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== Article purpose ==
This article explains how to configure the ''DSI'' <ref name="DSI">[[DSI internal peripheral]]</ref> ''' when the peripheral is assigned to the Linux<sup>&reg;</sup> OS'''. 

The configuration is performed using the '''device tree mechanism''' <ref> [[Device tree]]</ref>.

The [[Device tree]] provides a hardware description of the DSI <ref name="DSI"/> used by the STM32 ''DSI Linux driver''.

== DT bindings documentation ==
The DSI is represented by the STM32 DSI device tree bindings <ref>{{CodeSource | Linux kernel | Documentation/devicetree/bindings/display/st,stm32-ltdc.txt | st,stm32-ltdc.txt Linux kernel bindings (including dsi)}}</ref>.

== 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|How to configure the DT using STM32CubeMX]] for more details.

===DT configuration (STM32 level) ===
The DSI device tree node is declared in stm32mp157c.dtsi <ref name="stm32mp157c_dtsi">{{CodeSource | Linux kernel | arch/arm/boot/dts/stm32mp157c.dtsi | Linux kernel STM32MP157C device tree (stm32mp157c.dtsi)}}</ref>. The declaration (shown below) defines the hardware registers base address, the clocks and the reset.
<pre>
		dsi: dsi@5a000000 {
			compatible = "st,stm32-dsi";
			reg = <0x5a000000 0x800>;
			clocks = <&rcc DSI_K>, <&clk_hse>, <&rcc DSI_PX>;
			clock-names = "pclk", "ref", "px_clk";
			resets = <&rcc DSI_R>;
			reset-names = "apb";
			status = "disabled";
		};
</pre>

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

=== DT configuration (board level) ===
The DSI device tree related to a particular board may have the following nodes, depending on the board hardware:
* '''dsi''' node: containing the in/out port descriptions and a '''panel''' sub-node.
* '''ltdc''' node: containing the in/out port description related to the dsi node.
* '''panel_backlight''' node: related to the panel node.
 
A full example of the [[STM32MP157x-EV1 - hardware description | STM32MP157 Evaluation board]] device tree is available in stm32mp157c-ev1.dts <ref name="stm32mp157c_ev1_dts">{{CodeSource | Linux kernel | arch/arm/boot/dts/stm32mp157c-ev1.dts | Linux kernel STM32MP157 Evaluation board device tree (stm32mp157c-ev1.dts)}}</ref>.

<pre>
&dsi {
	#address-cells = <1>;
	#size-cells = <0>;
	status = "okay";

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

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

		port@1 {
			reg = <1>;
			dsi_out: endpoint {
				remote-endpoint = <&panel_in>;
			};
		};
	};

	panel@0 {
		compatible = "raydium,rm68200";
		reg = <0>;
		reset-gpios = <&gpiof 15 GPIO_ACTIVE_LOW>;
		backlight = <&panel_backlight>;
		status = "okay";

		port {
			panel_in: endpoint {
				remote-endpoint = <&dsi_out>;
			};
		};
	};
};

&ltdc {
	status = "okay";

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

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

...
	panel_backlight: panel-backlight {
		compatible = "gpio-backlight";
		gpios = <&gpiod 13 GPIO_ACTIVE_LOW>;
		default-on;
		status = "okay";
	};
};

</pre>

==How to configure the DT using STM32CubeMX==
The [[STM32CubeMX]] tool can be used to configure the STM32MPU device and get the corresponding [[Device_tree#STM32|platform configuration device tree]] files.<br />
The STM32CubeMX may not support all the properties described in the above [[#DT bindings documentation|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:

<references />

<noinclude>
{{ArticleBasedOnModel | Peripheral or framework device tree configuration model}}
{{PublicationRequestId | 9161| 2018-10-11 | BrunoB}}
[[Category:Device tree configuration]]
[[Category:DRM KMS]]
</noinclude>