Re: [PATCH] cpufreq: Use a non-boost reference frequency for pressure calculation

[Hongyan Xia]

On 9/15/2026 2:57 PM, Jianyong Wu wrote:
> Commit d2d5c129d07e ("cpufreq: Make cpufreq_update_pressure() fall
> back to cpuinfo.max_freq") introduced cpuinfo.max_freq as the reference
> frequency for cpufreq pressure when arch_scale_freq_ref() returns zero.
> 
> However, cpuinfo.max_freq may include boost frequencies and therefore
> does not necessarily represent the maximum sustainable frequency. On
> some systems using acpi-cpufreq, cpuinfo.max_freq includes boost while
> the frequency table only contains non-boost frequencies. Consequently,
> cpufreq pressure remains nonzero even without an additional frequency
> limit.
> 
> Furthermore, drivers may update cpuinfo.max_freq when boost is enabled
> or disabled. With a fixed policy limit below the maximum non-boost
> frequency, this changes the pressure reference and hence the reported
> pressure, although the non-boost frequency limit remains unchanged.
> 
> Add max_sustainable_freq to struct cpufreq_cpuinfo to provide a reference
> frequency excluding boost. Populate it from the nominal frequency in
> amd-pstate and cppc_cpufreq, the maximum non-turbo frequency in
> intel_pstate, and the highest frequency-table entry in acpi-cpufreq.
> 
> Use this value when arch_scale_freq_ref() returns zero. Preserve the
> existing cpuinfo.max_freq fallback for drivers that leave the new field
> at zero.

Actually, what remaining platforms are out there that can hit this path? 
 From a quick look I think no x86 or Arm platforms can hit the fallback.

> Tested with acpi-cpufreq, intel_pstate, and amd-pstate in active and
> passive modes. With no additional frequency limit, pressure is zero.
> With a fixed limit below the non-boost reference frequency, pressure
> remains unchanged across boost transitions.
> 
> Fixes: d2d5c129d07e ("cpufreq: Make cpufreq_update_pressure() fall back to cpuinfo.max_freq")
> Signed-off-by: Jianyong Wu <wujianyong@xxxxxxxx>

Looks okay to me.

Reviewed-by: Hongyan Xia <hongyan.xia@xxxxxxxxxxxxx>

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