Re: [PATCH v3 1/3] ACPI: CPPC: Reject desired_perf reads on ACPI 6.6+

On 8/3/26 15:38, Rafael J. Wysocki (Intel) wrote:
>> When CPPC feedback counters cannot provide a usable sample, cppc-cpufreq
>> calls cppc_get_desired_perf() because some platforms repurpose Desired
>> Performance to report actual delivered performance.
>>
>> The fallback was added for platforms on which Desired Performance reflects
>> delivered performance. ACPI 6.6 defines the register as write-only, so
>> invoking that workaround on an ACPI 6.6 or later platform would require an
>> invalid register read.
>>
>> Make cppc_get_desired_perf() return -EOPNOTSUPP in that case. When checking
>> the FADT minor revision, mask off its upper errata-generation bits and
>> compare only the specification minor version.
> I'm wondering if the _CPC revision can be used for this instead of the
> spec revision?
> 
> The _CPC revision changed from 3 to 4 between ACPI 6.5 and ACPI 6.6,
> so doing that should be straightforward.

Yup you're correct, much nicer, I'll fix that