linux-kernel - Re: [PATCH v8 0/8] AMD Pstate Fixes And Enhancements

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Date: Mon, 18 Mar 2024 13:49:55 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Perry Yuan <perry.yuan@....com>, mario.limonciello@....com, gautham.shenoy@....com
Cc: rafael.j.wysocki@...el.com, viresh.kumar@...aro.org, Ray.Huang@....com, 
	Borislav.Petkov@....com, Alexander.Deucher@....com, Xinmei.Huang@....com, 
	Xiaojian.Du@....com, Li.Meng@....com, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 0/8] AMD Pstate Fixes And Enhancements

On Mon, Mar 18, 2024 at 10:48 AM Perry Yuan <perry.yuan@....com> wrote:
>
> The patch series adds some fixes and enhancements to the AMD pstate
> driver.
> It enables CPPC v2 for certain processors in the family 17H, as
> requested
> by TR40 processor users who expect improved performance and lower system
> temperature.
>
> Additionally, it fixes the initialization of nominal_freq for each
> cpudata
> and changes latency and delay values to be read from platform firmware
> firstly
> for more accurate timing.
>
> A new quirk is also added for legacy processors that lack CPPC
> capabilities which caused the pstate driver to fail loading.
>
> Testing done with one APU system while cpb boost on:
>
> amd_pstate_lowest_nonlinear_freq:1701000
> amd_pstate_max_freq:3501000
> cpuinfo_max_freq:3501000
> cpuinfo_min_freq:400000
> scaling_cur_freq:3084836
> scaling_max_freq:3501000
> scaling_min_freq:400000
>
> analyzing CPU 6:
>   driver: amd-pstate-epp
>   CPUs which run at the same hardware frequency: 6
>   CPUs which need to have their frequency coordinated by software: 6
>   maximum transition latency:  Cannot determine or is not supported.
>   hardware limits: 400 MHz - 3.50 GHz
>   available cpufreq governors: performance powersave
>   current policy: frequency should be within 400 MHz and 3.50 GHz.
>                   The governor "powersave" may decide which speed to use
>                   within this range.
>   current CPU frequency: Unable to call hardware
>   current CPU frequency: 3.50 GHz (asserted by call to kernel)
>   boost state support:
>     Supported: yes
>     Active: yes
>     AMD PSTATE Highest Performance: 255. Maximum Frequency: 3.50 GHz.
>     AMD PSTATE Nominal Performance: 204. Nominal Frequency: 2.80 GHz.
>     AMD PSTATE Lowest Non-linear Performance: 124. Lowest Non-linear Frequency: 1.70 GHz.
>     AMD PSTATE Lowest Performance: 30. Lowest Frequency: 400 MHz.
>
> If someone would like to test this patchset, it would need to apply
> another patchset on top of this in case of some unexpected issue found.
>
> https://lore.kernel.org/lkml/cover.1707297581.git.perry.yuan@amd.com/
> It implements the amd pstate cpb boost feature
> the below patch link is old version, please apply the latest version
> while you start the testing work.
>
> I would greatly appreciate any feedbacks.

There are missing changelogs and S-o-b tags in a few messages in this series.

Overall, I would like someone, preferably at AMD, to take
responsibility for the amd-pstate driver, review patches modifying it
and ACK the approved ones.

Huang Rui, who is listed in MAINTAINERS as the official maintainer of
it, does not seem to be interested in it any more.

Can this be addressed, please?