Re: [PATCH v3 3/3] dt-bindings: thermal: Add yaml bindings for thermal zones
From: Lukasz Luba <lukasz.luba@arm.com>
Date: 2020-03-25 11:06:33
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linux-arm-msm, linux-pm, lkml
On 3/25/20 6:34 AM, Amit Kucheria wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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.yamldiff --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: + $nodename: + const: thermal-zones + description: + A /thermal-zones node is required in order to use the thermal framework to + manage input from the various thermal zones in the system in order to + mitigate thermal overload conditions. It does not represent a real device + in the system, but acts as a container to link thermal sensor devices,
I would say 'thermal sensor device', since there is 1-to-1 mapping and aggregating a few sensors inside one tz is not allowed (or I missed some patches queuing).
+ platform-data regarding temperature thresholds and the mitigation actions
+ to take when the temperature crosses those thresholds.
+
+patternProperties:
+ "^[a-zA-Z][a-zA-Z0-9\\-]{1,12}-thermal$":
+ 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:
+ $ref: /schemas/types.yaml#/definitions/phandle-array
+ description:
+ A list of thermal sensor phandles and sensor specifiers used to
+ monitor this thermal zone.I don't know why it's not consistent with the actual code in of-thermal.c, where there is even a comment stated: /* For now, thermal framework supports only 1 sensor per zone */ I think this is the place where developers should be informed about the limitation and not even try to put more sensors into the list.
+ + trips: + type: object + description: + This node describes a set of points in the temperature domain at + which the thermal framework needs to takes action. The actions to
s/needs to takes/needs to take/
+ be taken are defined in another node called cooling-maps.
+
+ patternProperties:
+ "^[a-zA-Z][a-zA-Z0-9\\-_]{0,63}$":
+ 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.This property is worth a bit longer description.
+ + 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.
[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";
+ };
+
+ 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>;
From this two examples of handling cpu0_alert0 and cpu0_alert1 you
cannot conclude anything (if you don't understand thermal framework (and
probably IPA). As a simple example it would be better to put a comment
with a description and limit min, max to a specific OPP:
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>;
};
IMHO this kind of example would tell more to an avg driver developer.
Regards,
Lukasz