linux-kernel - Re: [RFC PATCH v3 0/2] Add Krait Cache Scaling support

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Message-ID: <b339e01f9d1e955137120daa06d26228@codeaurora.org>
Date:   Mon, 31 Aug 2020 11:15:50 +0530
From:   Sibi Sankar <sibis@...eaurora.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Ansuel Smith <ansuelsmth@...il.com>, vincent.guittot@...aro.org,
        saravanak@...gle.com, Sudeep Holla <sudeep.holla@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Rob Herring <robh+dt@...nel.org>, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v3 0/2] Add Krait Cache Scaling support

On 2020-08-24 16:10, Viresh Kumar wrote:
> +Vincent/Saravana/Sibi
> 
> On 21-08-20, 16:00, Ansuel Smith wrote:
>> This adds Krait Cache scaling support using the cpufreq notifier.
>> I have some doubt about where this should be actually placed (clk or 
>> cpufreq)?
>> Also the original idea was to create a dedicated cpufreq driver (like 
>> it's done in
>> the codeaurora qcom repo) by copying the cpufreq-dt driver and adding 
>> the cache
>> scaling logic but i still don't know what is better. Have a very 
>> similar driver or
>> add a dedicated driver only for the cache using the cpufreq notifier 
>> and do the
>> scale on every freq transition.
>> Thanks to everyone who will review or answer these questions.
> 
> Saravana was doing something with devfreq to solve such issues if I
> wasn't mistaken.
> 
> Sibi ?

IIRC the final plan was to create a devfreq device
and devfreq-cpufreq based governor to scale them, this
way one can switch to a different governor if required.
(I don't see if ^^ applies well for l2 though). In the
interim until such a solution is acked on the list we
just scale the resources directly from the cpufreq
driver. On SDM845/SC7180 SoCs, L3 is modeled as a
interconnect provider and is directly scaled from the
cpufreq-hw driver.

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