Re: [RFC v2 1/3] PM: Add a sysfs files to represent sleep duration

["Limonciello, Mario" <mario.limonciello@amd.com>]

On 11/15/2022 08:45, Rafael J. Wysocki wrote:
> On Thu, Nov 10, 2022 at 7:49 AM Mario Limonciello
> <mario.limonciello@amd.com> wrote:
>>
>> Both AMD and Intel SoCs have a concept of reporting whether the hardware
>> reached a hardware sleep state over s2idle as well as how much
>> time was spent in such a state.
>>
>> This information is valuable to both chip designers and system designers
>> as it helps to identify when there are problems with power consumption
>> over an s2idle cycle.
>>
>> To make the information discoverable, create a new sysfs file and a symbol
>> that drivers from supported manufacturers can use to advertise this
>> information. This file will only be exported when the system supports low
>> power idle in the ACPI table.
>>
>> In order to effectively use this information you will ideally want to
>> compare against the total duration of sleep, so export a second sysfs file
>> that will show total time. This file will be exported on all systems and
>> used both for s2idle and s3.
> 
> Well, my first question would be how this is related to
> 
> /sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us
> 

This has a dependency on the platform firmware offering an ACPI LPIT 
table.  I don't know how common that is.  As this series started from 
the needs on ChromeOS I would ask is that typically populated by coreboot?

I would hope it's the same number that is populated in that file on 
supported systems though.

> and
> 
> /sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us
> 

No relation to this one for what's in the series.

>> Suggested-by: David E Box <david.e.box@intel.com>
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>>   Documentation/ABI/testing/sysfs-power | 17 +++++++++++
>>   include/linux/suspend.h               |  4 +++
>>   kernel/power/main.c                   | 42 +++++++++++++++++++++++++++
>>   kernel/power/suspend.c                |  2 ++
>>   kernel/time/timekeeping.c             |  2 ++
>>   5 files changed, 67 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
>> index f99d433ff311..5b47cbb4dc9e 100644
>> --- a/Documentation/ABI/testing/sysfs-power
>> +++ b/Documentation/ABI/testing/sysfs-power
>> @@ -413,6 +413,23 @@ Description:
>>                  The /sys/power/suspend_stats/last_failed_step file contains
>>                  the last failed step in the suspend/resume path.
>>
>> +What:          /sys/power/suspend_stats/last_hw_state_residency
>> +Date:          December 2022
>> +Contact:       Mario Limonciello <mario.limonciello@amd.com>
>> +Description:
>> +               The /sys/power/suspend_stats/last_hw_state_residency file contains
>> +               the amount of time spent in a hardware sleep state.
>> +               This attribute is only available if the system supports
>> +               low power idle.  This is measured in microseconds.
>> +
>> +What:          /sys/power/suspend_stats/last_suspend_total
>> +Date:          December 2022
>> +Contact:       Mario Limonciello <mario.limonciello@amd.com>
>> +Description:
>> +               The /sys/power/suspend_stats/last_suspend_total file contains
>> +               the total duration of the sleep cycle.
>> +               This is measured in microseconds.
>> +
>>   What:          /sys/power/sync_on_suspend
>>   Date:          October 2019
>>   Contact:       Jonas Meurer <jonas@freesources.org>
>> diff --git a/include/linux/suspend.h b/include/linux/suspend.h
>> index cfe19a028918..af343c3f8198 100644
>> --- a/include/linux/suspend.h
>> +++ b/include/linux/suspend.h
>> @@ -68,6 +68,8 @@ struct suspend_stats {
>>          int     last_failed_errno;
>>          int     errno[REC_FAILED_NUM];
>>          int     last_failed_step;
>> +       u64     last_hw_state_residency;
>> +       u64     last_suspend_total;
>>          enum suspend_stat_step  failed_steps[REC_FAILED_NUM];
>>   };
>>
>> @@ -489,6 +491,8 @@ void restore_processor_state(void);
>>   extern int register_pm_notifier(struct notifier_block *nb);
>>   extern int unregister_pm_notifier(struct notifier_block *nb);
>>   extern void ksys_sync_helper(void);
>> +extern void pm_set_hw_state_residency(u64 duration);
>> +extern void pm_account_suspend_type(const struct timespec64 *t);
>>
>>   #define pm_notifier(fn, pri) {                         \
>>          static struct notifier_block fn##_nb =                  \
>> diff --git a/kernel/power/main.c b/kernel/power/main.c
>> index 31ec4a9b9d70..11bd658583b0 100644
>> --- a/kernel/power/main.c
>> +++ b/kernel/power/main.c
>> @@ -6,6 +6,7 @@
>>    * Copyright (c) 2003 Open Source Development Lab
>>    */
>>
>> +#include <linux/acpi.h>
>>   #include <linux/export.h>
>>   #include <linux/kobject.h>
>>   #include <linux/string.h>
>> @@ -54,6 +55,19 @@ void unlock_system_sleep(unsigned int flags)
>>   }
>>   EXPORT_SYMBOL_GPL(unlock_system_sleep);
>>
>> +void pm_set_hw_state_residency(u64 duration)
>> +{
>> +       suspend_stats.last_hw_state_residency = duration;
>> +}
>> +EXPORT_SYMBOL_GPL(pm_set_hw_state_residency);
>> +
>> +void pm_account_suspend_type(const struct timespec64 *t)
>> +{
>> +       suspend_stats.last_suspend_total += (s64)t->tv_sec * USEC_PER_SEC +
>> +                                                t->tv_nsec / NSEC_PER_USEC;
>> +}
>> +EXPORT_SYMBOL_GPL(pm_account_suspend_type);
>> +
>>   void ksys_sync_helper(void)
>>   {
>>          ktime_t start;
>> @@ -377,6 +391,20 @@ static ssize_t last_failed_step_show(struct kobject *kobj,
>>   }
>>   static struct kobj_attribute last_failed_step = __ATTR_RO(last_failed_step);
>>
>> +static ssize_t last_hw_state_residency_show(struct kobject *kobj,
>> +               struct kobj_attribute *attr, char *buf)
>> +{
>> +       return sprintf(buf, "%llu\n", suspend_stats.last_hw_state_residency);
>> +}
>> +static struct kobj_attribute last_hw_state_residency = __ATTR_RO(last_hw_state_residency);
>> +
>> +static ssize_t last_suspend_total_show(struct kobject *kobj,
>> +               struct kobj_attribute *attr, char *buf)
>> +{
>> +       return sprintf(buf, "%llu\n", suspend_stats.last_suspend_total);
>> +}
>> +static struct kobj_attribute last_suspend_total = __ATTR_RO(last_suspend_total);
>> +
>>   static struct attribute *suspend_attrs[] = {
>>          &success.attr,
>>          &fail.attr,
>> @@ -391,12 +419,26 @@ static struct attribute *suspend_attrs[] = {
>>          &last_failed_dev.attr,
>>          &last_failed_errno.attr,
>>          &last_failed_step.attr,
>> +       &last_hw_state_residency.attr,
>> +       &last_suspend_total.attr,
>>          NULL,
>>   };
>>
>> +static umode_t suspend_attr_is_visible(struct kobject *kobj, struct attribute *attr, int idx)
>> +{
>> +       if (attr != &last_hw_state_residency.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
>> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
>> index fa3bf161d13f..b6c4a3733212 100644
>> --- a/kernel/power/suspend.c
>> +++ b/kernel/power/suspend.c
>> @@ -423,6 +423,8 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
>>          if (suspend_test(TEST_PLATFORM))
>>                  goto Platform_wake;
>>
>> +       suspend_stats.last_suspend_total = 0;
>> +
>>          if (state == PM_SUSPEND_TO_IDLE) {
>>                  s2idle_loop();
>>                  goto Platform_wake;
>> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
>> index f72b9f1de178..e1b356787e53 100644
>> --- a/kernel/time/timekeeping.c
>> +++ b/kernel/time/timekeeping.c
>> @@ -24,6 +24,7 @@
>>   #include <linux/compiler.h>
>>   #include <linux/audit.h>
>>   #include <linux/random.h>
>> +#include <linux/suspend.h>
>>
>>   #include "tick-internal.h"
>>   #include "ntp_internal.h"
>> @@ -1698,6 +1699,7 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
>>          tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *delta));
>>          tk_update_sleep_time(tk, timespec64_to_ktime(*delta));
>>          tk_debug_account_sleep_time(delta);
>> +       pm_account_suspend_type(delta);
>>   }
>>
>>   #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
>> --
>> 2.34.1
>>