Thread (26 messages) 26 messages, 7 authors, 2026-02-05

Re: [PATCH v7 4/7] ACPI: CPPC: add APIs and sysfs interface for min/max_perf

From: Artem Bityutskiy <dedekind1@gmail.com>
Date: 2026-02-05 13:10:16
Also in: linux-acpi, linux-pm, linux-tegra, lkml

On Tue, 2026-02-03 at 13:43 +0100, Rafael J. Wysocki wrote:
On Thu, Jan 29, 2026 at 11:49 AM Sumit Gupta [off-list ref] wrote:
quoted
Add cppc_get/set_min_perf() and cppc_get/set_max_perf() APIs to read and
write the MIN_PERF and MAX_PERF registers.

Also add sysfs interfaces (min_perf, max_perf) in cppc_cpufreq driver
to expose these controls to userspace. The sysfs values are in frequency
(kHz) for consistency with other cpufreq sysfs files.
But this is not cpufreq and it is not consistent.
Just my 2 cents to add:

CPPC and Intel CPUs don't use kHz for performance scaling. We should
avoid introducing additional kHz-based interfaces where possible, since
the performance units <-> kHz translation may become more complex over
time than today. Future implementations could involve non-linear
relationships and reduced accuracy. Minimizing kHz interfaces now may
help reduce future work.

Thanks,
Artem.
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