On Wed, 15 Apr 2020 00:08:31 +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@xxxxxxxxxx> > --- > - V3: > - Removed extra line with tab inside > - 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 | 145 ++++++++++++++++++ > 1 file changed, 145 insertions(+) > create mode 100644 Documentation/devicetree/bindings/thermal/thermal-idle.yaml > Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
