Thermal Development Guide

ID: RK-KF-YF-154

Release Version: V1.1.1

Date: 2021-03-02

Security Level: □Top-Secret □Secret □Internal ■Public

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Preface

Overview

This document mainly introduces the debugging methods for Thermal configuration on the RK platform.

Product Versions

Chip Name	Kernel Version
RK312x	Linux3.10
RK322x	Linux3.10
RK3288	Linux3.10
RK3368	Linux3.10
RK3328	Linux3.10

Intended Audience

This document (guide) is mainly applicable to the following engineers:

Technical Support Engineers

Software Development Engineers

Revision History

Version	Author	Revision Date	Description
V1.0.0	Hao Yongzhi	2017-02-16	Initial version
V1.1.0	Chen Liang	2018-07-24	Content and format adjustments
V1.1.1	Huang Ying	2021-03-02	Format modification

Table of Contents

[TOC]

Overview

This document mainly describes important concepts related to Thermal, configuration methods, and debugging interfaces.

Important Concepts

In the Linux kernel, a thermal control framework is defined. In the 3.10 kernel arm64 version, we use the sysfs interface of the thermal framework to read the current temperature. The thermal control strategy is customized:

performance strategy: When the current temperature exceeds the target temperature, the CPU is set to a fixed frequency. Specific values are configured in the chip-level dtsi file.
normal strategy: When the current temperature exceeds the target temperature by different values, the CPU reduces the frequency accordingly. Specific values are configured in the chip-level dtsi file.

Configuration Methods

TSADC Configuration

Menuconfig Configuration

make ARCH=arm64 menuconfig

thermal-Menuconfig01

thermal-Menuconfig02

thermal-Menuconfig03

dts Configuration

The following is the chip-level dtsi configuration:

tsadc: tsadc@ff250000 {
	compatible = "rockchip,rk322xh-tsadc"; /* Driver matching identifier string */
	reg = <0x0 0xff250000 0x0 0x100>;      /* Register base address and total register address length */
	interrupts = <GIC_SPI 58 IRQ_TYPE_LEVEL_HIGH>; /* Interrupt number */
	clock-frequency = <50000>; /* Operating clock is 50000; the configuration time period is based on this clock */
	clocks = <&clk_tsadc>, <&clk_gates16 14>;
	clock-names = "tsadc", "apb_pclk";      /* "tsadc" is the operating clock, "apb_pclk" is the configuration clock */
	pinctrl-names = "default", "tsadc_int"; /* "default" is GPIO function,
						   "tsadc_int" - refer to rockchip,hw-tshut-mode configuration below */
	pinctrl-0 = <&tsadc_gpio>;
	pinctrl-1 = <&tsadc_int>;
	resets = <&reset RK322XH_SRST_TSADC_P>;
	reset-names = "tsadc-apb";   /* Reset control, used to reset the TSADC module */
	hw-shut-temp = <120000>;     /* Set shutdown temperature to 120 degrees */
	tsadc-tshut-mode = <0>;      /* tshut mode 0:CRU 1:GPIO */
	tsadc-tshut-polarity = <1>;  /* tshut polarity 0:LOW 1:HIGH */
	#thermal-sensor-cells = <1>; /* Modules referencing the tsadc node need to pass one parameter to tsadc */
	status = "disabled";
};

	rockchip,hw-tshut-mode = <1>;

Configure the reset method when temperature exceeds the shutdown temperature. Setting 0 resets via the SoC's CRU module. Setting 1 is implemented by configuring the pinctrl = "tsadc_int" mentioned above. The tsadc_int pin is generally connected to the PMIC's reset pin (as shown below). Whether this pin is active-high or active-low needs to be configured via hw-tshut-polarity.

Note: On some chips, this pin is not routed out. Please refer to the TRM manual for details.

The TSADC module is disabled by default in the dtsi. To enable it, configure it in the board-level dts, for example:

&tsadc {
	rockchip,hw-tshut-mode = <1>; /* tshut mode 0:CRU 1:GPIO */
	rockchip,hw-tshut-polarity = <1>; /* tshut polarity 0:LOW 1:HIGH */
	status = "okay";
};

Strategy Configuration

Using Normal Strategy by Default, Taking CPU as Example

echo 1 > /sys/module/rockchip_pm/parameters/policy

Configure the policy parameter to 1 in the init.rc script.

The thermal control parameters are configured in dvfs. The specific configuration parameters are as follows:

temp-limit-enable = <1>; /* Enable thermal control */
tsadc-ch = <0>;          /* TSADC channel for temperature acquisition */
target-temp = <95>;      /* Set the thermal control target temperature to 95 degrees */

/*
 * When the temperature exceeds the target temperature,
 * the minimum CPU operating frequency is 600M.
 * For example, if the thermal control strategy calculates that
 * the frequency should be reduced to 400M, the CPU will still
 * operate at 600M.
 */
min_temp_limit = <600000>;

/*
 * When the temperature exceeds the target temperature,
 * the maximum CPU operating frequency is 1200M.
 * For example, if the current CPU frequency is 1400M and the
 * temperature exceeds the target temperature of 95 degrees,
 * the CPU will be sharply reduced to within 1200M.
 */
max_temp_limit = <1200000>;

/*
 * Normal strategy:
 * When the temperature exceeds the set target temperature by 3 degrees,
 * the CPU frequency is reduced by 96M steps. Other values are similar.
 */
normal-temp-limit = <
/*delta-temp    delta-freq*/
        3       96000
        6       144000
        9       192000
        15      384000
>;

Using Performance Strategy, Taking CPU as Example

echo 0 > /sys/module/rockchip_pm/parameters/policy

Configure policy to 0, or don't configure this parameter at all. The default policy is 0.

/*
 * Performance strategy:
 * When the temperature exceeds 110 degrees, the frequency
 * is limited to below 816M.
 */
performance-temp-limit = <
        /*temp    freq*/
        110     816000
>;

Thermal_zone Configuration

Taking RK3328 configuration as an example:

thermal-zones {
	cpu_thermal: cpu-thermal {
		/* When temperature exceeds the threshold, query temperature every 1000ms and limit frequency, unit: milliseconds */
		polling-delay-passive = <1000>;
		/* When temperature does not exceed the threshold, query temperature every 5000ms, unit: milliseconds */
		polling-delay = <5000>;
		/* Specify the tsadc used by the thermal-zone */
				/* sensor	ID */
		thermal-sensors = <&tsadc	0>;
	};
};

Debugging Interfaces

Disable Thermal Control

The main controller enables thermal control by default, meaning dvfs dts configures temp-limit-enable = <1>. To disable thermal control, configure temp-limit-enable = <0> in dvfs dts.

Get Current Temperature

Taking RK3328 as an example, to get the CPU temperature, enter the following command on the serial console:

cat /sys/class/thermal/thermal_zone0/temp

Overview​

Important Concepts​

Configuration Methods​

TSADC Configuration​

Menuconfig Configuration​

dts Configuration​

Strategy Configuration​

Using Normal Strategy by Default, Taking CPU as Example​

Using Performance Strategy, Taking CPU as Example​

Thermal_zone Configuration​

Debugging Interfaces​

Disable Thermal Control​

Get Current Temperature​