linux-kernel - Re: [Patch 0/5] Support Autonomous Selection mode in cppc

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Message-ID: <b45d0d81-e4f7-474e-a146-0075a6145cc2@huawei.com>
Date: Tue, 11 Feb 2025 20:01:11 +0800
From: "zhenglifeng (A)" <zhenglifeng1@...wei.com>
To: Viresh Kumar <viresh.kumar@...aro.org>, Sumit Gupta <sumitg@...dia.com>
CC: <rafael@...nel.org>, <lenb@...nel.org>, <robert.moore@...el.com>,
	<corbet@....net>, <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>, <linux-tegra@...r.kernel.org>,
	<treding@...dia.com>, <jonathanh@...dia.com>, <sashal@...dia.com>,
	<vsethi@...dia.com>, <ksitaraman@...dia.com>, <sanjayc@...dia.com>,
	<bbasu@...dia.com>
Subject: Re: [Patch 0/5] Support Autonomous Selection mode in cppc_cpufreq

On 2025/2/11 18:44, Viresh Kumar wrote:
> On 11-02-25, 16:07, Sumit Gupta wrote:
>> This patchset supports the Autonomous Performance Level Selection mode
>> in the cppc_cpufreq driver. The feature is part of the existing CPPC
>> specification and already present in Intel and AMD specific pstate
>> cpufreq drivers. The patchset adds the support in generic acpi cppc
>> cpufreq driver.
> 
> Is there an overlap with:
> 
> https://lore.kernel.org/all/20250206131428.3261578-1-zhenglifeng1@huawei.com/
> 
> ?

Ha, it looks like we're doing something very similar.

> 
>> It adds a new 'cppc_cpufreq_epp' instance of the 'cppc_cpufreq' driver
>> for supporting the Autonomous Performance Level Selection and Energy
>> Performance Preference (EPP).
>> Autonomous selection will get enabled during boot if 'cppc_auto_sel'
>> boot argument is passed or the 'Autonomous Selection Enable' register
>> is already set before kernel boot. When enabled, the hardware is
>> allowed to autonomously select the CPU frequency within the min and
>> max perf boundaries using the Engergy Performance Preference hints.
>> The EPP values range from '0x0'(performance preference) to '0xFF'
>> (energy efficiency preference).
>>
>> It also exposes the acpi_cppc sysfs nodes to update the epp, auto_sel
>> and {min|max_perf} registers for changing the hints to hardware for
>> Autonomous selection.
>>
>> In a followup patch, plan to add support to dynamically switch the
>> cpufreq driver instance from 'cppc_cpufreq_epp' to 'cppc_cpufreq' and
>> vice-versa without reboot.
>>
>> The patches are divided into below groups:
>> - Patch [1-2]: Improvements. Can be applied independently.
>> - Patch [3-4]: sysfs store nodes for Auto mode. Depend on Patch [1-2].
>> - Patch [5]: Support for 'cppc_cpufreq_epp'. Uses a macro from [3].
>>
>> Sumit Gupta (5):
>>   ACPI: CPPC: add read perf ctrls api and rename few existing
>>   ACPI: CPPC: expand macro to create store acpi_cppc sysfs node
>>   ACPI: CPPC: support updating epp, auto_sel and {min|max_perf} from
>>     sysfs
>>   Documentation: ACPI: add autonomous mode ctrls info in cppc_sysfs.txt
>>   cpufreq: CPPC: Add cppc_cpufreq_epp instance for Autonomous mode
>>
>>  Documentation/admin-guide/acpi/cppc_sysfs.rst |  28 ++
>>  .../admin-guide/kernel-parameters.txt         |  11 +
>>  drivers/acpi/cppc_acpi.c                      | 311 ++++++++++++++++--
>>  drivers/cpufreq/cppc_cpufreq.c                | 260 ++++++++++++++-
>>  include/acpi/cppc_acpi.h                      |  19 +-
>>  5 files changed, 572 insertions(+), 57 deletions(-)
>