// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains functions which manage clock event devices.
 *
 * Copyright(C) 2005-2006, Linutronix GmbH, Thomas Gleixner <tglx@kernel.org>
 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
 */

#include <linux/clockchips.h>
#include <linux/hrtimer.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/smp.h>
#include <linux/device.h>

#include "tick-internal.h"

/* The registered clock event devices */
static LIST_HEAD(clockevent_devices);
static LIST_HEAD(clockevents_released);
/* Protection for the above */
static DEFINE_RAW_SPINLOCK(clockevents_lock);
/* Protection for unbind operations */
static DEFINE_MUTEX(clockevents_mutex);

struct ce_unbind {
        struct clock_event_device *ce;
        int res;
};

static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
                        bool ismax)
{
        u64 clc = (u64) latch << evt->shift;
        u64 rnd;

        if (WARN_ON(!evt->mult))
                evt->mult = 1;
        rnd = (u64) evt->mult - 1;

        /*
         * Upper bound sanity check. If the backwards conversion is
         * not equal latch, we know that the above shift overflowed.
         */
        if ((clc >> evt->shift) != (u64)latch)
                clc = ~0ULL;

        /*
         * Scaled math oddities:
         *
         * For mult <= (1 << shift) we can safely add mult - 1 to
         * prevent integer rounding loss. So the backwards conversion
         * from nsec to device ticks will be correct.
         *
         * For mult > (1 << shift), i.e. device frequency is > 1GHz we
         * need to be careful. Adding mult - 1 will result in a value
         * which when converted back to device ticks can be larger
         * than latch by up to (mult - 1) >> shift. For the min_delta
         * calculation we still want to apply this in order to stay
         * above the minimum device ticks limit. For the upper limit
         * we would end up with a latch value larger than the upper
         * limit of the device, so we omit the add to stay below the
         * device upper boundary.
         *
         * Also omit the add if it would overflow the u64 boundary.
         */
        if ((~0ULL - clc > rnd) &&
            (!ismax || evt->mult <= (1ULL << evt->shift)))
                clc += rnd;

        do_div(clc, evt->mult);

        /* Deltas less than 1usec are pointless noise */
        return clc > 1000 ? clc : 1000;
}

/**
 * clockevent_delta2ns - Convert a latch value (device ticks) to nanoseconds
 * @latch:      value to convert
 * @evt:        pointer to clock event device descriptor
 *
 * Math helper, returns latch value converted to nanoseconds (bound checked)
 */
u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
{
        return cev_delta2ns(latch, evt, false);
}
EXPORT_SYMBOL_GPL(clockevent_delta2ns);

static int __clockevents_switch_state(struct clock_event_device *dev,
                                      enum clock_event_state state)
{
        if (dev->features & CLOCK_EVT_FEAT_DUMMY)
                return 0;

        /* Transition with new state-specific callbacks */
        switch (state) {
        case CLOCK_EVT_STATE_DETACHED:
                /* The clockevent device is getting replaced. Shut it down. */

        case CLOCK_EVT_STATE_SHUTDOWN:
                if (dev->set_state_shutdown)
                        return dev->set_state_shutdown(dev);
                return 0;

        case CLOCK_EVT_STATE_PERIODIC:
                /* Core internal bug */
                if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
                        return -ENOSYS;
                if (dev->set_state_periodic)
                        return dev->set_state_periodic(dev);
                return 0;

        case CLOCK_EVT_STATE_ONESHOT:
                /* Core internal bug */
                if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
                        return -ENOSYS;
                if (dev->set_state_oneshot)
                        return dev->set_state_oneshot(dev);
                return 0;

        case CLOCK_EVT_STATE_ONESHOT_STOPPED:
                /* Core internal bug */
                if (WARN_ONCE(!clockevent_state_oneshot(dev),
                              "Current state: %d\n",
                              clockevent_get_state(dev)))
                        return -EINVAL;

                if (dev->set_state_oneshot_stopped)
                        return dev->set_state_oneshot_stopped(dev);
                else
                        return -ENOSYS;

        default:
                return -ENOSYS;
        }
}

/**
 * clockevents_switch_state - set the operating state of a clock event device
 * @dev:        device to modify
 * @state:      new state
 *
 * Must be called with interrupts disabled !
 */
void clockevents_switch_state(struct clock_event_device *dev,
                              enum clock_event_state state)
{
        if (clockevent_get_state(dev) != state) {
                if (__clockevents_switch_state(dev, state))
                        return;

                clockevent_set_state(dev, state);

                /*
                 * A nsec2cyc multiplicator of 0 is invalid and we'd crash
                 * on it, so fix it up and emit a warning:
                 */
                if (clockevent_state_oneshot(dev)) {
                        if (WARN_ON(!dev->mult))
                                dev->mult = 1;
                }
        }
}

/**
 * clockevents_shutdown - shutdown the device and clear next_event
 * @dev:        device to shutdown
 */
void clockevents_shutdown(struct clock_event_device *dev)
{
        clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
        dev->next_event = KTIME_MAX;
}

/**
 * clockevents_tick_resume -    Resume the tick device before using it again
 * @dev:                        device to resume
 */
int clockevents_tick_resume(struct clock_event_device *dev)
{
        int ret = 0;

        if (dev->tick_resume)
                ret = dev->tick_resume(dev);

        return ret;
}

#ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST

/* Limit min_delta to a jiffy */
#define MIN_DELTA_LIMIT         (NSEC_PER_SEC / HZ)

/**
 * clockevents_increase_min_delta - raise minimum delta of a clock event device
 * @dev:       device to increase the minimum delta
 *
 * Returns 0 on success, -ETIME when the minimum delta reached the limit.
 */
static int clockevents_increase_min_delta(struct clock_event_device *dev)
{
        /* Nothing to do if we already reached the limit */
        if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
                printk_deferred(KERN_WARNING
                                "CE: Reprogramming failure. Giving up\n");
                dev->next_event = KTIME_MAX;
                return -ETIME;
        }

        if (dev->min_delta_ns < 5000)
                dev->min_delta_ns = 5000;
        else
                dev->min_delta_ns += dev->min_delta_ns >> 1;

        if (dev->min_delta_ns > MIN_DELTA_LIMIT)
                dev->min_delta_ns = MIN_DELTA_LIMIT;

        printk_deferred(KERN_WARNING
                        "CE: %s increased min_delta_ns to %llu nsec\n",
                        dev->name ? dev->name : "?",
                        (unsigned long long) dev->min_delta_ns);
        return 0;
}

/**
 * clockevents_program_min_delta - Set clock event device to the minimum delay.
 * @dev:        device to program
 *
 * Returns 0 on success, -ETIME when the retry loop failed.
 */
static int clockevents_program_min_delta(struct clock_event_device *dev)
{
        unsigned long long clc;
        int64_t delta;
        int i;

        for (i = 0;;) {
                delta = dev->min_delta_ns;
                dev->next_event = ktime_add_ns(ktime_get(), delta);

                if (clockevent_state_shutdown(dev))
                        return 0;

                dev->retries++;
                clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
                if (dev->set_next_event((unsigned long) clc, dev) == 0)
                        return 0;

                if (++i > 2) {
                        /*
                         * We tried 3 times to program the device with the
                         * given min_delta_ns. Try to increase the minimum
                         * delta, if that fails as well get out of here.
                         */
                        if (clockevents_increase_min_delta(dev))
                                return -ETIME;
                        i = 0;
                }
        }
}

#else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */

/**
 * clockevents_program_min_delta - Set clock event device to the minimum delay.
 * @dev:        device to program
 *
 * Returns 0 on success, -ETIME when the retry loop failed.
 */
static int clockevents_program_min_delta(struct clock_event_device *dev)
{
        unsigned long long clc;
        int64_t delta = 0;
        int i;

        for (i = 0; i < 10; i++) {
                delta += dev->min_delta_ns;
                dev->next_event = ktime_add_ns(ktime_get(), delta);

                if (clockevent_state_shutdown(dev))
                        return 0;

                dev->retries++;
                clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
                if (dev->set_next_event((unsigned long) clc, dev) == 0)
                        return 0;
        }
        return -ETIME;
}

#endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */

/**
 * clockevents_program_event - Reprogram the clock event device.
 * @dev:        device to program
 * @expires:    absolute expiry time (monotonic clock)
 * @force:      program minimum delay if expires can not be set
 *
 * Returns 0 on success, -ETIME when the event is in the past.
 */
int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
                              bool force)
{
        unsigned long long clc;
        int64_t delta;
        int rc;

        if (WARN_ON_ONCE(expires < 0))
                return -ETIME;

        dev->next_event = expires;

        if (clockevent_state_shutdown(dev))
                return 0;

        /* We must be in ONESHOT state here */
        WARN_ONCE(!clockevent_state_oneshot(dev), "Current state: %d\n",
                  clockevent_get_state(dev));

        /* Shortcut for clockevent devices that can deal with ktime. */
        if (dev->features & CLOCK_EVT_FEAT_KTIME)
                return dev->set_next_ktime(expires, dev);

        delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
        if (delta <= 0)
                return force ? clockevents_program_min_delta(dev) : -ETIME;

        delta = min(delta, (int64_t) dev->max_delta_ns);
        delta = max(delta, (int64_t) dev->min_delta_ns);

        clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
        rc = dev->set_next_event((unsigned long) clc, dev);

        return (rc && force) ? clockevents_program_min_delta(dev) : rc;
}

/*
 * Called after a clockevent has been added which might
 * have replaced a current regular or broadcast device. A
 * released normal device might be a suitable replacement
 * for the current broadcast device. Similarly a released
 * broadcast device might be a suitable replacement for a
 * normal device.
 */
static void clockevents_notify_released(void)
{
        struct clock_event_device *dev;

        /*
         * Keep iterating as long as tick_check_new_device()
         * replaces a device.
         */
        while (!list_empty(&clockevents_released)) {
                dev = list_entry(clockevents_released.next,
                                 struct clock_event_device, list);
                list_move(&dev->list, &clockevent_devices);
                tick_check_new_device(dev);
        }
}

/*
 * Try to install a replacement clock event device
 */
static int clockevents_replace(struct clock_event_device *ced)
{
        struct clock_event_device *dev, *newdev = NULL;

        list_for_each_entry(dev, &clockevent_devices, list) {
                if (dev == ced || !clockevent_state_detached(dev))
                        continue;

                if (!tick_check_replacement(newdev, dev))
                        continue;

                if (!try_module_get(dev->owner))
                        continue;

                if (newdev)
                        module_put(newdev->owner);
                newdev = dev;
        }
        if (newdev) {
                tick_install_replacement(newdev);
                list_del_init(&ced->list);
        }
        return newdev ? 0 : -EBUSY;
}

/*
 * Called with clockevents_mutex and clockevents_lock held
 */
static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
{
        /* Fast track. Device is unused */
        if (clockevent_state_detached(ced)) {
                list_del_init(&ced->list);
                return 0;
        }

        return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
}

/*
 * SMP function call to unbind a device
 */
static void __clockevents_unbind(void *arg)
{
        struct ce_unbind *cu = arg;
        int res;

        raw_spin_lock(&clockevents_lock);
        res = __clockevents_try_unbind(cu->ce, smp_processor_id());
        if (res == -EAGAIN)
                res = clockevents_replace(cu->ce);
        cu->res = res;
        raw_spin_unlock(&clockevents_lock);
}

/*
 * Issues smp function call to unbind a per cpu device. Called with
 * clockevents_mutex held.
 */
static int clockevents_unbind(struct clock_event_device *ced, int cpu)
{
        struct ce_unbind cu = { .ce = ced, .res = -ENODEV };

        smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
        return cu.res;
}

/*
 * Unbind a clockevents device.
 */
int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
{
        int ret;

        mutex_lock(&clockevents_mutex);
        ret = clockevents_unbind(ced, cpu);
        mutex_unlock(&clockevents_mutex);
        return ret;
}
EXPORT_SYMBOL_GPL(clockevents_unbind_device);

/**
 * clockevents_register_device - register a clock event device
 * @dev:        device to register
 */
void clockevents_register_device(struct clock_event_device *dev)
{
        unsigned long flags;

        /* Initialize state to DETACHED */
        clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);

        if (!dev->cpumask) {
                WARN_ON(num_possible_cpus() > 1);
                dev->cpumask = cpumask_of(smp_processor_id());
        }

        if (dev->cpumask == cpu_all_mask) {
                WARN(1, "%s cpumask == cpu_all_mask, using cpu_possible_mask instead\n",
                     dev->name);
                dev->cpumask = cpu_possible_mask;
        }

        raw_spin_lock_irqsave(&clockevents_lock, flags);

        list_add(&dev->list, &clockevent_devices);
        tick_check_new_device(dev);
        clockevents_notify_released();

        raw_spin_unlock_irqrestore(&clockevents_lock, flags);
}
EXPORT_SYMBOL_GPL(clockevents_register_device);

static void clockevents_config(struct clock_event_device *dev, u32 freq)
{
        u64 sec;

        if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
                return;

        /*
         * Calculate the maximum number of seconds we can sleep. Limit
         * to 10 minutes for hardware which can program more than
         * 32bit ticks so we still get reasonable conversion values.
         */
        sec = dev->max_delta_ticks;
        do_div(sec, freq);
        if (!sec)
                sec = 1;
        else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
                sec = 600;

        clockevents_calc_mult_shift(dev, freq, sec);
        dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
        dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
}

/**
 * clockevents_config_and_register - Configure and register a clock event device
 * @dev:        device to register
 * @freq:       The clock frequency
 * @min_delta:  The minimum clock ticks to program in oneshot mode
 * @max_delta:  The maximum clock ticks to program in oneshot mode
 *
 * min/max_delta can be 0 for devices which do not support oneshot mode.
 */
void clockevents_config_and_register(struct clock_event_device *dev,
                                     u32 freq, unsigned long min_delta,
                                     unsigned long max_delta)
{
        dev->min_delta_ticks = min_delta;
        dev->max_delta_ticks = max_delta;
        clockevents_config(dev, freq);
        clockevents_register_device(dev);
}
EXPORT_SYMBOL_GPL(clockevents_config_and_register);

int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
{
        clockevents_config(dev, freq);

        if (clockevent_state_oneshot(dev))
                return clockevents_program_event(dev, dev->next_event, false);

        if (clockevent_state_periodic(dev))
                return __clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);

        return 0;
}

/**
 * clockevents_update_freq - Update frequency and reprogram a clock event device.
 * @dev:        device to modify
 * @freq:       new device frequency
 *
 * Reconfigure and reprogram a clock event device in oneshot
 * mode. Must be called on the cpu for which the device delivers per
 * cpu timer events. If called for the broadcast device the core takes
 * care of serialization.
 *
 * Returns 0 on success, -ETIME when the event is in the past.
 */
int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
{
        unsigned long flags;
        int ret;

        local_irq_save(flags);
        ret = tick_broadcast_update_freq(dev, freq);
        if (ret == -ENODEV)
                ret = __clockevents_update_freq(dev, freq);
        local_irq_restore(flags);
        return ret;
}

/*
 * Noop handler when we shut down an event device
 */
void clockevents_handle_noop(struct clock_event_device *dev)
{
}

/**
 * clockevents_exchange_device - release and request clock devices
 * @old:        device to release (can be NULL)
 * @new:        device to request (can be NULL)
 *
 * Called from various tick functions with clockevents_lock held and
 * interrupts disabled.
 */
void clockevents_exchange_device(struct clock_event_device *old,
                                 struct clock_event_device *new)
{
        /*
         * Caller releases a clock event device. We queue it into the
         * released list and do a notify add later.
         */
        if (old) {
                module_put(old->owner);
                clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED);
                list_move(&old->list, &clockevents_released);
        }

        if (new) {
                BUG_ON(!clockevent_state_detached(new));
                clockevents_shutdown(new);
        }
}

/**
 * clockevents_suspend - suspend clock devices
 */
void clockevents_suspend(void)
{
        struct clock_event_device *dev;

        list_for_each_entry_reverse(dev, &clockevent_devices, list)
                if (dev->suspend && !clockevent_state_detached(dev))
                        dev->suspend(dev);
}

/**
 * clockevents_resume - resume clock devices
 */
void clockevents_resume(void)
{
        struct clock_event_device *dev;

        list_for_each_entry(dev, &clockevent_devices, list)
                if (dev->resume && !clockevent_state_detached(dev))
                        dev->resume(dev);
}

#ifdef CONFIG_HOTPLUG_CPU

/**
 * tick_offline_cpu - Shutdown all clock events related
 *                    to this CPU and take it out of the
 *                    broadcast mechanism.
 * @cpu:        The outgoing CPU
 *
 * Called by the dying CPU during teardown.
 */
void tick_offline_cpu(unsigned int cpu)
{
        struct clock_event_device *dev, *tmp;

        raw_spin_lock(&clockevents_lock);

        tick_broadcast_offline(cpu);
        tick_shutdown();

        /*
         * Unregister the clock event devices which were
         * released above.
         */
        list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
                list_del(&dev->list);

        /*
         * Now check whether the CPU has left unused per cpu devices
         */
        list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
                if (cpumask_test_cpu(cpu, dev->cpumask) &&
                    cpumask_weight(dev->cpumask) == 1 &&
                    !tick_is_broadcast_device(dev)) {
                        BUG_ON(!clockevent_state_detached(dev));
                        list_del(&dev->list);
                }
        }

        raw_spin_unlock(&clockevents_lock);
}
#endif

#ifdef CONFIG_SYSFS
static const struct bus_type clockevents_subsys = {
        .name           = "clockevents",
        .dev_name       = "clockevent",
};

static DEFINE_PER_CPU(struct device, tick_percpu_dev);
static struct tick_device *tick_get_tick_dev(struct device *dev);

static ssize_t current_device_show(struct device *dev,
                                   struct device_attribute *attr,
                                   char *buf)
{
        struct tick_device *td;
        ssize_t count = 0;

        raw_spin_lock_irq(&clockevents_lock);
        td = tick_get_tick_dev(dev);
        if (td && td->evtdev)
                count = sysfs_emit(buf, "%s\n", td->evtdev->name);
        raw_spin_unlock_irq(&clockevents_lock);
        return count;
}
static DEVICE_ATTR_RO(current_device);

/* We don't support the abomination of removable broadcast devices */
static ssize_t unbind_device_store(struct device *dev,
                                   struct device_attribute *attr,
                                   const char *buf, size_t count)
{
        char name[CS_NAME_LEN];
        ssize_t ret = sysfs_get_uname(buf, name, count);
        struct clock_event_device *ce = NULL, *iter;

        if (ret < 0)
                return ret;

        ret = -ENODEV;
        mutex_lock(&clockevents_mutex);
        raw_spin_lock_irq(&clockevents_lock);
        list_for_each_entry(iter, &clockevent_devices, list) {
                if (!strcmp(iter->name, name)) {
                        ret = __clockevents_try_unbind(iter, dev->id);
                        ce = iter;
                        break;
                }
        }
        raw_spin_unlock_irq(&clockevents_lock);
        /*
         * We hold clockevents_mutex, so ce can't go away
         */
        if (ret == -EAGAIN)
                ret = clockevents_unbind(ce, dev->id);
        mutex_unlock(&clockevents_mutex);
        return ret ? ret : count;
}
static DEVICE_ATTR_WO(unbind_device);

#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
static struct device tick_bc_dev = {
        .init_name      = "broadcast",
        .id             = 0,
        .bus            = &clockevents_subsys,
};

static struct tick_device *tick_get_tick_dev(struct device *dev)
{
        return dev == &tick_bc_dev ? tick_get_broadcast_device() :
                &per_cpu(tick_cpu_device, dev->id);
}

static __init int tick_broadcast_init_sysfs(void)
{
        int err = device_register(&tick_bc_dev);

        if (!err)
                err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
        return err;
}
#else
static struct tick_device *tick_get_tick_dev(struct device *dev)
{
        return &per_cpu(tick_cpu_device, dev->id);
}
static inline int tick_broadcast_init_sysfs(void) { return 0; }
#endif

static int __init tick_init_sysfs(void)
{
        int cpu;

        for_each_possible_cpu(cpu) {
                struct device *dev = &per_cpu(tick_percpu_dev, cpu);
                int err;

                dev->id = cpu;
                dev->bus = &clockevents_subsys;
                err = device_register(dev);
                if (!err)
                        err = device_create_file(dev, &dev_attr_current_device);
                if (!err)
                        err = device_create_file(dev, &dev_attr_unbind_device);
                if (err)
                        return err;
        }
        return tick_broadcast_init_sysfs();
}

static int __init clockevents_init_sysfs(void)
{
        int err = subsys_system_register(&clockevents_subsys, NULL);

        if (!err)
                err = tick_init_sysfs();
        return err;
}
device_initcall(clockevents_init_sysfs);
#endif /* SYSFS */