查看“Linux内核-摄像头驱动移植”的源代码

==实验原理==
DCMI(Digital Camera Interface)，DCMI是一个同步并行接口，能够从外部8bit、10bit、12bit或14bit的CMOS摄像头接收高速数据流，支持不同的数据格式：YCbCr4:2:2/RGB565渐进式视频和压缩数据（JPEG）。<br>

[[Image:58-1-1-1.png]] <br>

FS-MP1A可以外接8bit的COM Camera，接口定义如下:

[[Image:58-1-1-2.png]] <br>

接口与MPU管脚对应关系如下：

[[Image:58-1-1-3.png]] <br>

[[Image:58-1-1-4.png]] <br>

[[Image:58-1-1-5.png]] <br>

[[Image:58-1-1-6.png]] <br>

[[Image:58-1-1-7.png]] <br>

{|class="wikitable"
|-
!原理图网络编号 !! 对应管脚 !! 管脚功能 !! 管脚功能码
|-
| DCMI_D0
| PH9
| DCMI_D0
| AF13
|-
| DCMI_D1
| PH10 
| DCMI_D0
| AF13
|-
| DCMI_D2 
| PH11 
| DCMI_D0
| AF13
|-
| DCMI_D3 
| PH12 
| DCMI_D0
| AF13
|-
| DCMI_D4 
| PH14 
| DCMI_D0
| AF13
|-
| DCMI_D5
| PI4 
| DCMI_D0
| AF13
|-
| DCMI_D6 
| PB8
| DCMI_D0
| AF13
|-
| DCMI_D7 
| PE6 
| DCMI_D0
| AF13
|-
| DCMI_RESET 
| PA3 
| GPIO
| ANALOG
|-
| DCMI_PWDN 
| PA4 
| GPIO
| ANALOG
|-
| DCMI_PIXCK
| PA6 
| DCMI_PIXCLK
| AF13
|-
| DCMI_VSYNC
| PB7
| DCMI_VSYNC
| AF13
|}
*DCMI设备树节点<br>

参考文档：
<pre><nowiki>
Documentation/devicetree/bindings/media/st,stm32-dcmi.txt
Documentation/devicetree/bindings/media/video-interfaces.txt
</nowiki></pre>
内核中ST对STM32MP15x系列芯片的设备树资源了做了定义，可参见：
 arch/arm/boot/dts/stm32mp151.dtsi
stm32mp151中dcmi定义如下：
<pre><nowiki>
dcmi: dcmi@4c006000 {
	compatible = "st,stm32-dcmi";
	reg = <0x4c006000 0x400>;
	interrupts = <GIC_SPI 78 IRQ_TYPE_LEVEL_HIGH>;
	resets = <&rcc CAMITF_R>;
	clocks = <&rcc DCMI>;
	clock-names = "mclk";
	dmas = <&dmamux1 75 0x400 0xe0000001>;
	dma-names = "tx";
	status = "disabled";
};
</nowiki></pre>
上述代码只对dcmi做了基本的初始化，并没有针对不同的硬件设计做适配，所以需结合硬件补全设备树节点信息。<br>

参考帮助文档及内核中其它STM32MP157设备树中对于dcmi的定义，修改dcmi内容如下：
<pre><nowiki>
&dcmi {
	status = "okay";
	pinctrl-names = "default", "sleep";
	pinctrl-0 = <&dcmi_pins_a>;
	pinctrl-1 = <&dcmi_sleep_pins_a>;

	port {
		dcmi_0: endpoint {
			remote-endpoint = <&ov5640_0>;
			bus-width = <8>;
			hsync-active = <0>;
			vsync-active = <0>;
			pclk-sample = <1>;
			pclk-max-frequency = <77000000>;
		};
	};
};
</nowiki></pre>
由于stm32mp15-pinctrl.dtsi中对于DCMI管脚的定义与FS-MP1A实际使用管脚一致，所以无需修改

*CMOS Camera设备树节点<br>

FS-MP1A支持多款COMS Camera，本节以ov5640为例：<br>

参考文档：
 Documentation/devicetree/bindings/media/i2c/ov5640.txt
参考帮助文档及内核中其它STM32MP157设备树中对于ov5640的定义，修改dcmi内容如下：
<pre><nowiki>
ov5640: camera@3c {
	compatible = "ovti,ov5640";
	reg = <0x3c>;
	clocks = <&clk_ext_camera>;
	clock-names = "xclk";
	DOVDD-supply = <&v2v8>;
	powerdown-gpios = <&gpioa 4 (GPIO_ACTIVE_HIGH | GPIO_PUSH_PULL)>;
	reset-gpios = <&gpioa 3 (GPIO_ACTIVE_LOW | GPIO_PUSH_PULL)>;
	rotation = <180>;
	status = "okay";

	port {
		ov5640_0: endpoint {
			remote-endpoint = <&dcmi_0>;
			bus-width = <8>;
			data-shift = <2>; /* lines 9:2 are used */
			hsync-active = <0>;
			vsync-active = <0>;
			pclk-sample = <1>;
			pclk-max-frequency = <77000000>;
	  	};
	};
};	
</nowiki></pre>
*2.8V电源定义<br>

前文已经说过如何添加电源节点，本节不再重复，在根节点添加&v2v8节点，内容如下：
<pre><nowiki>
v2v8_audio: regulator-v2v8 {
	compatible = "regulator-fixed";
	regulator-name = "v2v8";
	regulator-min-microvolt = <2800000>;
	regulator-max-microvolt = <2800000>;
	regulator-always-on;
	regulator-boot-on;
};
</nowiki></pre>
*24M时钟定义<br>

参考文档：
 Documentation/devicetree/bindings/clock/fixed-clock.yaml
参考帮助文档或内核中其他设备树文件，对于时钟的定义，增加内容如下：
<pre><nowiki>
clocks {
	clk_ext_camera: clk-ext-camera {
		#clock-cells = <0>;
		compatible = "fixed-clock";
		clock-frequency = <24000000>;
	};
};
</nowiki></pre>

==实验目的==
==实验平台==
==实验步骤==