Re: [PATCH] cpufreq: intel_pstate: Fix cpuinfo_max_freq when MSR_TURBO_RATIO_LIMIT is 0

[Rafael J. Wysocki]

On Mon, Aug 3, 2020 at 8:37 PM Srinivas Pandruvada
<srinivas.pandruvada@xxxxxxxxxxxxxxx> wrote:
>
> The MSR_TURBO_RATIO_LIMIT can be 0. This is not an error. User can update
> this MSR via BIOS settings on some systems or can use msr tools to update.
> Also some systems boot with value = 0.
>
> This results in display of cpufreq/cpuinfo_max_freq wrong. This value
> will be equal to cpufreq/base_frequency, even though turbo is enabled.
>
> But platform will still function normally in HWP mode as we get max
> 1-core frequency from the MSR_HWP_CAPABILITIES. This MSR is already used
> to calculate cpu->pstate.turbo_freq, which is used for to set
> policy->cpuinfo.max_freq. But some other places cpu->pstate.turbo_pstate
> is used. For example to set policy->max.
>
> To fix this, also update cpu->pstate.turbo_pstate when updating
> cpu->pstate.turbo_freq.
>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>

Applied as a fix for 5.9-rc1, thanks!

> ---
>  drivers/cpufreq/intel_pstate.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index 7e0f7880b21a..c7540ad28995 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -1572,6 +1572,7 @@ static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
>
>                 intel_pstate_get_hwp_max(cpu->cpu, &phy_max, &current_max);
>                 cpu->pstate.turbo_freq = phy_max * cpu->pstate.scaling;
> +               cpu->pstate.turbo_pstate = phy_max;
>         } else {
>                 cpu->pstate.turbo_freq = cpu->pstate.turbo_pstate * cpu->pstate.scaling;
>         }
> --
> 2.17.1
>