Re: [PATCH] power: add an API to log wakeup reasons

[Ruchi Kandoi]

This API would be called from the platform specific code, or the
driver for the interrupt controller, when the system resumes from the
suspend because of an IRQ.

We track the reasons for which systems wake up from the low power
suspend mode. This is especially important on battery-powered consumer
electronic devices.

Analyzing the data helps us figure what caused the maximum wake ups
and if something can be done about the same to improve the battery
life.
For instances, if the wi-fi network traffic or the radio traffic
causes the system to frequently wakeup from the low-power mode.

This is already in use on some Android devices. We are trying to make
this a generic API which could be called by other platforms as well,
standardizing the format in which the info is
logged in dmesg and the format of the info exported to userspace for
collecting power management statistics.

Thanking you,
Ruchi Kandoi

On Tue, Mar 11, 2014 at 12:32 PM, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
> On Monday, March 10, 2014 07:02:02 PM Ruchi Kandoi wrote:
>> Add API log_wakeup_reason() and expose it to userspace via sysfs path
>> /sys/kernel/wakeup_reasons/last_resume_reason
>> This is useful for power management diagnostic purposes.
>
> What's the use case and how is it supposed to work?
>
>> Signed-off-by: Ruchi Kandoi <kandoiruchi@xxxxxxxxxx>
>> Signed-off-by: Greg Hackmann <ghackmann@xxxxxxxxxx>
>> ---
>>  include/linux/wakeup_reason.h |  23 +++++++
>>  kernel/power/Makefile         |   2 +-
>>  kernel/power/wakeup_reason.c  | 140 ++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 164 insertions(+), 1 deletion(-)
>>  create mode 100644 include/linux/wakeup_reason.h
>>  create mode 100644 kernel/power/wakeup_reason.c
>>
>> diff --git a/include/linux/wakeup_reason.h b/include/linux/wakeup_reason.h
>> new file mode 100644
>> index 0000000..7ce50f0
>> --- /dev/null
>> +++ b/include/linux/wakeup_reason.h
>> @@ -0,0 +1,23 @@
>> +/*
>> + * 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 */
>> diff --git a/kernel/power/Makefile b/kernel/power/Makefile
>> index 29472bf..f98f021 100644
>> --- a/kernel/power/Makefile
>> +++ b/kernel/power/Makefile
>> @@ -5,7 +5,7 @@ obj-y                         += qos.o
>>  obj-$(CONFIG_PM)             += main.o
>>  obj-$(CONFIG_VT_CONSOLE_SLEEP)       += console.o
>>  obj-$(CONFIG_FREEZER)                += process.o
>> -obj-$(CONFIG_SUSPEND)                += suspend.o
>> +obj-$(CONFIG_SUSPEND)                += suspend.o wakeup_reason.o
>>  obj-$(CONFIG_PM_TEST_SUSPEND)        += suspend_test.o
>>  obj-$(CONFIG_HIBERNATION)    += hibernate.o snapshot.o swap.o user.o \
>>                                  block_io.o
>> diff --git a/kernel/power/wakeup_reason.c b/kernel/power/wakeup_reason.c
>> new file mode 100644
>> index 0000000..188a6bf
>> --- /dev/null
>> +++ b/kernel/power/wakeup_reason.c
>> @@ -0,0 +1,140 @@
>> +/*
>> + * 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 irqcount;
>> +static struct kobject *wakeup_reason;
>> +static spinlock_t resume_reason_lock;
>> +
>> +static ssize_t reason_show(struct kobject *kobj, struct kobj_attribute *attr,
>> +             char *buf)
>> +{
>> +     int irq_no, buf_offset = 0;
>> +     struct irq_desc *desc;
>> +     spin_lock(&resume_reason_lock);
>> +     for (irq_no = 0; irq_no < irqcount; 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);
>> +     if (irqcount == MAX_WAKEUP_REASON_IRQS) {
>> +             spin_unlock(&resume_reason_lock);
>> +             printk(KERN_WARNING "Resume caused by more than %d IRQs\n",
>> +                             MAX_WAKEUP_REASON_IRQS);
>> +             return;
>> +     }
>> +
>> +     irq_list[irqcount++] = 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);
>> +             irqcount = 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
>> + */
>> +int __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 1;
>> +     }
>> +     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);
>> +     }
>> +     return 0;
>> +}
>> +
>> +late_initcall(wakeup_reason_init);
>>
>
> --
> I speak only for myself.
> Rafael J. Wysocki, Intel Open Source Technology Center.
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