linux-kernel - Re: [PATCH] cpufreq: intel_pstate: Allow firmware balance performance EPP without code change

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Date:   Tue, 5 Dec 2023 21:32:08 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     rafael@...nel.org, viresh.kumar@...aro.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: intel_pstate: Allow firmware balance performance
 EPP without code change

On Mon, Nov 20, 2023 at 7:59 PM Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
>
> Firmware can specify balance performance EPP value by enabling HWP and
> set EPP to a desired value. The current implementation requires code
> change for every generation to add an entry to intel_epp_balance_perf
> table.
>
> Some distributions like Chrome, which uses old kernels should be able
> to update balance performance EPP, without code change.
>
> There is a check to avoid updating EPP when the balance performance
> EPP is not changed and is power up default of 0x80. Move this check
> after checking if the HWP is enabled by the firmware and there is
> a valid EPP value set by the firmware.
>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> ---
>  drivers/cpufreq/intel_pstate.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index a534a1f7f1ee..dd6d23e389f1 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -1691,13 +1691,6 @@ static void intel_pstate_update_epp_defaults(struct cpudata *cpudata)
>  {
>         cpudata->epp_default = intel_pstate_get_epp(cpudata, 0);
>
> -       /*
> -        * If this CPU gen doesn't call for change in balance_perf
> -        * EPP return.
> -        */
> -       if (epp_values[EPP_INDEX_BALANCE_PERFORMANCE] == HWP_EPP_BALANCE_PERFORMANCE)
> -               return;
> -
>         /*
>          * If the EPP is set by firmware, which means that firmware enabled HWP
>          * - Is equal or less than 0x80 (default balance_perf EPP)
> @@ -1710,6 +1703,13 @@ static void intel_pstate_update_epp_defaults(struct cpudata *cpudata)
>                 return;
>         }
>
> +       /*
> +        * If this CPU gen doesn't call for change in balance_perf
> +        * EPP return.
> +        */
> +       if (epp_values[EPP_INDEX_BALANCE_PERFORMANCE] == HWP_EPP_BALANCE_PERFORMANCE)
> +               return;
> +
>         /*
>          * Use hard coded value per gen to update the balance_perf
>          * and default EPP.
> --

Applied as 6.8 material with modified subject and changelog, thanks!