Thermal architecture - Qualcomm Dragonwing Documentation

The thermal architecture shows how the Qualcomm Linux thermal framework interacts with temperature sensors (Tsens) hardware, cooling map interfaces, and user space clients.

Figure: Thermal architecture Table: Description of the components of thermal architecture

Components of Thermal Architecture	Description
Thermal device tree	A thermal device tree consists of various thermal zones. A thermal zone is configured for every Tsens. Each thermal zone consists of sensor hardware information, different levels of thermal thresholds, and their respective cooling actions. All rules for a thermal zone are defined in the device tree.
Thermal framework	The thermal framework parses the thermal zone rules from the device tree and configures Tsens hardware to generate interrupts when temperature crosses the threshold.
Thermal governor	The thermal governor is a temperature monitor algorithm that controls the temperature of a thermal zone. It mitigates the cooling devices associated with the zone and keeps the temperature within the limit. On receiving an interrupt notification from Tsens hardware, the thermal framework uses a stepwise thermal governor to communicate the cooling actions to the cooling map interface (CPU frequency driver).
Cooling map interface	A cooling map interface is a collection of devices that can be throttled to reduce the temperature of Qualcomm Linux. Every trip instance of the thermal zone is associated with a cooling device. The thermal core framework aggregates all the cooling device instance requests and places the aggregated requests to the cooling device.
User space clients	User space clients use the following interfaces to communicate with the thermal framework: The `sysfs` interface is used to read the temperature of Tsens and kernel trip information. The `Netlink` interface gets information on Tsens temperature notifications.

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