linux-kernel - Re: [RFC PATCH 0/4] cpufreq: qcom-hw: Move clocks to CPU node

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Message-ID: <20220830054042.akj7pf366inelvpo@vireshk-i7>
Date:   Tue, 30 Aug 2022 11:10:42 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Bjorn Andersson <andersson@...nel.org>
Cc:     Manivannan Sadhasivam <mani@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Johan Hovold <johan@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [RFC PATCH 0/4] cpufreq: qcom-hw: Move clocks to CPU node

On 29-08-22, 22:24, Bjorn Andersson wrote:
> Conceptually, it sounds like a good idea to express the clock feeding
> the CPU clusters, which is controlled by the OSM/EPSS.  But do you
> expect the OPP framework to actually do something with the clock, or
> just to ensure that the relationship is properly described?

No, the OPP core will never try to set the clock rate in your case,
though it will do clk_get().

> FWIW, the possible discrepancy between the requested frequency and the
> actual frequency comes from the fact that OSM/EPSS throttles the cluster
> frequency based on a number of different factors (thermal, voltages
> ...).
> This is reported back to the kernel using the thermal pressure
> interface. It would be quite interesting to see some investigation in
> how efficient the kernel is at making use of this feedback.

-- 
viresh