linux-kernel - Re: [PATCH v5 4/4] platform/x86/intel/pmc: core: Report duration of time in HW sleep state

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Date:   Mon, 3 Apr 2023 18:00:44 +0000
From:   "Box, David E" <david.e.box@...el.com>
To:     "rafael@...nel.org" <rafael@...nel.org>,
        "mario.limonciello@....com" <mario.limonciello@....com>
CC:     "jstultz@...gle.com" <jstultz@...gle.com>,
        "Shyam-sundar.S-k@....com" <Shyam-sundar.S-k@....com>,
        "markgross@...nel.org" <markgross@...nel.org>,
        "rrangel@...omium.org" <rrangel@...omium.org>,
        "Jain, Rajat" <rajatja@...gle.com>,
        "irenic.rajneesh@...il.com" <irenic.rajneesh@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "svenva@...omium.org" <svenva@...omium.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH v5 4/4] platform/x86/intel/pmc: core: Report duration of
 time in HW sleep state

On Fri, 2023-03-31 at 20:05 +0200, Rafael J. Wysocki wrote:
> On Thu, Mar 30, 2023 at 9:45 PM Mario Limonciello
> <mario.limonciello@....com> wrote:
> > 
> > intel_pmc_core displays a warning when the module parameter
> > `warn_on_s0ix_failures` is set and a suspend didn't get to a HW sleep
> > state.
> > 
> > Report this to the standard kernel reporting infrastructure so that
> > userspace software can query after the suspend cycle is done.
> > 
> > Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> > ---
> > v4->v5:
> >  * Reword commit message
> > ---
> >  drivers/platform/x86/intel/pmc/core.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/platform/x86/intel/pmc/core.c
> > b/drivers/platform/x86/intel/pmc/core.c
> > index e2f171fac094..980af32dd48a 100644
> > --- a/drivers/platform/x86/intel/pmc/core.c
> > +++ b/drivers/platform/x86/intel/pmc/core.c
> > @@ -1203,6 +1203,8 @@ static inline bool pmc_core_is_s0ix_failed(struct
> > pmc_dev *pmcdev)
> >         if (pmc_core_dev_state_get(pmcdev, &s0ix_counter))
> >                 return false;
> > 
> > +       pm_set_hw_sleep_time(s0ix_counter - pmcdev->s0ix_counter);
> > +
> 
> Maybe check if this is really accumulating?  In case of a counter
> overflow, for instance?

Overflow is likely on some systems. The counter is only 32-bit and at our
smallest granularity of 30.5us per tick it could overflow after a day and a half
of s0ix time, though most of our systems have a higher granularity that puts
them around 6 days.

This brings up an issue that the attribute cannot be trusted if the system is
suspended for longer than the maximum hardware counter time. Should be noted in
the Documentation.

David

> 
> >         if (s0ix_counter == pmcdev->s0ix_counter)
> >                 return true;
> > 
> > --