linux-kernel - Re: [PATCH v3] platform/x86:intel/pmc: Enable the ACPI PM Timer to be turned off when suspended

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Message-ID: <28567169-4588-002d-85b8-906d22f12f05@linux.intel.com>
Date: Tue, 6 Aug 2024 10:24:54 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Marek Maślanka <mmaslanka@...gle.com>
cc: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>, 
    Rajneesh Bhardwaj <irenic.rajneesh@...il.com>, 
    David E Box <david.e.box@...el.com>, Hans de Goede <hdegoede@...hat.com>, 
    John Stultz <jstultz@...gle.com>, Stephen Boyd <sboyd@...nel.org>, 
    platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH v3] platform/x86:intel/pmc: Enable the ACPI PM Timer to
 be turned off when suspended

On Wed, 31 Jul 2024, Marek Maślanka wrote:

> On Wed, Jul 31, 2024 at 6:33 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> >
> > Marek!
> >
> > On Wed, Jul 31 2024 at 16:44, Marek Maślanka wrote:
> > > On Tue, Jul 30, 2024 at 6:08 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> > >> On Tue, Jul 30 2024 at 12:05, Marek Maslanka wrote:
> > >> +static void acpi_pm_disable(struct clocksource *cs)
> > >> +{
> > >> +       acpi_pm_enabled = false;
> > >> +       if (enable_callback)
> > >> +               enable_callback(false);
> > >> +}
> > >> +
> > >>  static struct clocksource clocksource_acpi_pm = {
> > >>         .name           = "acpi_pm",
> > >>         .rating         = 200,
> > >>         .read           = acpi_pm_read,
> > >>         .mask           = (u64)ACPI_PM_MASK,
> > >>         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
> > >> +       .enable         = acpi_pm_enable,
> > >> +       .disable        = acpi_pm_disable,
> > >>  };
> > >>
> > > Thanks. I'll try do this in that way. But I need to disable/enable
> > > ACPI PM timer only on suspend/resume, so I'll use suspend/resume
> > > callbacks.
> >
> > Why? What's the point of keeping it running when nothing uses it?
> >
> > Thanks,
> >
> >         tglx
> 
> In case of Intel CPUs the watchdog (iTCO/wdat_wdt) is driven by ACPI PM
> Timer. But it may also be used by others that I don't know about, so I don't
> want to disable it.

Hi Marek,

This kind of non-obvious information should be put into the changelog 
because it helps if after ten years somebody is looking into this change 
and asks similar why questions.

-- 
 i.