Date:   Tue, 14 Apr 2020 16:45:09 -0500
From:   Rob Herring <robh@...nel.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     daniel.lezcano@...aro.org, rui.zhang@...el.com,
        amit.kucheria@...durent.com, 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 v2 2/4] dt-bindings: thermal: Add the idle cooling device

On Tue, 14 Apr 2020 18:26:27 +0200, 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 shown in the example.
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
>  - V2:
>    - Fixed comment type
>    - Added dual license
>    - Fixed description s/begins to/should/
>    - Changed name s/duration/duration-us/
>    - Changed name s/latency/exit-latency-us/
>    - Removed types for latency / duration
>    - Fixed s/idle-thermal/thermal-idle/
> ---
>  .../bindings/thermal/thermal-idle.yaml        | 146 ++++++++++++++++++
>  1 file changed, 146 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/thermal/thermal-idle.yaml
> 

My bot found errors running 'make dt_binding_check' on your patch:

Documentation/devicetree/bindings/thermal/thermal-idle.yaml:  while scanning a block scalar
  in "<unicode string>", line 39, column 20
found a tab character where an indentation space is expected
  in "<unicode string>", line 44, column 1
Documentation/devicetree/bindings/Makefile:12: recipe for target 'Documentation/devicetree/bindings/thermal/thermal-idle.example.dts' failed
make[1]: *** [Documentation/devicetree/bindings/thermal/thermal-idle.example.dts] Error 1
make[1]: *** Waiting for unfinished jobs....
warning: no schema found in file: Documentation/devicetree/bindings/thermal/thermal-idle.yaml
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/thermal/thermal-idle.yaml: ignoring, error parsing file
Makefile:1264: recipe for target 'dt_binding_check' failed
make: *** [dt_binding_check] Error 2

See https://patchwork.ozlabs.org/patch/1270492

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure dt-schema is up to date:

pip3 install git+https://github.com/devicetree-org/dt-schema.git@master --upgrade

Please check and re-submit.

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