linux-kernel - Re: [PATCH 2/4] dt-bindings: thermal: Add the idle cooling device

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Date:   Tue, 7 Apr 2020 15:36:20 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     rafael@...nel.org, robh@...nel.org
Cc:     Zhang Rui <rui.zhang@...el.com>,
        Amit Kucheria <amit.kucheria@...durent.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] dt-bindings: thermal: Add the idle cooling device


Hi Rob,

On 30/03/2020 00:03, Daniel Lezcano wrote:
> Some devices are not able to cool down by reducing their voltage /
> frequency because it could be not available or the system does not
> allow voltage scaling. In this configuration, it is not possible to
> use this strategy and the idle injection cooling device can be used
> instead.
> 
> One idle cooling device is now present for the CPU as implemented by
> the combination of the idle injection framework belonging to the power
> capping framework and the thermal cooling device. The missing part is
> the DT binding providing a way to describe how the cooling device will
> work on the system.
> 
> A first iteration was done by making the cooling device to point to
> the idle state. Unfortunately it does not make sense because it would
> need to duplicate the idle state description for each CPU in order to
> have a different phandle and make the thermal internal framework
> happy.
> 
> It was proposed to add an cooling-cells to <3>, unfortunately the
> thermal framework is expecting a value of <2> as stated by the
> documentation and it is not possible from the cooling device generic
> code to loop this third value to the back end cooling device.
> 
> Another proposal was to add a child 'thermal-idle' node as the SCMI
> does. This approach allows to have a self-contained configuration for
> the idle cooling device without colliding with the cpufreq cooling
> device which is based on the CPU node. In addition, it allows to have
> the cpufreq cooling device and the idle cooling device to co-exist
> together as showed in the example.

The other patches of the series are acked-by.

Do you think this patch is fine? I would like to apply the series.

Thanks

  -- Daniel


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