Re: [PATCH 2/2][v2] cpufreq: intel_pstate: Get percpu max freq via HWP MSR register if available

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

On Mon, 2021-01-11 at 15:43 +0800, Chen Yu wrote:
> Currently when turbo is disabled(either by BIOS or by the user), the
> intel_pstate
> driver reads the max 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 cpu frequency
max non-turbo frequency (although code call max_freq).

Thanks,
Srinivas

> , 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@intel.com>
> Signed-off-by: Chen Yu <yu.c.chen@intel.com>
> ---
> v2: per Srinivas' suggestion, avoid duplicated assignment of
> max_pstate.
> --
>  drivers/cpufreq/intel_pstate.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/intel_pstate.c
> b/drivers/cpufreq/intel_pstate.c
> index bd3dd1be73ba..f2d18991d969 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -1725,11 +1725,9 @@ 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, guar_state;
> @@ -1737,8 +1735,12 @@ static void
> intel_pstate_get_cpu_pstates(struct cpudata *cpu)
>                 intel_pstate_get_hwp_max(cpu, &phy_max, &current_max,
> &guar_state);
>                 cpu->pstate.turbo_freq = phy_max * cpu-
> >pstate.scaling;
>                 cpu->pstate.turbo_pstate = phy_max;
> +               cpu->pstate.max_pstate = guar_state;
> +               cpu->pstate.max_freq = guar_state * cpu-
> >pstate.scaling;
>         } 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)