// SPDX-License-Identifier: GPL-2.0
/*
 * CPUFreq governor based on scheduler-provided CPU utilization data.
 *
 * Copyright (C) 2016, Intel Corporation
 * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
 */
#include <uapi/linux/sched/types.h>
#include "sched.h"

#define IOWAIT_BOOST_MIN        (SCHED_CAPACITY_SCALE / 8)

struct sugov_tunables {
        struct gov_attr_set     attr_set;
        unsigned int            rate_limit_us;
};

struct sugov_policy {
        struct cpufreq_policy   *policy;

        struct sugov_tunables   *tunables;
        struct list_head        tunables_hook;

        raw_spinlock_t          update_lock;
        u64                     last_freq_update_time;
        s64                     freq_update_delay_ns;
        unsigned int            next_freq;
        unsigned int            cached_raw_freq;

        /* The next fields are only needed if fast switch cannot be used: */
        struct                  irq_work irq_work;
        struct                  kthread_work work;
        struct                  mutex work_lock;
        struct                  kthread_worker worker;
        struct task_struct      *thread;
        bool                    work_in_progress;

        bool                    limits_changed;
        bool                    need_freq_update;
};

struct sugov_cpu {
        struct update_util_data update_util;
        struct sugov_policy     *sg_policy;
        unsigned int            cpu;

        bool                    iowait_boost_pending;
        unsigned int            iowait_boost;
        u64                     last_update;

        unsigned long           util;
        unsigned long           bw_min;

        /* The field below is for single-CPU policies only: */
#ifdef CONFIG_NO_HZ_COMMON
        unsigned long           saved_idle_calls;
#endif
};

static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);

/************************ Governor internals ***********************/

static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
{
        s64 delta_ns;

        /*
         * Since cpufreq_update_util() is called with rq->lock held for
         * the @target_cpu, our per-CPU data is fully serialized.
         *
         * However, drivers cannot in general deal with cross-CPU
         * requests, so while get_next_freq() will work, our
         * sugov_update_commit() call may not for the fast switching platforms.
         *
         * Hence stop here for remote requests if they aren't supported
         * by the hardware, as calculating the frequency is pointless if
         * we cannot in fact act on it.
         *
         * This is needed on the slow switching platforms too to prevent CPUs
         * going offline from leaving stale IRQ work items behind.
         */
        if (!cpufreq_this_cpu_can_update(sg_policy->policy))
                return false;

        if (unlikely(READ_ONCE(sg_policy->limits_changed))) {
                WRITE_ONCE(sg_policy->limits_changed, false);
                sg_policy->need_freq_update = true;

                /*
                 * The above limits_changed update must occur before the reads
                 * of policy limits in cpufreq_driver_resolve_freq() or a policy
                 * limits update might be missed, so use a memory barrier to
                 * ensure it.
                 *
                 * This pairs with the write memory barrier in sugov_limits().
                 */
                smp_mb();

                return true;
        } else if (sg_policy->need_freq_update) {
                /* ignore_dl_rate_limit() wants a new frequency to be found. */
                return true;
        }

        delta_ns = time - sg_policy->last_freq_update_time;

        return delta_ns >= sg_policy->freq_update_delay_ns;
}

static bool sugov_update_next_freq(struct sugov_policy *sg_policy, u64 time,
                                   unsigned int next_freq)
{
        if (sg_policy->need_freq_update) {
                sg_policy->need_freq_update = false;
                /*
                 * The policy limits have changed, but if the return value of
                 * cpufreq_driver_resolve_freq() after applying the new limits
                 * is still equal to the previously selected frequency, the
                 * driver callback need not be invoked unless the driver
                 * specifically wants that to happen on every update of the
                 * policy limits.
                 */
                if (sg_policy->next_freq == next_freq &&
                    !cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS))
                        return false;
        } else if (sg_policy->next_freq == next_freq) {
                return false;
        }

        sg_policy->next_freq = next_freq;
        sg_policy->last_freq_update_time = time;

        return true;
}

static void sugov_deferred_update(struct sugov_policy *sg_policy)
{
        if (!sg_policy->work_in_progress) {
                sg_policy->work_in_progress = true;
                irq_work_queue(&sg_policy->irq_work);
        }
}

/**
 * get_capacity_ref_freq - get the reference frequency that has been used to
 * correlate frequency and compute capacity for a given cpufreq policy. We use
 * the CPU managing it for the arch_scale_freq_ref() call in the function.
 * @policy: the cpufreq policy of the CPU in question.
 *
 * Return: the reference CPU frequency to compute a capacity.
 */
static __always_inline
unsigned long get_capacity_ref_freq(struct cpufreq_policy *policy)
{
        unsigned int freq = arch_scale_freq_ref(policy->cpu);

        if (freq)
                return freq;

        if (arch_scale_freq_invariant())
                return policy->cpuinfo.max_freq;

        /*
         * Apply a 25% margin so that we select a higher frequency than
         * the current one before the CPU is fully busy:
         */
        return policy->cur + (policy->cur >> 2);
}

/**
 * get_next_freq - Compute a new frequency for a given cpufreq policy.
 * @sg_policy: schedutil policy object to compute the new frequency for.
 * @util: Current CPU utilization.
 * @max: CPU capacity.
 *
 * If the utilization is frequency-invariant, choose the new frequency to be
 * proportional to it, that is
 *
 * next_freq = C * max_freq * util / max
 *
 * Otherwise, approximate the would-be frequency-invariant utilization by
 * util_raw * (curr_freq / max_freq) which leads to
 *
 * next_freq = C * curr_freq * util_raw / max
 *
 * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8.
 *
 * The lowest driver-supported frequency which is equal or greater than the raw
 * next_freq (as calculated above) is returned, subject to policy min/max and
 * cpufreq driver limitations.
 */
static unsigned int get_next_freq(struct sugov_policy *sg_policy,
                                  unsigned long util, unsigned long max)
{
        struct cpufreq_policy *policy = sg_policy->policy;
        unsigned int freq;

        freq = get_capacity_ref_freq(policy);
        freq = map_util_freq(util, freq, max);

        if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update)
                return sg_policy->next_freq;

        sg_policy->cached_raw_freq = freq;
        return cpufreq_driver_resolve_freq(policy, freq);
}

unsigned long sugov_effective_cpu_perf(int cpu, unsigned long actual,
                                 unsigned long min,
                                 unsigned long max)
{
        /* Add dvfs headroom to actual utilization */
        actual = map_util_perf(actual);
        /* Actually we don't need to target the max performance */
        if (actual < max)
                max = actual;

        /*
         * Ensure at least minimum performance while providing more compute
         * capacity when possible.
         */
        return max(min, max);
}

static void sugov_get_util(struct sugov_cpu *sg_cpu, unsigned long boost)
{
        unsigned long min, max, util = scx_cpuperf_target(sg_cpu->cpu);

        if (!scx_switched_all())
                util += cpu_util_cfs_boost(sg_cpu->cpu);
        util = effective_cpu_util(sg_cpu->cpu, util, &min, &max);
        util = max(util, boost);
        sg_cpu->bw_min = min;
        sg_cpu->util = sugov_effective_cpu_perf(sg_cpu->cpu, util, min, max);
}

/**
 * sugov_iowait_reset() - Reset the IO boost status of a CPU.
 * @sg_cpu: the sugov data for the CPU to boost
 * @time: the update time from the caller
 * @set_iowait_boost: true if an IO boost has been requested
 *
 * The IO wait boost of a task is disabled after a tick since the last update
 * of a CPU. If a new IO wait boost is requested after more then a tick, then
 * we enable the boost starting from IOWAIT_BOOST_MIN, which improves energy
 * efficiency by ignoring sporadic wakeups from IO.
 */
static bool sugov_iowait_reset(struct sugov_cpu *sg_cpu, u64 time,
                               bool set_iowait_boost)
{
        s64 delta_ns = time - sg_cpu->last_update;

        /* Reset boost only if a tick has elapsed since last request */
        if (delta_ns <= TICK_NSEC)
                return false;

        sg_cpu->iowait_boost = set_iowait_boost ? IOWAIT_BOOST_MIN : 0;
        sg_cpu->iowait_boost_pending = set_iowait_boost;

        return true;
}

/**
 * sugov_iowait_boost() - Updates the IO boost status of a CPU.
 * @sg_cpu: the sugov data for the CPU to boost
 * @time: the update time from the caller
 * @flags: SCHED_CPUFREQ_IOWAIT if the task is waking up after an IO wait
 *
 * Each time a task wakes up after an IO operation, the CPU utilization can be
 * boosted to a certain utilization which doubles at each "frequent and
 * successive" wakeup from IO, ranging from IOWAIT_BOOST_MIN to the utilization
 * of the maximum OPP.
 *
 * To keep doubling, an IO boost has to be requested at least once per tick,
 * otherwise we restart from the utilization of the minimum OPP.
 */
static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
                               unsigned int flags)
{
        bool set_iowait_boost = flags & SCHED_CPUFREQ_IOWAIT;

        /* Reset boost if the CPU appears to have been idle enough */
        if (sg_cpu->iowait_boost &&
            sugov_iowait_reset(sg_cpu, time, set_iowait_boost))
                return;

        /* Boost only tasks waking up after IO */
        if (!set_iowait_boost)
                return;

        /* Ensure boost doubles only one time at each request */
        if (sg_cpu->iowait_boost_pending)
                return;
        sg_cpu->iowait_boost_pending = true;

        /* Double the boost at each request */
        if (sg_cpu->iowait_boost) {
                sg_cpu->iowait_boost =
                        min_t(unsigned int, sg_cpu->iowait_boost << 1, SCHED_CAPACITY_SCALE);
                return;
        }

        /* First wakeup after IO: start with minimum boost */
        sg_cpu->iowait_boost = IOWAIT_BOOST_MIN;
}

/**
 * sugov_iowait_apply() - Apply the IO boost to a CPU.
 * @sg_cpu: the sugov data for the cpu to boost
 * @time: the update time from the caller
 * @max_cap: the max CPU capacity
 *
 * A CPU running a task which woken up after an IO operation can have its
 * utilization boosted to speed up the completion of those IO operations.
 * The IO boost value is increased each time a task wakes up from IO, in
 * sugov_iowait_apply(), and it's instead decreased by this function,
 * each time an increase has not been requested (!iowait_boost_pending).
 *
 * A CPU which also appears to have been idle for at least one tick has also
 * its IO boost utilization reset.
 *
 * This mechanism is designed to boost high frequently IO waiting tasks, while
 * being more conservative on tasks which does sporadic IO operations.
 */
static unsigned long sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time,
                               unsigned long max_cap)
{
        /* No boost currently required */
        if (!sg_cpu->iowait_boost)
                return 0;

        /* Reset boost if the CPU appears to have been idle enough */
        if (sugov_iowait_reset(sg_cpu, time, false))
                return 0;

        if (!sg_cpu->iowait_boost_pending) {
                /*
                 * No boost pending; reduce the boost value.
                 */
                sg_cpu->iowait_boost >>= 1;
                if (sg_cpu->iowait_boost < IOWAIT_BOOST_MIN) {
                        sg_cpu->iowait_boost = 0;
                        return 0;
                }
        }

        sg_cpu->iowait_boost_pending = false;

        /*
         * sg_cpu->util is already in capacity scale; convert iowait_boost
         * into the same scale so we can compare.
         */
        return (sg_cpu->iowait_boost * max_cap) >> SCHED_CAPACITY_SHIFT;
}

#ifdef CONFIG_NO_HZ_COMMON
static bool sugov_hold_freq(struct sugov_cpu *sg_cpu)
{
        unsigned long idle_calls;
        bool ret;

        /*
         * The heuristics in this function is for the fair class. For SCX, the
         * performance target comes directly from the BPF scheduler. Let's just
         * follow it.
         */
        if (scx_switched_all())
                return false;

        /* if capped by uclamp_max, always update to be in compliance */
        if (uclamp_rq_is_capped(cpu_rq(sg_cpu->cpu)))
                return false;

        /*
         * Maintain the frequency if the CPU has not been idle recently, as
         * reduction is likely to be premature.
         */
        idle_calls = tick_nohz_get_idle_calls_cpu(sg_cpu->cpu);
        ret = idle_calls == sg_cpu->saved_idle_calls;

        sg_cpu->saved_idle_calls = idle_calls;
        return ret;
}
#else /* !CONFIG_NO_HZ_COMMON: */
static inline bool sugov_hold_freq(struct sugov_cpu *sg_cpu) { return false; }
#endif /* !CONFIG_NO_HZ_COMMON */

/*
 * Make sugov_should_update_freq() ignore the rate limit when DL
 * has increased the utilization.
 */
static inline void ignore_dl_rate_limit(struct sugov_cpu *sg_cpu)
{
        if (cpu_bw_dl(cpu_rq(sg_cpu->cpu)) > sg_cpu->bw_min)
                sg_cpu->sg_policy->need_freq_update = true;
}

static inline bool sugov_update_single_common(struct sugov_cpu *sg_cpu,
                                              u64 time, unsigned long max_cap,
                                              unsigned int flags)
{
        unsigned long boost;

        sugov_iowait_boost(sg_cpu, time, flags);
        sg_cpu->last_update = time;

        ignore_dl_rate_limit(sg_cpu);

        if (!sugov_should_update_freq(sg_cpu->sg_policy, time))
                return false;

        boost = sugov_iowait_apply(sg_cpu, time, max_cap);
        sugov_get_util(sg_cpu, boost);

        return true;
}

static void sugov_update_single_freq(struct update_util_data *hook, u64 time,
                                     unsigned int flags)
{
        struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
        struct sugov_policy *sg_policy = sg_cpu->sg_policy;
        unsigned int cached_freq = sg_policy->cached_raw_freq;
        unsigned long max_cap;
        unsigned int next_f;

        max_cap = arch_scale_cpu_capacity(sg_cpu->cpu);

        if (!sugov_update_single_common(sg_cpu, time, max_cap, flags))
                return;

        next_f = get_next_freq(sg_policy, sg_cpu->util, max_cap);

        if (sugov_hold_freq(sg_cpu) && next_f < sg_policy->next_freq &&
            !sg_policy->need_freq_update) {
                next_f = sg_policy->next_freq;

                /* Restore cached freq as next_freq has changed */
                sg_policy->cached_raw_freq = cached_freq;
        }

        if (!sugov_update_next_freq(sg_policy, time, next_f))
                return;

        /*
         * This code runs under rq->lock for the target CPU, so it won't run
         * concurrently on two different CPUs for the same target and it is not
         * necessary to acquire the lock in the fast switch case.
         */
        if (sg_policy->policy->fast_switch_enabled) {
                cpufreq_driver_fast_switch(sg_policy->policy, next_f);
        } else {
                raw_spin_lock(&sg_policy->update_lock);
                sugov_deferred_update(sg_policy);
                raw_spin_unlock(&sg_policy->update_lock);
        }
}

static void sugov_update_single_perf(struct update_util_data *hook, u64 time,
                                     unsigned int flags)
{
        struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
        unsigned long prev_util = sg_cpu->util;
        unsigned long max_cap;

        /*
         * Fall back to the "frequency" path if frequency invariance is not
         * supported, because the direct mapping between the utilization and
         * the performance levels depends on the frequency invariance.
         */
        if (!arch_scale_freq_invariant()) {
                sugov_update_single_freq(hook, time, flags);
                return;
        }

        max_cap = arch_scale_cpu_capacity(sg_cpu->cpu);

        if (!sugov_update_single_common(sg_cpu, time, max_cap, flags))
                return;

        if (sugov_hold_freq(sg_cpu) && sg_cpu->util < prev_util)
                sg_cpu->util = prev_util;

        cpufreq_driver_adjust_perf(sg_cpu->cpu, sg_cpu->bw_min,
                                   sg_cpu->util, max_cap);

        sg_cpu->sg_policy->last_freq_update_time = time;
}

static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
{
        struct sugov_policy *sg_policy = sg_cpu->sg_policy;
        struct cpufreq_policy *policy = sg_policy->policy;
        unsigned long util = 0, max_cap;
        unsigned int j;

        max_cap = arch_scale_cpu_capacity(sg_cpu->cpu);

        for_each_cpu(j, policy->cpus) {
                struct sugov_cpu *j_sg_cpu = &per_cpu(sugov_cpu, j);
                unsigned long boost;

                boost = sugov_iowait_apply(j_sg_cpu, time, max_cap);
                sugov_get_util(j_sg_cpu, boost);

                util = max(j_sg_cpu->util, util);
        }

        return get_next_freq(sg_policy, util, max_cap);
}

static void
sugov_update_shared(struct update_util_data *hook, u64 time, unsigned int flags)
{
        struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
        struct sugov_policy *sg_policy = sg_cpu->sg_policy;
        unsigned int next_f;

        raw_spin_lock(&sg_policy->update_lock);

        sugov_iowait_boost(sg_cpu, time, flags);
        sg_cpu->last_update = time;

        ignore_dl_rate_limit(sg_cpu);

        if (sugov_should_update_freq(sg_policy, time)) {
                next_f = sugov_next_freq_shared(sg_cpu, time);

                if (!sugov_update_next_freq(sg_policy, time, next_f))
                        goto unlock;

                if (sg_policy->policy->fast_switch_enabled)
                        cpufreq_driver_fast_switch(sg_policy->policy, next_f);
                else
                        sugov_deferred_update(sg_policy);
        }
unlock:
        raw_spin_unlock(&sg_policy->update_lock);
}

static void sugov_work(struct kthread_work *work)
{
        struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work);
        unsigned int freq;
        unsigned long flags;

        /*
         * Hold sg_policy->update_lock shortly to handle the case where:
         * in case sg_policy->next_freq is read here, and then updated by
         * sugov_deferred_update() just before work_in_progress is set to false
         * here, we may miss queueing the new update.
         *
         * Note: If a work was queued after the update_lock is released,
         * sugov_work() will just be called again by kthread_work code; and the
         * request will be proceed before the sugov thread sleeps.
         */
        raw_spin_lock_irqsave(&sg_policy->update_lock, flags);
        freq = sg_policy->next_freq;
        sg_policy->work_in_progress = false;
        raw_spin_unlock_irqrestore(&sg_policy->update_lock, flags);

        mutex_lock(&sg_policy->work_lock);
        __cpufreq_driver_target(sg_policy->policy, freq, CPUFREQ_RELATION_L);
        mutex_unlock(&sg_policy->work_lock);
}

static void sugov_irq_work(struct irq_work *irq_work)
{
        struct sugov_policy *sg_policy;

        sg_policy = container_of(irq_work, struct sugov_policy, irq_work);

        kthread_queue_work(&sg_policy->worker, &sg_policy->work);
}

/************************** sysfs interface ************************/

static struct sugov_tunables *global_tunables;
static DEFINE_MUTEX(global_tunables_lock);

static inline struct sugov_tunables *to_sugov_tunables(struct gov_attr_set *attr_set)
{
        return container_of(attr_set, struct sugov_tunables, attr_set);
}

static ssize_t rate_limit_us_show(struct gov_attr_set *attr_set, char *buf)
{
        struct sugov_tunables *tunables = to_sugov_tunables(attr_set);

        return sprintf(buf, "%u\n", tunables->rate_limit_us);
}

static ssize_t
rate_limit_us_store(struct gov_attr_set *attr_set, const char *buf, size_t count)
{
        struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
        struct sugov_policy *sg_policy;
        unsigned int rate_limit_us;

        if (kstrtouint(buf, 10, &rate_limit_us))
                return -EINVAL;

        tunables->rate_limit_us = rate_limit_us;

        list_for_each_entry(sg_policy, &attr_set->policy_list, tunables_hook)
                sg_policy->freq_update_delay_ns = rate_limit_us * NSEC_PER_USEC;

        return count;
}

static struct governor_attr rate_limit_us = __ATTR_RW(rate_limit_us);

static struct attribute *sugov_attrs[] = {
        &rate_limit_us.attr,
        NULL
};
ATTRIBUTE_GROUPS(sugov);

static void sugov_tunables_free(struct kobject *kobj)
{
        struct gov_attr_set *attr_set = to_gov_attr_set(kobj);

        kfree(to_sugov_tunables(attr_set));
}

static const struct kobj_type sugov_tunables_ktype = {
        .default_groups = sugov_groups,
        .sysfs_ops = &governor_sysfs_ops,
        .release = &sugov_tunables_free,
};

/********************** cpufreq governor interface *********************/

static struct cpufreq_governor schedutil_gov;

static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
{
        struct sugov_policy *sg_policy;

        sg_policy = kzalloc_obj(*sg_policy);
        if (!sg_policy)
                return NULL;

        sg_policy->policy = policy;
        raw_spin_lock_init(&sg_policy->update_lock);
        return sg_policy;
}

static void sugov_policy_free(struct sugov_policy *sg_policy)
{
        kfree(sg_policy);
}

static int sugov_kthread_create(struct sugov_policy *sg_policy)
{
        struct task_struct *thread;
        struct sched_attr attr = {
                .size           = sizeof(struct sched_attr),
                .sched_policy   = SCHED_DEADLINE,
                .sched_flags    = SCHED_FLAG_SUGOV,
                .sched_nice     = 0,
                .sched_priority = 0,
                /*
                 * Fake (unused) bandwidth; workaround to "fix"
                 * priority inheritance.
                 */
                .sched_runtime  = NSEC_PER_MSEC,
                .sched_deadline = 10 * NSEC_PER_MSEC,
                .sched_period   = 10 * NSEC_PER_MSEC,
        };
        struct cpufreq_policy *policy = sg_policy->policy;
        int ret;

        /* kthread only required for slow path */
        if (policy->fast_switch_enabled)
                return 0;

        kthread_init_work(&sg_policy->work, sugov_work);
        kthread_init_worker(&sg_policy->worker);
        thread = kthread_create(kthread_worker_fn, &sg_policy->worker,
                                "sugov:%d",
                                cpumask_first(policy->related_cpus));
        if (IS_ERR(thread)) {
                pr_err("failed to create sugov thread: %pe\n", thread);
                return PTR_ERR(thread);
        }

        ret = sched_setattr_nocheck(thread, &attr);
        if (ret) {
                kthread_stop(thread);
                pr_warn("%s: failed to set SCHED_DEADLINE\n", __func__);
                return ret;
        }

        sg_policy->thread = thread;
        if (policy->dvfs_possible_from_any_cpu)
                set_cpus_allowed_ptr(thread, policy->related_cpus);
        else
                kthread_bind_mask(thread, policy->related_cpus);

        init_irq_work(&sg_policy->irq_work, sugov_irq_work);
        mutex_init(&sg_policy->work_lock);

        wake_up_process(thread);

        return 0;
}

static void sugov_kthread_stop(struct sugov_policy *sg_policy)
{
        /* kthread only required for slow path */
        if (sg_policy->policy->fast_switch_enabled)
                return;

        kthread_flush_worker(&sg_policy->worker);
        kthread_stop(sg_policy->thread);
        mutex_destroy(&sg_policy->work_lock);
}

static struct sugov_tunables *sugov_tunables_alloc(struct sugov_policy *sg_policy)
{
        struct sugov_tunables *tunables;

        tunables = kzalloc_obj(*tunables);
        if (tunables) {
                gov_attr_set_init(&tunables->attr_set, &sg_policy->tunables_hook);
                if (!have_governor_per_policy())
                        global_tunables = tunables;
        }
        return tunables;
}

static void sugov_clear_global_tunables(void)
{
        if (!have_governor_per_policy())
                global_tunables = NULL;
}

static int sugov_init(struct cpufreq_policy *policy)
{
        struct sugov_policy *sg_policy;
        struct sugov_tunables *tunables;
        int ret = 0;

        /* State should be equivalent to EXIT */
        if (policy->governor_data)
                return -EBUSY;

        cpufreq_enable_fast_switch(policy);

        sg_policy = sugov_policy_alloc(policy);
        if (!sg_policy) {
                ret = -ENOMEM;
                goto disable_fast_switch;
        }

        ret = sugov_kthread_create(sg_policy);
        if (ret)
                goto free_sg_policy;

        mutex_lock(&global_tunables_lock);

        if (global_tunables) {
                if (WARN_ON(have_governor_per_policy())) {
                        ret = -EINVAL;
                        goto stop_kthread;
                }
                policy->governor_data = sg_policy;
                sg_policy->tunables = global_tunables;

                gov_attr_set_get(&global_tunables->attr_set, &sg_policy->tunables_hook);
                goto out;
        }

        tunables = sugov_tunables_alloc(sg_policy);
        if (!tunables) {
                ret = -ENOMEM;
                goto stop_kthread;
        }

        tunables->rate_limit_us = cpufreq_policy_transition_delay_us(policy);

        policy->governor_data = sg_policy;
        sg_policy->tunables = tunables;

        ret = kobject_init_and_add(&tunables->attr_set.kobj, &sugov_tunables_ktype,
                                   get_governor_parent_kobj(policy), "%s",
                                   schedutil_gov.name);
        if (ret)
                goto fail;

out:
        /*
         * Schedutil is the preferred governor for EAS, so rebuild sched domains
         * on governor changes to make sure the scheduler knows about them.
         */
        em_rebuild_sched_domains();
        mutex_unlock(&global_tunables_lock);
        return 0;

fail:
        kobject_put(&tunables->attr_set.kobj);
        policy->governor_data = NULL;
        sugov_clear_global_tunables();

stop_kthread:
        sugov_kthread_stop(sg_policy);
        mutex_unlock(&global_tunables_lock);

free_sg_policy:
        sugov_policy_free(sg_policy);

disable_fast_switch:
        cpufreq_disable_fast_switch(policy);

        pr_err("initialization failed (error %d)\n", ret);
        return ret;
}

static void sugov_exit(struct cpufreq_policy *policy)
{
        struct sugov_policy *sg_policy = policy->governor_data;
        struct sugov_tunables *tunables = sg_policy->tunables;
        unsigned int count;

        mutex_lock(&global_tunables_lock);

        count = gov_attr_set_put(&tunables->attr_set, &sg_policy->tunables_hook);
        policy->governor_data = NULL;
        if (!count)
                sugov_clear_global_tunables();

        mutex_unlock(&global_tunables_lock);

        sugov_kthread_stop(sg_policy);
        sugov_policy_free(sg_policy);
        cpufreq_disable_fast_switch(policy);

        em_rebuild_sched_domains();
}

static int sugov_start(struct cpufreq_policy *policy)
{
        struct sugov_policy *sg_policy = policy->governor_data;
        void (*uu)(struct update_util_data *data, u64 time, unsigned int flags);
        unsigned int cpu;

        sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
        sg_policy->last_freq_update_time        = 0;
        sg_policy->next_freq                    = 0;
        sg_policy->work_in_progress             = false;
        sg_policy->limits_changed               = false;
        sg_policy->cached_raw_freq              = 0;

        sg_policy->need_freq_update = cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS);

        if (policy_is_shared(policy))
                uu = sugov_update_shared;
        else if (policy->fast_switch_enabled && cpufreq_driver_has_adjust_perf())
                uu = sugov_update_single_perf;
        else
                uu = sugov_update_single_freq;

        for_each_cpu(cpu, policy->cpus) {
                struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu);

                memset(sg_cpu, 0, sizeof(*sg_cpu));
                sg_cpu->cpu = cpu;
                sg_cpu->sg_policy = sg_policy;
                cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util, uu);
        }
        return 0;
}

static void sugov_stop(struct cpufreq_policy *policy)
{
        struct sugov_policy *sg_policy = policy->governor_data;
        unsigned int cpu;

        for_each_cpu(cpu, policy->cpus)
                cpufreq_remove_update_util_hook(cpu);

        synchronize_rcu();

        if (!policy->fast_switch_enabled) {
                irq_work_sync(&sg_policy->irq_work);
                kthread_cancel_work_sync(&sg_policy->work);
        }
}

static void sugov_limits(struct cpufreq_policy *policy)
{
        struct sugov_policy *sg_policy = policy->governor_data;

        if (!policy->fast_switch_enabled) {
                mutex_lock(&sg_policy->work_lock);
                cpufreq_policy_apply_limits(policy);
                mutex_unlock(&sg_policy->work_lock);
        }

        /*
         * The limits_changed update below must take place before the updates
         * of policy limits in cpufreq_set_policy() or a policy limits update
         * might be missed, so use a memory barrier to ensure it.
         *
         * This pairs with the memory barrier in sugov_should_update_freq().
         */
        smp_wmb();

        WRITE_ONCE(sg_policy->limits_changed, true);
}

static struct cpufreq_governor schedutil_gov = {
        .name                   = "schedutil",
        .owner                  = THIS_MODULE,
        .flags                  = CPUFREQ_GOV_DYNAMIC_SWITCHING,
        .init                   = sugov_init,
        .exit                   = sugov_exit,
        .start                  = sugov_start,
        .stop                   = sugov_stop,
        .limits                 = sugov_limits,
};

#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL
struct cpufreq_governor *cpufreq_default_governor(void)
{
        return &schedutil_gov;
}
#endif

bool sugov_is_governor(struct cpufreq_policy *policy)
{
        return policy->governor == &schedutil_gov;
}

cpufreq_governor_init(schedutil_gov);