void kmain(void)

{

    /* 早期初始化线程池的上下文，包括运行队列、线程链表的建立等， lk架构支持多线程，但是此阶段只有一个cpu处于online，所以也只有一条代码执行路径. */

    Thread＿init＿early();

    /* 架构初始化，包括DRAM,MMU初始化使能，使能协处理器， preloader运行在ISRAM，属于物理地址，而lk运行在DRAM，可以选择开启MMU或者关闭，开启MMU可以加速lk的加载过程. */

    Arch＿early＿init();

   /* 平台硬件早期初始化，包括irq、timer，wdt，uart，led，pmic，i2c，gpio等, 初始化平台硬件，建立lk基本运行环境。 */    

platform＿early＿init();

// 目前为空方法

    Target＿early＿init();

//初始化构造函数

    Call＿constructors();

//内核堆链表上下文初始化等.

 Heap＿init();

// 线程池初始化,前提是PLATFORM_HAS_DYNAMIC_TIMER需要支持.

    Thread＿init();

    // 初始化dpc 系统

    Dpc＿init();

    // 初始化timer

    Timer＿init();

#if (!ENABLE_NANDWRITE)

  // 创建系统初始化工作线程,执行app初始化，lk把业务部分当成一个app.

    Thread＿resume(thread＿create("bootstrap2", &bootstrap2, NULL, DEFAULT＿PRIORITY, DEFAULT＿STACK＿SIZE));

    // 使能中断

    Exit＿critical＿section();

    // 设置为一个低优先级的线程，只有系统空闲时才运行

    Thread＿become＿idle();

#else

        Bootstrap＿nandwrite();

#endif

}

static intbootstrap2(void *arg)

{

    Arch＿init();

    /* 平台相关初始化，包括nand/emmc，LCM显示驱动，启动模式选择，加载logo资源. */

    Platform＿init();

    // initialize the target

    Target＿init();

    /* app初始化，跳转到mt_boot_init入口开始执行,对应的 ".apps" 这个section. */

    Apps＿init();

    return 0;

}

void apps_init(void)

{

   const struct app_descriptor *app;

   /* call all the init routines */

   for (app = &__apps_start; app != &__apps_end; app++) {

      if (app->init)

         app->init(app);

   }

   /* start any that want to start on boot */

   for (app = &__apps_start; app != &__apps_end; app++) {

      if (app->entry && (app->flags & APP_FLAG_DONT_START_ON_BOOT) == 0) {

         start_app(app);

      }

   }

}

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

void mt_boot_init(const struct app_descriptor *app)

{

//设置序列号

    sn_buf[SN_BUF_LEN] = '\0';

    surf_udc_device.serialno = sn_buf;

    if (g_boot_mode == FASTBOOT)

        goto fastboot;

//检查secure boot 校验boot/recovery分区的签名

#ifdef MTK＿SECURITY＿SW＿SUPPORT

#if MTK_FORCE_VERIFIED_BOOT_SIG_VFY

    /* verify oem image with android verified boot signature instead of mediatek proprietary signature */

    /* verification is postponed to boot image loading stage */

    /* note in this case, boot/recovery image will be verified even when secure boot is disabled */

    g_boot_state = BOOT_STATE_RED;

#else

    if (0 != sec_boot_check(0)) {

        g_boot_state = BOOT_STATE_RED;

    }

#endif

#endif

//加载boot image

    /* Will not return */

    boot_linux_from_storage();

int boot_linux_from_storage(void)

{

       switch (g_boot_mode) {

              case NORMAL_BOOT:

// bootimg_hrd加载地址 0x40080000

ret=mboot_android_load_bootimg_hdr("boot", CFG_BOOTIMG_LOAD_ADDR);

//bootimg加载地址 kimg_load_addr = 0x45000000

                            kimg_load_addr = (unsigned int)target_get_scratch_address();

//加载bootimg

                     ret = mboot_android_load_bootimg("boot", kimg_load_addr);

                     break;

              case RECOVERY_BOOT:

......//如果是recovery模式，加载recovery image

                     break;

……

       }

//获取ramdisk的大小

                     g_rimg_sz = g_boot_hdr->ramdisk_size;

//重定位根文件系统（ramdisk）地址  0x44000000

       memcpy((g_boot_hdr!=NULL) ? (char *)g_boot_hdr->ramdisk_addr : (char *)CFG_RAMDISK_LOAD_ADDR, (char *)(g_rmem_off), g_rimg_sz);

       g_rmem_off = (g_boot_hdr!=NULL) ? g_boot_hdr->ramdisk_addr : CFG_RAMDISK_LOAD_ADDR;

       // 2 weak function for mt6572 memory preserved mode

       platform_mem_preserved_load_img();

       platform_mem_preserved_dump_mem();

       custom_port_in_kernel(g_boot_mode, cmdline_get());

......//设置cmdline,包括tembuf,seliux状态等

cmdline_append(cmdline_tmpbuf);

//准备启动Linux kernel

boot_linux((void*)CFG_BOOTIMG_LOAD_ADDR,(unsigned*)CFG_BOOTARGS_ADDR,(char*)cmdline_get(),board_machtype(),(void*)CFG_RAMDISK_LOAD_ADDR, g_rimg_sz);

       while (1) ;

       return 0;

}

void boot_linux(void *kernel, unsigned *tags,

                char *cmdline, unsigned machtype,

                void *ramdisk, unsigned ramdisk_size)

{

//加载设备树

#ifdef DEVICE_TREE_SUPPORT

       boot_linux_fdt((void *)kernel, (unsigned *)tags,

                      (char *)cmdline, machtype,

                      (void *)ramdisk, ramdisk_size);

       while (1) ;

#endif

//准备各种cmdline参数传入kernel

       /* CORE */

       *ptr++ = 2;

       *ptr++ = 0x54410001;

       ptr = target_atag_boot(ptr);

       ptr = target_atag_mem(ptr);

       if (target_atag_partition_data) {

              ptr = target_atag_partition_data(ptr);

       }

#if !(defined(MTK_UFS_BOOTING) || defined(MTK_EMMC_SUPPORT))

       if (target_atag_nand_data) {

              ptr = target_atag_nand_data(ptr);

       }

#endif

       //some platform might not have this function, use weak reference for

       extern unsigned *target_atag_dfo(unsigned *ptr)__attribute__((weak));

       if (target_atag_dfo) {

              ptr = target_atag_dfo(ptr);

       }

       ptr = target_atag_devinfo_data(ptr);

       check_hibernation(cmdline);

       ptr = target_atag_commmandline(ptr, cmdline);

       ptr = target_atag_initrd(ptr,(unsigned long) ramdisk, ramdisk_size);

       ptr = target_atag_videolfb(ptr); 

       extern unsigned int *target_atag_mdinfo(unsigned *ptr)__attribute__((weak));

       if (target_atag_mdinfo) {

              ptr = target_atag_mdinfo(ptr);

       } else {

              dprintf(CRITICAL,"DFO_MODEN_INFO Only support in MT6582/MT6592\n");

       }

       extern unsigned int *target_atag_masp_data(unsigned *ptr)__attribute__((weak));

       if (target_atag_masp_data) {

              ptr = (char *)target_atag_masp_data((unsigned *)ptr);

       } else {

              dprintf(CRITICAL,"masp atag not support in this platform\n");

       }

       /* END */

       *ptr++ = 0;

       *ptr++ = 0; 

       enter_critical_section();

// led,irq关闭

       platform_uninit();

// 关闭I/D-cache，关闭MMU

       arch_disable_cache(UCACHE);

       arch_disable_mmu();

       extern void platform_sec_post_init(void)__attribute__((weak));

       if (platform_sec_post_init) {

              platform_sec_post_init();

       }

       arch_uninit();

       //进入kernel

       entry(0, machtype, tags);

}