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Date: Tue, 15 Nov 2022 18:52:44 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: "Limonciello, Mario" <mario.limonciello@....com>
Cc: Raul Rangel <rrangel@...omium.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Sven van Ashbrook <svenva@...omium.org>,
linux-pm@...r.kernel.org, platform-driver-x86@...r.kernel.org,
Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
John Stultz <jstultz@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Stephen Boyd <sboyd@...nel.org>,
Rajneesh Bhardwaj <irenic.rajneesh@...il.com>,
S-k Shyam-sundar <Shyam-sundar.S-k@....com>,
Rajat Jain <rajatja@...gle.com>,
David E Box <david.e.box@...el.com>,
Hans de Goede <hdegoede@...hat.com>,
linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 1/3] PM: Add a sysfs files to represent sleep duration
On Tue, Nov 15, 2022 at 6:27 PM Limonciello, Mario
<mario.limonciello@....com> wrote:
>
> On 11/15/2022 11:20, Raul Rangel wrote:
> >
> >
> > On Tue, Nov 15, 2022 at 9:35 AM Rafael J. Wysocki <rafael@...nel.org
> > <mailto:rafael@...nel.org>> wrote:
> >
> > On Tue, Nov 15, 2022 at 4:17 PM Limonciello, Mario
> > <mario.limonciello@....com <mailto:mario.limonciello@....com>> wrote:
> > >
> > > On 11/15/2022 08:45, Rafael J. Wysocki wrote:
> > > > On Thu, Nov 10, 2022 at 7:49 AM Mario Limonciello
> > > > <mario.limonciello@....com <mailto:mario.limonciello@....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.
> >
> > Required for running Windows with Modern Standby AFAICS.
> >
> > > As this series started from the needs on ChromeOS I would ask is
> > that typically populated by coreboot?
> >
> > It should be, but I'd need to ask for confirmation.
> >
> >
> > It looks like Intel platforms have support for the LPIT table:
> > https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/third_party/coreboot/src/soc/intel/common/block/acpi/lpit.c?q=f:LPIT%20f:coreboot&ss=chromiumos <https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsource.chromium.org%2Fchromiumos%2Fchromiumos%2Fcodesearch%2F%2B%2Fmain%3Asrc%2Fthird_party%2Fcoreboot%2Fsrc%2Fsoc%2Fintel%2Fcommon%2Fblock%2Facpi%2Flpit.c%3Fq%3Df%3ALPIT%2520f%3Acoreboot%26ss%3Dchromiumos&data=05%7C01%7Cmario.limonciello%40amd.com%7C701602845ad14f37abbb08dac72db514%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638041296400209575%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=9ig2jlDevXMjzmTUf42WS5Ey3rLd2lDUXjncz3mbyMI%3D&reserved=0>
> >
> > For AMD, we had some patches to add _LPIL
> > https://review.coreboot.org/c/coreboot/+/52381/1
> > <https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Freview.coreboot.org%2Fc%2Fcoreboot%2F%2B%2F52381%2F1&data=05%7C01%7Cmario.limonciello%40amd.com%7C701602845ad14f37abbb08dac72db514%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638041296400209575%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=KV6ASbdfNOex%2FZtJYcdItZU1gdjCIXEcP1ExiY0pkf8%3D&reserved=0>
> > They never got merged though. We could add an LPIT table to coreboot for
> > AMD platforms if necessary.
>
> _LPI I don't think makes a lot of sense on X86 today, which is why this
> was sent up:
> eb087f305919e ("ACPI: processor idle: Check for architectural support
> for LPI")
Well, LPI has nothing to do with LPIT. [I guess this could not be
even more confusing, but that's what you get in the world of 4-letter
TLAs.]
> As for LPIT - I've never seen LPIT on AMD UEFI systems either. I guess
> it's an Intel specific table?
It used to be. The spec is UEFI-hosted now.
> >
> > > I would hope it's the same number that is populated in that file on
> > > supported systems though.
> >
> > Well, which is exactly where I'm going.
> >
> > Since there is one sysfs file for exposing this value already and it
> > is used (for example, by sleepgraph), perhaps the way to go would be
> > to extend this interface to systems that don't have LPIT instead of
> > introducing a new one possibly exposing the same value?
> >
>
> Ah; so since Raul confirmed coreboot on Chrome exports that maybe we
> just need to add another way to populate that sysfs file for systems
> without LPIT (IE AMD). I think that's a very good idea; thanks.
>
> I think we still probably want to have a way to get the total suspend
> time out programmatically though to compare to. So perhaps the other
> sysfs file I had in the RFC v2 makes sense still.
Well there are trace points to get that (sleepgraph uses these too),
see Documentation/trace/events-power.rst (and you can git grep for
"machine_suspend" to find where this comes from).
I guess there could be a sysfs file in addition to them, but I'm not
sure if the extra overhead would be worth the benefit.
> > > > 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@...el.com
> > <mailto:david.e.box@...el.com>>
> > > >> Signed-off-by: Mario Limonciello <mario.limonciello@....com
> > <mailto:mario.limonciello@....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@....com
> > <mailto:mario.limonciello@....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@....com
> > <mailto:mario.limonciello@....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@...esources.org
> > <mailto:jonas@...esources.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
> > > >>
> > >
> >
>
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