android2.3.4----5.ov9650驱动分析--附clk设置

原文地址：http://blog.chinaunix.net/uid-26009923-id-4050452.html

一. V4L2的模块的初始化过程
module_init(videodev_init)
    --> videodev_init
在drivers/media/video/v4l2-dev.c中

static int __init videodev_init(void)
{
    dev_t dev = MKDEV(VIDEO_MAJOR, 0);  //请求设备号VIDEO_MAJOR=81
    register_chrdev_region(dev, VIDEO_NUM_DEVICES, VIDEO_NAME);
    class_register(&video_class);      //注册一个class
}

v4l2这个模块好像没有干什么事.
二. s3c_fimc_driver的初始化过程
1.  
module_init(s3c_fimc_register);
    -->s3c_fimc_register
在drivers/media/video/samsung/fimc/s3c_fimc_core.c中

static int s3c_fimc_register(void)
{
    platform_driver_register(&s3c_fimc_driver);
}

platform_driver的结构如下:

static struct platform_driver s3c_fimc_driver = {
    .probe     = s3c_fimc_probe,
    .remove    = s3c_fimc_remove,
    .suspend   = s3c_fimc_suspend,
    .resume    = s3c_fimc_resume,
    .driver    = {
        .name  = "s3c-fimc",
        .owner = THIS_MODULE,
    },
};

先看一下s3cfimc的设备
在arch/arm/plat-samsun/dev-fimc0.c中

static struct s3c_platform_fimc default_fimc0_data __initdata = {
    .srclk_name    = "hclk",
    .clk_name    = "fimc",
    .clockrate    = 133000000,
    .line_length    = 720,
    .nr_frames    = 4,
    .shared_io    = 0,
};

下一步进入probe过程

static int s3c_fimc_probe(struct platform_device *pdev)
{
    struct s3c_platform_fimc *pdata;
    struct s3c_fimc_control *ctrl;
    struct clk *srclk;
    int ret;

    ctrl = s3c_fimc_register_controller(pdev);     //

    pdata = to_fimc_plat(&pdev->dev);
    if (pdata->cfg_gpio)
        pdata->cfg_gpio(pdev);                     //gpio的初始化调用s3c_fimc0_cfg_gpio

    srclk = clk_get(&pdev->dev, pdata->srclk_name);      //获取srclk_name
    ctrl->clock = clk_get(&pdev->dev, pdata->clk_name);  //获取fimc_clk并enable
    clk_enable(ctrl->clock);
    //向v4l2注册TYPE_GRABBER即图像采集设备
    ret = video_register_device(ctrl->vd, VFL_TYPE_GRABBER, ctrl->id);    //VFL_TYPE_GRABBER 图像采集设备
    return 0;
}

简要说明一下
module_init(s3c_fimc_register);
    -->s3c_fimc_register
        --> s3c_fimc_probe
            --> s3c_fimc_register_controller

struct s3c_fimc_control *s3c_fimc_register_controller(struct platform_device *pdev)
{
    struct s3c_platform_fimc *pdata;
    struct s3c_fimc_control *ctrl;
    int id = pdev->id;
    pdata = to_fimc_plat(&pdev->dev);
    ctrl = &s3c_fimc.ctrl[id];
    ctrl->id = id;
    ctrl->dev = &pdev->dev;
    ctrl->vd = &s3c_fimc_video_device[id]; //这句代码很关键

    return ctrl;
}

看一下s3c_fimc_video_deivce的定义就知道了:

struct video_device s3c_fimc_video_device[S3C_FIMC_MAX_CTRLS] = {
    [0] = {
        .vfl_type = VID_TYPE_OVERLAY | VID_TYPE_CAPTURE | VID_TYPE_CLIPPING | VID_TYPE_SCALES,
        .fops = &s3c_fimc_fops,
        .ioctl_ops = &s3c_fimc_v4l2_ops,
        .release = s3c_fimc_vdev_release,
        .name = "sc3_video0",
    },
};

这实际上是注册了一两套函数指针,s3c_fimc_fops与s3c_fimc_v4l2_ops
以后就可以通过vl42_fops来操作fimc设备了

static const struct file_operations v4l2_fops = {
    .owner = THIS_MODULE,
    .read = v4l2_read,
    .write = v4l2_write,
    .open = v4l2_open,
    .get_unmapped_area = v4l2_get_unmapped_area,
    .mmap = v4l2_mmap,
    .unlocked_ioctl = v4l2_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl = v4l2_compat_ioctl32,
#endif
    .release = v4l2_release,
    .poll = v4l2_poll,
    .llseek = no_llseek,
};

---

三. ov965x_i2c_driver的初始化过程
1. 硬件的定义
ov9650的硬件定义在arch/arm/mach-s3c64xx/mach-smdk6410.c中

在arch/arm/mach-s3c64xx/mach-smdk6410.c中
static struct i2c_board_info i2c_devs0[] __initdata = {
    { I2C_BOARD_INFO("ov965x", 0x30), }, // gjl
};
//这个定义会被smdk6410_machine_init调用,添加到I2C的链表中
在arch/arm/mach-s3c64xx/mach-smdk6410.c中
static void __init smdk6410_machine_init(void)
{
    i2c_register_board_info(0, i2c_devs0, ARRAY_SIZE(i2c_devs0));
}

2. ov9650驱动初始化
ov9650的驱动在drivers/media/video/samsung/fimc/ov965x.c中
module_init(ov965x_init)
    --> ov965x_init   >> i2c_add_driver

static __init int ov965x_init(void)
{
    return i2c_add_driver(&ov965x_i2c_driver);
}

这个i2c_add_driver也是调用了driver_register,最终会调用ov965x的probe函数

在include/linux/i2c.h中
static inline int i2c_add_driver(struct i2c_driver *driver)
{
    return i2c_register_driver(THIS_MODULE, driver);
}
//driver_register中会调用具体函数的probe
在drivers/i2c/i2c-core.c中
int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
{
    res = driver_register(&driver->driver);
    if (res)
        return res;
}

3. ov9650的probe函数
module_init(ov965x_init)
    --> ov965x_init   >> i2c_add_driver
        --> ov965x_probe
drivers/media/video/samsung/fimc/ov965x.c

static int ov965x_probe(struct i2c_client *c, const struct i2c_device_id *id)
{
    int i;
    int ret;
    ov965x_data.client = c;
    s3c_fimc_register_camera(&ov965x_data);     //3.1向s3c-fimc注册camera
    for (i = 0; i < OV965X_INIT_REGS; i++) {     //通过I2C向ov965x中的寄存器写入配置信息
        ret = i2c_smbus_write_byte_data(c, OV965X_init_reg[i].subaddr, OV965X_init_reg[i].value);
    } //在.config 中定义了CONFIG_OV965X_QVGA=y,所以这儿是QVGA(320*240)模式
    return 0;
}

3.1 向s3c_fimc_driver注册camera
先看一下s3c_fimc_camera是个什么东东

static struct s3c_fimc_camera ov965x_data = {
    .id         = CONFIG_VIDEO_FIMC_CAM_CH,
    .type        = CAM_TYPE_ITU,
    .mode        = ITU_601_YCBCR422_8BIT,
    .order422    = CAM_ORDER422_8BIT_YCBYCR,//YCRYCB,
    .clockrate    = 24000000,
    .width        = 640,//800,
    .height        = 480,//600,
    .offset        = {
        .h1 = 0,
        .h2 = 0,
        .v1 = 0,
        .v2 = 0,
    },
    .polarity    = {
        .pclk    = 0,
        .vsync    = 1,
        .href    = 0,
        .hsync    = 0,
    },
    .initialized    = 0,
};

module_init(ov965x_init)
    --> ov965x_init   >> i2c_add_driver
        --> ov965x_probe
                --> s3c_fimc_register_camera >>>s3c_fimc_register_camera(&ov965x_data);
在drivers/media/video/samsung/fimc/s3c_fimc_core.c中

void s3c_fimc_register_camera(struct s3c_fimc_camera *cam)
{
    int i;
    static int once=0;
    //通过索引全局数组s3c_fimc_camer就可以找到ov9650的控制指针
    s3c_fimc.camera[cam->id] = cam;

    for (i = 0; i < S3C_FIMC_MAX_CTRLS; i++) {
        s3c_fimc.ctrl[i].in_cam = s3c_fimc.camera[cam->id];
    }

    //设置摄像头的clock: disable, set, enable
    clk_disable(s3c_fimc.cam_clock);
    clk_set_rate(s3c_fimc.cam_clock, cam->clockrate);
    clk_enable(s3c_fimc.cam_clock);

    s3c_fimc_reset_camera();                     //3.1.1复位后,设置的clock就起作用了
    if((once==0)&&(cam->client!=0))
    {
        for (i = 0; i < S3C_FIMC_MAX_CTRLS; i++)
            s3c_fimc_init_camera(&s3c_fimc.ctrl[i]);  //3.1.2复位后,设置的clock就起作用了
        once = 1;
    }
}

3.1.1 复位camera
module_init(ov965x_init)
    --> ov965x_init   >> i2c_add_driver
        --> ov965x_probe
                --> s3c_fimc_register_camera >>>s3c_fimc_register_camera(&ov965x_data);
                    --> s3c_fimc_reset_camera

void s3c_fimc_reset_camera(void)
{
    //对寄存器一个ioremap然后直接使用
    void __iomem *regs = ioremap(S3C64XX_PA_FIMC, SZ_4K);
    u32 cfg = readl(regs + S3C_CIGCTRL);
    cfg |= S3C_CIGCTRL_CAMRST;
    writel(cfg, regs + S3C_CIGCTRL);
    mdelay(200);

    cfg = readl(regs + S3C_CIGCTRL);
    cfg &= ~S3C_CIGCTRL_CAMRST;
    writel(cfg, regs + S3C_CIGCTRL);
    udelay(2000);
    //使用完后iounmap
    iounmap(regs);
}

3.1.2 将初始化标志设为1
module_init(ov965x_init)
    --> ov965x_init   >> i2c_add_driver
        --> ov965x_probe
                --> s3c_fimc_register_camera >>>s3c_fimc_register_camera(&ov965x_data);
                    --> s3c_fimc_init_camera   

void s3c_fimc_init_camera(struct s3c_fimc_control *ctrl)
{
    struct s3c_fimc_camera *cam = ctrl->in_cam;
    if (cam && cam->id != S3C_FIMC_TPID && !cam->initialized) {
        cam->initialized = 1;
    }
}

4. 总结
初始化完成了,总结一下
    ov9650 --> s3c_fimc_core注册
           s3c_fimc_core --> v4l2注册
这样上层就可以调用v4l2-->s3c_fimc_core来间接的控制ov9650了.

---

附录一. camera 的clk设置
1. 获取clk的结构体
在drivers/media/video/samsung/fimc/s3c_fimc_core.c中
s3c_fimc_probe
--> s3c_fimc_init_global

static int s3c_fimc_init_global(struct platform_device *pdev)
{
    s3c_fimc.cam_clock = clk_get(&pdev->dev, "sclk_cam");
}

其中sclk_cam是定义在arch/arm/mach-s3c64xx/clock.c中

static struct clk init_clocks[] =
{
    .name = "sclk_cam",
    .id = -1,
    .parent = &clk_h2,
    .enable = s3c64xx_sclk_ctrl,
    .ctrlbit = S3C_CLKCON_SCLK_CAM,
    .ops = &(struct clk_ops) {
        .set_rate = s3c64xx_setrate_sclk_cam,
    }
}

2.clk的初始化
module_init(ov965x_init)
    --> ov965x_init   >> i2c_add_driver
        --> ov965x_probe
                --> s3c_fimc_register_camera
在drivers/media/video/samsung/fimc/s3c_fimc_core.c中

void s3c_fimc_register_camera(struct s3c_fimc_camera *cam)
{
    //设置摄像头的clock频率为24M
    clk_disable(s3c_fimc.cam_clock);
    //cam->clockrate是在ov965x_data中设定的数值
    clk_set_rate(s3c_fimc.cam_clock, cam->clockrate);   //cam->clockrate=24000000=24M
    clk_enable(s3c_fimc.cam_clock);
}

2.1 clk_disable
module_init(ov965x_init)
    --> ov965x_init   >> i2c_add_driver
        --> ov965x_probe
                --> s3c_fimc_register_camera
                        --> clock_disable
在arch/arm/plat-samsung/clock.c中

void clk_disable(struct clk *clk)
{
    spin_lock(&clocks_lock);
    (clk->enable)(clk, 0);   //这个enabel也就是调用"sclk_cam"的enable
    spin_unlock(&clocks_lock);
    clk_disable(clk->parent);
}

module_init(ov965x_init)
    --> ov965x_init   >> i2c_add_driver
        --> ov965x_probe
                --> s3c_fimc_register_camera
                        --> clock_disable

int s3c64xx_sclk_ctrl(struct clk *clk, int enable)
{
    //enable=0或1控制打开或关闭
    return s3c64xx_gate(S3C_SCLK_GATE, clk, enable);
}

2.2 clk_set_rate
module_init(ov965x_init)
    --> ov965x_init   >> i2c_add_driver
        --> ov965x_probe
                --> s3c_fimc_register_camera
                        -->clk_set_rate
在arch/arm/plat-samsung/clock.c中

int clk_set_rate(struct clk *clk, unsigned long rate)
{
    spin_lock(&clocks_lock);
    //这个clk_set_rate也就是调用"sclk_cam"的clk_set_rate
    ret = (clk->ops->set_rate)(clk, rate);
    spin_unlock(&clocks_lock);
}

2.2.1设置camra的clk是24M
module_init(ov965x_init)
    --> ov965x_init   >> i2c_add_driver
        --> ov965x_probe
                --> s3c_fimc_register_camera
                        -->clk_set_rate
                            --> s3c64xx_setrate_sclk_cam
在arch/arm/mach-s3c64xx/clock.c中

static int s3c64xx_setrate_sclk_cam(struct clk *clk, unsigned long rate)
{
    u32 shift = 20;
    u32 cam_div, cfg;
    unsigned long src_clk = clk_get_rate(clk->parent); //parent=266M

    cam_div = src_clk / rate;   //cam_div=266M/24M=11
    // 手册P147 CLK_DIV0  0x7E00_F020 
    // CAM_RATIO [23:20] --> CAM clock divider ratio 
    // CLKCAM = HCLKX2 / (CAM_RATIO + 1)
    cfg = __raw_readl(S3C_CLK_DIV0);
    cfg &= ~(0xf << shift);
    cfg |= ((cam_div - 1) << shift);
    __raw_writel(cfg, S3C_CLK_DIV0);
    return 0;
}