linux-kernel - Re: [PATCH 1/6] arm64: dts: amlogic: Add missing cooling device properties for CPUs

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Message-ID: <20180525211025.c73zdcdtyuvlewng@localhost>
Date:   Fri, 25 May 2018 14:10:25 -0700
From:   Olof Johansson <olof@...om.net>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     arm@...nel.org, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        ionela.voinescu@....com,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        chris.redpath@....com, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] arm64: dts: amlogic: Add missing cooling device
 properties for CPUs

On Fri, May 25, 2018 at 11:10:01AM +0530, Viresh Kumar wrote:
> The cooling device properties, like "#cooling-cells" and
> "dynamic-power-coefficient", should either be present for all the CPUs
> of a cluster or none. If these are present only for a subset of CPUs of
> a cluster then things will start falling apart as soon as the CPUs are
> brought online in a different order. For example, this will happen
> because the operating system looks for such properties in the CPU node
> it is trying to bring up, so that it can register a cooling device.
> 
> Add such missing properties.

This seems awkward compared to just having one cooling-cells in the /cpus node
instead.

What's it used for? I don't see any properties in the device nodes on meson-gxm
that have any cooling-foo cells in them? So why should #cooling-cells be
needed?


-Olof