linux-kernel - Re: [PATCH v2] cpufreq: intel_pstate: Override parameters if HWP forced by BIOS

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Date:   Mon, 13 Sep 2021 19:27:47 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Doug Smythies <doug.smythies@...il.com>
Cc:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <len.brown@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Doug Smythies <dsmythies@...us.net>
Subject: Re: [PATCH v2] cpufreq: intel_pstate: Override parameters if HWP
 forced by BIOS

On Sun, Sep 12, 2021 at 8:51 PM Doug Smythies <doug.smythies@...il.com> wrote:
>
> If HWP has been already been enabled by BIOS, it may be
> necessary to override some kernel command line parameters.
> Once it has been enabled it requires a reset to be disabled.
>
> Suggested-by: Rafael J. Wysocki <rafael@...nel.org>
> Signed-off-by: Doug Smythies <dsmythies@...us.net>
> ---
>  drivers/cpufreq/intel_pstate.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index 1097f826ad70..8c176b7dae41 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -3205,11 +3205,15 @@ static int __init intel_pstate_init(void)
>         if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
>                 return -ENODEV;
>
> -       if (no_load)
> -               return -ENODEV;
> -
>         id = x86_match_cpu(hwp_support_ids);
>         if (id) {
> +               bool hwp_forced = intel_pstate_hwp_is_enabled();
> +
> +               if (hwp_forced)
> +                       pr_info("HWP enabled by BIOS\n");
> +               else if (no_load)
> +                       return -ENODEV;
> +
>                 copy_cpu_funcs(&core_funcs);
>                 /*
>                  * Avoid enabling HWP for processors without EPP support,
> @@ -3219,8 +3223,7 @@ static int __init intel_pstate_init(void)
>                  * If HWP is enabled already, though, there is no choice but to
>                  * deal with it.
>                  */
> -               if ((!no_hwp && boot_cpu_has(X86_FEATURE_HWP_EPP)) ||
> -                   intel_pstate_hwp_is_enabled()) {
> +               if ((!no_hwp && boot_cpu_has(X86_FEATURE_HWP_EPP)) || hwp_forced) {
>                         hwp_active++;
>                         hwp_mode_bdw = id->driver_data;
>                         intel_pstate.attr = hwp_cpufreq_attrs;
> @@ -3235,7 +3238,11 @@ static int __init intel_pstate_init(void)
>
>                         goto hwp_cpu_matched;
>                 }
> +               pr_info("HWP not enabled\n");
>         } else {
> +               if (no_load)
> +                       return -ENODEV;
> +
>                 id = x86_match_cpu(intel_pstate_cpu_ids);
>                 if (!id) {
>                         pr_info("CPU model not supported\n");
> @@ -3314,10 +3321,9 @@ static int __init intel_pstate_setup(char *str)
>         else if (!strcmp(str, "passive"))
>                 default_driver = &intel_cpufreq;
>
> -       if (!strcmp(str, "no_hwp")) {
> -               pr_info("HWP disabled\n");
> +       if (!strcmp(str, "no_hwp"))
>                 no_hwp = 1;
> -       }
> +
>         if (!strcmp(str, "force"))
>                 force_load = 1;
>         if (!strcmp(str, "hwp_only"))
> --

Applied as 5.15-rc material, thanks!