linux-kernel - Re: [PATCH v2 6/7] cpufreq: CPPC: Add sysfs for min/max_perf and perf

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Message-ID: <769e0ce4-1f96-4de5-a8a9-48166d6e3a91@infradead.org>
Date: Sat, 23 Aug 2025 17:08:01 -0700
From: Randy Dunlap <rdunlap@...radead.org>
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,
 ray.huang@....com, gautham.shenoy@....com, mario.limonciello@....com,
 perry.yuan@....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,
 bbasu@...dia.com
Subject: Re: [PATCH v2 6/7] cpufreq: CPPC: Add sysfs for min/max_perf and
 perf_limited



On 8/23/25 1:01 PM, Sumit Gupta wrote:
> Add sysfs interfaces for Minimum Performance, Maximum Performance
> and Performance Limited Register in the cppc_cpufreq driver.
> 
> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
> ---
>  .../ABI/testing/sysfs-devices-system-cpu      | 43 +++++++++++++++++++
>  1 file changed, 43 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
> index ab8cd337f43a..4bce0dbc48c9 100644
> --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
> +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
> @@ -327,6 +327,49 @@ Description:	Energy performance preference
>  
>  		This file is only present if the cppc-cpufreq driver is in use.
>  
> +What:           /sys/devices/system/cpu/cpuX/cpufreq/min_perf
> +Date:           Aug 2025
> +Contact:        linux-pm@...r.kernel.org
> +Description:    Minimum Performance

Preferably these 4 lines above use tab(s) after the ':' for indentation
instead of spaces. (in 3 places, i.e., each sysfs file entry).

> +
> +		Read/write a 32 bits value from/to this file. This file
> +		conveys the minimum performance level at which the platform
> +		may run. Minimum performance may be set to any performance
> +		value in the range [Lowest Performance, Highest Performance],
> +		inclusive but must be set to a value that is less than or
> +		equal to that specified by the Maximum Performance Register.
> +
> +		Writing to this file only has meaning when Autonomous Selection
> +		is enabled.
> +
> +		This file is only present if the cppc-cpufreq driver is in use.
> +
> +What:           /sys/devices/system/cpu/cpuX/cpufreq/max_perf
> +Date:           Aug 2025
> +Contact:        linux-pm@...r.kernel.org
> +Description:    Minimum Performance
> +
> +		Read/write a 32 bits value from/to this file. This file conveys
> +		the maximum performance level at which the platform may run.
> +		Maximum performance may be set to any performance value in the
> +		range [Lowest Performance, Highest Performance], inclusive.
> +
> +		Writing to this file only has meaning when Autonomous Selection is
> +		enabled.
> +
> +		This file is only present if the cppc-cpufreq driver is in use.
> +
> +What:           /sys/devices/system/cpu/cpuX/cpufreq/perf_limited
> +Date:           Aug 2025
> +Contact:        linux-pm@...r.kernel.org
> +Description:    Minimum Performance
> +
> +		Read/write a 32 bits value from/to this file. This file indicates
> +		to OSPM that an unpredictable event has limited processor
> +		performance, and the delivered performance may be less than
> +		desired/minimum performance.
> +
> +		This file is only present if the cppc-cpufreq driver is in use.
>  
>  What:		/sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
>  Date:		August 2008

Reviewed-by: Randy Dunlap <rdunlap@...radead.org>

Thanks.

-- 
~Randy