// SPDX-License-Identifier: GPL-2.0
/*
 * drivers/base/power/domain_governor.c - Governors for device PM domains.
 *
 * Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
 */
#include <linux/kernel.h>
#include <linux/pm_domain.h>
#include <linux/pm_qos.h>
#include <linux/hrtimer.h>
#include <linux/cpuidle.h>
#include <linux/cpumask.h>
#include <linux/ktime.h>

static int dev_update_qos_constraint(struct device *dev, void *data)
{
        s64 *constraint_ns_p = data;
        s64 constraint_ns;

        if (dev->power.subsys_data && dev->power.subsys_data->domain_data) {
                /*
                 * Only take suspend-time QoS constraints of devices into
                 * account, because constraints updated after the device has
                 * been suspended are not guaranteed to be taken into account
                 * anyway.  In order for them to take effect, the device has to
                 * be resumed and suspended again.
                 */
                constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
        } else {
                /*
                 * The child is not in a domain and there's no info on its
                 * suspend/resume latencies, so assume them to be negligible and
                 * take its current PM QoS constraint (that's the only thing
                 * known at this point anyway).
                 */
                constraint_ns = dev_pm_qos_read_value(dev, DEV_PM_QOS_RESUME_LATENCY);
                constraint_ns *= NSEC_PER_USEC;
        }

        if (constraint_ns < *constraint_ns_p)
                *constraint_ns_p = constraint_ns;

        return 0;
}

/**
 * default_suspend_ok - Default PM domain governor routine to suspend devices.
 * @dev: Device to check.
 */
static bool default_suspend_ok(struct device *dev)
{
        struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
        unsigned long flags;
        s64 constraint_ns;

        dev_dbg(dev, "%s()\n", __func__);

        spin_lock_irqsave(&dev->power.lock, flags);

        if (!td->constraint_changed) {
                bool ret = td->cached_suspend_ok;

                spin_unlock_irqrestore(&dev->power.lock, flags);
                return ret;
        }
        td->constraint_changed = false;
        td->cached_suspend_ok = false;
        td->effective_constraint_ns = 0;
        constraint_ns = __dev_pm_qos_resume_latency(dev);

        spin_unlock_irqrestore(&dev->power.lock, flags);

        if (constraint_ns == 0)
                return false;

        constraint_ns *= NSEC_PER_USEC;
        /*
         * We can walk the children without any additional locking, because
         * they all have been suspended at this point and their
         * effective_constraint_ns fields won't be modified in parallel with us.
         */
        if (!dev->power.ignore_children)
                device_for_each_child(dev, &constraint_ns,
                                      dev_update_qos_constraint);

        if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS) {
                /* "No restriction", so the device is allowed to suspend. */
                td->effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS;
                td->cached_suspend_ok = true;
        } else if (constraint_ns == 0) {
                /*
                 * This triggers if one of the children that don't belong to a
                 * domain has a zero PM QoS constraint and it's better not to
                 * suspend then.  effective_constraint_ns is zero already and
                 * cached_suspend_ok is false, so bail out.
                 */
                return false;
        } else {
                constraint_ns -= td->suspend_latency_ns +
                                td->resume_latency_ns;
                /*
                 * effective_constraint_ns is zero already and cached_suspend_ok
                 * is false, so if the computed value is not positive, return
                 * right away.
                 */
                if (constraint_ns <= 0)
                        return false;

                td->effective_constraint_ns = constraint_ns;
                td->cached_suspend_ok = true;
        }

        /*
         * The children have been suspended already, so we don't need to take
         * their suspend latencies into account here.
         */
        return td->cached_suspend_ok;
}

static void update_domain_next_wakeup(struct generic_pm_domain *genpd, ktime_t now)
{
        ktime_t domain_wakeup = KTIME_MAX;
        ktime_t next_wakeup;
        struct pm_domain_data *pdd;
        struct gpd_link *link;

        if (!(genpd->flags & GENPD_FLAG_MIN_RESIDENCY))
                return;

        /*
         * Devices that have a predictable wakeup pattern, may specify
         * their next wakeup. Let's find the next wakeup from all the
         * devices attached to this domain and from all the sub-domains.
         * It is possible that component's a next wakeup may have become
         * stale when we read that here. We will ignore to ensure the domain
         * is able to enter its optimal idle state.
         */
        list_for_each_entry(pdd, &genpd->dev_list, list_node) {
                next_wakeup = to_gpd_data(pdd)->next_wakeup;
                if (next_wakeup != KTIME_MAX && !ktime_before(next_wakeup, now))
                        if (ktime_before(next_wakeup, domain_wakeup))
                                domain_wakeup = next_wakeup;
        }

        list_for_each_entry(link, &genpd->parent_links, parent_node) {
                next_wakeup = link->child->next_wakeup;
                if (next_wakeup != KTIME_MAX && !ktime_before(next_wakeup, now))
                        if (ktime_before(next_wakeup, domain_wakeup))
                                domain_wakeup = next_wakeup;
        }

        genpd->next_wakeup = domain_wakeup;
}

static bool next_wakeup_allows_state(struct generic_pm_domain *genpd,
                                     unsigned int state, ktime_t now)
{
        ktime_t domain_wakeup = genpd->next_wakeup;
        s64 idle_time_ns, min_sleep_ns;

        min_sleep_ns = genpd->states[state].power_off_latency_ns +
                       genpd->states[state].residency_ns;

        idle_time_ns = ktime_to_ns(ktime_sub(domain_wakeup, now));

        return idle_time_ns >= min_sleep_ns;
}

static bool __default_power_down_ok(struct dev_pm_domain *pd,
                                     unsigned int state)
{
        struct generic_pm_domain *genpd = pd_to_genpd(pd);
        struct gpd_link *link;
        struct pm_domain_data *pdd;
        s64 min_off_time_ns;
        s64 off_on_time_ns;

        off_on_time_ns = genpd->states[state].power_off_latency_ns +
                genpd->states[state].power_on_latency_ns;

        min_off_time_ns = -1;
        /*
         * Check if subdomains can be off for enough time.
         *
         * All subdomains have been powered off already at this point.
         */
        list_for_each_entry(link, &genpd->parent_links, parent_node) {
                struct generic_pm_domain *sd = link->child;
                s64 sd_max_off_ns = sd->max_off_time_ns;

                if (sd_max_off_ns < 0)
                        continue;

                /*
                 * Check if the subdomain is allowed to be off long enough for
                 * the current domain to turn off and on (that's how much time
                 * it will have to wait worst case).
                 */
                if (sd_max_off_ns <= off_on_time_ns)
                        return false;

                if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
                        min_off_time_ns = sd_max_off_ns;
        }

        /*
         * Check if the devices in the domain can be off enough time.
         */
        list_for_each_entry(pdd, &genpd->dev_list, list_node) {
                struct gpd_timing_data *td;
                s64 constraint_ns;

                /*
                 * Check if the device is allowed to be off long enough for the
                 * domain to turn off and on (that's how much time it will
                 * have to wait worst case).
                 */
                td = &to_gpd_data(pdd)->td;
                constraint_ns = td->effective_constraint_ns;
                /*
                 * Zero means "no suspend at all" and this runs only when all
                 * devices in the domain are suspended, so it must be positive.
                 */
                if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS)
                        continue;

                if (constraint_ns <= off_on_time_ns)
                        return false;

                if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
                        min_off_time_ns = constraint_ns;
        }

        /*
         * If the computed minimum device off time is negative, there are no
         * latency constraints, so the domain can spend arbitrary time in the
         * "off" state.
         */
        if (min_off_time_ns < 0)
                return true;

        /*
         * The difference between the computed minimum subdomain or device off
         * time and the time needed to turn the domain on is the maximum
         * theoretical time this domain can spend in the "off" state.
         */
        genpd->max_off_time_ns = min_off_time_ns -
                genpd->states[state].power_on_latency_ns;
        return true;
}

/**
 * _default_power_down_ok - Default generic PM domain power off governor routine.
 * @pd: PM domain to check.
 * @now: current ktime.
 *
 * This routine must be executed under the PM domain's lock.
 */
static bool _default_power_down_ok(struct dev_pm_domain *pd, ktime_t now)
{
        struct generic_pm_domain *genpd = pd_to_genpd(pd);
        int state_idx = genpd->state_count - 1;
        struct gpd_link *link;

        /*
         * Find the next wakeup from devices that can determine their own wakeup
         * to find when the domain would wakeup and do it for every device down
         * the hierarchy. It is not worth while to sleep if the state's residency
         * cannot be met.
         */
        update_domain_next_wakeup(genpd, now);
        if ((genpd->flags & GENPD_FLAG_MIN_RESIDENCY) && (genpd->next_wakeup != KTIME_MAX)) {
                /* Let's find out the deepest domain idle state, the devices prefer */
                while (state_idx >= 0) {
                        if (next_wakeup_allows_state(genpd, state_idx, now)) {
                                genpd->max_off_time_changed = true;
                                break;
                        }
                        state_idx--;
                }

                if (state_idx < 0) {
                        state_idx = 0;
                        genpd->cached_power_down_ok = false;
                        goto done;
                }
        }

        if (!genpd->max_off_time_changed) {
                genpd->state_idx = genpd->cached_power_down_state_idx;
                return genpd->cached_power_down_ok;
        }

        /*
         * We have to invalidate the cached results for the parents, so
         * use the observation that default_power_down_ok() is not
         * going to be called for any parent until this instance
         * returns.
         */
        list_for_each_entry(link, &genpd->child_links, child_node)
                link->parent->max_off_time_changed = true;

        genpd->max_off_time_ns = -1;
        genpd->max_off_time_changed = false;
        genpd->cached_power_down_ok = true;

        /*
         * Find a state to power down to, starting from the state
         * determined by the next wakeup.
         */
        while (!__default_power_down_ok(pd, state_idx)) {
                if (state_idx == 0) {
                        genpd->cached_power_down_ok = false;
                        break;
                }
                state_idx--;
        }

done:
        genpd->state_idx = state_idx;
        genpd->cached_power_down_state_idx = genpd->state_idx;
        return genpd->cached_power_down_ok;
}

static bool default_power_down_ok(struct dev_pm_domain *pd)
{
        return _default_power_down_ok(pd, ktime_get());
}

static bool always_on_power_down_ok(struct dev_pm_domain *domain)
{
        return false;
}

#ifdef CONFIG_CPU_IDLE
static bool cpu_power_down_ok(struct dev_pm_domain *pd)
{
        struct generic_pm_domain *genpd = pd_to_genpd(pd);
        struct cpuidle_device *dev;
        ktime_t domain_wakeup, next_hrtimer;
        ktime_t now = ktime_get();
        s64 idle_duration_ns;
        int cpu, i;

        /* Validate dev PM QoS constraints. */
        if (!_default_power_down_ok(pd, now))
                return false;

        if (!(genpd->flags & GENPD_FLAG_CPU_DOMAIN))
                return true;

        /*
         * Find the next wakeup for any of the online CPUs within the PM domain
         * and its subdomains. Note, we only need the genpd->cpus, as it already
         * contains a mask of all CPUs from subdomains.
         */
        domain_wakeup = ktime_set(KTIME_SEC_MAX, 0);
        for_each_cpu_and(cpu, genpd->cpus, cpu_online_mask) {
                dev = per_cpu(cpuidle_devices, cpu);
                if (dev) {
                        next_hrtimer = READ_ONCE(dev->next_hrtimer);
                        if (ktime_before(next_hrtimer, domain_wakeup))
                                domain_wakeup = next_hrtimer;
                }
        }

        /* The minimum idle duration is from now - until the next wakeup. */
        idle_duration_ns = ktime_to_ns(ktime_sub(domain_wakeup, now));
        if (idle_duration_ns <= 0)
                return false;

        /*
         * Find the deepest idle state that has its residency value satisfied
         * and by also taking into account the power off latency for the state.
         * Start at the state picked by the dev PM QoS constraint validation.
         */
        i = genpd->state_idx;
        do {
                if (idle_duration_ns >= (genpd->states[i].residency_ns +
                    genpd->states[i].power_off_latency_ns)) {
                        genpd->state_idx = i;
                        return true;
                }
        } while (--i >= 0);

        return false;
}

struct dev_power_governor pm_domain_cpu_gov = {
        .suspend_ok = default_suspend_ok,
        .power_down_ok = cpu_power_down_ok,
};
#endif

struct dev_power_governor simple_qos_governor = {
        .suspend_ok = default_suspend_ok,
        .power_down_ok = default_power_down_ok,
};

/**
 * pm_genpd_gov_always_on - A governor implementing an always-on policy
 */
struct dev_power_governor pm_domain_always_on_gov = {
        .power_down_ok = always_on_power_down_ok,
        .suspend_ok = default_suspend_ok,
};