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

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

[Srinivas Pandruvada]

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@linux.intel.com>
---
 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

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@linux.intel.com> 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@linux.intel.com>

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
>