/*
 * linux/kernel/time/tick-common.c
 *
 * This file contains the base functions to manage periodic tick
 * related events.
 *
 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
 *
 * This code is licenced under the GPL version 2. For details see
 * kernel-base/COPYING.
 */
#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/hrtimer.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/profile.h>
#include <linux/sched.h>

#include <asm/irq_regs.h>

#include "tick-internal.h"

/*
 * Tick devices
 */
DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
/*
 * Tick next event: keeps track of the tick time
 */
ktime_t tick_next_period;
ktime_t tick_period;
int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
static DEFINE_RAW_SPINLOCK(tick_device_lock);

/*
 * Debugging: see timer_list.c
 */
struct tick_device *tick_get_device(int cpu)
{
        return &per_cpu(tick_cpu_device, cpu);
}

/**
 * tick_is_oneshot_available - check for a oneshot capable event device
 */
int tick_is_oneshot_available(void)
{
        struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);

        if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
                return 0;
        if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
                return 1;
        return tick_broadcast_oneshot_available();
}

/*
 * Periodic tick
 */
static void tick_periodic(int cpu)
{
        if (tick_do_timer_cpu == cpu) {
                write_seqlock(&jiffies_lock);

                /* Keep track of the next tick event */
                tick_next_period = ktime_add(tick_next_period, tick_period);

                do_timer(1);
                write_sequnlock(&jiffies_lock);
        }

        update_process_times(user_mode(get_irq_regs()));
        profile_tick(CPU_PROFILING);
}

/*
 * Event handler for periodic ticks
 */
void tick_handle_periodic(struct clock_event_device *dev)
{
        int cpu = smp_processor_id();
        ktime_t next;

        tick_periodic(cpu);

        if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
                return;
        /*
         * Setup the next period for devices, which do not have
         * periodic mode:
         */
        next = ktime_add(dev->next_event, tick_period);
        for (;;) {
                if (!clockevents_program_event(dev, next, false))
                        return;
                /*
                 * Have to be careful here. If we're in oneshot mode,
                 * before we call tick_periodic() in a loop, we need
                 * to be sure we're using a real hardware clocksource.
                 * Otherwise we could get trapped in an infinite
                 * loop, as the tick_periodic() increments jiffies,
                 * when then will increment time, posibly causing
                 * the loop to trigger again and again.
                 */
                if (timekeeping_valid_for_hres())
                        tick_periodic(cpu);
                next = ktime_add(next, tick_period);
        }
}

/*
 * Setup the device for a periodic tick
 */
void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
{
        tick_set_periodic_handler(dev, broadcast);

        /* Broadcast setup ? */
        if (!tick_device_is_functional(dev))
                return;

        if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
            !tick_broadcast_oneshot_active()) {
                clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
        } else {
                unsigned long seq;
                ktime_t next;

                do {
                        seq = read_seqbegin(&jiffies_lock);
                        next = tick_next_period;
                } while (read_seqretry(&jiffies_lock, seq));

                clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);

                for (;;) {
                        if (!clockevents_program_event(dev, next, false))
                                return;
                        next = ktime_add(next, tick_period);
                }
        }
}

/*
 * Setup the tick device
 */
static void tick_setup_device(struct tick_device *td,
                              struct clock_event_device *newdev, int cpu,
                              const struct cpumask *cpumask)
{
        ktime_t next_event;
        void (*handler)(struct clock_event_device *) = NULL;

        /*
         * First device setup ?
         */
        if (!td->evtdev) {
                /*
                 * If no cpu took the do_timer update, assign it to
                 * this cpu:
                 */
                if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
                        if (!tick_nohz_full_cpu(cpu))
                                tick_do_timer_cpu = cpu;
                        else
                                tick_do_timer_cpu = TICK_DO_TIMER_NONE;
                        tick_next_period = ktime_get();
                        tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
                }

                /*
                 * Startup in periodic mode first.
                 */
                td->mode = TICKDEV_MODE_PERIODIC;
        } else {
                handler = td->evtdev->event_handler;
                next_event = td->evtdev->next_event;
                td->evtdev->event_handler = clockevents_handle_noop;
        }

        td->evtdev = newdev;

        /*
         * When the device is not per cpu, pin the interrupt to the
         * current cpu:
         */
        if (!cpumask_equal(newdev->cpumask, cpumask))
                irq_set_affinity(newdev->irq, cpumask);

        /*
         * When global broadcasting is active, check if the current
         * device is registered as a placeholder for broadcast mode.
         * This allows us to handle this x86 misfeature in a generic
         * way.
         */
        if (tick_device_uses_broadcast(newdev, cpu))
                return;

        if (td->mode == TICKDEV_MODE_PERIODIC)
                tick_setup_periodic(newdev, 0);
        else
                tick_setup_oneshot(newdev, handler, next_event);
}

/*
 * Check, if the new registered device should be used.
 */
static int tick_check_new_device(struct clock_event_device *newdev)
{
        struct clock_event_device *curdev;
        struct tick_device *td;
        int cpu, ret = NOTIFY_OK;
        unsigned long flags;

        raw_spin_lock_irqsave(&tick_device_lock, flags);

        cpu = smp_processor_id();
        if (!cpumask_test_cpu(cpu, newdev->cpumask))
                goto out_bc;

        td = &per_cpu(tick_cpu_device, cpu);
        curdev = td->evtdev;

        /* cpu local device ? */
        if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {

                /*
                 * If the cpu affinity of the device interrupt can not
                 * be set, ignore it.
                 */
                if (!irq_can_set_affinity(newdev->irq))
                        goto out_bc;

                /*
                 * If we have a cpu local device already, do not replace it
                 * by a non cpu local device
                 */
                if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
                        goto out_bc;
        }

        /*
         * If we have an active device, then check the rating and the oneshot
         * feature.
         */
        if (curdev) {
                /*
                 * Prefer one shot capable devices !
                 */
                if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
                    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
                        goto out_bc;
                /*
                 * Check the rating
                 */
                if (curdev->rating >= newdev->rating)
                        goto out_bc;
        }

        /*
         * Replace the eventually existing device by the new
         * device. If the current device is the broadcast device, do
         * not give it back to the clockevents layer !
         */
        if (tick_is_broadcast_device(curdev)) {
                clockevents_shutdown(curdev);
                curdev = NULL;
        }
        clockevents_exchange_device(curdev, newdev);
        tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
        if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
                tick_oneshot_notify();

        raw_spin_unlock_irqrestore(&tick_device_lock, flags);
        return NOTIFY_STOP;

out_bc:
        /*
         * Can the new device be used as a broadcast device ?
         */
        if (tick_check_broadcast_device(newdev))
                ret = NOTIFY_STOP;

        raw_spin_unlock_irqrestore(&tick_device_lock, flags);

        return ret;
}

/*
 * Transfer the do_timer job away from a dying cpu.
 *
 * Called with interrupts disabled.
 */
static void tick_handover_do_timer(int *cpup)
{
        if (*cpup == tick_do_timer_cpu) {
                int cpu = cpumask_first(cpu_online_mask);

                tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
                        TICK_DO_TIMER_NONE;
        }
}

/*
 * Shutdown an event device on a given cpu:
 *
 * This is called on a life CPU, when a CPU is dead. So we cannot
 * access the hardware device itself.
 * We just set the mode and remove it from the lists.
 */
static void tick_shutdown(unsigned int *cpup)
{
        struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
        struct clock_event_device *dev = td->evtdev;
        unsigned long flags;

        raw_spin_lock_irqsave(&tick_device_lock, flags);
        td->mode = TICKDEV_MODE_PERIODIC;
        if (dev) {
                /*
                 * Prevent that the clock events layer tries to call
                 * the set mode function!
                 */
                dev->mode = CLOCK_EVT_MODE_UNUSED;
                clockevents_exchange_device(dev, NULL);
                dev->event_handler = clockevents_handle_noop;
                td->evtdev = NULL;
        }
        raw_spin_unlock_irqrestore(&tick_device_lock, flags);
}

static void tick_suspend(void)
{
        struct tick_device *td = &__get_cpu_var(tick_cpu_device);
        unsigned long flags;

        raw_spin_lock_irqsave(&tick_device_lock, flags);
        clockevents_shutdown(td->evtdev);
        raw_spin_unlock_irqrestore(&tick_device_lock, flags);
}

static void tick_resume(void)
{
        struct tick_device *td = &__get_cpu_var(tick_cpu_device);
        unsigned long flags;
        int broadcast = tick_resume_broadcast();

        raw_spin_lock_irqsave(&tick_device_lock, flags);
        clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);

        if (!broadcast) {
                if (td->mode == TICKDEV_MODE_PERIODIC)
                        tick_setup_periodic(td->evtdev, 0);
                else
                        tick_resume_oneshot();
        }
        raw_spin_unlock_irqrestore(&tick_device_lock, flags);
}

/*
 * Notification about clock event devices
 */
static int tick_notify(struct notifier_block *nb, unsigned long reason,
                               void *dev)
{
        switch (reason) {

        case CLOCK_EVT_NOTIFY_ADD:
                return tick_check_new_device(dev);

        case CLOCK_EVT_NOTIFY_BROADCAST_ON:
        case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
        case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
                tick_broadcast_on_off(reason, dev);
                break;

        case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
        case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
                tick_broadcast_oneshot_control(reason);
                break;

        case CLOCK_EVT_NOTIFY_CPU_DYING:
                tick_handover_do_timer(dev);
                break;

        case CLOCK_EVT_NOTIFY_CPU_DEAD:
                tick_shutdown_broadcast_oneshot(dev);
                tick_shutdown_broadcast(dev);
                tick_shutdown(dev);
                break;

        case CLOCK_EVT_NOTIFY_SUSPEND:
                tick_suspend();
                tick_suspend_broadcast();
                break;

        case CLOCK_EVT_NOTIFY_RESUME:
                tick_resume();
                break;

        default:
                break;
        }

        return NOTIFY_OK;
}

static struct notifier_block tick_notifier = {
        .notifier_call = tick_notify,
};

/**
 * tick_init - initialize the tick control
 *
 * Register the notifier with the clockevents framework
 */
void __init tick_init(void)
{
        clockevents_register_notifier(&tick_notifier);
        tick_broadcast_init();
}