/*
 * cpuidle.c - core cpuidle infrastructure
 *
 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 *               Shaohua Li <shaohua.li@intel.com>
 *               Adam Belay <abelay@novell.com>
 *
 * This code is licenced under the GPL.
 */

#include <linux/clockchips.h>
#include <linux/kernel.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
#include <linux/notifier.h>
#include <linux/pm_qos.h>
#include <linux/cpu.h>
#include <linux/cpuidle.h>
#include <linux/ktime.h>
#include <linux/hrtimer.h>
#include <linux/module.h>
#include <linux/suspend.h>
#include <linux/tick.h>
#include <linux/mmu_context.h>
#include <trace/events/power.h>

#include "cpuidle.h"

DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
DEFINE_PER_CPU(struct cpuidle_device, cpuidle_dev);

DEFINE_MUTEX(cpuidle_lock);
LIST_HEAD(cpuidle_detected_devices);

static int enabled_devices;
static int off __read_mostly;
static int initialized __read_mostly;

int cpuidle_disabled(void)
{
        return off;
}
void disable_cpuidle(void)
{
        off = 1;
}

bool cpuidle_not_available(struct cpuidle_driver *drv,
                           struct cpuidle_device *dev)
{
        return off || !initialized || !drv || !dev || !dev->enabled;
}

/**
 * cpuidle_play_dead - cpu off-lining
 *
 * Returns in case of an error or no driver
 */
int cpuidle_play_dead(void)
{
        struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
        struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
        int i;

        if (!drv)
                return -ENODEV;

        /* Find lowest-power state that supports long-term idle */
        for (i = drv->state_count - 1; i >= 0; i--)
                if (drv->states[i].enter_dead)
                        return drv->states[i].enter_dead(dev, i);

        return -ENODEV;
}

static int find_deepest_state(struct cpuidle_driver *drv,
                              struct cpuidle_device *dev,
                              u64 max_latency_ns,
                              unsigned int forbidden_flags,
                              bool s2idle)
{
        u64 latency_req = 0;
        int i, ret = 0;

        for (i = 1; i < drv->state_count; i++) {
                struct cpuidle_state *s = &drv->states[i];

                if (dev->states_usage[i].disable ||
                    s->exit_latency_ns <= latency_req ||
                    s->exit_latency_ns > max_latency_ns ||
                    (s->flags & forbidden_flags) ||
                    (s2idle && !s->enter_s2idle))
                        continue;

                latency_req = s->exit_latency_ns;
                ret = i;
        }
        return ret;
}

/**
 * cpuidle_use_deepest_state - Set/unset governor override mode.
 * @latency_limit_ns: Idle state exit latency limit (or no override if 0).
 *
 * If @latency_limit_ns is nonzero, set the current CPU to use the deepest idle
 * state with exit latency within @latency_limit_ns (override governors going
 * forward), or do not override governors if it is zero.
 */
void cpuidle_use_deepest_state(u64 latency_limit_ns)
{
        struct cpuidle_device *dev;

        preempt_disable();
        dev = cpuidle_get_device();
        if (dev)
                dev->forced_idle_latency_limit_ns = latency_limit_ns;
        preempt_enable();
}

/**
 * cpuidle_find_deepest_state - Find the deepest available idle state.
 * @drv: cpuidle driver for the given CPU.
 * @dev: cpuidle device for the given CPU.
 * @latency_limit_ns: Idle state exit latency limit
 *
 * Return: the index of the deepest available idle state.
 */
int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
                               struct cpuidle_device *dev,
                               u64 latency_limit_ns)
{
        return find_deepest_state(drv, dev, latency_limit_ns, 0, false);
}

#ifdef CONFIG_SUSPEND
static void enter_s2idle_proper(struct cpuidle_driver *drv,
                                struct cpuidle_device *dev, int index)
{
        ktime_t time_start, time_end;
        struct cpuidle_state *target_state = &drv->states[index];

        time_start = ns_to_ktime(local_clock());

        tick_freeze();
        /*
         * The state used here cannot be a "coupled" one, because the "coupled"
         * cpuidle mechanism enables interrupts and doing that with timekeeping
         * suspended is generally unsafe.
         */
        stop_critical_timings();
        if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
                rcu_idle_enter();
        target_state->enter_s2idle(dev, drv, index);
        if (WARN_ON_ONCE(!irqs_disabled()))
                local_irq_disable();
        if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
                rcu_idle_exit();
        tick_unfreeze();
        start_critical_timings();

        time_end = ns_to_ktime(local_clock());

        dev->states_usage[index].s2idle_time += ktime_us_delta(time_end, time_start);
        dev->states_usage[index].s2idle_usage++;
}

/**
 * cpuidle_enter_s2idle - Enter an idle state suitable for suspend-to-idle.
 * @drv: cpuidle driver for the given CPU.
 * @dev: cpuidle device for the given CPU.
 *
 * If there are states with the ->enter_s2idle callback, find the deepest of
 * them and enter it with frozen tick.
 */
int cpuidle_enter_s2idle(struct cpuidle_driver *drv, struct cpuidle_device *dev)
{
        int index;

        /*
         * Find the deepest state with ->enter_s2idle present, which guarantees
         * that interrupts won't be enabled when it exits and allows the tick to
         * be frozen safely.
         */
        index = find_deepest_state(drv, dev, U64_MAX, 0, true);
        if (index > 0) {
                enter_s2idle_proper(drv, dev, index);
                local_irq_enable();
        }
        return index;
}
#endif /* CONFIG_SUSPEND */

/**
 * cpuidle_enter_state - enter the state and update stats
 * @dev: cpuidle device for this cpu
 * @drv: cpuidle driver for this cpu
 * @index: index into the states table in @drv of the state to enter
 */
int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
                        int index)
{
        int entered_state;

        struct cpuidle_state *target_state = &drv->states[index];
        bool broadcast = !!(target_state->flags & CPUIDLE_FLAG_TIMER_STOP);
        ktime_t time_start, time_end;

        /*
         * Tell the time framework to switch to a broadcast timer because our
         * local timer will be shut down.  If a local timer is used from another
         * CPU as a broadcast timer, this call may fail if it is not available.
         */
        if (broadcast && tick_broadcast_enter()) {
                index = find_deepest_state(drv, dev, target_state->exit_latency_ns,
                                           CPUIDLE_FLAG_TIMER_STOP, false);
                if (index < 0) {
                        default_idle_call();
                        return -EBUSY;
                }
                target_state = &drv->states[index];
                broadcast = false;
        }

        if (target_state->flags & CPUIDLE_FLAG_TLB_FLUSHED)
                leave_mm(dev->cpu);

        /* Take note of the planned idle state. */
        sched_idle_set_state(target_state);

        trace_cpu_idle(index, dev->cpu);
        time_start = ns_to_ktime(local_clock());

        stop_critical_timings();
        if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
                rcu_idle_enter();
        entered_state = target_state->enter(dev, drv, index);
        if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
                rcu_idle_exit();
        start_critical_timings();

        sched_clock_idle_wakeup_event();
        time_end = ns_to_ktime(local_clock());
        trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);

        /* The cpu is no longer idle or about to enter idle. */
        sched_idle_set_state(NULL);

        if (broadcast) {
                if (WARN_ON_ONCE(!irqs_disabled()))
                        local_irq_disable();

                tick_broadcast_exit();
        }

        if (!cpuidle_state_is_coupled(drv, index))
                local_irq_enable();

        if (entered_state >= 0) {
                s64 diff, delay = drv->states[entered_state].exit_latency_ns;
                int i;

                /*
                 * Update cpuidle counters
                 * This can be moved to within driver enter routine,
                 * but that results in multiple copies of same code.
                 */
                diff = ktime_sub(time_end, time_start);

                dev->last_residency_ns = diff;
                dev->states_usage[entered_state].time_ns += diff;
                dev->states_usage[entered_state].usage++;

                if (diff < drv->states[entered_state].target_residency_ns) {
                        for (i = entered_state - 1; i >= 0; i--) {
                                if (dev->states_usage[i].disable)
                                        continue;

                                /* Shallower states are enabled, so update. */
                                dev->states_usage[entered_state].above++;
                                break;
                        }
                } else if (diff > delay) {
                        for (i = entered_state + 1; i < drv->state_count; i++) {
                                if (dev->states_usage[i].disable)
                                        continue;

                                /*
                                 * Update if a deeper state would have been a
                                 * better match for the observed idle duration.
                                 */
                                if (diff - delay >= drv->states[i].target_residency_ns)
                                        dev->states_usage[entered_state].below++;

                                break;
                        }
                }
        } else {
                dev->last_residency_ns = 0;
                dev->states_usage[index].rejected++;
        }

        return entered_state;
}

/**
 * cpuidle_select - ask the cpuidle framework to choose an idle state
 *
 * @drv: the cpuidle driver
 * @dev: the cpuidle device
 * @stop_tick: indication on whether or not to stop the tick
 *
 * Returns the index of the idle state.  The return value must not be negative.
 *
 * The memory location pointed to by @stop_tick is expected to be written the
 * 'false' boolean value if the scheduler tick should not be stopped before
 * entering the returned state.
 */
int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
                   bool *stop_tick)
{
        return cpuidle_curr_governor->select(drv, dev, stop_tick);
}

/**
 * cpuidle_enter - enter into the specified idle state
 *
 * @drv:   the cpuidle driver tied with the cpu
 * @dev:   the cpuidle device
 * @index: the index in the idle state table
 *
 * Returns the index in the idle state, < 0 in case of error.
 * The error code depends on the backend driver
 */
int cpuidle_enter(struct cpuidle_driver *drv, struct cpuidle_device *dev,
                  int index)
{
        int ret = 0;

        /*
         * Store the next hrtimer, which becomes either next tick or the next
         * timer event, whatever expires first. Additionally, to make this data
         * useful for consumers outside cpuidle, we rely on that the governor's
         * ->select() callback have decided, whether to stop the tick or not.
         */
        WRITE_ONCE(dev->next_hrtimer, tick_nohz_get_next_hrtimer());

        if (cpuidle_state_is_coupled(drv, index))
                ret = cpuidle_enter_state_coupled(dev, drv, index);
        else
                ret = cpuidle_enter_state(dev, drv, index);

        WRITE_ONCE(dev->next_hrtimer, 0);
        return ret;
}

/**
 * cpuidle_reflect - tell the underlying governor what was the state
 * we were in
 *
 * @dev  : the cpuidle device
 * @index: the index in the idle state table
 *
 */
void cpuidle_reflect(struct cpuidle_device *dev, int index)
{
        if (cpuidle_curr_governor->reflect && index >= 0)
                cpuidle_curr_governor->reflect(dev, index);
}

/*
 * Min polling interval of 10usec is a guess. It is assuming that
 * for most users, the time for a single ping-pong workload like
 * perf bench pipe would generally complete within 10usec but
 * this is hardware dependant. Actual time can be estimated with
 *
 * perf bench sched pipe -l 10000
 *
 * Run multiple times to avoid cpufreq effects.
 */
#define CPUIDLE_POLL_MIN 10000
#define CPUIDLE_POLL_MAX (TICK_NSEC / 16)

/**
 * cpuidle_poll_time - return amount of time to poll for,
 * governors can override dev->poll_limit_ns if necessary
 *
 * @drv:   the cpuidle driver tied with the cpu
 * @dev:   the cpuidle device
 *
 */
u64 cpuidle_poll_time(struct cpuidle_driver *drv,
                      struct cpuidle_device *dev)
{
        int i;
        u64 limit_ns;

        BUILD_BUG_ON(CPUIDLE_POLL_MIN > CPUIDLE_POLL_MAX);

        if (dev->poll_limit_ns)
                return dev->poll_limit_ns;

        limit_ns = CPUIDLE_POLL_MAX;
        for (i = 1; i < drv->state_count; i++) {
                u64 state_limit;

                if (dev->states_usage[i].disable)
                        continue;

                state_limit = drv->states[i].target_residency_ns;
                if (state_limit < CPUIDLE_POLL_MIN)
                        continue;

                limit_ns = min_t(u64, state_limit, CPUIDLE_POLL_MAX);
                break;
        }

        dev->poll_limit_ns = limit_ns;

        return dev->poll_limit_ns;
}

/**
 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
 */
void cpuidle_install_idle_handler(void)
{
        if (enabled_devices) {
                /* Make sure all changes finished before we switch to new idle */
                smp_wmb();
                initialized = 1;
        }
}

/**
 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
 */
void cpuidle_uninstall_idle_handler(void)
{
        if (enabled_devices) {
                initialized = 0;
                wake_up_all_idle_cpus();
        }

        /*
         * Make sure external observers (such as the scheduler)
         * are done looking at pointed idle states.
         */
        synchronize_rcu();
}

/**
 * cpuidle_pause_and_lock - temporarily disables CPUIDLE
 */
void cpuidle_pause_and_lock(void)
{
        mutex_lock(&cpuidle_lock);
        cpuidle_uninstall_idle_handler();
}

EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);

/**
 * cpuidle_resume_and_unlock - resumes CPUIDLE operation
 */
void cpuidle_resume_and_unlock(void)
{
        cpuidle_install_idle_handler();
        mutex_unlock(&cpuidle_lock);
}

EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);

/* Currently used in suspend/resume path to suspend cpuidle */
void cpuidle_pause(void)
{
        mutex_lock(&cpuidle_lock);
        cpuidle_uninstall_idle_handler();
        mutex_unlock(&cpuidle_lock);
}

/* Currently used in suspend/resume path to resume cpuidle */
void cpuidle_resume(void)
{
        mutex_lock(&cpuidle_lock);
        cpuidle_install_idle_handler();
        mutex_unlock(&cpuidle_lock);
}

/**
 * cpuidle_enable_device - enables idle PM for a CPU
 * @dev: the CPU
 *
 * This function must be called between cpuidle_pause_and_lock and
 * cpuidle_resume_and_unlock when used externally.
 */
int cpuidle_enable_device(struct cpuidle_device *dev)
{
        int ret;
        struct cpuidle_driver *drv;

        if (!dev)
                return -EINVAL;

        if (dev->enabled)
                return 0;

        if (!cpuidle_curr_governor)
                return -EIO;

        drv = cpuidle_get_cpu_driver(dev);

        if (!drv)
                return -EIO;

        if (!dev->registered)
                return -EINVAL;

        ret = cpuidle_add_device_sysfs(dev);
        if (ret)
                return ret;

        if (cpuidle_curr_governor->enable) {
                ret = cpuidle_curr_governor->enable(drv, dev);
                if (ret)
                        goto fail_sysfs;
        }

        smp_wmb();

        dev->enabled = 1;

        enabled_devices++;
        return 0;

fail_sysfs:
        cpuidle_remove_device_sysfs(dev);

        return ret;
}

EXPORT_SYMBOL_GPL(cpuidle_enable_device);

/**
 * cpuidle_disable_device - disables idle PM for a CPU
 * @dev: the CPU
 *
 * This function must be called between cpuidle_pause_and_lock and
 * cpuidle_resume_and_unlock when used externally.
 */
void cpuidle_disable_device(struct cpuidle_device *dev)
{
        struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);

        if (!dev || !dev->enabled)
                return;

        if (!drv || !cpuidle_curr_governor)
                return;

        dev->enabled = 0;

        if (cpuidle_curr_governor->disable)
                cpuidle_curr_governor->disable(drv, dev);

        cpuidle_remove_device_sysfs(dev);
        enabled_devices--;
}

EXPORT_SYMBOL_GPL(cpuidle_disable_device);

static void __cpuidle_unregister_device(struct cpuidle_device *dev)
{
        struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);

        list_del(&dev->device_list);
        per_cpu(cpuidle_devices, dev->cpu) = NULL;
        module_put(drv->owner);

        dev->registered = 0;
}

static void __cpuidle_device_init(struct cpuidle_device *dev)
{
        memset(dev->states_usage, 0, sizeof(dev->states_usage));
        dev->last_residency_ns = 0;
        dev->next_hrtimer = 0;
}

/**
 * __cpuidle_register_device - internal register function called before register
 * and enable routines
 * @dev: the cpu
 *
 * cpuidle_lock mutex must be held before this is called
 */
static int __cpuidle_register_device(struct cpuidle_device *dev)
{
        struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
        int i, ret;

        if (!try_module_get(drv->owner))
                return -EINVAL;

        for (i = 0; i < drv->state_count; i++) {
                if (drv->states[i].flags & CPUIDLE_FLAG_UNUSABLE)
                        dev->states_usage[i].disable |= CPUIDLE_STATE_DISABLED_BY_DRIVER;

                if (drv->states[i].flags & CPUIDLE_FLAG_OFF)
                        dev->states_usage[i].disable |= CPUIDLE_STATE_DISABLED_BY_USER;
        }

        per_cpu(cpuidle_devices, dev->cpu) = dev;
        list_add(&dev->device_list, &cpuidle_detected_devices);

        ret = cpuidle_coupled_register_device(dev);
        if (ret)
                __cpuidle_unregister_device(dev);
        else
                dev->registered = 1;

        return ret;
}

/**
 * cpuidle_register_device - registers a CPU's idle PM feature
 * @dev: the cpu
 */
int cpuidle_register_device(struct cpuidle_device *dev)
{
        int ret = -EBUSY;

        if (!dev)
                return -EINVAL;

        mutex_lock(&cpuidle_lock);

        if (dev->registered)
                goto out_unlock;

        __cpuidle_device_init(dev);

        ret = __cpuidle_register_device(dev);
        if (ret)
                goto out_unlock;

        ret = cpuidle_add_sysfs(dev);
        if (ret)
                goto out_unregister;

        ret = cpuidle_enable_device(dev);
        if (ret)
                goto out_sysfs;

        cpuidle_install_idle_handler();

out_unlock:
        mutex_unlock(&cpuidle_lock);

        return ret;

out_sysfs:
        cpuidle_remove_sysfs(dev);
out_unregister:
        __cpuidle_unregister_device(dev);
        goto out_unlock;
}

EXPORT_SYMBOL_GPL(cpuidle_register_device);

/**
 * cpuidle_unregister_device - unregisters a CPU's idle PM feature
 * @dev: the cpu
 */
void cpuidle_unregister_device(struct cpuidle_device *dev)
{
        if (!dev || dev->registered == 0)
                return;

        cpuidle_pause_and_lock();

        cpuidle_disable_device(dev);

        cpuidle_remove_sysfs(dev);

        __cpuidle_unregister_device(dev);

        cpuidle_coupled_unregister_device(dev);

        cpuidle_resume_and_unlock();
}

EXPORT_SYMBOL_GPL(cpuidle_unregister_device);

/**
 * cpuidle_unregister: unregister a driver and the devices. This function
 * can be used only if the driver has been previously registered through
 * the cpuidle_register function.
 *
 * @drv: a valid pointer to a struct cpuidle_driver
 */
void cpuidle_unregister(struct cpuidle_driver *drv)
{
        int cpu;
        struct cpuidle_device *device;

        for_each_cpu(cpu, drv->cpumask) {
                device = &per_cpu(cpuidle_dev, cpu);
                cpuidle_unregister_device(device);
        }

        cpuidle_unregister_driver(drv);
}
EXPORT_SYMBOL_GPL(cpuidle_unregister);

/**
 * cpuidle_register: registers the driver and the cpu devices with the
 * coupled_cpus passed as parameter. This function is used for all common
 * initialization pattern there are in the arch specific drivers. The
 * devices is globally defined in this file.
 *
 * @drv         : a valid pointer to a struct cpuidle_driver
 * @coupled_cpus: a cpumask for the coupled states
 *
 * Returns 0 on success, < 0 otherwise
 */
int cpuidle_register(struct cpuidle_driver *drv,
                     const struct cpumask *const coupled_cpus)
{
        int ret, cpu;
        struct cpuidle_device *device;

        ret = cpuidle_register_driver(drv);
        if (ret) {
                pr_err("failed to register cpuidle driver\n");
                return ret;
        }

        for_each_cpu(cpu, drv->cpumask) {
                device = &per_cpu(cpuidle_dev, cpu);
                device->cpu = cpu;

#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
                /*
                 * On multiplatform for ARM, the coupled idle states could be
                 * enabled in the kernel even if the cpuidle driver does not
                 * use it. Note, coupled_cpus is a struct copy.
                 */
                if (coupled_cpus)
                        device->coupled_cpus = *coupled_cpus;
#endif
                ret = cpuidle_register_device(device);
                if (!ret)
                        continue;

                pr_err("Failed to register cpuidle device for cpu%d\n", cpu);

                cpuidle_unregister(drv);
                break;
        }

        return ret;
}
EXPORT_SYMBOL_GPL(cpuidle_register);

/**
 * cpuidle_init - core initializer
 */
static int __init cpuidle_init(void)
{
        if (cpuidle_disabled())
                return -ENODEV;

        return cpuidle_add_interface(cpu_subsys.dev_root);
}

module_param(off, int, 0444);
module_param_string(governor, param_governor, CPUIDLE_NAME_LEN, 0444);
core_initcall(cpuidle_init);