项目情况：

pmic 的 vcamio_pmu ,vcama2_pmu,vcamd_pmu 这几个供电引脚默认情况下并未打开，项目中一些外设的电源由这几个引脚提供需要系统启动时默认打开

这里有两种方法打开这些供电引脚，第一种在kernel阶段pmic regulator驱动初始化时打开，另外一种在preloader阶段pmic初始化时打开

一．系统启动后在kernel阶段通过 pmic的 regulator 驱动的初始化阶段打开这些引脚的电源

驱动源码路径：
/kernel-4.14/drivers/regulator/mt6358-regulator.c

mt6358_regulator_probe
{
 → for (i = 0; i < regulator_init_data->size; i++)
     rdev = devm_regulator_register(&pdev->dev,
         &(mt_regulators + i)->desc, &config); 
　　//通过devm_regulator_register　注册　regulator
}

regulator_register(struct device *dev,                                                                                                                                     
                     const struct regulator_desc *regulator_desc,
                     const struct regulator_config *config)
{
  → rdev = regulator_register(regulator_desc, config);
      → init_data = regulator_of_get_init_data(dev, regulator_desc, config
                            &rdev->dev.of_node);
          → for_each_available_child_of_node(search, child) {
            ....
              init_data = of_get_regulator_init_data(dev, child, desc);
              //获取设备树信息进行初始化配置regulator
                      
            }
　　　　→　ret = set_machine_constraints(rdev, constraints);
　　　　　　→　if (rdev->constraints->always_on || rdev->constraints->boot_on)
　　　　　　　　　　ret = _regulator_do_enable(rdev);
                //根据　boot_on参数调用　_regulator_do_enable使能regulator从而使对应引
　　　　　　　    //脚输出电压
}

boot_on参数的初始化：

of_get_regulator_init_data(dev, child, desc);
{       
    → of_get_regulation_constraints(node, &init_data, desc);
        → constraints->boot_on = of_property_read_bool(np, "regulator-boot-on");
      //根据设备树节点regulator-boot-on　初始化boot_on属性
}

即在对应的vcamio ,vcamd或者vcama2的设备树节点加入　regulator-boot-on　属性即可在kernel阶段pmic初始化regulators时让其供电

例：
        mt_pmic_vcamd_ldo_reg: ldo_vcamd {
             regulator-name = "vcamd"; 
             regulator-min-microvolt = <900000>;
             regulator-max-microvolt = <1800000>;
             regulator-enable-ramp-delay = <270>;
             regulator-boot-on;　//加入此属性即可
         };

二．preloader阶段　pmic初始化时打开　vcamio, vcamd, vcama2

目录：/vendor/mediatek/proprietary/bootable/bootloader/preloader

preloader目录下涉及的文件：　

  platform/mt6768/src/drivers/inc/mt6358.h
  platform/mt6768/src/drivers/mt6358.c
  platform/mt6768/src/drivers/pmic_initial_setting.c

此处以打开vcamio为例，vcamd 以及vcama2打开的步骤与之相同

1./platform/mt6768/src/drivers/inc/mt6358.h　
　
　1.1．添加对应的id：

　enum {
        　MTK_REGULATOR_VDRAM2,
        　MTK_REGULATOR_LDO_SUPPORT = MTK_REGULATOR_VDRAM2,
        　MTK_REGULATOR_VIO18,
　+       MTK_REGULATOR_VCAMIO,   //添加id
        　.......
 　};

　1.2　添加寄存器，电压参数：

　+　#define vcamio_vol_reg                  PMIC_RG_VCAMIO_VOCAL_ADDR　
　+　#define vcamio_vol_mask                 0
　+　#define vcamio_vol_shift                0
　+　#define vcamio_da_vol_reg               0
　+　#define vcamio_da_vol_mask              0
　+　#define vcamio_da_vol_shift             0
　+　#define vcamio_enable_reg               PMIC_RG_LDO_VCAMIO_EN_ADDR
　+　#define vcamio_enable_shift             PMIC_RG_LDO_VCAMIO_EN_SHIFT
　+　#define vcamio_mode_reg                 0
　+　#define vcamio_mode_shift               0
　+　#define vcamio_trim_reg                 PMIC_RG_VCAMIO_VOTRIM_ADDR
　+　#define vcamio_trim_mask                PMIC_RG_VCAMIO_VOTRIM_MASK
　+　#define vcamio_trim_shift               PMIC_RG_VCAMIO_VOTRIM_SHIFT
　+　#define vcamio_min_uV                   1800000
　+　#define vcamio_max_uV                   1800000
　+　#define vcamio_step_uV                  0
　+　#define vcamio_volt_type                FIXED_REGULAR_VOLTAGE
　+　#define vcamio_stb                      270　

　preloader下的platform/mt6768/src/drivers/inc/upmu_hw.h文件定义了
　PMIC_RG_VCAMIO_VOCAL_ADDR　，PMIC_RG_LDO_VCAMIO_EN_ADDR　这些寄存器
　按照具体需求进行修改对应的寄存器

　vcamio_min_uV　，vcamio_max_uV，vcamio_stb　这三参数的数值可以按照pmic的dtsi文件去填写
　例：
　.kernel-4.14/arch/arm64/boot/dts/mediatek/mt6358.dtsi
　vcamio的节点信息：
        mt_pmic_vcamio_ldo_reg: ldo_vcamio {
             compatible = "regulator-fixed";
             regulator-name = "vcamio";                                                                                                                           
             regulator-min-microvolt = <1800000>;　//vcamio_min_uV
             regulator-max-microvolt = <1800000>;  //vcamio_max_uV
             regulator-enable-ramp-delay = <270>;  //vcamio_stb
         };

　vcamio_volt_type 可以依据kernel阶段vcamio　regulator的定义类型进行赋值
　例：
　/drivers/regulator/mt6358-regulator.c

　MT_REG_FIXED("ldo_vcamio", VCAMIO, PMIC_RG_LDO_VCAMIO_EN_ADDR,
            PMIC_DA_VCAMIO_EN_ADDR,                                                                                                                               
            1800000, MT_LDO_EN),
　MT_REG_FIXED接口定义的是fixed这种类型的所以：　
　#define vcamio_volt_type                FIXED_REGULAR_VOLTAGE

2．　/platform/mt6768/src/drivers/mt6358.c

　2.1　添加电压配置：

+static const unsigned int vcamio_volts[] = {
+       1800000,
+};

+static const int vcamio_idxs[] = {
+       0,
+};

 static struct mt6358_ldo_info ldo_ext_info[] = {
        mt6358_ldo_decl(vdram2_volts, vdram2_idxs),
        mt6358_ldo_decl(vio18_volts, fix_idxs),
+       mt6358_ldo_decl(vcamio_volts, vcamio_idxs),

 };

static struct mt6358_regulator_info mt6358_regu_info[] = {
 #ifdef LDO_SUPPORT
        mt6358_decl(vdram2),
        mt6358_decl(vio18),
+       mt6358_decl(vcamio),
 #endif /*--LDO_SUPPORT--*/
 #endif /*--CFG_MTK_TINYSYS_SSPM_SUPPORT--*/
 };


static struct mtk_regulator mt6358_regulator[] = {
                .id = MTK_REGULATOR_VIO18,
                .reg_ops = &mt6358_regulator_ctrl,
        },
+       {
+               .name = "vcamio",
+               .id = MTK_REGULATOR_VCAMIO,
+               .reg_ops = &mt6358_regulator_ctrl,
+       },


 #endif /*--LDO_SUPPORT--*/
 #endif /*--CFG_MTK_TINYSYS_SSPM_SUPPORT--*/
 };


vcamio_volts，以及vcamio_idxs　可以依据kernel阶段vcamio　regulator的定义类型进行定义
　例：
　/drivers/regulator/mt6358-regulator.c

static const u32 vcamio_voltages[] = {                                                                                                                      
        1800000,
  };
vcamio_volts 与vcamio_voltages定义一致即可，1800000是vcamio_voltages中的第一个元素
index：0所以vcamio_idxs一个元素初始化为0


3．/platform/mt6768/src/drivers/pmic_initial_setting.c

　3.1　pmic初始化阶段添加vcamio　enable操作打开vcamio

void pmic_default_voltage(void)
{
        struct mtk_regulator reg_vproc12 = empty_regulator;
        struct mtk_regulator reg_vgpu = empty_regulator;
        struct mtk_regulator reg_vmodem = empty_regulator;
+
+#ifdef LDO_SUPPORT
+    struct mtk_regulator reg_vcamio = empty_regulator;
+#endif
        int vmodem_vol = 750000, vproc11_vol = 962500, vproc12_vol = 962500,
            vsram_proc11_vol = 1062500, vsram_proc12_vol = 1062500;
 
        .............
 
        if (mtk_regulator_get("vmodem", &reg_vmodem))
                ret |= (1 << MTK_REGULATOR_VMODEM);
-
+#ifdef LDO_SUPPORT
+       if (mtk_regulator_get("vcamio", &reg_vcamio))
+               ret |= (1 << MTK_REGULATOR_VCAMIO);
+    
+#endif
        if (ret) {
                pal_log_err("mtk_regulator_get failed.(0x%x)\n", ret);
                return;
        ..............

        pal_log_info("vproc12 = %d uV\n",mtk_regulator_get_voltage(&reg_vproc12));
        pal_log_info("vgpu = %d uV\n", mtk_regulator_get_voltage(&reg_vgpu));
        pal_log_info("vmodem = %d uV\n", mtk_regulator_get_voltage(&reg_vmodem));
+#ifdef LDO_SUPPORT
+    if (mtk_regulator_enable(&reg_vcamio, 1))
+               ret |= (1 << MTK_REGULATOR_VCAMIO); //打开vcamio

+#endif
}