// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains functions which manage high resolution tick
 * related events.
 *
 * 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/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 "tick-internal.h"

/**
 * tick_program_event - program the CPU local timer device for the next event
 * @expires: the time at which the next timer event should occur
 * @force: flag to force reprograming even if the event time hasn't changed
 *
 * Return: 0 on success, negative error code on failure
 */
int tick_program_event(ktime_t expires, int force)
{
        struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);

        if (unlikely(expires == KTIME_MAX)) {
                /*
                 * We don't need the clock event device any more, stop it.
                 */
                clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
                dev->next_event = KTIME_MAX;
                return 0;
        }

        if (unlikely(clockevent_state_oneshot_stopped(dev))) {
                /*
                 * We need the clock event again, configure it in ONESHOT mode
                 * before using it.
                 */
                clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
        }

        return clockevents_program_event(dev, expires, force);
}

/**
 * tick_resume_oneshot - resume oneshot mode
 */
void tick_resume_oneshot(void)
{
        struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);

        clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
        clockevents_program_event(dev, ktime_get(), true);
}

/**
 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
 * @newdev: Pointer to the clock event device to configure
 * @handler: Function to be called when the event device triggers an interrupt
 * @next_event: Initial expiry time for the next event (in ktime)
 *
 * Configures the specified clock event device for onshot mode,
 * assigns the given handler as its event callback, and programs
 * the device to trigger at the specified next event time.
 */
void tick_setup_oneshot(struct clock_event_device *newdev,
                        void (*handler)(struct clock_event_device *),
                        ktime_t next_event)
{
        newdev->event_handler = handler;
        clockevents_switch_state(newdev, CLOCK_EVT_STATE_ONESHOT);
        clockevents_program_event(newdev, next_event, true);
}

/**
 * tick_switch_to_oneshot - switch to oneshot mode
 * @handler: function to call when an event occurs on the tick device
 *
 * Return: 0 on success, -EINVAL if the tick device is not present,
 *         not functional, or does not support oneshot mode.
 */
int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
{
        struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
        struct clock_event_device *dev = td->evtdev;

        if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
                    !tick_device_is_functional(dev)) {

                pr_info("Clockevents: could not switch to one-shot mode:");
                if (!dev) {
                        pr_cont(" no tick device\n");
                } else {
                        if (!tick_device_is_functional(dev))
                                pr_cont(" %s is not functional.\n", dev->name);
                        else
                                pr_cont(" %s does not support one-shot mode.\n",
                                        dev->name);
                }
                return -EINVAL;
        }

        td->mode = TICKDEV_MODE_ONESHOT;
        dev->event_handler = handler;
        clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
        tick_broadcast_switch_to_oneshot();
        return 0;
}

/**
 * tick_oneshot_mode_active - check whether the system is in oneshot mode
 *
 * Return: 1 when either nohz or highres are enabled, otherwise 0.
 */
int tick_oneshot_mode_active(void)
{
        unsigned long flags;
        int ret;

        local_irq_save(flags);
        ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT;
        local_irq_restore(flags);

        return ret;
}

#ifdef CONFIG_HIGH_RES_TIMERS
/**
 * tick_init_highres - switch to high resolution mode
 *
 * Called with interrupts disabled.
 *
 * Return: 0 on success, -EINVAL if the tick device cannot switch
 *         to oneshot/high-resolution mode.
 */
int tick_init_highres(void)
{
        return tick_switch_to_oneshot(hrtimer_interrupt);
}
#endif