mtk preloader学习笔记

1.先看preloader生成过程，mediatek/buid/makemtk.mk文件里

preloader:



　　...



$(hide) cd $(PRELOADER_WD) && \

(./build.sh $(PROJECT) $(ACTION) $(DEAL_STDOUT) && \

cd $(MKTOPDIR) && \

$(call chkImgSize,$(ACTION),$(PROJECT),$(SCATTER_FILE),$(PRELOADER_IMAGES),$(DEAL_STDOUT),&&) \

$(SHOWRSLT) $$? $(MODULE_LOG) || \

$(SHOWRSLT) $$? $(MODULE_LOG))



...

 

执行mediatek/source/preloader/build.sh生成的。

2.在build.sh里有

function build_preloader ()

{

　　　...

         make

　　.....

｝

3.执行mediatek/source/preloader/Makefile文件的make命令。

all: $(ALL)

# ELF Generation

#



$(D_BIN)/$(PL_IMAGE_NAME).elf:

$(LD) --gc-sections -Bstatic -T$(MTK_PATH_PLATFORM)/link_descriptor.ld \

$(wildcard $(D_OBJ)/*) $(SECURITY_LIB) -Map system.map -o $(D_BIN)/$(PL_IMAGE_NAME).elf

@$(OBJCOPY) ${OBJCFLAGS} $(D_BIN)/$(PL_IMAGE_NAME).elf -O binary $(D_BIN)/$(PL_IMAGE_NAME).bin 

cat $(MTK_PATH_CUSTOM)/MTK_Loader_Info.tag >> $(D_BIN)/$(PL_IMAGE_NAME).bin

 

这一句会最终解释为：

arm-eabi-ld --gc-sections -Bstatic -T/home/chyl411/android/alps/mediatek/platform/mt6573/preloader/link_descriptor.ld \

 /home/chyl411/android/alps/mediatek/source/preloader/out/assembly.o



/home/chyl411/android/alps/mediatek/source/preloader/out/... 



...............



/home/chyl411/android/alps/mediatek/platform/mt6573/preloader/src/SecLib.a -Map system.map -o /home/chyl411/android/alps/mediatek/source/preloader/bin/preloader_(工程名)_gb.elf。

用arm-eabi-ld工具配合ld文件生成最终elf。第一行/home/chyl411/android/alps/mediatek/source/preloader/out/assembly.o是指assembly.s文件。

4.assembly.s源码们于mediatek\platform\mt6573\preloader\src\init目录下:

 

....

entry :

    /* Disable watch dog timer & Init CP15 setting */                 

    BL      primary_sys_init

    B     C_Main

....
.globl JumpCmd 
JumpCmd:
      MOV  pc, r0

 

最终会转入C_Main执行。源码们于同一目录下。

5.C_Main进行一些初始化之后，将uboot拷入DRAM，并跳转到UBOOT命令模式。

void C_Main (void)

{

    SYS_BOOT_REASON reason;

    g_boot_mode = NORMAL_BOOT;



    // pre-process

    pl_sys_init();   



    // check boot reason

#ifdef ENABLE_POWER_ON_VIBRATOR

    reason=pl_check_boot_reason();

#else

    pl_check_boot_reason();

#endif



    //boot security tactics

    pl_security_init();



    // clear SGX core clock

    pl_operate_clock();  



#ifdef ENABLE_POWER_ON_VIBRATOR

    if(reason == BR_POWER_KEY){

              *(volatile unsigned short *)0x7002F7B0 |= 1 << 0 | 6 << 4;



          gpt4_busy_wait_ms (100);



        *(volatile unsigned short *)0x7002F7B0 &= ~(1 << 0);

    }

#endif



    // check cable in or not and charge type

    meta_detection_via_usb();



#ifndef CFG_UART_HANDSHAKE_DISABLE

    //via UART to detect tool 

    meta_detection_via_uart ();  

#endif



    pl_security_check();



    // post process

    pl_post_process ();



    // do other function

    pl_do_other_function();

    

    // load u-boot image to DRAM       

    pl_load_uboot_image ();



    // jump to DRAM to run u-boot image        

    pl_print_title ("Jump U-Boot");

    JumpCmd ((UBOOT_IMG_ADDR));



    while (1);

}

JumpCmd函数在步骤4代码中，跳转到UBOOT_IMG_ADDR处执行。