Power: add an API to log wakeup reasons

/*

 * include/linux/wakeup_reason.h

 *

 * Logs the reason which caused the kernel to resume

 * from the suspend mode.

 *

 * Copyright (C) 2014 Google, Inc.

 * This software is licensed under the terms of the GNU General Public

 * License version 2, as published by the Free Software Foundation, and

 * may be copied, distributed, and modified under those terms.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 */

#ifndef _LINUX_WAKEUP_REASON_H

#define _LINUX_WAKEUP_REASON_H

void log_wakeup_reason(int irq);

#endif /* _LINUX_WAKEUP_REASON_H */

obj-$(CONFIG_PM_WAKELOCKS)	+= wakelock.o

obj-$(CONFIG_MAGIC_SYSRQ)	+= poweroff.o

obj-$(CONFIG_SUSPEND)	+= wakeup_reason.o

/*

 * kernel/power/wakeup_reason.c

 *

 * Logs the reasons which caused the kernel to resume from

 * the suspend mode.

 *

 * Copyright (C) 2014 Google, Inc.

 * This software is licensed under the terms of the GNU General Public

 * License version 2, as published by the Free Software Foundation, and

 * may be copied, distributed, and modified under those terms.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 */

#include <linux/wakeup_reason.h>

#include <linux/kernel.h>

#include <linux/irq.h>

#include <linux/interrupt.h>

#include <linux/io.h>

#include <linux/kobject.h>

#include <linux/sysfs.h>

#include <linux/init.h>

#include <linux/spinlock.h>

#include <linux/notifier.h>

#include <linux/suspend.h>

#define MAX_WAKEUP_REASON_IRQS 32

static int irq_list[MAX_WAKEUP_REASON_IRQS];

static int irq_count;

static struct kobject *wakeup_reason;

static spinlock_t resume_reason_lock;

static ssize_t reason_show(struct kobject *kobj, struct kobj_attribute *attr,

		const char *buf, size_t count)

{

	int irq_no, buf_offset = 0;

	struct irq_desc *desc;

	spin_lock(&resume_reason_lock);

	for (irq_no = 0; irq_no < irq_count; irq_no++) {

		desc = irq_to_desc(irq_list[irq_no]);

		if (desc && desc->action && desc->action->name)

			buf_offset += sprintf(buf + buf_offset, "%d %s\n",

					irq_list[irq_no], desc->action->name);

		else

			buf_offset += sprintf(buf + buf_offset, "%d\n",

					irq_list[irq_no]);

	}

	spin_unlock(&resume_reason_lock);

	return buf_offset;

}

static struct kobj_attribute resume_reason = __ATTR(last_resume_reason, 0666,

		reason_show, NULL);

static struct attribute *attrs[] = {

	&resume_reason.attr,

	NULL,

};

static struct attribute_group attr_group = {

	.attrs = attrs,

};

/*

 * logs all the wake up reasons to the kernel

 * stores the irqs to expose them to the userspace via sysfs

 */

void log_wakeup_reason(int irq)

{

	struct irq_desc *desc;

	desc = irq_to_desc(irq);

	if (desc && desc->action && desc->action->name)

		printk(KERN_INFO "Resume caused by IRQ %d, %s\n", irq,

				desc->action->name);

	else

		printk(KERN_INFO "Resume caused by IRQ %d\n", irq);

	spin_lock(&resume_reason_lock);

	irq_list[irq_count++] = irq;

	spin_unlock(&resume_reason_lock);

}

/* Detects a suspend and clears all the previous wake up reasons*/

static int wakeup_reason_pm_event(struct notifier_block *notifier,

		unsigned long pm_event, void *unused)

{

	switch (pm_event) {

	case PM_SUSPEND_PREPARE:

		spin_lock(&resume_reason_lock);

		irq_count = 0;

		spin_unlock(&resume_reason_lock);

		break;

	default:

		break;

	}

	return NOTIFY_DONE;

}

static struct notifier_block wakeup_reason_pm_notifier_block = {

	.notifier_call = wakeup_reason_pm_event,

};

/* Initializes the sysfs parameter

 * registers the pm_event notifier

 */

void __init wakeup_reason_init(void)

{

	int retval;

	spin_lock_init(&resume_reason_lock);

	retval = register_pm_notifier(&wakeup_reason_pm_notifier_block);

	if (retval)

		printk(KERN_WARNING "[%s] failed to register PM notifier %d\n",

				__func__, retval);

	wakeup_reason = kobject_create_and_add("wakeup_reasons", kernel_kobj);

	if (!wakeup_reason) {

		printk(KERN_WARNING "[%s] failed to create a sysfs kobject\n",

				__func__);

		return;

	}

	retval = sysfs_create_group(wakeup_reason, &attr_group);

	if (retval) {

		kobject_put(wakeup_reason);

		printk(KERN_WARNING "[%s] failed to create a sysfs group %d\n",

				__func__, retval);

	}

}

late_initcall(wakeup_reason_init);