linux-kernel - Re: [PATCH][v3] cpufreq: intel_pstate: Get percpu max freq via HWP MSR register if available

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Message-ID: <CAJZ5v0i5jdp6YcpvVuLyxGePRAsFPUPL6=iQC7PEFSzjNRUJLw@mail.gmail.com>
Date:   Tue, 12 Jan 2021 14:52:50 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][v3] cpufreq: intel_pstate: Get percpu max freq via HWP
 MSR register if available

On Tue, Jan 12, 2021 at 6:19 AM Chen Yu <yu.c.chen@...el.com> wrote:
>
> Currently when turbo is disabled(either by BIOS or by the user), the
> intel_pstate driver reads the max non-turbo frequency from the package-wide
> MSR_PLATFORM_INFO(0xce) register. However on asymmetric platforms it is
> possible in theory that small and big core with HWP enabled might have
> different max non-turbo cpu frequency, because the MSR_HWP_CAPABILITIES
> is percpu scope according to Intel Software Developer Manual.
>
> The turbo max freq is already percpu basis in current code, thus make
> similar change to the max non-turbo frequency as well.
>
> Reported-by: Wendy Wang <wendy.wang@...el.com>
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> ---
> v2: Per Srinivas' suggestion, avoid duplicated assignment of max_pstate.
> v3: Per Rafael's suggestion, do not add new argument in intel_pstate_get_hwp_max()
>     to avoid redundant local vars.
>     Per Srinivas' suggestion, refined the commit log to reflect the 'non-turbo'
>     max frequency.

Looks good now, thanks!

Is it needed in -stable and if so, which -stable series should it go into?

> --
>  drivers/cpufreq/intel_pstate.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index eaf32ef7a030..99e180f644c3 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -1724,11 +1724,9 @@ static void intel_pstate_max_within_limits(struct cpudata *cpu)
>  static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
>  {
>         cpu->pstate.min_pstate = pstate_funcs.get_min();
> -       cpu->pstate.max_pstate = pstate_funcs.get_max();
>         cpu->pstate.max_pstate_physical = pstate_funcs.get_max_physical();
>         cpu->pstate.turbo_pstate = pstate_funcs.get_turbo();
>         cpu->pstate.scaling = pstate_funcs.get_scaling();
> -       cpu->pstate.max_freq = cpu->pstate.max_pstate * cpu->pstate.scaling;
>
>         if (hwp_active && !hwp_mode_bdw) {
>                 unsigned int phy_max, current_max;
> @@ -1736,9 +1734,12 @@ static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
>                 intel_pstate_get_hwp_max(cpu, &phy_max, &current_max);
>                 cpu->pstate.turbo_freq = phy_max * cpu->pstate.scaling;
>                 cpu->pstate.turbo_pstate = phy_max;
> +               cpu->pstate.max_pstate = HWP_GUARANTEED_PERF(READ_ONCE(cpu->hwp_cap_cached));
>         } else {
>                 cpu->pstate.turbo_freq = cpu->pstate.turbo_pstate * cpu->pstate.scaling;
> +               cpu->pstate.max_pstate = pstate_funcs.get_max();
>         }
> +       cpu->pstate.max_freq = cpu->pstate.max_pstate * cpu->pstate.scaling;
>
>         if (pstate_funcs.get_aperf_mperf_shift)
>                 cpu->aperf_mperf_shift = pstate_funcs.get_aperf_mperf_shift();
> --
> 2.17.1
>