linux-kernel - Re: [PATCH V12 4/7] cpufreq: Add a notification message that the highest perf has changed

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Message-ID: <CAJZ5v0gYj6C_-m7dD_aN-FWiuLn6bG9MRTe_c7SryTtJJN7FKA@mail.gmail.com>
Date:   Tue, 12 Dec 2023 14:43:42 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Meng Li <li.meng@....com>
Cc:     "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Huang Rui <ray.huang@....com>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-acpi@...r.kernel.org, Shuah Khan <skhan@...uxfoundation.org>,
        linux-kselftest@...r.kernel.org,
        Nathan Fontenot <nathan.fontenot@....com>,
        Deepak Sharma <deepak.sharma@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Mario Limonciello <mario.limonciello@....com>,
        Shimmer Huang <shimmer.huang@....com>,
        Perry Yuan <Perry.Yuan@....com>,
        Xiaojian Du <Xiaojian.Du@....com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Borislav Petkov <bp@...en8.de>,
        Oleksandr Natalenko <oleksandr@...alenko.name>
Subject: Re: [PATCH V12 4/7] cpufreq: Add a notification message that the
 highest perf has changed

On Wed, Dec 6, 2023 at 10:13 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Wed, Dec 6, 2023 at 9:58 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
> >
> > On Tue, Dec 5, 2023 at 7:38 AM Meng Li <li.meng@....com> wrote:
> > >
> > > ACPI 6.5 section 8.4.6.1.1.1 specifies that Notify event 0x85 can be
> > > emmitted to cause the the OSPM to re-evaluate the highest performance
> >
> > Typos above.  Given the number of iterations of this patch, this is
> > kind of disappointing.
> >
> > > register. Add support for this event.
> >
> > Also it would be nice to describe how this is supposed to work at
> > least roughly, so it is not necessary to reverse-engineer the patch to
> > find out that.
> >
> > > Tested-by: Oleksandr Natalenko <oleksandr@...alenko.name>
> > > Reviewed-by: Mario Limonciello <mario.limonciello@....com>
> > > Reviewed-by: Huang Rui <ray.huang@....com>
> > > Reviewed-by: Perry Yuan <perry.yuan@....com>
> > > Signed-off-by: Meng Li <li.meng@....com>
> > > Link: https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#processor-device-notification-values
> > > ---
> > >  drivers/acpi/processor_driver.c |  6 ++++++
> > >  drivers/cpufreq/cpufreq.c       | 13 +++++++++++++
> > >  include/linux/cpufreq.h         |  5 +++++
> > >  3 files changed, 24 insertions(+)
> > >
> > > diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
> > > index 4bd16b3f0781..29b2fb68a35d 100644
> > > --- a/drivers/acpi/processor_driver.c
> > > +++ b/drivers/acpi/processor_driver.c
> > > @@ -27,6 +27,7 @@
> > >  #define ACPI_PROCESSOR_NOTIFY_PERFORMANCE 0x80
> > >  #define ACPI_PROCESSOR_NOTIFY_POWER    0x81
> > >  #define ACPI_PROCESSOR_NOTIFY_THROTTLING       0x82
> > > +#define ACPI_PROCESSOR_NOTIFY_HIGEST_PERF_CHANGED      0x85
> > >
> > >  MODULE_AUTHOR("Paul Diefenbaugh");
> > >  MODULE_DESCRIPTION("ACPI Processor Driver");
> > > @@ -83,6 +84,11 @@ static void acpi_processor_notify(acpi_handle handle, u32 event, void *data)
> > >                 acpi_bus_generate_netlink_event(device->pnp.device_class,
> > >                                                   dev_name(&device->dev), event, 0);
> > >                 break;
> > > +       case ACPI_PROCESSOR_NOTIFY_HIGEST_PERF_CHANGED:
> > > +               cpufreq_update_highest_perf(pr->id);
> >
> > And the design appears to be a bit ad-hoc here.
> >
> > Because why does it have anything to do with cpufreq?
>
> Well, clearly, cpufreq can be affected by this, but why would it be
> not affected the same way as in the ACPI_PROCESSOR_NOTIFY_PERFORMANCE
> case?
>
> That is, why isn't cpufreq_update_limits() the right thing to do?

Seriously, I'm not going to apply this patch so long as my comments
above are not addressed.