linux-kernel - Re: [PATCH v4] dt-bindings: dvfs: Add support for generic performance domains

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Date:   Wed, 20 Oct 2021 11:54:20 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Sudeep Holla <sudeep.holla@....com>, Rob Herring <robh@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Hector Yuan <hector.yuan@...iatek.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v4] dt-bindings: dvfs: Add support for generic
 performance domains

On 19-10-21, 15:58, Ulf Hansson wrote:
> To me, this looks doable from a genpd provider too. Of course, we may
> need to extend the genpd interface a bit to make it fit well for this
> new use case, of course. And I am happy to help, if that is needed.
> 
> One thing though; how is the aggregation of the OPP votes expected to
> be done? Is that entirely managed by FW - or is it expected that the
> cpufreq driver, in this case, keeps track of the aggregated votes too?

In case of cpufreq drivers, the voting is never required since there
is always a single request from cpufreq core to change the freq for a
group of devices (CPUs). And these genpds will only have a bunch of
CPUs to serve.

> Don't get me wrong, I am not pushing for these DT bindings to be
> deprecated (at least not yet :-)), but I would certainly like to
> understand more about them. In the end, we haven't walked this far, by
> extending genpd and inventing new DT bindings to enable it to support
> "performance management" - then just to just forget about them again.
> :-)

I am happy to move to genpd if this can be done in a sane way there :)

-- 
viresh