linux OBM分析

marvell的bootloader是blob+OBM+bootROM，所以还得编译OBM。

下面就对OBM进行分析。

查看OBM/Build/obm_linux.mak 文件，找到需要编译的文件。

OBJS =          obm_startup.o           \

                $(DDROBJS)              \

                $(DOWNLOADOBJS)         \

                $(DFCOBJS)              \

                $(MAINOBJS)             \

                $(FLASHOBJS)            \

                $(MISCOBJS)             \

                $(PLATFORMOBJS)         \

                $(SECUREOBJS)           \

                $(DMAOBJS)              \

                $(ONENANDOBJS)          \

                $(MDOCOBJS)                      \

                $(TAVOROBJS)

可以看到首先需要的是obm_startup.o

obm_startup.o: $(TOPDIR)/StartUp/obm_startup.S

        $(AS) $(INCLUDE_DIRS) "$(TOPDIR)/StartUp/obm_startup.S" -o "$(OUTDIR)/obm_startup.o"

而它需要StartUp/obm_startup.S，所以我们查看obm_startup.S这个文件。从__main入口

__main:

    @NOT SUPPORTED: ENTRY""

        B ResetHandler                    //初始化中断，关闭MMU，刷新列表，堆栈

        B UndefinedHandler

        B SwiHandler

        B PrefetchHandler

        B AbortHandler

        NOP                             @ Reserved Vector

        B SaveProgramState               @ B IRQ Interrupt SaveProgramState

        B FiqHandler @ FIQ interrupts not anabled

        NOP

        .align 2

        .word   MajorMinor, Date, Processor

        NOP

        @ RESET entry point

ResetHandler之后，使能所有协处理器的寄存器，从 0x5c0127F0 保存版本。

初始化DDR，使能MMU，初始化PVCR(VCO寄存器，用于PLL)，然后跳到DDRInit。

查看OBM/MHLV/DDR/ddr_init.S,

ldr     r2,     =PLATFORMCLOCKVALUE             //设置时钟，DDR读取速度

初始化DDR memory，

初始化SDRAM

    bl      xlli_Dmem_initP1                        @ init DDR-SDRAM (Part 1)

    ldr     r0,     =xlli_DMEMREGS_PHYSICAL_BASE    @ Dynamic Mem Controller base

    orr     r0, r0, #0x1

    bl      xlli_Rcomp                              @ Perform inital Rcomp calculation

    ldr     r0,     =xlli_DMEMREGS_PHYSICAL_BASE    @ Dynamic Mem Controller base

    ldr     r1,     =0x80000000                                @ DDR SDRAM base address

    bl      xlli_Dmem_initP2                        @ init DDR-SDRAM (Part 2)

@   Set up HCAL register with a preliminary value

@

    ldr     r1,     =xlli_DMEMREGS_PHYSICAL_BASE    @ Dynamic Memory Control Reg Base

    ldr     r2,     =0x90001102                     @ Preliminary value

    str     r2,     [r1, #xlli_DDR_HCAL_offset]     @ Write it out

    .ifdef xlli_stack_pointer     @ If stack pointer has been defined,

    ldmfd   sp!,    {r0-r11, pc}            @ Return to caller via the stack

    .else

    mov     pc,     lr                      @ Non stack return

    .endif

以上跳转的，都可以查看mini_xlli_lowlev_init.S文件找到。

地址参数查看xlli_board_defs.inc文件。

回到obm_startup.S文件，继续往下看，是判定是否休眠唤醒，主要看PSR（程序状态寄存器）。假如符合情况，就拷贝DKB到0x80000000。

后面可以在 Branch to OEM Boot Main program看到下面这段代码

LDR     r1, =ISRAMDateSpaceBase                 @ Restore platform configuration passed in by the BootROM

        LDR             r0, [r1]

        B               OBMBootMain

LOOPFOREVER:  B         LOOPFOREVER        

在OBM/MainProgram/obm.c查看

先看 void OBMBootMain(UINT_T PlatformSettings)

// Initialize any fuse information passed in by the BootROM

        Fuses.value = PlatformSettings;

        #if VERBOSE_DEBUG

        Fuses.bits.Download_Disable = 0;  //  allows ports to be enabled 

        #endif

        #if OBMTEST

         //Fuses.bits.PlatformState = 0x5;      // Default to CS2 Sibley

        Fuses.bits.PlatformState = 0x4;   // Default to NAND x16

        Fuses.bits.BootPlatformState = 0x9;

        #endif

结构体如下：

typedef union{

unsigned int value;

struct PLATFORM_FUSES bits;

}FUSE_SET, *pFUSE_SET;

struct PLATFORM_FUSES{

unsigned int DebugEn:1;     // Bit 0 of FMRD8

unsigned int PlatformState:4;   // Bit 1-4 of FMRD8

unsigned int Caddo_Disable:1;  // Bit 5 of FMRD8

unsigned int JTAG_Disable:1; // Bit 6 of FMRD8

unsigned int Patching_Disable:1;// Bit 7 of FMRD8

unsigned int Patching_Revision:4;// Bit 8-11of FMRD8

    unsigned int UARTPort           :1;     // 0 - FFUART, 1 - AltUART

    unsigned int USBPort            :1;     // 0 - DIFFUSB 1 - SEUSB

unsigned int CaddoDead:1;// 1 = Caddo did not come up.

unsigned int Resume:1;// 1 = resume from sleep in process

unsigned int USBWakeup:1;// 1 = USB wakeup from WSOTG

unsigned int PortEnabled:1;// 1 = Ports have been enabled

unsigned int DDRInitialized:1; // If the BootROM already initializes the DDR

unsigned int Download_Disable:1;// Bit 19 of services FMRD2 - Used to be MH-TV if 1 disable ports

unsigned int SBE:1;// Bit 20 of services FMRD2

unsigned int SDE:1;// Bit 21 of services FMRD2

unsigned int BootPlatformState:4;// There are the bits the BootROM booted from

unsigned int res:6;

};

读取版本信息

Version = (UINT_T *) 0x5c0127F0;

if ( (*Version >> 16) ==  VERSION_2_XX)

        {

           LoadVersion2XXImage(Fuses, &pFlashProp[0]);

        }

使能中断，初始化端口

EnableIrqInterrupts();

对BootROM检测flashes

if ((Fuses.bits.PlatformState == 0)     && (Fuses.bits.BootPlatformState == 0))

按照TIM（Trusted Image Module）/NTIM设置端口，或默认值

RetStatus.ErrorCode = InitTIMPort(&Fuses, &TIM_h);

if (RetStatus.ErrorCode == DownloadPortError)

                InitDefaultPort(&Fuses);

// TIM structure for use by DKB/OBM/BootROM

typedef struct

{

 pCTIM  pConsTIM;// Constant part

 pIMAGE_INFO pImg;// Pointer to Images

 pKEY_MOD pKey;// Pointer to Keys

 PUINT pReserved;// Pointer to Reserved Area

 pPLAT_DS       pTBTIM_DS; // Pointer to Digital Signature

} TIM, *pTIM;

imageInfo = FindImageInTIM(&TIM_h, OSLOADERID);

if(imageInfo == NULL)

        {

                imageInfo = FindImageInTIM(&TIM_h, OBMIDENTIFIER);

                ImageID =  imageInfo->NextImageID;

                //update the imageInfo structure for the image being booted to

                imageInfo = FindImageInTIM(&TIM_h, ImageID);

                if(imageInfo == NULL)

                {

                        //if we cannot find an image to boot to, error out

                        OBMFinalize(ImageNotFound, &pFlashProp[0]);

                }

        }

        else

        {

           ImageID = OSLOADERID;

        }

读取DDR EMRS（拓展寄存器，用于初始化DLL）的值

iemrs = *gDDREMRSValue;

        for(i =0;i<32;i++){

                itemp = iemrs;

                itemp = itemp & 0x80000000;

                if(itemp)

                        stemp[i] = 0x31;

                else

                        stemp[i] = 0x30;

                iemrs = (iemrs<<1);

        }

装载映像

Retval = CopyImageFlashToLocal(ImageID, &TIM_h, pFlashProp, NULL);

确认NTIM 或者TIM

Retval = ValidateCheckSum(TIMIDENTIFIER, &TIM_h, &pFlashProp[0]);

最后的处理：

Retval = PlatformOBMPostbootCode(&TIM_h, &pFlashProp[0]);

        if (Retval != NoError)

                OBMFinalize(Retval, &pFlashProp[0]);

        HandleDisconnect();

        ShutdownPort(FFUART_D);

        ShutdownPort(ALTUART_D);

        ShutdownPort(DIFF_USB_D);

        ShutdownPort(U2D_USB_D);

        DisableIrqInterrupts();            

    SaveParamsForEboot(Fuses);        //保存参数

    // TRANSFER CONTROL TO OS

        TransferControl(imageInfo->LoadAddr, 0, imageInfo->LoadAddr);

        _mod0();        //void _mod0(void) {while (1);}

1st step - Move Transfer Control to a Non-MMU translated area of the DDR

2nd Step - Turn OFF MMU, Flush TLB's

3nd Step - Copy the boot image to it's load address

回到obm_linux.mak文件中查看还需要编译DDR，Flash，Uart，USB，Boot保护等。

到此分析结束。

编译配置命令：
./configure --prefix=/home/wang/project/blob/bootloader/bin --with-board=littleton --host=arm-linux --with-linux-prefix=/home/wang/william/linux-2.6.25  --enable-xlli --enable-xllp --with-cpu-product-id=MonahansLV --with-commands=all --with-network=eth --with-nand-layout=comm_v75 --enable-xmodem  --enable-nand --enable-lcd
make -f obm_linux.mak