GPU device tree configuration

Applicable for

STM32MP15x lines, STM32MP23x lines, STM32MP25x lines

---

1. Article purpose

The purpose of this article is to explain how to configure the GPU internal peripheral using the device tree mechanism, relying on the bindings documentation, that is the description of the required and optional device-tree properties.

2. DT bindings documentation

The device tree binding documents are stored either in the given applicable components listed below, or in the Linux kernel repository:

• Linux^® OS :
  • STM32 GPU device tree bindings, based on "vivante,gc" documentation: Linux kernel bindings for "vivante,gc" (vivante,gc.yaml)

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/SoC level)

The GPU node is located in the device tree file for the software components, supporting the peripheral and listed in the above DT bindings documentation paragraph.

Click here to show the example

• arch/arm/boot/dts/st/stm32mp157.dtsi on STM32MP15x lines 

The declaration (shown below) defines the hardware registers base address, the interrupt, the clocks and the reset.

...
	soc {
		gpu: gpu@59000000 {
			compatible = "vivante,gc";
			reg = <0x59000000 0x800>;
			interrupts = <GIC_SPI 109 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&rcc GPU>, <&rcc GPU_K>;
			clock-names = "bus" ,"core";
			resets = <&rcc GPU_R>;
		};
...

Click here to show the example

• arch/arm64/boot/dts/st/stm32mp235.dtsi on STM32MP23x lines 

The declaration (shown below) defines the hardware registers base address, the interrupt, the clocks and the reset.

...
/ {
	thermal-zones {
		cpu-thermal {
			trips {
				gpu_alert: gpu-alert {
					temperature = <110000>;
					hysteresis = <10000>;
					type = "passive";
				};
			};

			cooling-maps {
				map1 {
					trip = <&gpu_alert>;
					cooling-device = <&gpu 1 6>;
				};
			};
		};
	};
};
...
&rifsc {
...
	gpu: gpu@48280000 {
		compatible = "vivante,gc";
		reg = <0x48280000 0x800>;
		interrupts = <GIC_SPI 183 IRQ_TYPE_LEVEL_HIGH>;
		resets = <&rcc GPU_R>;
		clock-names = "bus", "core";
		clocks = <&rcc CK_BUS_GPU>, <&rcc CK_KER_GPU>;
		power-domains = <&scmi_devpd PD_SCMI_GPU>, <&CLUSTER_PD>;
		access-controllers = <&rifsc 79>;
		status = "disabled";

		throttle,max_state = <6>;
		#cooling-cells = <2>;
	};
...

Click here to show the example

• arch/arm64/boot/dts/st/stm32mp255.dtsi on STM32MP25x lines 

The declaration (shown below) defines the hardware registers base address, the interrupt, the clocks and the reset.

...
/ {
	thermal-zones {
		cpu-thermal {
			trips {
				gpu_alert: gpu-alert {
					temperature = <110000>;
					hysteresis = <10000>;
					type = "passive";
				};
			};

			cooling-maps {
				map1 {
					trip = <&gpu_alert>;
					cooling-device = <&gpu 1 6>;
				};
			};
		};
	};
};
...
&rifsc {
...
	gpu: gpu@48280000 {
		compatible = "vivante,gc";
		reg = <0x48280000 0x800>;
		interrupts = <GIC_SPI 183 IRQ_TYPE_LEVEL_HIGH>;
		resets = <&rcc GPU_R>;
		clock-names = "bus", "core";
		clocks = <&rcc CK_BUS_GPU>, <&rcc CK_KER_GPU>;
		power-domains = <&scmi_devpd PD_SCMI_GPU>, <&CLUSTER_PD>;
		access-controllers = <&rifsc 79>;
		status = "disabled";

		throttle,max_state = <6>;
		#cooling-cells = <2>;
	};
...

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)

The objective of this chapter is to explain how to enable and configure the GPU DT nodes for a board.

Peripheral configuration should be done in specific board device tree files (board dts file).

Add information on gpu_reserved memory configuration and a link to its related "how to" article.

3.2.1. On STM32MP15x lines 

A full example of the STM32MP157 Evaluation board device tree is available in stm32mp157c-ed1.dts , included in stm32mp157c-ev1.dts :

...
	reserved-memory {
		#address-cells = <1>;
		#size-cells = <1>;
		ranges;
...
		gpu_reserved: gpu@e8000000 {
			reg = <0xe8000000 0x8000000>;
			no-map;
		};
...
&gpu {
	contiguous-area = <&gpu_reserved>;
};
...

3.2.2. On STM32MP23x lines  and STM32MP25x lines 

A full example of the STM32MP257 Evaluation board device tree is available in stm32mp257f-ev1.dts :

...
&gpu {
	contiguous-area = <&gpu_reserved>;
	status = "okay";
};

The related "<&gpu_reserved>" node is located in stm32mp257f-ev1-ca35tdcid-resmem.dtsi :

...
/ {
	reserved-memory {
		#address-cells = <2>;
		#size-cells = <2>;
		ranges;
...
		gpu_reserved: gpu-reserved@fa800000 {
			reg = <0x0 0xfa800000 0x0 0x4000000>;
			no-map;
		};
...

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.