xref: /linux/kernel/power/main.c (revision a5dbbb39e11d50a8c426b8d88f5b12031fee49f3)

// SPDX-License-Identifier: GPL-2.0-only
/*
 * kernel/power/main.c - PM subsystem core functionality.
 *
 * Copyright (c) 2003 Patrick Mochel
 * Copyright (c) 2003 Open Source Development Lab
 */

#include <linux/acpi.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/kobject.h>
#include <linux/string.h>
#include <linux/pm-trace.h>
#include <linux/workqueue.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/suspend.h>
#include <linux/syscalls.h>
#include <linux/pm_runtime.h>

#include "power.h"

#ifdef CONFIG_PM_SLEEP
/*
 * The following functions are used by the suspend/hibernate code to temporarily
 * change gfp_allowed_mask in order to avoid using I/O during memory allocations
 * while devices are suspended.  To avoid races with the suspend/hibernate code,
 * they should always be called with system_transition_mutex held
 * (gfp_allowed_mask also should only be modified with system_transition_mutex
 * held, unless the suspend/hibernate code is guaranteed not to run in parallel
 * with that modification).
 */
static unsigned int saved_gfp_count;
static gfp_t saved_gfp_mask;

void pm_restore_gfp_mask(void)
{
	WARN_ON(!mutex_is_locked(&system_transition_mutex));

	if (WARN_ON(!saved_gfp_count) || --saved_gfp_count)
		return;

	gfp_allowed_mask = saved_gfp_mask;
	saved_gfp_mask = 0;

	pm_pr_dbg("GFP mask restored\n");
}

void pm_restrict_gfp_mask(void)
{
	WARN_ON(!mutex_is_locked(&system_transition_mutex));

	if (saved_gfp_count++) {
		WARN_ON((saved_gfp_mask & ~(__GFP_IO | __GFP_FS)) != gfp_allowed_mask);
		return;
	}

	saved_gfp_mask = gfp_allowed_mask;
	gfp_allowed_mask &= ~(__GFP_IO | __GFP_FS);

	pm_pr_dbg("GFP mask restricted\n");
}

unsigned int lock_system_sleep(void)
{
	unsigned int flags = current->flags;
	current->flags |= PF_NOFREEZE;
	mutex_lock(&system_transition_mutex);
	return flags;
}
EXPORT_SYMBOL_GPL(lock_system_sleep);

void unlock_system_sleep(unsigned int flags)
{
	if (!(flags & PF_NOFREEZE))
		current->flags &= ~PF_NOFREEZE;
	mutex_unlock(&system_transition_mutex);
}
EXPORT_SYMBOL_GPL(unlock_system_sleep);

void ksys_sync_helper(void)
{
	ktime_t start;
	long elapsed_msecs;

	start = ktime_get();
	ksys_sync();
	elapsed_msecs = ktime_to_ms(ktime_sub(ktime_get(), start));
	pr_info("Filesystems sync: %ld.%03ld seconds\n",
		elapsed_msecs / MSEC_PER_SEC, elapsed_msecs % MSEC_PER_SEC);
}
EXPORT_SYMBOL_GPL(ksys_sync_helper);

/* Routines for PM-transition notifications */

static BLOCKING_NOTIFIER_HEAD(pm_chain_head);

int register_pm_notifier(struct notifier_block *nb)
{
	return blocking_notifier_chain_register(&pm_chain_head, nb);
}
EXPORT_SYMBOL_GPL(register_pm_notifier);

int unregister_pm_notifier(struct notifier_block *nb)
{
	return blocking_notifier_chain_unregister(&pm_chain_head, nb);
}
EXPORT_SYMBOL_GPL(unregister_pm_notifier);

int pm_notifier_call_chain_robust(unsigned long val_up, unsigned long val_down)
{
	int ret;

	ret = blocking_notifier_call_chain_robust(&pm_chain_head, val_up, val_down, NULL);

	return notifier_to_errno(ret);
}

int pm_notifier_call_chain(unsigned long val)
{
	return blocking_notifier_call_chain(&pm_chain_head, val, NULL);
}

/* If set, devices may be suspended and resumed asynchronously. */
int pm_async_enabled = 1;

static int __init pm_async_setup(char *str)
{
	if (!strcmp(str, "off"))
		pm_async_enabled = 0;
	return 1;
}
__setup("pm_async=", pm_async_setup);

static ssize_t pm_async_show(struct kobject *kobj, struct kobj_attribute *attr,
			     char *buf)
{
	return sysfs_emit(buf, "%d\n", pm_async_enabled);
}

static ssize_t pm_async_store(struct kobject *kobj, struct kobj_attribute *attr,
			      const char *buf, size_t n)
{
	unsigned long val;

	if (kstrtoul(buf, 10, &val))
		return -EINVAL;

	if (val > 1)
		return -EINVAL;

	pm_async_enabled = val;
	return n;
}

power_attr(pm_async);

#ifdef CONFIG_SUSPEND
static ssize_t mem_sleep_show(struct kobject *kobj, struct kobj_attribute *attr,
			      char *buf)
{
	ssize_t count = 0;
	suspend_state_t i;

	for (i = PM_SUSPEND_MIN; i < PM_SUSPEND_MAX; i++) {
		if (i >= PM_SUSPEND_MEM && cxl_mem_active())
			continue;
		if (mem_sleep_states[i]) {
			const char *label = mem_sleep_states[i];

			if (mem_sleep_current == i)
				count += sysfs_emit_at(buf, count, "[%s] ", label);
			else
				count += sysfs_emit_at(buf, count, "%s ", label);
		}
	}

	/* Convert the last space to a newline if needed. */
	if (count > 0)
		buf[count - 1] = '\n';

	return count;
}

static suspend_state_t decode_suspend_state(const char *buf, size_t n)
{
	suspend_state_t state;
	char *p;
	int len;

	p = memchr(buf, '\n', n);
	len = p ? p - buf : n;

	for (state = PM_SUSPEND_MIN; state < PM_SUSPEND_MAX; state++) {
		const char *label = mem_sleep_states[state];

		if (label && len == strlen(label) && !strncmp(buf, label, len))
			return state;
	}

	return PM_SUSPEND_ON;
}

static ssize_t mem_sleep_store(struct kobject *kobj, struct kobj_attribute *attr,
			       const char *buf, size_t n)
{
	suspend_state_t state;
	int error;

	error = pm_autosleep_lock();
	if (error)
		return error;

	if (pm_autosleep_state() > PM_SUSPEND_ON) {
		error = -EBUSY;
		goto out;
	}

	state = decode_suspend_state(buf, n);
	if (state < PM_SUSPEND_MAX && state > PM_SUSPEND_ON)
		mem_sleep_current = state;
	else
		error = -EINVAL;

 out:
	pm_autosleep_unlock();
	return error ? error : n;
}

power_attr(mem_sleep);

/*
 * sync_on_suspend: invoke ksys_sync_helper() before suspend.
 *
 * show() returns whether ksys_sync_helper() is invoked before suspend.
 * store() accepts 0 or 1.  0 disables ksys_sync_helper() and 1 enables it.
 */
bool sync_on_suspend_enabled = !IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC);

static ssize_t sync_on_suspend_show(struct kobject *kobj,
				   struct kobj_attribute *attr, char *buf)
{
	return sysfs_emit(buf, "%d\n", sync_on_suspend_enabled);
}

static ssize_t sync_on_suspend_store(struct kobject *kobj,
				    struct kobj_attribute *attr,
				    const char *buf, size_t n)
{
	unsigned long val;

	if (kstrtoul(buf, 10, &val))
		return -EINVAL;

	if (val > 1)
		return -EINVAL;

	sync_on_suspend_enabled = !!val;
	return n;
}

power_attr(sync_on_suspend);
#endif /* CONFIG_SUSPEND */

#ifdef CONFIG_PM_SLEEP_DEBUG
int pm_test_level = TEST_NONE;

static const char * const pm_tests[__TEST_AFTER_LAST] = {
	[TEST_NONE] = "none",
	[TEST_CORE] = "core",
	[TEST_CPUS] = "processors",
	[TEST_PLATFORM] = "platform",
	[TEST_DEVICES] = "devices",
	[TEST_FREEZER] = "freezer",
};

static ssize_t pm_test_show(struct kobject *kobj, struct kobj_attribute *attr,
				char *buf)
{
	ssize_t count = 0;
	int level;

	for (level = TEST_FIRST; level <= TEST_MAX; level++)
		if (pm_tests[level]) {
			if (level == pm_test_level)
				count += sysfs_emit_at(buf, count, "[%s] ", pm_tests[level]);
			else
				count += sysfs_emit_at(buf, count, "%s ", pm_tests[level]);
		}

	/* Convert the last space to a newline if needed. */
	if (count > 0)
		buf[count - 1] = '\n';

	return count;
}

static ssize_t pm_test_store(struct kobject *kobj, struct kobj_attribute *attr,
				const char *buf, size_t n)
{
	unsigned int sleep_flags;
	const char * const *s;
	int error = -EINVAL;
	int level;
	char *p;
	int len;

	p = memchr(buf, '\n', n);
	len = p ? p - buf : n;

	sleep_flags = lock_system_sleep();

	level = TEST_FIRST;
	for (s = &pm_tests[level]; level <= TEST_MAX; s++, level++)
		if (*s && len == strlen(*s) && !strncmp(buf, *s, len)) {
			pm_test_level = level;
			error = 0;
			break;
		}

	unlock_system_sleep(sleep_flags);

	return error ? error : n;
}

power_attr(pm_test);
#endif /* CONFIG_PM_SLEEP_DEBUG */

#define SUSPEND_NR_STEPS	SUSPEND_RESUME
#define REC_FAILED_NUM		2

struct suspend_stats {
	unsigned int step_failures[SUSPEND_NR_STEPS];
	unsigned int success;
	unsigned int fail;
	int last_failed_dev;
	char failed_devs[REC_FAILED_NUM][40];
	int last_failed_errno;
	int errno[REC_FAILED_NUM];
	int last_failed_step;
	u64 last_hw_sleep;
	u64 total_hw_sleep;
	u64 max_hw_sleep;
	enum suspend_stat_step failed_steps[REC_FAILED_NUM];
};

static struct suspend_stats suspend_stats;
static DEFINE_MUTEX(suspend_stats_lock);

void dpm_save_failed_dev(const char *name)
{
	mutex_lock(&suspend_stats_lock);

	strscpy(suspend_stats.failed_devs[suspend_stats.last_failed_dev],
		name, sizeof(suspend_stats.failed_devs[0]));
	suspend_stats.last_failed_dev++;
	suspend_stats.last_failed_dev %= REC_FAILED_NUM;

	mutex_unlock(&suspend_stats_lock);
}

void dpm_save_failed_step(enum suspend_stat_step step)
{
	suspend_stats.step_failures[step-1]++;
	suspend_stats.failed_steps[suspend_stats.last_failed_step] = step;
	suspend_stats.last_failed_step++;
	suspend_stats.last_failed_step %= REC_FAILED_NUM;
}

void dpm_save_errno(int err)
{
	if (!err) {
		suspend_stats.success++;
		return;
	}

	suspend_stats.fail++;

	suspend_stats.errno[suspend_stats.last_failed_errno] = err;
	suspend_stats.last_failed_errno++;
	suspend_stats.last_failed_errno %= REC_FAILED_NUM;
}

void pm_report_hw_sleep_time(u64 t)
{
	suspend_stats.last_hw_sleep = t;
	suspend_stats.total_hw_sleep += t;
}
EXPORT_SYMBOL_GPL(pm_report_hw_sleep_time);

void pm_report_max_hw_sleep(u64 t)
{
	suspend_stats.max_hw_sleep = t;
}
EXPORT_SYMBOL_GPL(pm_report_max_hw_sleep);

static const char * const suspend_step_names[] = {
	[SUSPEND_WORKING] = "",
	[SUSPEND_FREEZE] = "freeze",
	[SUSPEND_PREPARE] = "prepare",
	[SUSPEND_SUSPEND] = "suspend",
	[SUSPEND_SUSPEND_LATE] = "suspend_late",
	[SUSPEND_SUSPEND_NOIRQ] = "suspend_noirq",
	[SUSPEND_RESUME_NOIRQ] = "resume_noirq",
	[SUSPEND_RESUME_EARLY] = "resume_early",
	[SUSPEND_RESUME] = "resume",
};

#define suspend_attr(_name, format_str)				\
static ssize_t _name##_show(struct kobject *kobj,		\
		struct kobj_attribute *attr, char *buf)		\
{								\
	return sysfs_emit(buf, format_str, suspend_stats._name);\
}								\
static struct kobj_attribute _name = __ATTR_RO(_name)

suspend_attr(success, "%u\n");
suspend_attr(fail, "%u\n");
suspend_attr(last_hw_sleep, "%llu\n");
suspend_attr(total_hw_sleep, "%llu\n");
suspend_attr(max_hw_sleep, "%llu\n");

#define suspend_step_attr(_name, step)		\
static ssize_t _name##_show(struct kobject *kobj,		\
		struct kobj_attribute *attr, char *buf)		\
{								\
	return sysfs_emit(buf, "%u\n",				\
		       suspend_stats.step_failures[step-1]);	\
}								\
static struct kobj_attribute _name = __ATTR_RO(_name)

suspend_step_attr(failed_freeze, SUSPEND_FREEZE);
suspend_step_attr(failed_prepare, SUSPEND_PREPARE);
suspend_step_attr(failed_suspend, SUSPEND_SUSPEND);
suspend_step_attr(failed_suspend_late, SUSPEND_SUSPEND_LATE);
suspend_step_attr(failed_suspend_noirq, SUSPEND_SUSPEND_NOIRQ);
suspend_step_attr(failed_resume, SUSPEND_RESUME);
suspend_step_attr(failed_resume_early, SUSPEND_RESUME_EARLY);
suspend_step_attr(failed_resume_noirq, SUSPEND_RESUME_NOIRQ);

static ssize_t last_failed_dev_show(struct kobject *kobj,
		struct kobj_attribute *attr, char *buf)
{
	int index;
	char *last_failed_dev = NULL;

	index = suspend_stats.last_failed_dev + REC_FAILED_NUM - 1;
	index %= REC_FAILED_NUM;
	last_failed_dev = suspend_stats.failed_devs[index];

	return sysfs_emit(buf, "%s\n", last_failed_dev);
}
static struct kobj_attribute last_failed_dev = __ATTR_RO(last_failed_dev);

static ssize_t last_failed_errno_show(struct kobject *kobj,
		struct kobj_attribute *attr, char *buf)
{
	int index;
	int last_failed_errno;

	index = suspend_stats.last_failed_errno + REC_FAILED_NUM - 1;
	index %= REC_FAILED_NUM;
	last_failed_errno = suspend_stats.errno[index];

	return sysfs_emit(buf, "%d\n", last_failed_errno);
}
static struct kobj_attribute last_failed_errno = __ATTR_RO(last_failed_errno);

static ssize_t last_failed_step_show(struct kobject *kobj,
		struct kobj_attribute *attr, char *buf)
{
	enum suspend_stat_step step;
	int index;

	index = suspend_stats.last_failed_step + REC_FAILED_NUM - 1;
	index %= REC_FAILED_NUM;
	step = suspend_stats.failed_steps[index];

	return sysfs_emit(buf, "%s\n", suspend_step_names[step]);
}
static struct kobj_attribute last_failed_step = __ATTR_RO(last_failed_step);

static struct attribute *suspend_attrs[] = {
	&success.attr,
	&fail.attr,
	&failed_freeze.attr,
	&failed_prepare.attr,
	&failed_suspend.attr,
	&failed_suspend_late.attr,
	&failed_suspend_noirq.attr,
	&failed_resume.attr,
	&failed_resume_early.attr,
	&failed_resume_noirq.attr,
	&last_failed_dev.attr,
	&last_failed_errno.attr,
	&last_failed_step.attr,
	&last_hw_sleep.attr,
	&total_hw_sleep.attr,
	&max_hw_sleep.attr,
	NULL,
};

static umode_t suspend_attr_is_visible(struct kobject *kobj, struct attribute *attr, int idx)
{
	if (attr != &last_hw_sleep.attr &&
	    attr != &total_hw_sleep.attr &&
	    attr != &max_hw_sleep.attr)
		return 0444;

#ifdef CONFIG_ACPI
	if (acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)
		return 0444;
#endif
	return 0;
}

static const struct attribute_group suspend_attr_group = {
	.name = "suspend_stats",
	.attrs = suspend_attrs,
	.is_visible = suspend_attr_is_visible,
};

#ifdef CONFIG_DEBUG_FS
static int suspend_stats_show(struct seq_file *s, void *unused)
{
	int i, index, last_dev, last_errno, last_step;
	enum suspend_stat_step step;

	last_dev = suspend_stats.last_failed_dev + REC_FAILED_NUM - 1;
	last_dev %= REC_FAILED_NUM;
	last_errno = suspend_stats.last_failed_errno + REC_FAILED_NUM - 1;
	last_errno %= REC_FAILED_NUM;
	last_step = suspend_stats.last_failed_step + REC_FAILED_NUM - 1;
	last_step %= REC_FAILED_NUM;

	seq_printf(s, "success: %u\nfail: %u\n",
		   suspend_stats.success, suspend_stats.fail);

	for (step = SUSPEND_FREEZE; step <= SUSPEND_NR_STEPS; step++)
		seq_printf(s, "failed_%s: %u\n", suspend_step_names[step],
			   suspend_stats.step_failures[step-1]);

	seq_printf(s,	"failures:\n  last_failed_dev:\t%-s\n",
		   suspend_stats.failed_devs[last_dev]);
	for (i = 1; i < REC_FAILED_NUM; i++) {
		index = last_dev + REC_FAILED_NUM - i;
		index %= REC_FAILED_NUM;
		seq_printf(s, "\t\t\t%-s\n", suspend_stats.failed_devs[index]);
	}
	seq_printf(s,	"  last_failed_errno:\t%-d\n",
			suspend_stats.errno[last_errno]);
	for (i = 1; i < REC_FAILED_NUM; i++) {
		index = last_errno + REC_FAILED_NUM - i;
		index %= REC_FAILED_NUM;
		seq_printf(s, "\t\t\t%-d\n", suspend_stats.errno[index]);
	}
	seq_printf(s,	"  last_failed_step:\t%-s\n",
		   suspend_step_names[suspend_stats.failed_steps[last_step]]);
	for (i = 1; i < REC_FAILED_NUM; i++) {
		index = last_step + REC_FAILED_NUM - i;
		index %= REC_FAILED_NUM;
		seq_printf(s, "\t\t\t%-s\n",
			   suspend_step_names[suspend_stats.failed_steps[index]]);
	}

	return 0;
}
DEFINE_SHOW_ATTRIBUTE(suspend_stats);

static int __init pm_debugfs_init(void)
{
	debugfs_create_file("suspend_stats", S_IFREG | S_IRUGO,
			NULL, NULL, &suspend_stats_fops);
	return 0;
}

late_initcall(pm_debugfs_init);
#endif /* CONFIG_DEBUG_FS */

bool pm_sleep_transition_in_progress(void)
{
	return pm_suspend_in_progress() || hibernation_in_progress();
}
#endif /* CONFIG_PM_SLEEP */

#ifdef CONFIG_PM_SLEEP_DEBUG
/*
 * pm_print_times: print time taken by devices to suspend and resume.
 *
 * show() returns whether printing of suspend and resume times is enabled.
 * store() accepts 0 or 1.  0 disables printing and 1 enables it.
 */
bool pm_print_times_enabled;

static ssize_t pm_print_times_show(struct kobject *kobj,
				   struct kobj_attribute *attr, char *buf)
{
	return sysfs_emit(buf, "%d\n", pm_print_times_enabled);
}

static ssize_t pm_print_times_store(struct kobject *kobj,
				    struct kobj_attribute *attr,
				    const char *buf, size_t n)
{
	unsigned long val;

	if (kstrtoul(buf, 10, &val))
		return -EINVAL;

	if (val > 1)
		return -EINVAL;

	pm_print_times_enabled = !!val;
	return n;
}

power_attr(pm_print_times);

static inline void pm_print_times_init(void)
{
	pm_print_times_enabled = initcall_debug;
}

static ssize_t pm_wakeup_irq_show(struct kobject *kobj,
					struct kobj_attribute *attr,
					char *buf)
{
	if (!pm_wakeup_irq())
		return -ENODATA;

	return sysfs_emit(buf, "%u\n", pm_wakeup_irq());
}

power_attr_ro(pm_wakeup_irq);

bool pm_debug_messages_on __read_mostly;

bool pm_debug_messages_should_print(void)
{
	return pm_debug_messages_on && pm_sleep_transition_in_progress();
}
EXPORT_SYMBOL_GPL(pm_debug_messages_should_print);

static ssize_t pm_debug_messages_show(struct kobject *kobj,
				      struct kobj_attribute *attr, char *buf)
{
	return sysfs_emit(buf, "%d\n", pm_debug_messages_on);
}

static ssize_t pm_debug_messages_store(struct kobject *kobj,
				       struct kobj_attribute *attr,
				       const char *buf, size_t n)
{
	unsigned long val;

	if (kstrtoul(buf, 10, &val))
		return -EINVAL;

	if (val > 1)
		return -EINVAL;

	pm_debug_messages_on = !!val;
	return n;
}

power_attr(pm_debug_messages);

static int __init pm_debug_messages_setup(char *str)
{
	pm_debug_messages_on = true;
	return 1;
}
__setup("pm_debug_messages", pm_debug_messages_setup);

#else /* !CONFIG_PM_SLEEP_DEBUG */
static inline void pm_print_times_init(void) {}
#endif /* CONFIG_PM_SLEEP_DEBUG */

struct kobject *power_kobj;

/*
 * state - control system sleep states.
 *
 * show() returns available sleep state labels, which may be "mem", "standby",
 * "freeze" and "disk" (hibernation).
 * See Documentation/admin-guide/pm/sleep-states.rst for a description of
 * what they mean.
 *
 * store() accepts one of those strings, translates it into the proper
 * enumerated value, and initiates a suspend transition.
 */
static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
			  char *buf)
{
	ssize_t count = 0;
#ifdef CONFIG_SUSPEND
	suspend_state_t i;

	for (i = PM_SUSPEND_MIN; i < PM_SUSPEND_MAX; i++)
		if (pm_states[i])
			count += sysfs_emit_at(buf, count, "%s ", pm_states[i]);

#endif
	if (hibernation_available())
		count += sysfs_emit_at(buf, count, "disk ");

	/* Convert the last space to a newline if needed. */
	if (count > 0)
		buf[count - 1] = '\n';

	return count;
}

static suspend_state_t decode_state(const char *buf, size_t n)
{
#ifdef CONFIG_SUSPEND
	suspend_state_t state;
#endif
	char *p;
	int len;

	p = memchr(buf, '\n', n);
	len = p ? p - buf : n;

	/* Check hibernation first. */
	if (len == 4 && str_has_prefix(buf, "disk"))
		return PM_SUSPEND_MAX;

#ifdef CONFIG_SUSPEND
	for (state = PM_SUSPEND_MIN; state < PM_SUSPEND_MAX; state++) {
		const char *label = pm_states[state];

		if (label && len == strlen(label) && !strncmp(buf, label, len))
			return state;
	}
#endif

	return PM_SUSPEND_ON;
}

static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
			   const char *buf, size_t n)
{
	suspend_state_t state;
	int error;

	error = pm_autosleep_lock();
	if (error)
		return error;

	if (pm_autosleep_state() > PM_SUSPEND_ON) {
		error = -EBUSY;
		goto out;
	}

	state = decode_state(buf, n);
	if (state < PM_SUSPEND_MAX) {
		if (state == PM_SUSPEND_MEM)
			state = mem_sleep_current;

		error = pm_suspend(state);
	} else if (state == PM_SUSPEND_MAX) {
		error = hibernate();
	} else {
		error = -EINVAL;
	}

 out:
	pm_autosleep_unlock();
	return error ? error : n;
}

power_attr(state);

#ifdef CONFIG_PM_SLEEP
/*
 * The 'wakeup_count' attribute, along with the functions defined in
 * drivers/base/power/wakeup.c, provides a means by which wakeup events can be
 * handled in a non-racy way.
 *
 * If a wakeup event occurs when the system is in a sleep state, it simply is
 * woken up.  In turn, if an event that would wake the system up from a sleep
 * state occurs when it is undergoing a transition to that sleep state, the
 * transition should be aborted.  Moreover, if such an event occurs when the
 * system is in the working state, an attempt to start a transition to the
 * given sleep state should fail during certain period after the detection of
 * the event.  Using the 'state' attribute alone is not sufficient to satisfy
 * these requirements, because a wakeup event may occur exactly when 'state'
 * is being written to and may be delivered to user space right before it is
 * frozen, so the event will remain only partially processed until the system is
 * woken up by another event.  In particular, it won't cause the transition to
 * a sleep state to be aborted.
 *
 * This difficulty may be overcome if user space uses 'wakeup_count' before
 * writing to 'state'.  It first should read from 'wakeup_count' and store
 * the read value.  Then, after carrying out its own preparations for the system
 * transition to a sleep state, it should write the stored value to
 * 'wakeup_count'.  If that fails, at least one wakeup event has occurred since
 * 'wakeup_count' was read and 'state' should not be written to.  Otherwise, it
 * is allowed to write to 'state', but the transition will be aborted if there
 * are any wakeup events detected after 'wakeup_count' was written to.
 */

static ssize_t wakeup_count_show(struct kobject *kobj,
				struct kobj_attribute *attr,
				char *buf)
{
	unsigned int val;

	return pm_get_wakeup_count(&val, true) ?
		sysfs_emit(buf, "%u\n", val) : -EINTR;
}

static ssize_t wakeup_count_store(struct kobject *kobj,
				struct kobj_attribute *attr,
				const char *buf, size_t n)
{
	unsigned int val;
	int error;

	error = pm_autosleep_lock();
	if (error)
		return error;

	if (pm_autosleep_state() > PM_SUSPEND_ON) {
		error = -EBUSY;
		goto out;
	}

	error = -EINVAL;
	if (sscanf(buf, "%u", &val) == 1) {
		if (pm_save_wakeup_count(val))
			error = n;
		else
			pm_print_active_wakeup_sources();
	}

 out:
	pm_autosleep_unlock();
	return error;
}

power_attr(wakeup_count);

#ifdef CONFIG_PM_AUTOSLEEP
static ssize_t autosleep_show(struct kobject *kobj,
			      struct kobj_attribute *attr,
			      char *buf)
{
	suspend_state_t state = pm_autosleep_state();

	if (state == PM_SUSPEND_ON)
		return sysfs_emit(buf, "off\n");

#ifdef CONFIG_SUSPEND
	if (state < PM_SUSPEND_MAX)
		return sysfs_emit(buf, "%s\n", pm_states[state] ?
					pm_states[state] : "error");
#endif
#ifdef CONFIG_HIBERNATION
	return sysfs_emit(buf, "disk\n");
#else
	return sysfs_emit(buf, "error\n");
#endif
}

static ssize_t autosleep_store(struct kobject *kobj,
			       struct kobj_attribute *attr,
			       const char *buf, size_t n)
{
	suspend_state_t state = decode_state(buf, n);
	int error;

	if (state == PM_SUSPEND_ON
	    && strcmp(buf, "off") && strcmp(buf, "off\n"))
		return -EINVAL;

	if (state == PM_SUSPEND_MEM)
		state = mem_sleep_current;

	error = pm_autosleep_set_state(state);
	return error ? error : n;
}

power_attr(autosleep);
#endif /* CONFIG_PM_AUTOSLEEP */

#ifdef CONFIG_PM_WAKELOCKS
static ssize_t wake_lock_show(struct kobject *kobj,
			      struct kobj_attribute *attr,
			      char *buf)
{
	return pm_show_wakelocks(buf, true);
}

static ssize_t wake_lock_store(struct kobject *kobj,
			       struct kobj_attribute *attr,
			       const char *buf, size_t n)
{
	int error = pm_wake_lock(buf);
	return error ? error : n;
}

power_attr(wake_lock);

static ssize_t wake_unlock_show(struct kobject *kobj,
				struct kobj_attribute *attr,
				char *buf)
{
	return pm_show_wakelocks(buf, false);
}

static ssize_t wake_unlock_store(struct kobject *kobj,
				 struct kobj_attribute *attr,
				 const char *buf, size_t n)
{
	int error = pm_wake_unlock(buf);
	return error ? error : n;
}

power_attr(wake_unlock);

#endif /* CONFIG_PM_WAKELOCKS */
#endif /* CONFIG_PM_SLEEP */

#ifdef CONFIG_PM_TRACE
int pm_trace_enabled;

static ssize_t pm_trace_show(struct kobject *kobj, struct kobj_attribute *attr,
			     char *buf)
{
	return sysfs_emit(buf, "%d\n", pm_trace_enabled);
}

static ssize_t
pm_trace_store(struct kobject *kobj, struct kobj_attribute *attr,
	       const char *buf, size_t n)
{
	int val;

	if (sscanf(buf, "%d", &val) == 1) {
		pm_trace_enabled = !!val;
		if (pm_trace_enabled) {
			pr_warn("PM: Enabling pm_trace changes system date and time during resume.\n"
				"PM: Correct system time has to be restored manually after resume.\n");
		}
		return n;
	}
	return -EINVAL;
}

power_attr(pm_trace);

static ssize_t pm_trace_dev_match_show(struct kobject *kobj,
				       struct kobj_attribute *attr,
				       char *buf)
{
	return show_trace_dev_match(buf, PAGE_SIZE);
}

power_attr_ro(pm_trace_dev_match);

#endif /* CONFIG_PM_TRACE */

#ifdef CONFIG_FREEZER
static ssize_t pm_freeze_timeout_show(struct kobject *kobj,
				      struct kobj_attribute *attr, char *buf)
{
	return sysfs_emit(buf, "%u\n", freeze_timeout_msecs);
}

static ssize_t pm_freeze_timeout_store(struct kobject *kobj,
				       struct kobj_attribute *attr,
				       const char *buf, size_t n)
{
	unsigned long val;

	if (kstrtoul(buf, 10, &val))
		return -EINVAL;

	freeze_timeout_msecs = val;
	return n;
}

power_attr(pm_freeze_timeout);

#endif	/* CONFIG_FREEZER*/

#if defined(CONFIG_SUSPEND) || defined(CONFIG_HIBERNATION)
bool filesystem_freeze_enabled = false;

static ssize_t freeze_filesystems_show(struct kobject *kobj,
				       struct kobj_attribute *attr, char *buf)
{
	return sysfs_emit(buf, "%d\n", filesystem_freeze_enabled);
}

static ssize_t freeze_filesystems_store(struct kobject *kobj,
					struct kobj_attribute *attr,
					const char *buf, size_t n)
{
	unsigned long val;

	if (kstrtoul(buf, 10, &val))
		return -EINVAL;

	if (val > 1)
		return -EINVAL;

	filesystem_freeze_enabled = !!val;
	return n;
}

power_attr(freeze_filesystems);
#endif /* CONFIG_SUSPEND || CONFIG_HIBERNATION */

static struct attribute * g[] = {
	&state_attr.attr,
#ifdef CONFIG_PM_TRACE
	&pm_trace_attr.attr,
	&pm_trace_dev_match_attr.attr,
#endif
#ifdef CONFIG_PM_SLEEP
	&pm_async_attr.attr,
	&wakeup_count_attr.attr,
#ifdef CONFIG_SUSPEND
	&mem_sleep_attr.attr,
	&sync_on_suspend_attr.attr,
#endif
#ifdef CONFIG_PM_AUTOSLEEP
	&autosleep_attr.attr,
#endif
#ifdef CONFIG_PM_WAKELOCKS
	&wake_lock_attr.attr,
	&wake_unlock_attr.attr,
#endif
#ifdef CONFIG_PM_SLEEP_DEBUG
	&pm_test_attr.attr,
	&pm_print_times_attr.attr,
	&pm_wakeup_irq_attr.attr,
	&pm_debug_messages_attr.attr,
#endif
#endif
#ifdef CONFIG_FREEZER
	&pm_freeze_timeout_attr.attr,
#endif
#if defined(CONFIG_SUSPEND) || defined(CONFIG_HIBERNATION)
	&freeze_filesystems_attr.attr,
#endif
	NULL,
};

static const struct attribute_group attr_group = {
	.attrs = g,
};

static const struct attribute_group *attr_groups[] = {
	&attr_group,
#ifdef CONFIG_PM_SLEEP
	&suspend_attr_group,
#endif
	NULL,
};

struct workqueue_struct *pm_wq;
EXPORT_SYMBOL_GPL(pm_wq);

static int __init pm_start_workqueue(void)
{
	pm_wq = alloc_workqueue("pm", WQ_FREEZABLE, 0);

	return pm_wq ? 0 : -ENOMEM;
}

static int __init pm_init(void)
{
	int error = pm_start_workqueue();
	if (error)
		return error;
	hibernate_image_size_init();
	hibernate_reserved_size_init();
	pm_states_init();
	power_kobj = kobject_create_and_add("power", NULL);
	if (!power_kobj)
		return -ENOMEM;
	error = sysfs_create_groups(power_kobj, attr_groups);
	if (error)
		return error;
	pm_print_times_init();
	return pm_autosleep_init();
}

core_initcall(pm_init);