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diff --git a/Documentation/devicetree/bindings/thermal/thermal.txt b/Documentation/devicetree/bindings/thermal/thermal.txt deleted file mode 100644 index f78bec19ca35..000000000000 --- a/Documentation/devicetree/bindings/thermal/thermal.txt +++ /dev/null @@ -1,586 +0,0 @@ -* Thermal Framework Device Tree descriptor - -This file describes a generic binding to provide a way of -defining hardware thermal structure using device tree. -A thermal structure includes thermal zones and their components, -such as trip points, polling intervals, sensors and cooling devices -binding descriptors. - -The target of device tree thermal descriptors is to describe only -the hardware thermal aspects. The thermal device tree bindings are -not about how the system must control or which algorithm or policy -must be taken in place. - -There are five types of nodes involved to describe thermal bindings: -- thermal sensors: devices which may be used to take temperature - measurements. -- cooling devices: devices which may be used to dissipate heat. -- trip points: describe key temperatures at which cooling is recommended. The - set of points should be chosen based on hardware limits. -- cooling maps: used to describe links between trip points and cooling devices; -- thermal zones: used to describe thermal data within the hardware; - -The following is a description of each of these node types. - -* Thermal sensor devices - -Thermal sensor devices are nodes providing temperature sensing capabilities on -thermal zones. Typical devices are I2C ADC converters and bandgaps. These are -nodes providing temperature data to thermal zones. Thermal sensor devices may -control one or more internal sensors. - -Required property: -- #thermal-sensor-cells: Used to provide sensor device specific information - Type: unsigned while referring to it. Typically 0 on thermal sensor - Size: one cell nodes with only one sensor, and at least 1 on nodes - with several internal sensors, in order - to identify uniquely the sensor instances within - the IC. See thermal zone binding for more details - on how consumers refer to sensor devices. - -* Cooling device nodes - -Cooling devices are nodes providing control on power dissipation. There -are essentially two ways to provide control on power dissipation. First -is by means of regulating device performance, which is known as passive -cooling. A typical passive cooling is a CPU that has dynamic voltage and -frequency scaling (DVFS), and uses lower frequencies as cooling states. -Second is by means of activating devices in order to remove -the dissipated heat, which is known as active cooling, e.g. regulating -fan speeds. In both cases, cooling devices shall have a way to determine -the state of cooling in which the device is. - -Any cooling device has a range of cooling states (i.e. different levels -of heat dissipation). 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. -For more examples of cooling devices, refer to the example sections below. - -Required properties: -- #cooling-cells: Used to provide cooling device specific information - Type: unsigned while referring to it. Must be at least 2, in order - Size: one cell to specify minimum and maximum cooling state used - in the reference. The first cell is the minimum - cooling state requested and the second cell is - the maximum cooling state requested in the reference. - See Cooling device maps section below for more details - on how consumers refer to cooling devices. - -* Trip points - -The trip node is a node to describe a point in the temperature domain -in which the system takes an action. This node describes just the point, -not the action. - -Required properties: -- temperature: An integer indicating the trip temperature level, - Type: signed in millicelsius. - Size: one cell - -- hysteresis: A low hysteresis value on temperature property (above). - Type: unsigned This is a relative value, in millicelsius. - Size: one cell - -- type: a string containing the trip type. Expected values are: - "active": A trip point to enable active cooling - "passive": A trip point to enable passive cooling - "hot": A trip point to notify emergency - "critical": Hardware not reliable. - Type: string - -* Cooling device maps - -The cooling device maps node is a node to describe how cooling devices -get assigned to trip points of the zone. The cooling devices are expected -to be loaded in the target system. - -Required properties: -- cooling-device: A list of phandles of cooling devices with their specifiers, - Type: phandle + referring to which cooling devices are used in this - cooling specifier binding. In the cooling specifier, the first cell - is the minimum cooling state and the second cell - is the maximum cooling state used in this map. -- trip: A phandle of a trip point node within the same thermal - Type: phandle of zone. - trip point node - -Optional property: -- contribution: The cooling contribution to the thermal zone of the - Type: unsigned referred cooling device at the referred trip point. - Size: one cell The contribution is a ratio of the sum - of all cooling contributions within a thermal zone. - -Note: Using the THERMAL_NO_LIMIT (-1UL) constant in the cooling-device phandle -limit specifier means: -(i) - minimum state allowed for minimum cooling state used in the reference. -(ii) - maximum state allowed for maximum cooling state used in the reference. -Refer to include/dt-bindings/thermal/thermal.h for definition of this constant. - -* Thermal zone nodes - -The thermal zone node is the node containing all the required info -for describing a thermal zone, including its cooling device bindings. The -thermal zone node must contain, apart from its own properties, one sub-node -containing trip nodes and one sub-node containing all the zone cooling maps. - -Required properties: -- polling-delay: The maximum number of milliseconds to wait between polls - Type: unsigned when checking this thermal zone. - Size: one cell - -- polling-delay-passive: The maximum number of milliseconds to wait - Type: unsigned between polls when performing passive cooling. - Size: one cell - -- thermal-sensors: A list of thermal sensor phandles and sensor specifier - Type: list of used while monitoring the thermal zone. - phandles + sensor - specifier - -- trips: A sub-node which is a container of only trip point nodes - Type: sub-node required to describe the thermal zone. - -Optional property: -- cooling-maps: A sub-node which is a container of only cooling device - Type: sub-node map nodes, used to describe the relation between trips - and cooling devices. - -- coefficients: An array of integers (one signed cell) containing - Type: array coefficients to compose a linear relation between - Elem size: one cell the sensors listed in the thermal-sensors property. - Elem type: signed Coefficients defaults to 1, in case this property - is not specified. A simple linear polynomial is used: - Z = c0 * x0 + c1 * x1 + ... + c(n-1) * x(n-1) + cn. - - The coefficients are ordered and they match with sensors - by means of sensor ID. Additional coefficients are - interpreted as constant offset. - -- sustainable-power: An estimate of the sustainable power (in mW) that the - Type: unsigned thermal zone can dissipate at the desired - Size: one cell control temperature. For reference, the - sustainable power of a 4'' phone is typically - 2000mW, while on a 10'' tablet is around - 4500mW. - -Note: The delay properties are bound to the maximum dT/dt (temperature -derivative over time) in two situations for a thermal zone: -(i) - when passive cooling is activated (polling-delay-passive); and -(ii) - 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. - -* The thermal-zones node - -The "thermal-zones" node is a container for all thermal zone nodes. It shall -contain only sub-nodes describing thermal zones as in the section -"Thermal zone nodes". The "thermal-zones" node appears under "/". - -* Examples - -Below are several examples on how to use thermal data descriptors -using device tree bindings: - -(a) - CPU thermal zone - -The CPU thermal zone example below describes how to setup one thermal zone -using one single sensor as temperature source and many cooling devices and -power dissipation control sources. - -#include <dt-bindings/thermal/thermal.h> - -cpus { - /* - * Here is an example of describing a cooling device for a DVFS - * capable CPU. The CPU node describes its four OPPs. - * The cooling states possible are 0..3, and they are - * used as OPP indexes. The minimum cooling state is 0, which means - * all four OPPs can be available to the system. The maximum - * cooling state is 3, which means only the lowest OPPs (198MHz@0.85V) - * can be available in the system. - */ - cpu0: cpu@0 { - ... - operating-points = < - /* kHz uV */ - 970000 1200000 - 792000 1100000 - 396000 950000 - 198000 850000 - >; - #cooling-cells = <2>; /* min followed by max */ - }; - ... -}; - -&i2c1 { - ... - /* - * A simple fan controller which supports 10 speeds of operation - * (represented as 0-9). - */ - fan0: fan@48 { - ... - #cooling-cells = <2>; /* min followed by max */ - }; -}; - -ocp { - ... - /* - * A simple IC with a single bandgap temperature sensor. - */ - bandgap0: bandgap@0000ed00 { - ... - #thermal-sensor-cells = <0>; - }; -}; - -thermal-zones { - cpu_thermal: cpu-thermal { - polling-delay-passive = <250>; /* milliseconds */ - polling-delay = <1000>; /* milliseconds */ - - thermal-sensors = <&bandgap0>; - - trips { - cpu_alert0: cpu-alert0 { - temperature = <90000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "active"; - }; - cpu_alert1: cpu-alert1 { - temperature = <100000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "passive"; - }; - cpu_crit: cpu-crit { - temperature = <125000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "critical"; - }; - }; - - cooling-maps { - map0 { - trip = <&cpu_alert0>; - cooling-device = <&fan0 THERMAL_NO_LIMIT 4>; - }; - map1 { - trip = <&cpu_alert1>; - cooling-device = <&fan0 5 THERMAL_NO_LIMIT>, <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>; - }; - }; - }; -}; - -In the example above, the ADC sensor (bandgap0) at address 0x0000ED00 is -used to monitor the zone 'cpu-thermal' using its sole sensor. A fan -device (fan0) is controlled via I2C bus 1, at address 0x48, and has ten -different cooling states 0-9. It is used to remove the heat out of -the thermal zone 'cpu-thermal' using its cooling states -from its minimum to 4, when it reaches trip point 'cpu_alert0' -at 90C, as an example of active cooling. The same cooling device is used at -'cpu_alert1', but from 5 to its maximum state. The cpu@0 device is also -linked to the same thermal zone, 'cpu-thermal', as a passive cooling device, -using all its cooling states at trip point 'cpu_alert1', -which is a trip point at 100C. On the thermal zone 'cpu-thermal', at the -temperature of 125C, represented by the trip point 'cpu_crit', the silicon -is not reliable anymore. - -(b) - IC with several internal sensors - -The example below describes how to deploy several thermal zones based off a -single sensor IC, assuming it has several internal sensors. This is a common -case on SoC designs with several internal IPs that may need different thermal -requirements, and thus may have their own sensor to monitor or detect internal -hotspots in their silicon. - -#include <dt-bindings/thermal/thermal.h> - -ocp { - ... - /* - * A simple IC with several bandgap temperature sensors. - */ - bandgap0: bandgap@0000ed00 { - ... - #thermal-sensor-cells = <1>; - }; -}; - -thermal-zones { - cpu_thermal: cpu-thermal { - polling-delay-passive = <250>; /* milliseconds */ - polling-delay = <1000>; /* milliseconds */ - - /* sensor ID */ - thermal-sensors = <&bandgap0 0>; - - trips { - /* each zone within the SoC may have its own trips */ - cpu_alert: cpu-alert { - temperature = <100000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "passive"; - }; - cpu_crit: cpu-crit { - temperature = <125000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "critical"; - }; - }; - - cooling-maps { - /* each zone within the SoC may have its own cooling */ - ... - }; - }; - - gpu_thermal: gpu-thermal { - polling-delay-passive = <120>; /* milliseconds */ - polling-delay = <1000>; /* milliseconds */ - - /* sensor ID */ - thermal-sensors = <&bandgap0 1>; - - trips { - /* each zone within the SoC may have its own trips */ - gpu_alert: gpu-alert { - temperature = <90000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "passive"; - }; - gpu_crit: gpu-crit { - temperature = <105000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "critical"; - }; - }; - - cooling-maps { - /* each zone within the SoC may have its own cooling */ - ... - }; - }; - - dsp_thermal: dsp-thermal { - polling-delay-passive = <50>; /* milliseconds */ - polling-delay = <1000>; /* milliseconds */ - - /* sensor ID */ - thermal-sensors = <&bandgap0 2>; - - trips { - /* each zone within the SoC may have its own trips */ - dsp_alert: dsp-alert { - temperature = <90000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "passive"; - }; - dsp_crit: gpu-crit { - temperature = <135000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "critical"; - }; - }; - - cooling-maps { - /* each zone within the SoC may have its own cooling */ - ... - }; - }; -}; - -In the example above, there is one bandgap IC which has the capability to -monitor three sensors. The hardware has been designed so that sensors are -placed on different places in the DIE to monitor different temperature -hotspots: one for CPU thermal zone, one for GPU thermal zone and the -other to monitor a DSP thermal zone. - -Thus, there is a need to assign each sensor provided by the bandgap IC -to different thermal zones. This is achieved by means of using the -#thermal-sensor-cells property and using the first cell of the sensor -specifier as sensor ID. In the example, then, <bandgap 0> is used to -monitor CPU thermal zone, <bandgap 1> is used to monitor GPU thermal -zone and <bandgap 2> is used to monitor DSP thermal zone. Each zone -may be uncorrelated, having its own dT/dt requirements, trips -and cooling maps. - - -(c) - Several sensors within one single thermal zone - -The example below illustrates how to use more than one sensor within -one thermal zone. - -#include <dt-bindings/thermal/thermal.h> - -&i2c1 { - ... - /* - * A simple IC with a single temperature sensor. - */ - adc: sensor@49 { - ... - #thermal-sensor-cells = <0>; - }; -}; - -ocp { - ... - /* - * A simple IC with a single bandgap temperature sensor. - */ - bandgap0: bandgap@0000ed00 { - ... - #thermal-sensor-cells = <0>; - }; -}; - -thermal-zones { - cpu_thermal: cpu-thermal { - polling-delay-passive = <250>; /* milliseconds */ - polling-delay = <1000>; /* milliseconds */ - - thermal-sensors = <&bandgap0>, /* cpu */ - <&adc>; /* pcb north */ - - /* hotspot = 100 * bandgap - 120 * adc + 484 */ - coefficients = <100 -120 484>; - - trips { - ... - }; - - cooling-maps { - ... - }; - }; -}; - -In some cases, there is a need to use more than one sensor to extrapolate -a thermal hotspot in the silicon. The above example illustrates this situation. -For instance, it may be the case that a sensor external to CPU IP may be placed -close to CPU hotspot and together with internal CPU sensor, it is used -to determine the hotspot. Assuming this is the case for the above example, -the hypothetical extrapolation rule would be: - hotspot = 100 * bandgap - 120 * adc + 484 - -In other context, the same idea can be used to add fixed offset. For instance, -consider the hotspot extrapolation rule below: - hotspot = 1 * adc + 6000 - -In the above equation, the hotspot is always 6C higher than what is read -from the ADC sensor. The binding would be then: - thermal-sensors = <&adc>; - - /* hotspot = 1 * adc + 6000 */ - coefficients = <1 6000>; - -(d) - Board thermal - -The board thermal example below illustrates how to setup one thermal zone -with many sensors and many cooling devices. - -#include <dt-bindings/thermal/thermal.h> - -&i2c1 { - ... - /* - * An IC with several temperature sensor. - */ - adc_dummy: sensor@50 { - ... - #thermal-sensor-cells = <1>; /* sensor internal ID */ - }; -}; - -thermal-zones { - batt-thermal { - polling-delay-passive = <500>; /* milliseconds */ - polling-delay = <2500>; /* milliseconds */ - - /* sensor ID */ - thermal-sensors = <&adc_dummy 4>; - - trips { - ... - }; - - cooling-maps { - ... - }; - }; - - board_thermal: board-thermal { - polling-delay-passive = <1000>; /* milliseconds */ - polling-delay = <2500>; /* milliseconds */ - - /* sensor ID */ - thermal-sensors = <&adc_dummy 0>, /* pcb top edge */ - <&adc_dummy 1>, /* lcd */ - <&adc_dummy 2>; /* back cover */ - /* - * An array of coefficients describing the sensor - * linear relation. E.g.: - * z = c1*x1 + c2*x2 + c3*x3 - */ - coefficients = <1200 -345 890>; - - sustainable-power = <2500>; - - trips { - /* Trips are based on resulting linear equation */ - cpu_trip: cpu-trip { - temperature = <60000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "passive"; - }; - gpu_trip: gpu-trip { - temperature = <55000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "passive"; - } - lcd_trip: lcp-trip { - temperature = <53000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "passive"; - }; - crit_trip: crit-trip { - temperature = <68000>; /* millicelsius */ - hysteresis = <2000>; /* millicelsius */ - type = "critical"; - }; - }; - - cooling-maps { - map0 { - trip = <&cpu_trip>; - cooling-device = <&cpu0 0 2>; - contribution = <55>; - }; - map1 { - trip = <&gpu_trip>; - cooling-device = <&gpu0 0 2>; - contribution = <20>; - }; - map2 { - trip = <&lcd_trip>; - cooling-device = <&lcd0 5 10>; - contribution = <15>; - }; - }; - }; -}; - -The above example is a mix of previous examples, a sensor IP with several internal -sensors used to monitor different zones, one of them is composed by several sensors and -with different cooling devices. |