14. Thermal Control Strategy and Test Operation Guide¶

This documentDescriptionin CV184x on the platformView CPU/TPU clocksand 、Thermal Control Strategyand trip Correspondence、（hysteresis）、Simulated Temperature Test Steps，withandinDevice TreeinModify Valueand of 。

14.1. Preparation¶

1. Kernel Requirements

Use SDK Providekernel，andEnsureKernel Configurationinalready CONFIG_THERMAL_EMULATION=y （ Tests need ， emul_temp Write ，not Driver ）。

14.2. Operation Flow¶

14.2.1. View CPU/TPU clocks¶

cat /sys/kernel/debug/clk/clk_summary | grep -E '\b(clk_cpu|clk_tpu)\b'

CPU and TPU of beforeFrequency。

14.2.2. View the current temperature¶

cat /sys/class/thermal/thermal_zone0/temp

Unitis millicelsius （），for example 90000 Indicates 90°C。

14.2.3. Thermal Control Strategy（and trip Correspondence）¶

Through thermal zone of trip and cooling device ； of CPU/TPU Frequency cv184x_cooling Nodeof dev-freqs （ NodeDefinition build/boards/default/dts/cv184x_arm/cv184x_base_arm.dtsi）。

Table 14.1 andFrequency、Description¶
	CPU Frequency (Hz)	TPU Frequency (Hz)	Description
tmp < 90°C	1000000000	500000000	passive trip，cooling state 0
90 ≤ tmp < 100°C	500000000	375000000	trip_0，cooling state 1
100 ≤ tmp < 120°C	500000000	300000000	trip_1，cooling state 2
tmp ≥ 120°C	—	—	（critical trip）

IfBoard-levelor SoC of dev-freqs andonTablenot ，with build/boards/default/dts/cv184x_arm/cv184x_base_arm.dtsi in cv184x_cooling { dev-freqs = ... } andActual clk_summary is 。Default ARM DTS is ：(1100M,750M) / (500M,375M) / (500M,300M)，and cooling state 0/1/2 。

14.2.4. Hysteresis Description¶

hysteresis not in Value ， Frequency 。

Unitand temperature ，is millicelsius。
Configuration：5000 5°C 。
（）： ≥ trip of temperature 。
（）： need temperature - hysteresis 。

Example （ trip 90°C、 5°C）：

from 91°C to 89°C：（ 90-5=85°C，not ）。
to 84°C： 85°C after ，Frequency to 。

：If trip is 100°C、 5°C， need to 95°C following from to 。

14.3. Operation Example¶

14.3.1. Simulated Temperature Test Steps¶

14.3.2. ¶

cat /sys/class/thermal/thermal_zone0/temp
cat /sys/kernel/debug/clk/clk_summary | grep -E '\b(clk_cpu|clk_tpu)\b'

14.3.3. Simulate 90°C (should enter the first throttling level)¶

echo 90000 > /sys/class/thermal/thermal_zone0/emul_temp
cat /sys/kernel/debug/clk/clk_summary | grep -E '\b(clk_cpu|clk_tpu)\b'

14.3.4. Simulate 100°C (should enter the second throttling level)¶

echo 100000 > /sys/class/thermal/thermal_zone0/emul_temp
cat /sys/kernel/debug/clk/clk_summary | grep -E '\b(clk_cpu|clk_tpu)\b'

14.3.5. Simulate a drop to 95°C (with hysteresis, the frequency should remain at the second level)¶

echo 95000 > /sys/class/thermal/thermal_zone0/emul_temp
cat /sys/kernel/debug/clk/clk_summary | grep -E '\b(clk_cpu|clk_tpu)\b'

14.3.6. Simulate a drop to 94°C (below the hysteresis exit threshold; it should return to the first or a higher level, depending on the policy)¶

echo 94000 > /sys/class/thermal/thermal_zone0/emul_temp
cat /sys/kernel/debug/clk/clk_summary | grep -E '\b(clk_cpu|clk_tpu)\b'

Ifwith 100°C/5°C is ，need 95°C ； with before DTS in soc_thermal_trip_1 of temperature and hysteresis is 。

14.3.7. Simulate 120°C (trigger critical and force shutdown)¶

echo 120000 > /sys/class/thermal/thermal_zone0/emul_temp

Devicewill Kernel thermal critical isExecute or ，Do not in Execute。

14.3.8. Modify Thermal Thresholds, Shutdown Temperature, and Hysteresis in the Device Tree¶

DefaultDefinitionin build/boards/default/dts/cv184x/cv184x_base.dtsi of thermal-zones → soc_thermal_0 → trips in：

Table 14.2 trip NodeDefaultValue¶
Node	Default temperature	Default hysteresis	type
`soc_thermal_trip_0`	90000 (90°C)	5000 (5°C)	passive	trip
`soc_thermal_trip_1`	100000 (100°C)	5000 (5°C)	passive	trip
`soc_thermal_crtical_0`	120000 (120°C)	0	critical	/

not Default DTS，with Board Variant：

build/boards/default/dts/cv184x/cv184x_base.dtsi

in Board-level DTS trip Attribute（Board NameReplaceisActual ）：

build/boards/cv184x/Board Name/dts_arm/Board Name.dts
Use &label 。

14.3.9. Board-Level Override Example¶

in ofBoard-level DTS（Pathusually build/boards/cv184x/Board Name/dts_arm/Board Name.dts）：

/ {

};

/*   base in thermal trip：temperature/hysteresis  is millicelsius */

&soc_thermal_trip_0 {
     temperature = <90000>;   /*  ，for example 90°C */
     hysteresis = <5000>;     /* 5°C  ， to  trip following 5°C   */
};

&soc_thermal_trip_1 {
     temperature = <100000>;  /*  ，for example 100°C */
     hysteresis = <5000>;
};

&soc_thermal_crtical_0 {
     temperature = <120000>;  /* shutdown  ，for example 120°C；type   critical */
     hysteresis = <0>;
};

ModifyafterRebuildDevice Treeand Image，cooling-maps trip ，No need to map， trip Value 。

14.4. Related File Index¶

Table 14.3 Related FilesandPath¶
FilePath	Description
`build/boards/default/dts/cv184x/cv184x_base.dtsi`	Default thermal-zones、trip、cooling-maps
`build/boards/default/dts/cv184x_arm/cv184x_base_arm.dtsi`	cv184x_cooling and dev-freqs
`linux_5.10/drivers/soc/cvitek/clock_cooling/cv184x/clock_cooling.c`	cooling and clk_set_rate Implementation
Board-level `build/boards/cv184x/Board Name/dts_arm/Board Name.dts`	`&soc_thermal_trip_0`、`&soc_thermal_trip_1`、`&soc_thermal_crtical_0` Value