path: root/kernel/time/tick-broadcast.c

// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains functions which emulate a local clock-event
 * device via a broadcast event source.
 *
 * 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
 */
#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 <linux/smp.h>
#include <linux/module.h>

#include "tick-internal.h"

/*
 * Broadcast support for broken x86 hardware, where the local apic
 * timer stops in C3 state.
 */

static struct tick_device tick_broadcast_device;
static cpumask_var_t tick_broadcast_mask __cpumask_var_read_mostly;
static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly;
static cpumask_var_t tmpmask __cpumask_var_read_mostly;
static int tick_broadcast_forced;

static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);

#ifdef CONFIG_TICK_ONESHOT
static DEFINE_PER_CPU(struct clock_event_device *, tick_oneshot_wakeup_device);

static void tick_broadcast_setup_oneshot(struct clock_event_device *bc);
static void tick_broadcast_clear_oneshot(int cpu);
static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
# ifdef CONFIG_HOTPLUG_CPU
static void tick_broadcast_oneshot_offline(unsigned int cpu);
# endif
#else
static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc) { BUG(); }
static inline void tick_broadcast_clear_oneshot(int cpu) { }
static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
# ifdef CONFIG_HOTPLUG_CPU
static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }
# endif
#endif

/*
 * Debugging: see timer_list.c
 */
struct tick_device *tick_get_broadcast_device(void)
{
	return &tick_broadcast_device;
}

struct cpumask *tick_get_broadcast_mask(void)
{
	return tick_broadcast_mask;
}

static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu);

const struct clock_event_device *tick_get_wakeup_device(int cpu)
{
	return tick_get_oneshot_wakeup_device(cpu);
}

/*
 * Start the device in periodic mode
 */
static void tick_broadcast_start_periodic(struct clock_event_device *bc)
{
	if (bc)
		tick_setup_periodic(bc, 1);
}

/*
 * Check, if the device can be utilized as broadcast device:
 */
static bool tick_check_broadcast_device(struct clock_event_device *curdev,
					struct clock_event_device *newdev)
{
	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
	    (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
		return false;

	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
		return false;

	return !curdev || newdev->rating > curdev->rating;
}

#ifdef CONFIG_TICK_ONESHOT
static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
{
	return per_cpu(tick_oneshot_wakeup_device, cpu);
}

static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
{
	/*
	 * If we woke up early and the tick was reprogrammed in the
	 * meantime then this may be spurious but harmless.
	 */
	tick_receive_broadcast();
}

static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
					   int cpu)
{
	struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);

	if (!newdev)
		goto set_device;

	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
		 return false;

	if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
		return false;

	if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
		return false;

	if (curdev && newdev->rating <= curdev->rating)
		return false;

	if (!try_module_get(newdev->owner))
		return false;

	newdev->event_handler = tick_oneshot_wakeup_handler;
set_device:
	clockevents_exchange_device(curdev, newdev);
	per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
	return true;
}
#else
static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
{
	return NULL;
}

static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
					   int cpu)
{
	return false;
}
#endif

/*
 * Conditionally install/replace broadcast device
 */
void