[PATCH v5 3/3] dt-bindings: thermal: Add yaml bindings for thermal zones

Amit Kucheria
2020-04-03T07:02:13Z

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>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
---
.../bindings/thermal/thermal-zones.yaml | 341 ++++++++++++++++++
1 file changed, 341 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 0000000000000..b8515d3eeaa2b
--- /dev/null
+++ b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
@@ -0,0 +1,341 @@
+# 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:
+ $nodename:
+ const: thermal-zones
+ description:
+ A /thermal-zones node is required in order to use the thermal framework to
+ manage input from the various thermal zones in the system in order to
+ mitigate thermal overload conditions. It does not represent a real device
+ in the system, but acts as a container to link a thermal sensor device,
+ platform-data regarding temperature thresholds and the mitigation actions
+ to take when the temperature crosses those thresholds.
+
+patternProperties:
+ "^[a-zA-Z][a-zA-Z0-9\\-]{1,12}-thermal$":
+ 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
+ maxItems: 1
+ description:
+ The thermal sensor phandle and sensor specifier used to monitor this
+ thermal zone.
+
+ coefficients:
+ $ref: /schemas/types.yaml#/definitions/uint32-array
+ description:
+ An array of integers containing the coefficients of a linear equation
+ that binds all the sensors listed in this thermal zone.
+
+ The linear equation used is as follows,
+ z = c0 * x0 + c1 * x1 + ... + c(n-1) * x(n-1) + cn
+ where c0, c1, .., cn are the coefficients.
+
+ Coefficients default to 1 in case this property is not specified. The
+ coefficients are ordered and are matched with sensors by means of the
+ sensor ID. Additional coefficients are interpreted as constant offset.
+
+ sustainable-power:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description:
+ An estimate of the sustainable power (in mW) that this thermal zone
+ can dissipate at the desired control temperature. For reference, the
+ sustainable power of a 4-inch phone is typically 2000mW, while on a
+ 10-inch tablet is around 4500mW.
+
+ trips:
+ type: object
+ description:
+ This node describes a set of points in the temperature domain at
+ which the thermal framework needs to take action. The actions to
+ be taken are defined in another node called cooling-maps.
+
+ patternProperties:
+ "^[a-zA-Z][a-zA-Z0-9\\-_]{0,63}$":
+ 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. Any cooling action initiated by the framework is
+ maintained until the temperature falls below
+ (trip temperature - hysteresis). This potentially prevents a
+ situation where the trip gets constantly triggered soon after
+ cooling action is removed.
+
+ 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 percentage contribution of the cooling devices at the
+ specific trip temperature referenced in this map
+ to this thermal zone
+
+ 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>;
+ /* Corresponds to 1400MHz in OPP table */
+ cooling-device = <&CPU0 3 3>, <&CPU1 3 3>,
+ <&CPU2 3 3>, <&CPU3 3 3>;
+ };
+
+ map1 {
+ trip = <&cpu0_alert1>;
+ /* Corresponds to 1000MHz in OPP table */
+ cooling-device = <&CPU0 5 5>, <&CPU1 5 5>,
+ <&CPU2 5 5>, <&CPU3 5 5>;
+ };
+ };
+ };
+
+ /* ... */
+
+ 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