linux-kernel - Re: [PATCH v4 0/8] Enhanced autonomous selection and improvements

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Message-ID: <14efdd1b-677d-488b-8dce-b1131d6928ae@hisilicon.com>
Date: Tue, 18 Nov 2025 16:45:10 +0800
From: Jie Zhan <zhanjie9@...ilicon.com>
To: Sumit Gupta <sumitg@...dia.com>, <rafael@...nel.org>,
	<viresh.kumar@...aro.org>, <lenb@...nel.org>, <robert.moore@...el.com>,
	<corbet@....net>, <pierre.gondois@....com>, <zhenglifeng1@...wei.com>,
	<rdunlap@...radead.org>, <ray.huang@....com>, <gautham.shenoy@....com>,
	<mario.limonciello@....com>, <perry.yuan@....com>, <ionela.voinescu@....com>,
	<linux-pm@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <acpica-devel@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>
CC: <linux-tegra@...r.kernel.org>, <treding@...dia.com>,
	<jonathanh@...dia.com>, <vsethi@...dia.com>, <ksitaraman@...dia.com>,
	<sanjayc@...dia.com>, <nhartman@...dia.com>, <bbasu@...dia.com>
Subject: Re: [PATCH v4 0/8] Enhanced autonomous selection and improvements



On 11/5/2025 7:38 PM, Sumit Gupta wrote:
> This patch series enhances the ACPI CPPC CPUFREQ driver with
> comprehensive support for autonomous performance selection, expanded
> runtime control interfaces and improvements.
> 
> It adds support for below:
> - Expose sysfs to read/write the Minimum/Maximum Performance Registers
>   using frequency (kHz), with internal conversion to performance values.
>   Also, update the policy min/max accordingly.
>     /sys/.../cpufreq/policy*/min_perf and max_perf
> 
> - Expose sysfs to read/write the Performance Limited Register.
>     /sys/.../cpufreq/policy*/perf_limited
> 
> - When toggling autonomous selection, synchronize the policy limits
>   by updating the policy min/max.
> 
> - System-wide autonomous mode configuration via 'auto_sel_mode' boot
>   parameter. Mode can be switched dynamically on individual CPUs.
> 
> - Generic sysfs helper functions to reduce code duplication.

Hi Sumit,

My biggest question is what do we design for users to use all this CPPC
autosel stuff in the cppc_cpufreq driver?

Is it just exposing most of the related interfaces through sysfs and then
we let userspace to play with it (probably with a userspace tool) or
something like the amd_pstate_epp driver?

Since this is quite a large change, we may need a guideline of how it's
gonna be used so we would have a clue of how it should be made.

Cheers,
Jie