Chapter 22
Thermal Driver
22.1 Introduction
Thermal driver is a necessary driver for monitoring and protecting the SoC. The thermal
driver will monitor the SoC temperature in a certain frequency.
It defines three trip points: critical, hot, and active. Cooling device will take actions to
protect the SoC according to different trip points that SoC has reached:
• When reaching critical point, cooling device will reset the system.
• When reaching hot point, cooling device will lower CPU frequency and notify GPU
to run at a lower frequency.
• When the temperature drops to below active point, cooling device will release all the
cooling actions.
Thermal driver has two parts:
• Thermal zone defines trip points and monitors the SoC's temperature.
• Cooling device takes the actions according to different trip points.
22.1.1 Thermal Driver Overview
The thermal driver implements the SoC temperature monitoring function and protection.
It creates a system file interface of /sys/class/thermal/thermal_zone0/ for user. Internally,
the thermal driver will monitor the SoC temperature and do necessary protection
according to different trip points that SoC's temperature reaches.
22.2 Hardware Operation
The thermal driver uses an internal thermal sensor to monitor the SoC temperature. The
cooling device uses the CPU frequency to protect the SoC.
i.MX 6Solo/6DualLite Linux Reference Manual, Rev. L3.0.35_4.1.0, 09/2013
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