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    Subject[PATCH v3 3/3] dt-bindings: thermal: Add yaml bindings for thermal zones
    Date
    As part of moving the thermal bindings to YAML, split it up into 3
    bindings: thermal sensors, cooling devices and thermal zones.

    The thermal-zone binding is a software abstraction to capture the
    properties of each zone - how often they should be checked, the
    temperature thresholds (trips) at which mitigation actions need to be
    taken and the level of mitigation needed at those thresholds.

    Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
    ---
    Changes since v2:
    - Addressed review comment from Rob
    - Added required properties for thermal-zones node
    - Added select: true to thermal-cooling-devices.yaml
    - Fixed up example to pass dt_binding_check

    .../bindings/thermal/thermal-zones.yaml | 324 ++++++++++++++++++
    1 file changed, 324 insertions(+)
    create mode 100644 Documentation/devicetree/bindings/thermal/thermal-zones.yaml

    diff --git a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
    new file mode 100644
    index 000000000000..5632304dcf62
    --- /dev/null
    +++ b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
    @@ -0,0 +1,324 @@
    +# SPDX-License-Identifier: (GPL-2.0)
    +# Copyright 2020 Linaro Ltd.
    +%YAML 1.2
    +---
    +$id: http://devicetree.org/schemas/thermal/thermal-zones.yaml#
    +$schema: http://devicetree.org/meta-schemas/base.yaml#
    +
    +title: Thermal zone 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 overloads.
    +
    + 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 actively
    + - thermal-zones: a container of the following node types used to describe all
    + thermal data for the platform
    +
    + This binding describes the thermal-zones.
    +
    + The polling-delay properties of a thermal-zone are bound to the maximum dT/dt
    + (temperature derivative over time) in two situations for a thermal zone:
    + 1. when passive cooling is activated (polling-delay-passive)
    + 2. when the zone just needs to be monitored (polling-delay) or when
    + active cooling is activated.
    +
    + The maximum dT/dt is highly bound to hardware power consumption and
    + dissipation capability. The delays should be chosen to account for said
    + max dT/dt, such that a device does not cross several trip boundaries
    + unexpectedly between polls. Choosing the right polling delays shall avoid
    + having the device in temperature ranges that may damage the silicon structures
    + and reduce silicon lifetime.
    +
    +properties:
    + $nodename:
    + const: thermal-zones
    + description:
    + A /thermal-zones node is required in order to use the thermal framework to
    + manage input from the various thermal zones in the system in order to
    + mitigate thermal overload conditions. It does not represent a real device
    + in the system, but acts as a container to link thermal sensor devices,
    + platform-data regarding temperature thresholds and the mitigation actions
    + to take when the temperature crosses those thresholds.
    +
    +patternProperties:
    + "^[a-zA-Z][a-zA-Z0-9\\-]{1,12}-thermal$":
    + type: object
    + description:
    + Each thermal zone node contains information about how frequently it
    + must be checked, the sensor responsible for reporting temperature for
    + this zone, one sub-node containing the various trip points for this
    + zone and one sub-node containing all the zone cooling-maps.
    +
    + properties:
    + polling-delay:
    + $ref: /schemas/types.yaml#/definitions/uint32
    + description:
    + The maximum number of milliseconds to wait between polls when
    + checking this thermal zone. Setting this to 0 disables the polling
    + timers setup by the thermal framework and assumes that the thermal
    + sensors in this zone support interrupts.
    +
    + polling-delay-passive:
    + $ref: /schemas/types.yaml#/definitions/uint32
    + description:
    + The maximum number of milliseconds to wait between polls when
    + checking this thermal zone while doing passive cooling. Setting
    + this to 0 disables the polling timers setup by the thermal
    + framework and assumes that the thermal sensors in this zone
    + support interrupts.
    +
    + thermal-sensors:
    + $ref: /schemas/types.yaml#/definitions/phandle-array
    + description:
    + A list of thermal sensor phandles and sensor specifiers used to
    + monitor this thermal zone.
    +
    + trips:
    + type: object
    + description:
    + This node describes a set of points in the temperature domain at
    + which the thermal framework needs to takes action. The actions to
    + be taken are defined in another node called cooling-maps.
    +
    + patternProperties:
    + "^[a-zA-Z][a-zA-Z0-9\\-_]{0,63}$":
    + type: object
    +
    + properties:
    + temperature:
    + $ref: /schemas/types.yaml#/definitions/int32
    + minimum: -273000
    + maximum: 200000
    + description:
    + An integer expressing the trip temperature in millicelsius.
    +
    + hysteresis:
    + $ref: /schemas/types.yaml#/definitions/uint32
    + description:
    + An unsigned integer expressing the hysteresis delta with
    + respect to the trip temperature property above, also in
    + millicelsius.
    +
    + type:
    + $ref: /schemas/types.yaml#/definitions/string
    + enum:
    + - active # enable active cooling e.g. fans
    + - passive # enable passive cooling e.g. throttling cpu
    + - hot # send notification to driver
    + - critical # send notification to driver, trigger shutdown
    + description: |
    + There are four valid trip types: active, passive, hot,
    + critical.
    +
    + The critical trip type is used to set the maximum
    + temperature threshold above which the HW becomes
    + unstable and underlying firmware might even trigger a
    + reboot. Hitting the critical threshold triggers a system
    + shutdown.
    +
    + The hot trip type can be used to send a notification to
    + the thermal driver (if a .notify callback is registered).
    + The action to be taken is left to the driver.
    +
    + The passive trip type can be used to slow down HW e.g. run
    + the CPU, GPU, bus at a lower frequency.
    +
    + The active trip type can be used to control other HW to
    + help in cooling e.g. fans can be sped up or slowed down
    +
    + required:
    + - temperature
    + - hysteresis
    + - type
    + additionalProperties: false
    +
    + additionalProperties: false
    +
    + cooling-maps:
    + type: object
    + description:
    + This node describes the action to be taken when a thermal zone
    + crosses one of the temperature thresholds described in the trips
    + node. The action takes the form of a mapping relation between a
    + trip and the target cooling device state.
    +
    + patternProperties:
    + "^map[-a-zA-Z0-9]*$":
    + type: object
    +
    + properties:
    + trip:
    + $ref: /schemas/types.yaml#/definitions/phandle
    + description:
    + A phandle of a trip point node within this thermal zone.
    +
    + cooling-device:
    + $ref: /schemas/types.yaml#/definitions/phandle-array
    + description:
    + A list of cooling device phandles along with the minimum
    + and maximum cooling state specifiers for each cooling
    + device. Using the THERMAL_NO_LIMIT (-1UL) constant in the
    + cooling-device phandle limit specifier lets the framework
    + use the minimum and maximum cooling state for that cooling
    + device automatically.
    +
    + contribution:
    + $ref: /schemas/types.yaml#/definitions/uint32
    + minimum: 0
    + maximum: 100
    + description:
    + The contribution of the cooling devices at the trip
    + temperature, both referenced in this map, to this thermal
    + zone as a percentage.
    +
    + required:
    + - trip
    + - cooling-device
    + additionalProperties: false
    +
    + required:
    + - polling-delay
    + - polling-delay-passive
    + - thermal-sensors
    + - trips
    + additionalProperties: false
    +
    +examples:
    + - |
    + #include <dt-bindings/interrupt-controller/arm-gic.h>
    + #include <dt-bindings/thermal/thermal.h>
    +
    + // Example 1: SDM845 TSENS
    + soc: soc@0 {
    + #address-cells = <2>;
    + #size-cells = <2>;
    +
    + /* ... */
    +
    + tsens0: thermal-sensor@c263000 {
    + compatible = "qcom,sdm845-tsens", "qcom,tsens-v2";
    + reg = <0 0x0c263000 0 0x1ff>, /* TM */
    + <0 0x0c222000 0 0x1ff>; /* SROT */
    + #qcom,sensors = <13>;
    + interrupts = <GIC_SPI 506 IRQ_TYPE_LEVEL_HIGH>,
    + <GIC_SPI 508 IRQ_TYPE_LEVEL_HIGH>;
    + interrupt-names = "uplow", "critical";
    + #thermal-sensor-cells = <1>;
    + };
    +
    + tsens1: thermal-sensor@c265000 {
    + compatible = "qcom,sdm845-tsens", "qcom,tsens-v2";
    + reg = <0 0x0c265000 0 0x1ff>, /* TM */
    + <0 0x0c223000 0 0x1ff>; /* SROT */
    + #qcom,sensors = <8>;
    + interrupts = <GIC_SPI 507 IRQ_TYPE_LEVEL_HIGH>,
    + <GIC_SPI 509 IRQ_TYPE_LEVEL_HIGH>;
    + interrupt-names = "uplow", "critical";
    + #thermal-sensor-cells = <1>;
    + };
    + };
    +
    + /* ... */
    +
    + 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";
    + };
    +
    + cpu0_alert1: trip-point1 {
    + temperature = <95000>;
    + hysteresis = <2000>;
    + type = "passive";
    + };
    +
    + cpu0_crit: cpu_crit {
    + temperature = <110000>;
    + hysteresis = <1000>;
    + type = "critical";
    + };
    + };
    +
    + cooling-maps {
    + map0 {
    + trip = <&cpu0_alert0>;
    + cooling-device = <&CPU0 THERMAL_NO_LIMIT
    + THERMAL_NO_LIMIT>,
    + <&CPU1 THERMAL_NO_LIMIT
    + THERMAL_NO_LIMIT>,
    + <&CPU2 THERMAL_NO_LIMIT
    + THERMAL_NO_LIMIT>,
    + <&CPU3 THERMAL_NO_LIMIT
    + THERMAL_NO_LIMIT>;
    + };
    +
    + map1 {
    + trip = <&cpu0_alert1>;
    + cooling-device = <&CPU0 THERMAL_NO_LIMIT
    + THERMAL_NO_LIMIT>,
    + <&CPU1 THERMAL_NO_LIMIT
    + THERMAL_NO_LIMIT>,
    + <&CPU2 THERMAL_NO_LIMIT
    + THERMAL_NO_LIMIT>,
    + <&CPU3 THERMAL_NO_LIMIT
    + THERMAL_NO_LIMIT>;
    + };
    + };
    + };
    +
    + /* ... */
    +
    + cluster0-thermal {
    + polling-delay-passive = <250>;
    + polling-delay = <1000>;
    +
    + thermal-sensors = <&tsens0 5>;
    +
    + trips {
    + cluster0_alert0: trip-point0 {
    + temperature = <90000>;
    + hysteresis = <2000>;
    + type = "hot";
    + };
    + cluster0_crit: cluster0_crit {
    + temperature = <110000>;
    + hysteresis = <2000>;
    + type = "critical";
    + };
    + };
    + };
    +
    + /* ... */
    +
    + gpu-top-thermal {
    + polling-delay-passive = <250>;
    + polling-delay = <1000>;
    +
    + thermal-sensors = <&tsens0 11>;
    +
    + trips {
    + gpu1_alert0: trip-point0 {
    + temperature = <90000>;
    + hysteresis = <2000>;
    + type = "hot";
    + };
    + };
    + };
    + };
    +...
    --
    2.20.1
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