linux-kernel - Re: [PATCH v1 1/2] ACPI: processor: perflib: Use the "no limit" frequency QoS

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Message-ID: <mafs0zgb7boba.fsf@amazon.de>
Date:   Wed, 28 Dec 2022 15:22:33 +0100
From:   Pratyush Yadav <ptyadav@...zon.de>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
CC:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH v1 1/2] ACPI: processor: perflib: Use the "no limit"
 frequency QoS

On Tue, Dec 27 2022, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> When _PPC returns 0, it means that the CPU frequency is not limited by
> the platform firmware, so make acpi_processor_get_platform_limit()
> update the frequency QoS request used by it to "no limit" in that case
> and avoid updating the QoS request when the _PPC return value has not
> changed.
>
> This addresses a problem with limiting CPU frequency artificially on
> some systems after CPU offline/online to the frequency that corresponds
> to the first entry in the _PSS return package.
>
> While at it, move the _PPC return value check against the state count
> earlier to avoid setting performance_platform_limit to an invalid value.
>
> Reported-by: Pratyush Yadav <ptyadav@...zon.de>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Tested-by: Pratyush Yadav <ptyadav@...zon.de>

-- 
Regards,
Pratyush Yadav



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