// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2020 Linaro Limited
 *
 * Author: Daniel Lezcano <daniel.lezcano@linaro.org>
 *
 * The DTPM CPU is based on the energy model. It hooks the CPU in the
 * DTPM tree which in turns update the power number by propagating the
 * power number from the CPU energy model information to the parents.
 *
 * The association between the power and the performance state, allows
 * to set the power of the CPU at the OPP granularity.
 *
 * The CPU hotplug is supported and the power numbers will be updated
 * if a CPU is hot plugged / unplugged.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/cpumask.h>
#include <linux/cpufreq.h>
#include <linux/cpuhotplug.h>
#include <linux/dtpm.h>
#include <linux/energy_model.h>
#include <linux/of.h>
#include <linux/pm_qos.h>
#include <linux/slab.h>

struct dtpm_cpu {
        struct dtpm dtpm;
        struct freq_qos_request qos_req;
        int cpu;
};

static DEFINE_PER_CPU(struct dtpm_cpu *, dtpm_per_cpu);

static struct dtpm_cpu *to_dtpm_cpu(struct dtpm *dtpm)
{
        return container_of(dtpm, struct dtpm_cpu, dtpm);
}

static u64 set_pd_power_limit(struct dtpm *dtpm, u64 power_limit)
{
        struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
        struct em_perf_domain *pd = em_cpu_get(dtpm_cpu->cpu);
        struct em_perf_state *table;
        unsigned long freq;
        u64 power;
        int i, nr_cpus;

        nr_cpus = cpumask_weight_and(cpu_online_mask, to_cpumask(pd->cpus));

        rcu_read_lock();
        table = em_perf_state_from_pd(pd);
        for (i = 0; i < pd->nr_perf_states; i++) {

                power = table[i].power * nr_cpus;

                if (power > power_limit)
                        break;
        }

        freq = table[i - 1].frequency;
        power_limit = table[i - 1].power * nr_cpus;
        rcu_read_unlock();

        freq_qos_update_request(&dtpm_cpu->qos_req, freq);

        return power_limit;
}

static u64 scale_pd_power_uw(struct cpumask *pd_mask, u64 power)
{
        unsigned long max, sum_util = 0;
        int cpu;

        /*
         * The capacity is the same for all CPUs belonging to
         * the same perf domain.
         */
        max = arch_scale_cpu_capacity(cpumask_first(pd_mask));

        for_each_cpu_and(cpu, pd_mask, cpu_online_mask)
                sum_util += sched_cpu_util(cpu);

        return (power * ((sum_util << 10) / max)) >> 10;
}

static u64 get_pd_power_uw(struct dtpm *dtpm)
{
        struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
        struct em_perf_state *table;
        struct em_perf_domain *pd;
        struct cpumask *pd_mask;
        unsigned long freq;
        u64 power = 0;
        int i;

        pd = em_cpu_get(dtpm_cpu->cpu);
        if (!pd)
                return 0;

        pd_mask = em_span_cpus(pd);

        freq = cpufreq_quick_get(dtpm_cpu->cpu);

        rcu_read_lock();
        table = em_perf_state_from_pd(pd);
        for (i = 0; i < pd->nr_perf_states; i++) {

                if (table[i].frequency < freq)
                        continue;

                power = scale_pd_power_uw(pd_mask, table[i].power);
                break;
        }
        rcu_read_unlock();

        return power;
}

static int update_pd_power_uw(struct dtpm *dtpm)
{
        struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
        struct em_perf_domain *em = em_cpu_get(dtpm_cpu->cpu);
        struct em_perf_state *table;
        int nr_cpus;

        nr_cpus = cpumask_weight_and(cpu_online_mask, to_cpumask(em->cpus));

        rcu_read_lock();
        table = em_perf_state_from_pd(em);

        dtpm->power_min = table[0].power;
        dtpm->power_min *= nr_cpus;

        dtpm->power_max = table[em->nr_perf_states - 1].power;
        dtpm->power_max *= nr_cpus;

        rcu_read_unlock();

        return 0;
}

static void pd_release(struct dtpm *dtpm)
{
        struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
        struct cpufreq_policy *policy;

        if (freq_qos_request_active(&dtpm_cpu->qos_req))
                freq_qos_remove_request(&dtpm_cpu->qos_req);

        policy = cpufreq_cpu_get(dtpm_cpu->cpu);
        if (policy) {
                for_each_cpu(dtpm_cpu->cpu, policy->related_cpus)
                        per_cpu(dtpm_per_cpu, dtpm_cpu->cpu) = NULL;

                cpufreq_cpu_put(policy);
        }

        kfree(dtpm_cpu);
}

static struct dtpm_ops dtpm_ops = {
        .set_power_uw    = set_pd_power_limit,
        .get_power_uw    = get_pd_power_uw,
        .update_power_uw = update_pd_power_uw,
        .release         = pd_release,
};

static int cpuhp_dtpm_cpu_offline(unsigned int cpu)
{
        struct dtpm_cpu *dtpm_cpu;

        dtpm_cpu = per_cpu(dtpm_per_cpu, cpu);
        if (dtpm_cpu)
                dtpm_update_power(&dtpm_cpu->dtpm);

        return 0;
}

static int cpuhp_dtpm_cpu_online(unsigned int cpu)
{
        struct dtpm_cpu *dtpm_cpu;

        dtpm_cpu = per_cpu(dtpm_per_cpu, cpu);
        if (dtpm_cpu)
                return dtpm_update_power(&dtpm_cpu->dtpm);

        return 0;
}

static int __dtpm_cpu_setup(int cpu, struct dtpm *parent)
{
        struct dtpm_cpu *dtpm_cpu;
        struct cpufreq_policy *policy;
        struct em_perf_state *table;
        struct em_perf_domain *pd;
        char name[CPUFREQ_NAME_LEN];
        int ret = -ENOMEM;

        dtpm_cpu = per_cpu(dtpm_per_cpu, cpu);
        if (dtpm_cpu)
                return 0;

        policy = cpufreq_cpu_get(cpu);
        if (!policy)
                return 0;

        pd = em_cpu_get(cpu);
        if (!pd || em_is_artificial(pd)) {
                ret = -EINVAL;
                goto release_policy;
        }

        dtpm_cpu = kzalloc_obj(*dtpm_cpu);
        if (!dtpm_cpu) {
                ret = -ENOMEM;
                goto release_policy;
        }

        dtpm_init(&dtpm_cpu->dtpm, &dtpm_ops);
        dtpm_cpu->cpu = cpu;

        for_each_cpu(cpu, policy->related_cpus)
                per_cpu(dtpm_per_cpu, cpu) = dtpm_cpu;

        snprintf(name, sizeof(name), "cpu%d-cpufreq", dtpm_cpu->cpu);

        ret = dtpm_register(name, &dtpm_cpu->dtpm, parent);
        if (ret)
                goto out_kfree_dtpm_cpu;

        rcu_read_lock();
        table = em_perf_state_from_pd(pd);
        ret = freq_qos_add_request(&policy->constraints,
                                   &dtpm_cpu->qos_req, FREQ_QOS_MAX,
                                   table[pd->nr_perf_states - 1].frequency);
        rcu_read_unlock();
        if (ret < 0)
                goto out_dtpm_unregister;

        cpufreq_cpu_put(policy);
        return 0;

out_dtpm_unregister:
        dtpm_unregister(&dtpm_cpu->dtpm);
        dtpm_cpu = NULL;

out_kfree_dtpm_cpu:
        for_each_cpu(cpu, policy->related_cpus)
                per_cpu(dtpm_per_cpu, cpu) = NULL;
        kfree(dtpm_cpu);

release_policy:
        cpufreq_cpu_put(policy);
        return ret;
}

static int dtpm_cpu_setup(struct dtpm *dtpm, struct device_node *np)
{
        int cpu;

        cpu = of_cpu_node_to_id(np);
        if (cpu < 0)
                return 0;

        return __dtpm_cpu_setup(cpu, dtpm);
}

static int dtpm_cpu_init(void)
{
        int ret;

        /*
         * The callbacks at CPU hotplug time are calling
         * dtpm_update_power() which in turns calls update_pd_power().
         *
         * The function update_pd_power() uses the online mask to
         * figure out the power consumption limits.
         *
         * At CPUHP_AP_ONLINE_DYN, the CPU is present in the CPU
         * online mask when the cpuhp_dtpm_cpu_online function is
         * called, but the CPU is still in the online mask for the
         * tear down callback. So the power can not be updated when
         * the CPU is unplugged.
         *
         * At CPUHP_AP_DTPM_CPU_DEAD, the situation is the opposite as
         * above. The CPU online mask is not up to date when the CPU
         * is plugged in.
         *
         * For this reason, we need to call the online and offline
         * callbacks at different moments when the CPU online mask is
         * consistent with the power numbers we want to update.
         */
        ret = cpuhp_setup_state(CPUHP_AP_DTPM_CPU_DEAD, "dtpm_cpu:offline",
                                NULL, cpuhp_dtpm_cpu_offline);
        if (ret < 0)
                return ret;

        ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "dtpm_cpu:online",
                                cpuhp_dtpm_cpu_online, NULL);
        if (ret < 0)
                return ret;

        return 0;
}

static void dtpm_cpu_exit(void)
{
        cpuhp_remove_state_nocalls(CPUHP_AP_ONLINE_DYN);
        cpuhp_remove_state_nocalls(CPUHP_AP_DTPM_CPU_DEAD);
}

struct dtpm_subsys_ops dtpm_cpu_ops = {
        .name = KBUILD_MODNAME,
        .init = dtpm_cpu_init,
        .exit = dtpm_cpu_exit,
        .setup = dtpm_cpu_setup,
};