linux-kernel - Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

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Date:   Tue, 27 Dec 2022 16:57:34 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Pratyush Yadav <ptyadav@...zon.de>
Cc:     srinivas pandruvada <srinivas.pandruvada@...ux.intel.com>,
        linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Robert Moore <robert.moore@...el.com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        devel@...ica.org
Subject: Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a
 processor is rebooted

On Tue, Dec 27, 2022 at 4:38 PM Pratyush Yadav <ptyadav@...zon.de> wrote:
>
> Hi Srinivas,
>
> On Sat, Dec 24 2022, srinivas pandruvada wrote:
>
> > On Fri, 2022-12-23 at 10:10 -0800, srinivas pandruvada wrote:
> >> Hi Pratyush,
> >>
> >> On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
> >> >
> >> > Hi Srinivas,
> >> >
> >> > On Wed, Dec 21 2022, srinivas pandruvada wrote:
> >> > > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
> >> > > > When a processor is brought offline and online again, it is
> >> > > > unable to
> >> > > > use Turbo mode because the _PSS table does not contain the whole
> >> > > > turbo
> >> > > > frequency range, but only +1 MHz above the max non-turbo
> >> > > > frequency.
> >> > > > This
> >> > > > causes problems when ACPI processor driver tries to set frequency
> >> > > > constraints. See patch 2 for more details.
> >> > > >
> >> I can reproduce on a Broadwell server platform. But not on a client
> >> system with acpi_ppc usage.
> >>
> >> Need to check what change broke this.
> >
> > When PPC limits enforcement changed to PM QOS, this broke. Previously
> > acpi_processor_get_platform_limit() was not enforcing any limits. It
> > was just setting variable. So any update done after
> > acpi_register_performance_state() call to pr->performance-
> >>states[ppc].core_frequency, was effective.
> >
> > We don't really need to call
> >         ret = freq_qos_update_request(&pr->perflib_req,
> >                         pr->performance->states[ppc].core_frequency *
> > 1000);
> >
> > if the PPC is not changed. When PPC is changed, this gets called again,
> > so then we can call the above function to update cpufreq limit.
> >
> > The below change fixed for me.
>
> Right. Should I re-roll my patches with your diff below then? Or do you
> think my patches should be good to merge as-is?

No, they are not good to merge.