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

[Rafael J. Wysocki]

On Wed, Dec 21, 2022 at 4:52 PM Pratyush Yadav <ptyadav@xxxxxxxxx> 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.

That's because of the way P-state limits in the turbo range are
handled by the given processor.

Some of them restrict the P-state even if the limit is located within
the turbo range and some of them don't (that is, requesting any
P-state in the turbo range gives the processor a license to use the
whole of it).

> This causes problems when ACPI processor driver tries to set frequency
> constraints.

The problem is that acpi_processor_get_platform_limit() sets the limit
to the frequency for all of the _PSS states including the last special
one and it should update the QoS to "no limit" in that case.