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Wysocki (Intel)" Cc: Linux PM , Linux ACPI , Srinivas Pandruvada References: <13049690.O9o76ZdvQC@rafael.j.wysocki> <91039d3d-4438-486f-926b-8befd5a530b5@arm.com> Content-Language: en-US From: Christian Loehle In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 11/12/26 21:02, Rafael J. Wysocki (Intel) wrote: > On Thu, Nov 12, 2026 at 9:55 PM Christian Loehle > wrote: >> >> On 11/12/26 17:42, Rafael J. Wysocki (Intel) wrote: >>> On Thu, Nov 12, 2026 at 6:39 PM Rafael J. Wysocki wrote: >>>> >>>> From: "Rafael J. Wysocki" >>>> >>>> On a number of Intel platforms in the field, the nominal performance >>>> value in ACPI _CPC (which is an integer) is larger than the guaranteed >>> >>> I said "larger", but should have said "less". Sorry about this. >>> >>> Will fix this when applying the patch unless there are other comments. >>> >>>> performance value and it may even be larger than the highest performance >>>> value (that come from register reads). >>>> >>>> The new specification compliance checks involving those values added >>>> by commit 32299b29a887 ("ACPI: CPPC: Validate _CPC entry and control >>>> semantics") cause the CPPC library to refuse to work for some CPUs >>>> on the affected systems which in turn causes the intel_pstate driver >>>> to overestimate the maximum performance levels for those CPUs. One >>>> of the affected systems is Dell Pro 5 14 P514260. >>>> >>>> In this particular case, the fact that the specification is not >>>> exactly followed has no implications and the checks enforcing >>>> compliance are not useful, so drop them from the CPPC library. >>>> >>>> If really necessary, they will need to be done elsewhere. >> >> They would've made things a littler clearer but I don't see why >> we strictly need them right now. >> >>>> >>>> Fixes: 32299b29a887 ("ACPI: CPPC: Validate _CPC entry and control semantics") >>>> Signed-off-by: Rafael J. Wysocki >> >> Reviewed-by: Christian Loehle > > Thank you! > > I will need to update the patch because the nom vs min_nonlinear check > is also affected. > > I'll send a v2 tomorrow with your R-by if that's OK. All good! > [snip]