Messages in this thread | | | Subject | Re: [PATCH v3 2/3] dt-bindings: thermal: Add yaml bindings for thermal cooling-devices | From | Lukasz Luba <> | Date | Wed, 25 Mar 2020 10:21:14 +0000 |
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Hi Amit,
On 3/25/20 6:34 AM, Amit Kucheria wrote: > As part of moving the thermal bindings to YAML, split it up into 3 > bindings: thermal sensors, cooling devices and thermal zones. > > The property #cooling-cells is required in each device that acts as a > cooling device - whether active or passive. So any device that can > throttle its performance to passively reduce heat dissipation (e.g. > cpus, gpus) and any device that can actively dissipate heat at different > levels (e.g. fans) will contain this property. > > Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org> > --- > .../thermal/thermal-cooling-devices.yaml | 116 ++++++++++++++++++ > 1 file changed, 116 insertions(+) > create mode 100644 Documentation/devicetree/bindings/thermal/thermal-cooling-devices.yaml > > diff --git a/Documentation/devicetree/bindings/thermal/thermal-cooling-devices.yaml b/Documentation/devicetree/bindings/thermal/thermal-cooling-devices.yaml > new file mode 100644 > index 000000000000..b5599f7859f8 > --- /dev/null > +++ b/Documentation/devicetree/bindings/thermal/thermal-cooling-devices.yaml > @@ -0,0 +1,116 @@ > +# SPDX-License-Identifier: (GPL-2.0) > +# Copyright 2020 Linaro Ltd. > +%YAML 1.2 > +--- > +$id: http://devicetree.org/schemas/thermal/thermal-cooling-devices.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: Thermal cooling device binding > + > +maintainers: > + - Amit Kucheria <amitk@kernel.org> > + > +description: | > + Thermal management is achieved in devicetree by describing the sensor hardware > + and the software abstraction of cooling devices and thermal zones required to > + take appropriate action to mitigate thermal overload. > + > + The following node types are used to completely describe a thermal management > + system in devicetree: > + - thermal-sensor: device that measures temperature, has SoC-specific bindings > + - cooling-device: device used to dissipate heat either passively or artively > + - thermal-zones: a container of the following node types used to describe all > + thermal data for the platform > + > + This binding describes the cooling devices. > + > + There are essentially two ways to provide control on power dissipation: > + - Passive cooling: by means of regulating device performance. A typical > + passive cooling mechanism is a CPU that has dynamic voltage and frequency > + scaling (DVFS), and uses lower frequencies as cooling states. > + - Active cooling: by means of activating devices in order to remove the > + dissipated heat, e.g. regulating fan speeds. > + > + Any cooling device has a range of cooling states (i.e. different levels of > + heat dissipation). They also have a way to determine the state of cooling in > + which the device is. For example, a fan's cooling states correspond to the > + different fan speeds possible. Cooling states are referred to by single > + unsigned integers, where larger numbers mean greater heat dissipation. The > + precise set of cooling states associated with a device should be defined in > + a particular device's binding.
[snip]
> + > + thermal-zones { > + cpu0-thermal { > + polling-delay-passive = <250>; > + polling-delay = <1000>; > + > + thermal-sensors = <&tsens0 1>; > + > + trips { > + cpu0_alert0: trip-point0 { > + temperature = <90000>; > + hysteresis = <2000>; > + type = "passive"; > + }; > + }; > + > + cooling-maps { > + map0 { > + trip = <&cpu0_alert0>; > + cooling-device = <&CPU0 THERMAL_NO_LIMIT > + THERMAL_NO_LIMIT>;
Maybe add something like this, to better reflect the description:
trip = <&cpu0_alert0>; /* Corresponds to 1000MHz in OPP table */ cooling-device = <&CPU0 5 5>;
This is less confusing than THERMAL_NO_LIMIT. Regards, Lukasz
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