Re: [PATCH v3 1/3] ACPI: CPPC: Refactor boost ratio handling

[Rafael J. Wysocki (Intel)]

On Fri, Sep 25, 2026 at 4:54 PM Mario Limonciello <superm1@xxxxxxxxxx> wrote:
>
> On 9/25/26 04:40, Christian Loehle wrote:
> > On 9/24/26 17:00, Mario Limonciello (AMD) wrote:
> >> From: Mario Limonciello <mario.limonciello@xxxxxxx>
> >>
> >> Rename amd_get_boost_ratio_numerator() to amd_get_effective_highest_perf()
> >> to better reflect that it returns the effective highest performance value
> >> for a CPU, accounting for preferred cores and heterogeneous topologies.
> >>
> >> Add a new helper amd_get_boost_ratio() for doing both for boost
> >> ratio calculations and update callers to use it.
> >>
> >> This refactoring is needed because on some AMD systems (Zen6+),
> >> the boost ratio should be calculated from frequency values rather than
> >> performance values.
> >
> > I think I see why you chose to implement it this way (the x86 APERF / MPERF)
> > issue, but I'd still prefer it to be spelled out here why this is necessary.
> >
>
> Do you mean in the commit message, like spin the patch?  Or just in this
> thread?
>
> Not all cores will operate at the same frequency and fixed scaling
> values from CPPC perf don't apply anymore.

Well, CPPC is per-CPU at least in principle, so the above doesn't
explain much TBH.

It kind of follows from the cover letter that there's something
missing in CPPC, so this is a stop-gap thing, but it would be good to
put the information from the cover letter to the changelog of this
patch.