Linux内核-摄像头驱动移植

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FarSight讨论 | 贡献2020年7月28日 (二) 16:43的版本 实验原理

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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)。

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FS-MP1A可以外接8bit的COM Camera,接口定义如下:

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接口与MPU管脚对应关系如下:

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58-1-1-5.png 58-1-1-6.png

58-1-1-7.png

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

参考文档:

Documentation/devicetree/bindings/media/st,stm32-dcmi.txt
Documentation/devicetree/bindings/media/video-interfaces.txt

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:

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";
};

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。

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:

&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>;
		};
	};
};

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

FS-MP1A支持多款COMS Camera,本节以ov5640为例:

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:

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>;
	  	};
	};
};	
  • 2.8V电源定义

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:

v2v8_audio: regulator-v2v8 {
	compatible = "regulator-fixed";
	regulator-name = "v2v8";
	regulator-min-microvolt = <2800000>;
	regulator-max-microvolt = <2800000>;
	regulator-always-on;
	regulator-boot-on;
};
  • 24M时钟定义

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:

clocks {
	clk_ext_camera: clk-ext-camera {
		#clock-cells = <0>;
		compatible = "fixed-clock";
		clock-frequency = <24000000>;
	};
};

实验目的

熟悉基于Linux操作系统下的摄像头设备驱动移植配置过程。

实验平台

华清远见开发环境,FS-MP1A平台;

实验步骤

  • 增加DCMI设备树节点

修改arch/arm/dts/stm32mp15xx-fsmp1x.dts文件,在文件末尾添加如下内容:

&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>;
		};
	};
};
  • 增加OV5640节点

修改arch/arm/dts/stm32mp15xx-fsmp1x.dts文件,在I2C5节点中添加OV5640设备信息,红色字体为增加内容:

&i2c5 {
pinctrl-names = "default", "sleep";
pinctrl-0 = <&i2c5_pins_a>;
……

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>;
};
};
};

};

  • 增加2.8V电源和24M时钟

修改arch/arm/dts/stm32mp15xx-fsmp1x.dts文件,在根节点最后添加2.8V电源和24M时钟,红色字体为增加内容:

/{
memory@c0000000 {
device_type = "memory";
reg = <0xc0000000 0x20000000>;
};
……

v2v8: regulator-2p8v {
compatible = "regulator-fixed";
regulator-name = "v2v8";
regulator-min-microvolt = <2800000>;
regulator-max-microvolt = <2800000>;
regulator-always-on;
regulator-boot-on;
};
clocks {
clk_ext_camera: clk-ext-camera {
#clock-cells = <0>;
compatible = "fixed-clock";
clock-frequency = <24000000>;
};
};

};

  • 配置内核

配置内核支持ov5640,并列出主要选项,如下

linux@ubuntu:$ make menuconfig
Device Drivers  --->
	<*> Multimedia support  --->
		[*]   V4L platform devices  --->
			<*>   STM32 Digital Camera Memory Interface (DCMI) support 
		I2C Encoders, decoders, sensors and other helper chips  --->
			<*> OmniVision OV5640 sensor support
  • 编译内核及设备树
linux@ubuntu:$ make -j4 uImage dtbs LOADADDR=0xC2000040
  • 重启测试

将编译好的设备树和内核镜像拷贝到/tftpboot目录下,通过tftp引导内核,系统启动后启动信息中包含如下信息:

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在屏幕的界面上选择“Camera preview”应用进入摄像头预览程序,启动界面后即可看到摄像头实时采集的图像。

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