linux-kernel - Re: [PATCH v3 0/5] cpupower: Add various feature control support for amd

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Date:   Tue, 18 Jul 2023 16:17:59 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Thomas Renninger <trenn@...e.de>, trenn@...e.com, shuah@...nel.org,
        Wyes Karny <wyes.karny@....com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        rafael@...nel.org, gautham.shenoy@....com,
        Mario.Limonciello@....com, Ray.Huang@....com, Perry.Yuan@....com,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v3 0/5] cpupower: Add various feature control support for
 amd_pstate

On 7/14/23 05:19, Thomas Renninger wrote:
> Hi,
> 
> sorry for the late answer, I wanted to give this a test, but could not
> make it (yet).
> 
> My 2 cents on this one:
> 
> what Ray already mentioned is greatly appreciated: Find common APIs, not only
> AMD vs Intel, but general ones, outside of the driver specific sysfs dir, e.g.:
> /sys/devices/system/cpu/cpufreq/...
> 
> But not at all costs and if the epp part is (AMD) specific and varies to others
> in meaning or in values, it has to be a specific file/API.
> 
> (Another Example/Request at the end)
> 
> And...: It would be nice to see some documentation in form of manpage
> enhancements. At least for the newly introduced arguments.
> If not yet, there should be: possible value range, which machines (CPU flags,
> Zen 4, ...), if more complex technology, some kind of introduction or
> reference where to find things would be really great.
> 
> I wonder whether it could be possible to connect this with:
> Documentation/admin-guide/pm/intel_pstate.rst
> Documentation/admin-guide/pm/amd-pstate.rst
> 
> I guess there is a static web site address people could rely on where above
> kernel docs are hosted forever?
> Then it would make sense to link the cpupower manpage with it and keep the
> description short and avoid duplication?
> 
>               Thomas
> 
> 
> Another Example/Request at the end:
> 
> One example I recently got asked for, the bug is private:
> "cpupower is not returning max turbo active cores information on latest Intel
> processors."
> 
> Here are examples of 2 newer cpus that don't return the active core
> information like this:
>      3600 MHz max turbo 4 active cores
>      3600 MHz max turbo 3 active cores
>      3700 MHz max turbo 2 active cores
>      3800 MHz max turbo 1 active cores
> 
> Not sure whether there finally is some kind of consolidation on turbo/boost/
> dynamic/hw/bios interfaces in respect to turbo/boosting technology. But if
> anyhow possible and it makes sense, it would be really great to see one sysfs
> file exposed to userspace to read/enable/disable.
> 
> Possible cpufreqs (including or only) boost freqs, maybe with active cores if
> this is a general technique optionally added if avail?
> 
> Nothing which has to be implemented at all costs and right now, just an idea
> on how things could be consolidated at some point of time which might be wise
> to think about now already...
> 

I applied these for Linux 6.6-rc1 - ran quick tests.

Please act on feedback from Thomas and send me patches on top of

https://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux.git/log/?h=cpupower

thanks,
-- Shuah