Android 相机启动流程笔记

和你一起终身学 习，这里是程序员Android

经典好文推荐，通过阅读本文，您将收获以下知识点:

一、Camera 框架介绍：

Camera的框架分为Kernel部分和hal部分，其中kernel部分主要有两块：

image sensor driver，负责具体型号的sensor的id检测，上电，以及在preview、capture、初始化、3A等等功能设定时的寄存器配置；
isp driver，通过DMA将sensor数据流上传；

HAL层部分主要有三部分组成：

imageio，主要负责数据buffer上传的pipe；
drv，包含imgsensor和isp的hal层控制；
feature io，包含各种3A等性能配置；

这篇内容主要介绍开机过程中search sensor以及上电流程等内容。

二、Camera 启动流程

1、CameraService是在开机时启动的，启动后进行searchSensor的操作，会search系统有多少camera，开机时的search操作，只进行camera支持数量的遍历，以及sensor ID的读取操作，如下是hal部分的ASTAH绘制调用流程图，对应的接口的文件路径：

HalSensorList：
vendor/mediatek/proprietary/hardware/mtkcam/drv/src/sensor/common/v1/HalSensorList.enumList.cpp
vendor/mediatek/proprietary/hardware/mtkcam/drv/src/sensor/common/v1/HalSensorList.cpp
SeninfDrv：
vendor/mediatek/proprietary/hardware/mtkcam/drv/src/sensor/mt6765/seninf_drv.cpp
SensorDrv：
vendor/mediatek/proprietary/hardware/mtkcam/drv/src/sensor/common/v1/imgsensor_drv.cpp

(1) 这里先看enumerateSensor_Locked完成的工作，直接看代码：

go 复制代码

MUINT HalSensorList::searchSensors()
{
    Mutex::Autolock _l(mEnumSensorMutex);
    MY_LOGD("searchSensors");
    return  enumerateSensor_Locked();
}

MUINT HalSensorList::enumerateSensor_Locked()
{
    SensorDrv *const pSensorDrv = SensorDrv::get();
    SeninfDrv *const pSeninfDrv = SeninfDrv::createInstance();
    //初始化seninf,配置ISP相关内容
    pSeninfDrv->init();

    //将所有的clk全部打开
    pSeninfDrv->setAllMclkOnOff(ISP_DRIVING_8MA, TRUE);

    pSensorDrv->init();
    for (MUINT i = IMGSENSOR_SENSOR_IDX_MIN_NUM; i <= max_index_of_camera; i++) {
        if((ret = pSensorDrv->searchSensor((IMGSENSOR_SENSOR_IDX)i)) == SENSOR_NO_ERROR){
            //query sensorinfo
           querySensorDrvInfo((IMGSENSOR_SENSOR_IDX)i);
           //fill in metadata
           buildSensorMetadata((IMGSENSOR_SENSOR_IDX)i);
           pSensorInfo = pSensorDrv->getSensorInfo((IMGSENSOR_SENSOR_IDX)i);
           addAndInitSensorEnumInfo_Locked(
                (IMGSENSOR_SENSOR_IDX)i,
                mapToSensorType(pSensorInfo->GetType()),
                pSensorInfo->getDrvMacroName());
        }
    }     
}

(２) 下面主要看下searchSensor的流程，这里有去获取sensorList的内容：

go 复制代码

MINT32 ImgSensorDrv::searchSensor(IMGSENSOR_SENSOR_IDX sensorIdx)
{
    GetSensorInitFuncList(&pSensorInitFunc);

    featureControl(sensorIdx, SENSOR_FEATURE_SET_DRIVER, (MUINT8 *)&idx, &featureParaLen);

    NSFeature::SensorInfoBase* pSensorInfo = pSensorInitFunc[idx].pSensorInfo;
}

GetSensorInitFuncList是获取到配置的sensorList的内容，此sensorList需要与kernel层配置的一致，不一致的话在打开camera时会出现异常：

文件位置：
vendor/mediatek/proprietary/custom/mt6765/hal/imgsensor_src/sensorlist.cpp

go 复制代码

MSDK_SENSOR_INIT_FUNCTION_STRUCT SensorList[] =
{
#if defined(IMX486_MIPI_RAW)
    RAW_INFO(IMX486_SENSOR_ID, SENSOR_DRVNAME_IMX486_MIPI_RAW, CAM_CALGetCalData),
#endif
//.....
}

UINT32 GetSensorInitFuncList(MSDK_SENSOR_INIT_FUNCTION_STRUCT **ppSensorList)
{
    if (NULL == ppSensorList) {
        ALOGE("ERROR: NULL pSensorList\n");
        return MHAL_UNKNOWN_ERROR;
    }
    *ppSensorList = &SensorList[0];
    return MHAL_NO_ERROR;
}

对应的MSDK_SENSOR_INIT_FUNCTION_STRUCT的结构体如下：

go 复制代码

typedef struct
{
    MUINT32 sensorType;
    MUINT32 SensorId;
    MUINT8  drvname[32];
    NSFeature::SensorInfoBase* pSensorInfo;
    MUINT32 (*getCameraIndexMgr)(CAMERA_DATA_TYPE_ENUM CameraDataType, MVOID *pDataBuf, MUINT32 size);
    MUINT32 (*getCameraCalData)(UINT32* pGetSensorCalData);
} MSDK_SENSOR_INIT_FUNCTION_STRUCT, *PMSDK_SENSOR_INIT_FUNCTION_STRUCT;

(3) featureControl的setDriver流程：

文件位置：
vendor/mediatek/proprietary/hardware/mtkcam/drv/src/sensor/common/v1/imgsensor_drv.cpp

go 复制代码

MINT32  ImgSensorDrv::featureControl(
    IMGSENSOR_SENSOR_IDX sensorIdx,
    ACDK_SENSOR_FEATURE_ENUM FeatureId,
    MUINT8 *pFeaturePara,
    MUINT32 *pFeatureParaLen
)
{
    //结构ACDK_SENSOR_FEATURECONTROL_STRUCT和kernel中一致
    featureCtrl.InvokeCamera = sensorIdx;
    featureCtrl.FeatureId = FeatureId;//SENSOR_FEATURE_SET_DRIVER
    featureCtrl.pFeaturePara = pFeaturePara;
    featureCtrl.pFeatureParaLen = pFeatureParaLen;

    if (ioctl(m_fdSensor, KDIMGSENSORIOC_X_FEATURECONCTROL , &featureCtrl) < 0) {
        LOG_ERR("[featureControl] Err-ctrlCode (%s)", strerror(errno));
        return -errno;
    }

    return SENSOR_NO_ERROR;
}

三、kernel 启动流程

先来看整体的框架图如下：

1、set clock 设置时钟

go 复制代码

static long imgsensor_ioctl(
    struct file *a_pstFile,
    unsigned int a_u4Command,
    unsigned long a_u4Param)
{
    case KDIMGSENSORIOC_X_SET_MCLK_PLL:
        i4RetValue = imgsensor_clk_set(
            &pgimgsensor->clk,
            (struct ACDK_SENSOR_MCLK_STRUCT *)pBuff);
        break;
        //......
}

int imgsensor_clk_set(
    struct IMGSENSOR_CLK *pclk, struct ACDK_SENSOR_MCLK_STRUCT *pmclk)
{
    if (pmclk->on) {
        clk_prepare_enable(pclk->imgsensor_ccf[mclk_index])
        ret = clk_set_parent(
            pclk->imgsensor_ccf[pmclk->TG],
            pclk->imgsensor_ccf[mclk_index]);
    } else {
        clk_disable_unprepare(pclk->imgsensor_ccf[mclk_index]);
    }
}

2、set driver

go 复制代码

static long imgsensor_ioctl(
    struct file *a_pstFile,
    unsigned int a_u4Command,
    unsigned long a_u4Param) 
{
    case KDIMGSENSORIOC_X_FEATURECONCTROL:
        i4RetValue = adopt_CAMERA_HW_FeatureControl(pBuff);
        break;
        //......
}

static inline int adopt_CAMERA_HW_FeatureControl(void *pBuf)
{
    /* copy from user */
    switch (pFeatureCtrl->FeatureId) {
        case SENSOR_FEATURE_SET_DRIVER:
        {
            MINT32 drv_idx;

            psensor->inst.sensor_idx = pFeatureCtrl->InvokeCamera;
            drv_idx = imgsensor_set_driver(psensor);

            memcpy(pFeaturePara, &drv_idx, FeatureParaLen);
            break;
        }
    }
}

遍历CONFIG_CUSTOM_KERNEL_IMGSENSOR的内容，然后看sensorList是否对应，并获取对应的下标，调用imgsensor_check_is_alive进行上下电并读取ID 的操作：

go 复制代码

struct IMGSENSOR_INIT_FUNC_LIST kdSensorList[MAX_NUM_OF_SUPPORT_SENSOR] = {
#if defined(XXXXXX_MIPI_RAW)
        {XXXXXX_SENSOR_ID,
        SENSOR_DRVNAME_XXXXXX_MIPI_RAW,
        XXXXXX_MIPI_RAW_SensorInit},
#endif
    //......
}

int imgsensor_set_driver(struct IMGSENSOR_SENSOR *psensor)
{
    struct IMGSENSOR_SENSOR_INST    *psensor_inst = &psensor->inst;
    struct IMGSENSOR_INIT_FUNC_LIST *pSensorList  = kdSensorList;
    //获取config的size
    char *sensor_configs = STRINGIZE(CONFIG_CUSTOM_KERNEL_IMGSENSOR);
    imgsensor_i2c_init(&psensor_inst->i2c_cfg,
    imgsensor_custom_config[psensor->inst.sensor_idx].i2c_dev);

    memcpy(psensor_list_config, sensor_configs+1, strlen(sensor_configs)-2);
    //对应config字符串进行按空格进行拆解
    driver_name = strsep(&psensor_list_config, " \0");

    while (driver_name != NULL) {
        for (j = 0; j < MAX_NUM_OF_SUPPORT_SENSOR; j++) {
            //判断对应的init函数是否存在
            if (pSensorList[j].init == NULL)
                break;
            else if (!strcmp(driver_name, pSensorList[j].name)) {
                //如果在config中和sensorlist中同时有定义进行赋值
                orderedSearchList[i++] = j;
                break;
            }
        }
        driver_name = strsep(&psensor_list_config, " \0");
    }

    for (i = 0; i < MAX_NUM_OF_SUPPORT_SENSOR; i++) {
        //上面获取到的sensorlist的下标
        drv_idx = orderedSearchList[i];
        if (pSensorList[drv_idx].init) {
            //调用对应驱动的init函数
            pSensorList[drv_idx].init(&psensor->pfunc);
            if (psensor->pfunc) {
                psensor_inst->psensor_name =
                    (char *)pSensorList[drv_idx].name;
                    //到这里是重点，进行上电读取ID的操作
                if (!imgsensor_check_is_alive(psensor)) {
                    ret = drv_idx;
                }
            }
        }
    }
}

下面看对应的上下电以及读取ID的操作：

go 复制代码

static inline int imgsensor_check_is_alive(struct IMGSENSOR_SENSOR *psensor)
{
    struct IMGSENSOR_SENSOR_INST  *psensor_inst = &psensor->inst;
    //上电
    err = imgsensor_hw_power(&pgimgsensor->hw,
                psensor,
                psensor_inst->psensor_name,
                IMGSENSOR_HW_POWER_STATUS_ON);
    //读取ID
    imgsensor_sensor_feature_control(
            psensor,
            SENSOR_FEATURE_CHECK_SENSOR_ID,
            (MUINT8 *)&sensorID,
            &retLen);

    if (sensorID == 0 || sensorID == 0xFFFFFFFF) {
        pr_info("Fail to get sensor ID %x\n", sensorID);
        err = ERROR_SENSOR_CONNECT_FAIL;
    } else {
        pr_info(" Sensor found ID = 0x%x\n", sensorID);
        err = ERROR_NONE;
    }
    //下电
    imgsensor_hw_power(&pgimgsensor->hw,
        psensor,
        psensor_inst->psensor_name,
        IMGSENSOR_HW_POWER_STATUS_OFF);

    return err ? -EIO:err;
}

3、上电相关

上电时序配置：

go 复制代码

struct IMGSENSOR_HW_POWER_INFO {
    enum IMGSENSOR_HW_PIN       pin;
    enum IMGSENSOR_HW_PIN_STATE pin_state_on;
    u32  pin_on_delay;
    enum IMGSENSOR_HW_PIN_STATE pin_state_off;
    u32  pin_off_delay;
};

struct IMGSENSOR_HW_POWER_SEQ sensor_power_sequence[] = {
    //......
    #if defined(XXXXXX_MIPI_RAW)
        {
            SENSOR_DRVNAME_XXXXXX_MIPI_RAW,
            {
                {RST, Vol_Low, 0},
                {DVDD, Vol_1100, 1},
                {AVDD, Vol_2800, 1},
                {DOVDD, Vol_1800, 1},
                {RST, Vol_High, 1},
                {SensorMCLK, Vol_High, 0},
            },
        },
    #endif
}

对应的控制的流程如下：

go 复制代码

static enum IMGSENSOR_RETURN imgsensor_hw_power_sequence(
    struct IMGSENSOR_HW             *phw,
    enum   IMGSENSOR_SENSOR_IDX      sensor_idx,
    enum   IMGSENSOR_HW_POWER_STATUS pwr_status,
    struct IMGSENSOR_HW_POWER_SEQ   *ppower_sequence,
    char *pcurr_idx)
{
    ppwr_info = ppwr_seq->pwr_info;
    // 上电
    while (ppwr_info->pin != IMGSENSOR_HW_PIN_NONE &&
        ppwr_info < ppwr_seq->pwr_info + IMGSENSOR_HW_POWER_INFO_MAX) {

        if (pwr_status == IMGSENSOR_HW_POWER_STATUS_ON &&
           ppwr_info->pin != IMGSENSOR_HW_PIN_UNDEF) {
            pdev = phw->pdev[psensor_pwr->id[ppwr_info->pin]];
            if (pdev->set != NULL)
                //调用GPIO或者regulator的set 电压操作，这里的pdev在imgsensor_probe中已经设置
                pdev->set( 
                    pdev->pinstance,
                    sensor_idx,
                    ppwr_info->pin,
                    ppwr_info->pin_state_on);

            mdelay(ppwr_info->pin_on_delay);
        }
        // 从上到下依次上电
        ppwr_info++;
        pin_cnt++;
    }

    // 下电操作
    if (pwr_status == IMGSENSOR_HW_POWER_STATUS_OFF) {
        while (pin_cnt) {
            //从下到上依次下电
            ppwr_info--;
            pin_cnt--;

            if (ppwr_info->pin != IMGSENSOR_HW_PIN_UNDEF) {
                pdev =
                    phw->pdev[psensor_pwr->id[ppwr_info->pin]];
                mdelay(ppwr_info->pin_on_delay);

                if (pdev->set != NULL)
                    pdev->set(
                        pdev->pinstance,
                        sensor_idx,
                        ppwr_info->pin,
                        ppwr_info->pin_state_off);
            }
        }
    }

    /* wait for power stable */
    if (pwr_status == IMGSENSOR_HW_POWER_STATUS_ON)
        mdelay(5);
    return IMGSENSOR_RETURN_SUCCESS;
}

四、总结

通过上面的代码流程，可以知道上开机时，camera模块先会将所有的MCLK打开，然后对依次对对应的sensor进行上电，读取ID(判断I2C是否正常通讯)。这部分调试过程中遇到的问题总结如下：

1、ID读取不到，I2C不通

检查上电时序，３项电压（AVDD/DVDD/IOVDD）是否正确；
I2C地址及通道设置是否正确；
检查cfg_setting_imgsensor.cpp中MCLK和HW链接配置是否正确；

2、Camera 启动时间过长

检查Sensor上电时序要求的延时，是否有偏长的情况；
去掉多余的I2C地址，因为大部分驱动会多添加一些地址；
OTP的加载调整到每次开机时第一次打开加载，之后不加载；
sensorInit如果时间过长，可以调节I2C speed(400->1000)；

3、preview 阶段耗时

检查streamOn/Off的耗时；
preview_init是否有较长时间的耗时
以及延时操作使用mdelay代替msleep；
pre_delay_frame/cap_delay_frame丢帧操作是否合适；

4、低电流、功耗相关问题

检查电压是否都有下电成功，防止漏电；
对于共pin的sensor，在操作时是否有做好workaround；
将I2C寄存器单个读写，调整为连续读写的方式也有一定优化；
sensor的PIN是否有被其他模块占用，异常操作的行为；

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