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

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Message-ID: <20220830062050.GA7066@workstation>
Date:   Tue, 30 Aug 2022 11:50:50 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Bjorn Andersson <andersson@...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 Tue, Aug 30, 2022 at 11:10:42AM +0530, Viresh Kumar wrote:
> 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().
> 

Okay. Then I think it is a fair argument to make qcom-cpufreq-hw as the
clock provider for CPUs.

I will send the RFC soon.

Thanks,
Mani

> > 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