Camera | 12.瑞芯微摄像头自动焦距马达驱动移植

本为你主要讲解如何让摄像头ov13850支持自动对焦功能。

摄像头的对角主要通过VCM马达驱动芯片DW9714来实现的。

一、环境

soc  : rk3568   
board: EVB1-DDR4-V10
软  件：Android 11
Linux：4.19.232
Camera:ov13850

二、DW9714

1.DW9714简介

DW9714专为自动对焦和光学变焦照相手机、数码相机和摄像机应用而设计，

由韩国动运国际有限公司（Dongwoon ）设计生产。

工作电压可达3.6V。

DAC通过I2C串行接口控制，该接口以高达400kHz的时钟速率操作DAC。

DW9714集成了上电复位电路、掉电功能和精确匹配的检测电阻。

上电复位电路确保当电源上电时，DAC输出为0V，直到发生有效的写位值。它具有断电功能，可将器件的电流消耗降至最大1uA。

2. 特征

用于自动对焦的VCM驱动程序
关机功能：XSD=低电平有效
VCM的10位分辨率电流吸收为120mA
I2C串行接口（可用于1.8V输入电平）
集成电流检测电阻
保证所有代码的单调性
低至0.5uA（典型值）
上电复位
掉电功能
2.3V至3.6V操作

3. 模块图

4. 引脚

序号	Pin Name	I/O Description Note
1	IOUT	Output current sink
2	VSS	接地
3	VDD	供电
4	SDA	I2C interface input (DATA)
5	SCL	I2C interface input/output (CLOCK)
6	XSD(1)	关机模式，低有效

5. 参考电路

6. i2c时序

由以下时序可以看到，vcm9714利用I2C接口通信时，每次读/写，直接传输2个字节的数据，通信之前，不需要发送内部寄存器地址。

7. 寄存器格式

引脚	说明
PD	Power down mode
	1: Power down mode (active high)
	0: Normal operation mode
FLAG	写操作时必须置为低
D[9:0]	Data input
	输出电流 = (D[9:0]/1023) X 120mA
	最大电流 = 120mA +/- 5%
S[3:2]	Codes per step
	0： 0 (no SRC) – direct driving
	1： 1
	2 ：2
	3： 4
S[1:0]	步进周期
	0： 81
	1： 162
	2： 324
	3： 648

三、驱动移植

vcm9714与rk3568连接图：

设备树：

@arch/arm64/boot/dts/rockchip/rk3568-evb1-ddr4-v10.dtsi
560     dw9714: dw9714@c {
561         compatible = "dongwoon,dw9714";
562         status = "okay";
563         reg = <0x0c>;
564         rockchip,camera-module-index = <0>;
565         rockchip,vcm-start-current = <10>;
566         rockchip,vcm-rated-current = <85>;
567         rockchip,vcm-step-mode = <5>;
568         rockchip,camera-module-facing = "back";
569     };
570 
571     ov13850: ov13850@10 {……
584         lens-focus = <&dw9714>;……                                                                                                                                                                                      
591     };

其中，下面这两个属性，必须要和对应的的摄像头ov13850信息保持一致

rockchip,camera-module-index = <0>;
rockchip,camera-module-facing = "back";

摄像头支持的马达驱动信息通过以下属性关联

lens-focus = <&dw9714>;

Makefile

@kernel\drivers\media\i2c\Makefile
obj-$(CONFIG_VIDEO_DW9714)  += dw9714.o

Kconfig

@kernel\drivers\media\i2c\Kconfig
config VIDEO_DW9714tristate "DW9714 lens voice coil support"depends on I2C && VIDEO_V4L2 && MEDIA_CONTROLLERdepends on VIDEO_V4L2_SUBDEV_API---help---This is a driver for the DW9714 camera lens voice coil.DW9714 is a 10 bit DAC with 120mA output current sinkcapability. This is designed for linear control ofvoice coil motors, controlled via I2C serial interface.

支持该驱动：

@ arch/arm64/configs/rockchip_defconfig 
572 CONFIG_VIDEO_DW9714=y

驱动：

rk_android11.0_sdk_220718\kernel\drivers\media\i2c\dw9714.c

四、调试信息

1. 启动的驱动log

	[    0.800799] vm149c 4-000c: probing...[    0.800820] vm149c 4-000c: driver version: 00.01.00[    0.800834] vm149c 4-000c: could not get module rockchip,vcm-max-current from dts![    0.800847] vm149c 4-000c: could not get module rockchip,vcm-start-current from dts![    0.800860] vm149c 4-000c: could not get module rockchip,vcm-rated-current from dts![    0.800872] vm149c 4-000c: could not get module rockchip,vcm-step-mode from dts![    0.800907] vm149c 4-000c: probing successful

2. 查看拓扑结构

media-ctl -p……………- entity 74: m00_b_ov13850 4-0010 (1 pad, 1 link)type V4L2 subdev subtype Sensordevice node name /dev/v4l-subdev4pad0: Source[fmt:SBGGR10/4224x3136]-> "rockchip-csi2-dphy0":0 []- entity 78: m00_b_gpio-flash (0 pad, 0 link)type V4L2 subdev subtype Flashdevice node name /dev/v4l-subdev5- entity 79: m00_b_dw9714 4-000c (0 pad, 0 link)type V4L2 subdev subtype Lensdevice node name /dev/v4l-subdev6

四、驱动分析

vcm9714驱动比较简单，基于i2c总线，

核心就是要注册基于v4l2的subdev，

提供给用户层调用的核心回调函数如下：

获取并设置当前马达的pos

static const struct v4l2_ctrl_ops dw9714_vcm_ctrl_ops = {.g_volatile_ctrl = dw9714_get_ctrl,.s_ctrl = dw9714_set_ctrl,
};
static int dw9714_init_controls(struct dw9714_device *dev_vcm)
{struct v4l2_ctrl_handler *hdl = &dev_vcm->ctrls_vcm;const struct v4l2_ctrl_ops *ops = &dw9714_vcm_ctrl_ops;v4l2_ctrl_handler_init(hdl, 1);v4l2_ctrl_new_std(hdl, ops, V4L2_CID_FOCUS_ABSOLUTE,0, VCMDRV_MAX_LOG, 1, VCMDRV_MAX_LOG);……
}

static const struct v4l2_subdev_core_ops dw9714_core_ops = {.ioctl = dw9714_ioctl,
};static const struct v4l2_subdev_ops dw9714_ops = {.core = &dw9714_core_ops,
};static int dw9714_probe(struct i2c_client *client,const struct i2c_device_id *id)
{v4l2_i2c_subdev_init(&dw9714_dev->sd, client, &dw9714_ops);
}