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    SubjectRe: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted
    On Tue, Dec 27, 2022 at 7:07 PM srinivas pandruvada
    <srinivas.pandruvada@linux.intel.com> wrote:
    >
    > On Tue, 2022-12-27 at 18:02 +0100, Rafael J. Wysocki wrote:
    > > On Tue, Dec 27, 2022 at 5:40 PM srinivas pandruvada
    > > <srinivas.pandruvada@linux.intel.com> wrote:
    > > >
    > > > On Tue, 2022-12-27 at 16:38 +0100, Pratyush Yadav 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.
    > > > I think, this is the only change you require to fix this. In
    > > > addition
    > > > set pr->performance_platform_limit = 0 in
    > > > acpi_processor_unregister_performance().
    > >
    > > Not really, because if the limit is set to a lower frequency and then
    > > reset to _PSS[0], it needs to be set back to "no limit".
    > >
    >
    > If PPC becomes 0 again after ppc > 0 during dynamic PPC change, pr-
    > >performance_platform_limit will not match current PPC, so will set to
    > PPC 0 performance ( which is already patched by driver after return
    > from acpi_register_performance_state()).

    I see.

    > But fine, you can always set freq qos to FREQ_QOS_MAX_DEFAULT_VALUE for
    > PPC 0 as you are doing in your patch.

    I think that using the "no limit" value to represent the "no limit"
    condition makes sense.

    Also, I'm wondering if the patching of states[0].core_frequency will
    still be necessary after this change.

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