HSEM device tree configuration

Applicable for

STM32MP15x lines

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1. Article purpose

This article explains how to configure the HSEM internal peripheral controlled by the Linux^® Hardware spinlock framework.

The configuration is performed using the device tree mechanism that provides a hardware description of the HSEM peripheral, used by the STM32 HSEM Linux driver.

2. DT bindings documentation

The HSEM internal peripheral is represented by:

• The generic hwlock device tree bindings
• The STM32 hardware spinlock device tree bindings

3. DT configuration

This hardware description is a combination of the STM32 microprocessor device tree files (.dtsi extension) and board device tree files (.dts extension). See the Device tree for an explanation of the device tree file split.

STM32CubeMX can be used to generate the board device tree. Refer to How to configure the DT using STM32CubeMX for more details.

3.1. DT configuration (STM32 level)

The HSEM peripheral node is located in stm32mp151.dtsi file.

hsem: hwspinlock@4c000000 {
	compatible = "st,stm32-hwspinlock";
	#hwlock-cells = <2>;
	reg = <0x4c000000 0x400>;
	clocks = <&rcc HSEM>;
	clock-names = "hsem";
};

Warning

This device tree part is related to STM32 microprocessors. It must be kept as is, without being modified by the end-user.

3.2. DT configuration (board level)

No board device tree configuration is required.

3.3. DT configuration examples

Below is an example of an HSEM user device:

pinctrl: pin-controller@50002000 {
	...
	hwlocks = <&hsem 0 1>;
	...

The pincrl device uses the semaphore ID 0 (first number) and this semaphore can be shared (second number = 1, meaning shared usage), which means it is used by another device.

4. How to configure the DT using STM32CubeMX

The STM32CubeMX tool can be used to configure the STM32MPU device and get the corresponding platform configuration device tree files.
The STM32CubeMX may not support all the properties described in the above DT bindings documentation paragraph. If so, the tool inserts user sections in the generated device tree. These sections can then be edited to add some properties and they are preserved from one generation to another. Refer to STM32CubeMX user manual for further information.

5. References

Refer to the following links for additional information:

Linux^® is a registered trademark of Linus Torvalds.

Hardware semaphore

Device tree

Linux^® is a registered trademark of Linus Torvalds.

Hardware semaphore

Device tree