic.
 * @cost:    The cost coefficient associated with this level, used during
 *        energy calculation. Equal to: power * max_frequency / frequency
 */
struct em_perf_state {
    unsigned long frequency;
    unsigned long power;
    unsigned long cost;
};

/**
 * em_perf_domain - Performance domain
 * @table:        List of performance states, in ascending order
 * @nr_perf_states:    Number of performance states
 * @milliwatts:        Flag indicating the power values are in milli-Watts
 *            or some other scale.
 * @cpus:        Cpumask covering the CPUs of the domain. It's here
 *            for performance reasons to avoid potential cache
 *            misses during energy calculations in the scheduler
 *            and simplifies allocating/freeing that memory region.
 *
 * In case of CPU device, 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. In case of other devices the @cpus
 * field is unused.
 */
struct em_perf_domain {
    struct em_perf_state *table;
    int nr_perf_states;
    int milliwatts;
    unsigned long cpus[];
};

#define em_span_cpus(em) (to_cpumask((em)->cpus))

#ifdef CONFIG_ENERGY_MODEL
#define EM_MAX_POWER 0xFFFF

/*
 * Increase resolution of energy estimation calculations for 64-bit
 * architectures. The extra resolution improves decision made by EAS for the
 * task placement when two Performance Domains might provide similar energy
 * estimation values (w/o better resolution the values could be equal).
 *
 * We increase resolution only if we have enough bits to allow this increased
 * resolution (i.e. 64-bit). The costs for increasing resolution when 32-bit
 * are pretty high and the returns do not justify the increased costs.
 */
#ifdef CONFIG_64BIT
#define em_scale_power(p) ((p)*1000)
#else
#define em_scale_power(p) (p)
#endif

struct em_data_callback {
    /**
     * active_power() - Provide power at the next performance state of
     *        a device
     * @power    : Active power at the performance state in mW
     *        (modified)
     * @freq    : Frequency at the performance state in kHz
     *        (modified)
     * @dev        : Device for which we do this operation (can be a CPU)
     *
     * active_power() must find the lowest performance state of 'dev' above
     * 'freq' and update 'power' and 'freq' to the matching active power
     * and frequency.
     *
     * In case of CPUs, 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_MAX_POWER] range.
     *
     * Return 0 on success.
     */
    int (*active_power)(unsigned long *power, unsigned long *freq, struct device *dev);
};
#define EM_DATA_CB(_active_power_cb)                                                                                   \
    {                                                                                                                  \
        .active_power = &_active_power_cb                                                                              \
    }

struct em_perf_domain *em_cpu_get(int cpu);
struct em_perf_domain *em_pd_get(struct device *dev);
int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states, struct em_data_callback *cb,
                                cpumask_t *span, bool milliwatts);
void em_dev_unregister_perf_domain(struct device *dev);

/**
 * em_cpu_energy() - Estimates the energy consumed by the CPUs of a
        performance 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
 *
 * This function must be used only for CPU devices. There is no validation,
 * i.e. if the EM is a CPU type and has cpumask allocated. It is called from
 * the scheduler code quite frequently and that is why there is not checks.
 *
 * 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_cpu_energy(struct em_perf_domain *pd, unsigned long max_util, unsigned long sum_util)
{
    unsigned long freq, scale_cpu;
    struct em_perf_state *ps;
    int i, cpu;

    if (!sum_util) {
        return 0;
    }

    /*
     * In order to predict the performance 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(cpu);
    ps = &pd->table[pd->nr_perf_states - 1];
    freq = map_util_freq(max_util, ps->frequency, scale_cpu);

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

    /*
     * The capacity of a CPU in the domain at the performance state (ps)
     * can be computed as:
     *
     *             ps->freq * scale_cpu
     *   ps->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 performance state
     * is estimated as:
     *
     *             ps->power * cpu_util
     *   cpu_nrg = --------------------                          (2)
     *                   ps->cap
     *
     * since 'cpu_util / ps->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:
     *
     *             ps->power * cpu_max_freq   cpu_util
     *   cpu_nrg = ------------------------ * ---------          (3)
     *                    ps->freq            scale_cpu
     *
     * The first term is static, and is stored in the em_perf_state struct
     * as 'ps->cost'.
     *
     * Since all CPUs of the domain have the same micro-architecture, they
     * share the same 'ps->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:
     *
     *            ps->cost * \Sum cpu_util
     *   pd_nrg = ------------------------                       (4)
     *                  scale_cpu
     */
    return ps->cost * sum_util / scale_cpu;
}

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

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

static inline int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states, struct em_data_callback *cb,
                                              cpumask_t *span, bool milliwatts)
{
    return -EINVAL;
}
static inline void em_dev_unregister_perf_domain(struct device *dev)
{
}
static inline struct em_perf_domain *em_cpu_get(int cpu)
{
    return NULL;
}
static inline struct em_perf_domain *em_pd_get(struct device *dev)
{
    return NULL;
}
static inline unsigned long em_cpu_energy(struct em_perf_domain *pd, unsigned long max_util, unsigned long sum_util)
{
    return 0;
}
static inline int em_pd_nr_perf_states(struct em_perf_domain *pd)
{
    return 0;
}
#endif

#endif