LTDC device tree configuration

Article purpose

本文介绍了如何在将外围设备分配给 Linux^®时配置“ LTDC” 操作系统。

使用设备树机制 执行配置。

The Device tree提供了STM32“ LTDC Linux驱动程序”使用的LTDC 的硬件描述。

DT bindings documentation

LTDC由STM32 LTDC设备树绑定表示 .

DT configuration

该硬件描述是“STM32微处理器”设备树文件（扩展名为.dtsi）和“板子”设备树文件（扩展名为.dts）的组合。 有关设备树文件分割的说明，请参见Device tree。

STM32CubeMX可用于生成板卡设备树。 有关更多详细信息，请参考How to configure the DT using STM32CubeMX。

DT configuration (STM32 level)

LTDC设备树节点在stm32mp157c.dtsi . 声明（如下所示）提供了硬件寄存器的基地址，时钟，中断和复位。

		ltdc: display-controller@5a001000 {
			compatible = "st,stm32-ltdc";
			reg = <0x5a001000 0x400>;
			interrupts = <GIC_SPI 88 IRQ_TYPE_LEVEL_HIGH>,
				     <GIC_SPI 89 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&rcc LTDC_PX>;
			clock-names = "lcd";
			resets = <&rcc LTDC_R>;
			status = "disabled";
		};

该设备树部分与STM32微处理器有关。 它必须保持原样，而不能由最终用户修改。

DT configuration (board level)

与特定板卡相关的LTDC设备树可能具有以下节点，具体取决于板卡硬件：

• ltdc节点：包含输入/输出端口说明。
• panel或i2cx网桥rgb节点（取决于板硬件）：包含LTDC Pinctrl和输入/输出端口说明
• panel_backlight节点（取决于板硬件）：与面板节点有关

LTDC引脚的完整示例 在stm32mp157-pinctrl.dtsi中提供

			ltdc_pins_a: ltdc-a-0 {
				pins {
					pinmux = <STM32_PINMUX('G',  7, AF14)>, /* LCD_CLK */
						 <STM32_PINMUX('I', 10, AF14)>, /* LCD_HSYNC */
						 <STM32_PINMUX('I',  9, AF14)>, /* LCD_VSYNC */
						 <STM32_PINMUX('F', 10, AF14)>, /* LCD_DE */
						 <STM32_PINMUX('H',  2, AF14)>, /* LCD_R0 */
						 <STM32_PINMUX('H',  3, AF14)>, /* LCD_R1 */
						 <STM32_PINMUX('H',  8, AF14)>, /* LCD_R2 */
						 <STM32_PINMUX('H',  9, AF14)>, /* LCD_R3 */
						 <STM32_PINMUX('H', 10, AF14)>, /* LCD_R4 */
						 <STM32_PINMUX('C',  0, AF14)>, /* LCD_R5 */
						 <STM32_PINMUX('H', 12, AF14)>, /* LCD_R6 */
						 <STM32_PINMUX('E', 15, AF14)>, /* LCD_R7 */
						 <STM32_PINMUX('E',  5, AF14)>, /* LCD_G0 */
						 <STM32_PINMUX('E',  6, AF14)>, /* LCD_G1 */
						 <STM32_PINMUX('H', 13, AF14)>, /* LCD_G2 */
						 <STM32_PINMUX('H', 14, AF14)>, /* LCD_G3 */
						 <STM32_PINMUX('H', 15, AF14)>, /* LCD_G4 */
						 <STM32_PINMUX('I',  0, AF14)>, /* LCD_G5 */
						 <STM32_PINMUX('I',  1, AF14)>, /* LCD_G6 */
						 <STM32_PINMUX('I',  2, AF14)>, /* LCD_G7 */
						 <STM32_PINMUX('D',  9, AF14)>, /* LCD_B0 */
						 <STM32_PINMUX('G', 12, AF14)>, /* LCD_B1 */
						 <STM32_PINMUX('G', 10, AF14)>, /* LCD_B2 */
						 <STM32_PINMUX('D', 10, AF14)>, /* LCD_B3 */
						 <STM32_PINMUX('I',  4, AF14)>, /* LCD_B4 */
						 <STM32_PINMUX('A',  3, AF14)>, /* LCD_B5 */
						 <STM32_PINMUX('B',  8, AF14)>, /* LCD_B6 */
						 <STM32_PINMUX('D',  8, AF14)>; /* LCD_B7 */
					bias-disable;
					drive-push-pull;
					slew-rate = <2>;
				};
			};

			ltdc_pins_sleep_a: ltdc-a-1 {
				pins {
					pinmux = <STM32_PINMUX('G',  7, ANALOG)>, /* LCD_CLK */
						 <STM32_PINMUX('I', 10, ANALOG)>, /* LCD_HSYNC */
						 <STM32_PINMUX('I',  9, ANALOG)>, /* LCD_VSYNC */
						 <STM32_PINMUX('F', 10, ANALOG)>, /* LCD_DE */
						 <STM32_PINMUX('H',  2, ANALOG)>, /* LCD_R0 */
						 <STM32_PINMUX('H',  3, ANALOG)>, /* LCD_R1 */
						 <STM32_PINMUX('H',  8, ANALOG)>, /* LCD_R2 */
						 <STM32_PINMUX('H',  9, ANALOG)>, /* LCD_R3 */
						 <STM32_PINMUX('H', 10, ANALOG)>, /* LCD_R4 */
						 <STM32_PINMUX('C',  0, ANALOG)>, /* LCD_R5 */
						 <STM32_PINMUX('H', 12, ANALOG)>, /* LCD_R6 */
						 <STM32_PINMUX('E', 15, ANALOG)>, /* LCD_R7 */
						 <STM32_PINMUX('E',  5, ANALOG)>, /* LCD_G0 */
						 <STM32_PINMUX('E',  6, ANALOG)>, /* LCD_G1 */
						 <STM32_PINMUX('H', 13, ANALOG)>, /* LCD_G2 */
						 <STM32_PINMUX('H', 14, ANALOG)>, /* LCD_G3 */
						 <STM32_PINMUX('H', 15, ANALOG)>, /* LCD_G4 */
						 <STM32_PINMUX('I',  0, ANALOG)>, /* LCD_G5 */
						 <STM32_PINMUX('I',  1, ANALOG)>, /* LCD_G6 */
						 <STM32_PINMUX('I',  2, ANALOG)>, /* LCD_G7 */
						 <STM32_PINMUX('D',  9, ANALOG)>, /* LCD_B0 */
						 <STM32_PINMUX('G', 12, ANALOG)>, /* LCD_B1 */
						 <STM32_PINMUX('G', 10, ANALOG)>, /* LCD_B2 */
						 <STM32_PINMUX('D', 10, ANALOG)>, /* LCD_B3 */
						 <STM32_PINMUX('I',  4, ANALOG)>, /* LCD_B4 */
						 <STM32_PINMUX('A',  3, ANALOG)>, /* LCD_B5 */
						 <STM32_PINMUX('B',  8, ANALOG)>, /* LCD_B6 */
						 <STM32_PINMUX('D',  8, ANALOG)>; /* LCD_B7 */
				};
			};

一个完整的例子 STM32MP157 Discovery board device tree is available in stm32mp157a-dk1.dts .

&ltdc {
	status = "okay";

	port {
		#address-cells = <1>;
		#size-cells = <0>;

		ltdc_ep0_out: endpoint@0 {
			reg = <0>;
			remote-endpoint = <&sii9022_in>;
		};
	};
};

&i2c1 {
...
	hdmi-transmitter@39 {
		compatible = "sil,sii9022";
		reg = <0x39>;
		iovcc-supply = <&v3v3_hdmi>;
		cvcc12-supply = <&v1v2_hdmi>;
		reset-gpios = <&gpioa 10 GPIO_ACTIVE_LOW>;
		interrupts = <1 IRQ_TYPE_EDGE_FALLING>;
		interrupt-parent = <&gpiog>;
		pinctrl-names = "default", "sleep";
		pinctrl-0 = <&ltdc_pins_a>;
		pinctrl-1 = <&ltdc_pins_sleep_a>;
		status = "okay";

		ports {
			#address-cells = <1>;
			#size-cells = <0>;

			port@0 {
				reg = <0>;
				sii9022_in: endpoint {
					remote-endpoint = <&ltdc_ep0_out>;
				};
			};

			port@1 {
				reg = <1>;
				sii9022_tx_endpoint: endpoint {
					remote-endpoint = <&i2s2_endpoint>;
				};
			};
		};
	};
};

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.

References

Please refer to the following links for additional information:

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