s5pv210-Uboot启动流程
一、启动流程
1.s5pv210的启动过程
根据三星公司的《S5PV210_UM_REV1.1》手册可知,S5PV210 启动过程主要可 分为 3 个阶段
S5PV210 上电复位后将从 IROM 处执行已固化的启动代码 -------BL0
在 BL0 里初始化过程中对启动设备进行判断,并从启动设备拷贝 BL1(最大16KB ) 到 IRAM 处 , 即 刚 才 所 说 的 0xD0020000 开 始 的 地 址 , 其 中0xD0020000~0xD0020010 的 16 字节为 BL1 的校验信息和 BL1 尺寸,并对 BL1进行校验,校验通过转入 BL1 进行执行,BL1 继续初始化,并拷贝 BL2(最大80KB)到 IRAM 中并对其校验,通过后转入 BL2。
BL2 完成一些比较复杂的初始化,包括 DRAM 的初始化,完成后将 OS 代码拷贝到 DRAM 中,并跳到 OS 中执行并完成启动引导。
BL0 固化代码主要完成以下初始化:
关闭看门狗;
初始化 icache;
初始化栈;
初始化堆;
初始化块设备拷贝功能;
设置系统时钟;
拷贝 BL1 到 iRAM;
检查 BL1 的校验和,如果失败则第二启动模式(安全启动模式),校验成功则跳到 0xD0020000(IRAM)处执行。
其中 0xD0020000 ~ 0xD0020010 里的 16 字节头部信息是什么呢?这 16 字节信息用户是不能随便设置的.在《S5PV210_iROM_ApplicationNote_Preliminary_20091126》文档中规定
2.uboot中s5pv210的启动
2.1 uboot启动流程简介
BL0是出厂的时候就固化在IROM里的，所以我们的uboot就要实现BL1和BL2，BL1在uboot里叫做u-boot-spl.bin，BL2就是我们很熟悉的u-boot.bin.上面的三个阶段对应于uboot启动，他们的功能如下：
BL0：出厂的时候就固化在irom中一段代码，主要负责拷贝8kb的bl1到s5pv210的一个96kb大小内部sram(Internal SRAM)中运行。值得注意的是s5pv210的Internal SRAM支持的bl1的大小可以达到16kb，容量的扩增是为了适应bootloder变得越来复杂而做的。虽然如此，但目前我们制作出来的bl1的大小仍然可以保持在8kb以内，同样能满足需求。
BL1：u-boot的前8kb代码(s5pv210也支持16kb大小，原因上一点提过了)，除了初始化系统时钟和一些基本的硬件外，主要负责完成代码的搬运工作(我设计成搬运bl1+bl2，而不仅仅是bl2)，也就是将完整的u-boot代码(bl1+bl2)从nand flash或者mmcSD等的存储器中读取到内存中，然后跳转到内存中运行u-boot
BL2：完成全面的硬件初始化和加载OS到内存中，接着运行OS。上述几个阶段的流程描述在s5pv210_irom_application手册中有详细描述.
在实际的编译中会生成两个uboot.bin。拿webee210的uboot来说，最后在根目录下生成了uboot.bin和webee210-uboot.bin连个.bin文件。其中webee210-uboot.bin是通过/board/samsung/webee210/tools目录下的mkwebee210spl.bin对uboot.bin处理 生成的。主要是为其添加16k的头文件信息。
首先把启动部分的代码分为3部分，以start.S为主，另外还有lowlevel_init.S，mem_setup.S，ctr0.S。
lowlevel_init.S:主要是一部分硬件的初始化，尤其是系统时钟和DRAM的初始化。如果u-boot一旦被搬运到内存中运行，那么是必须要跳过时钟和DRAM的初始化的，因为这在搬运之前已经做过了。并且如果代码在内存中运行的时侯你却去初始化DRAM，那必然导致崩溃！
mem_setup.S：DRAM初始化代码和MMU相关代码放在这个文件中。
ctr0.S：u-boot自带的代码文件，存放汇编函数main。
2.2 启动过程
必须要明白的一点是，当代码从存储介质(nand flash，SD，norflash，onenand等)中搬运到了DRAM中后随即会跳转到内存中运行u-boot，接着会有一个重定位(relocate_code)的过程，relocate_code子函数在start.S中，而给relocate_code子函数传参数的是crt0.S中的main子函数。当判断到当前u-boot在内存的低地址处，那么relocate_code就会工作，把u-boot代码从低地址处再搬运到内存地址的顶端，然后跳转到新的位置去继续运行u-boot。而搬运的目标地址是在board_init_f()函数(此函数在/arch/arm/lib/board.c中)中计算出来的
2.2.1 start.S
#include
#include
#include
#include
#include
#include
.globl _start
_start: b reset
ldr pc, _undefined_instruction /*未定义指令异常,0x04*/
ldr pc, _software_interrupt /*软中断异常,0x08*/
ldr pc, _prefetch_abort /*内存操作异常,0x0c*/
ldr pc, _data_abort /*数据异常,0x10*/
ldr pc, _not_used /*未适用,0x14*/
ldr pc, _irq /*慢速中断异常,0x1c*/
ldr pc, _fiq /*快速中断异常,0x1c*/
#ifdef CONFIG_SPL_BUILD
_undefined_instruction: .word _undefined_instruction
_software_interrupt: .word _software_interrupt
_prefetch_abort: .word _prefetch_abort
_data_abort: .word _data_abort
_not_used: .word _not_used
_irq: .word _irq
_fiq: .word _fiq
_pad: .word 0x12345678 /* now 16*4=64 */
#else
_undefined_instruction: .word undefined_instruction
_software_interrupt: .word software_interrupt
_prefetch_abort: .word prefetch_abort
_data_abort: .word data_abort
_not_used: .word not_used
_irq: .word irq
_fiq: .word fiq
_pad: .word 0x12345678 /* now 16*4=64 */
#endif /* CONFIG_SPL_BUILD */
.global _end_vect
_end_vect:
.balignl 16,0xdeadbeef //所以意思就是,接下来的代码,都要16字节对齐,不知之处,用0xdeadbeef填充。
/*************************************************************************
*
* Startup Code (reset vector)
*
* do important init only if we don't start from memory!
* setup Memory and board specific bits prior to relocation.
* relocate armboot to ram
* setup stack
*
*************************************************************************/
/*
此地址中是一个word类型的变量,变量名
是TEXT_BASE,此值见名知意,是text的base,即代码的基地址,
在include/configs/webee210.h
#define CONFIG_SYS_TEXT_BASE 0x23E00000*/
.globl _TEXT_BASE
_TEXT_BASE:
.word CONFIG_SYS_TEXT_BASE
#ifdef CONFIG_TEGRA2
/*
* Tegra2 uses 2 separate CPUs - the AVP (ARM7TDMI) and the CPU (dual A9s).
* U-Boot runs on the AVP first, setting things up for the CPU (PLLs,
* muxes, clocks, clamps, etc.). Then the AVP halts, and expects the CPU
* to pick up its reset vector, which points here.
*/
.globl _armboot_start
_armboot_start:
.word _start //*(_armboot_start) = _start
#endif
/*
* These are defined in the board-specific linker script.
*/
.globl _bss_start_ofs
_bss_start_ofs:
.word __bss_start - _start
.global _image_copy_end_ofs
_image_copy_end_ofs:
.word __image_copy_end - _start
.globl _bss_end_ofs
_bss_end_ofs:
.word __bss_end__ - _start
.globl _end_ofs
_end_ofs:
.word _end - _start
#ifdef CONFIG_USE_IRQ
/* IRQ stack memory (calculated at run-time) */
.globl IRQ_STACK_START
IRQ_STACK_START:
.word 0x0badc0de
/* IRQ stack memory (calculated at run-time) */
.globl FIQ_STACK_START
FIQ_STACK_START:
.word 0x0badc0de
#endif
/* IRQ stack memory (calculated at run-time) + 8 bytes */
.globl IRQ_STACK_START_IN
IRQ_STACK_START_IN:
.word 0x0badc0de reset函数里主要是设置了cpu的模式,然后就跳转到cpu_init_crit函数.
/*
* the actual reset code
*/
reset:
bl save_boot_params //其不做任何事情，直接返回
/*
* set the cpu to SVC32 mode //设置CPU模式为SVC32
*/
mrs r0, cpsr
bic r0, r0, #0x1f
orr r0, r0, #0xd3
msr cpsr,r0
#ifndef CONFIG_SKIP_LOWLEVEL_INIT
bl cpu_init_crit //
#endif/*************************************************************************
*
* CPU_init_critical registers
*
* setup important registers
* setup memory timing
*
*************************************************************************/
cpu_init_crit:
/*
* Invalidate L1 I/D
*/
mov r0, #0 @ set up for MCR
mcr p15, 0, r0, c8, c7, 0 @ invalidate TLBs
mcr p15, 0, r0, c7, c5, 0 @ invalidate icache
mcr p15, 0, r0, c7, c5, 6 @ invalidate BP array
mcr p15, 0, r0, c7, c10, 4 @ DSB
mcr p15, 0, r0, c7, c5, 4 @ ISB
/*
* disable MMU stuff and caches
*/
mrc p15, 0, r0, c1, c0, 0
bic r0, r0, #0x00002000 @ clear bits 13 (--V-)
bic r0, r0, #0x00000007 @ clear bits 2:0 (-CAM)
orr r0, r0, #0x00000002 @ set bit 1 (--A-) Align
orr r0, r0, #0x00000800 @ set bit 11 (Z---) BTB
#ifdef CONFIG_SYS_ICACHE_OFF
bic r0, r0, #0x00001000 @ clear bit 12 (I) I-cache
#else
orr r0, r0, #0x00001000 @ set bit 12 (I) I-cache
#endif
mcr p15, 0, r0, c1, c0, 0
/*
* Jump to board specific initialization...
* The Mask ROM will have already initialized
* basic memory. Go here to bump up clock rate and handle
* wake up conditions.
*/
mov ip, lr @ persevere link reg across call
bl lowlevel_init //跳转到lowlevel_init,与开发板相关的初始化
mov lr, ip @ restore link
mov pc, lr @ back to my caller
#endif
lowlevel_init.s存放于`board/samsung/webee210/lowlevel_init.s`
.globl lowlevel_init
lowlevel_init:
push {lr} //把返回地址保存到栈中
/* check reset status */
ldr r0, =(ELFIN_CLOCK_POWER_BASE+RST_STAT_OFFSET)
ldr r1, [r0]
bic r1, r1, #0xfff6ffff
cmp r1, #0x10000
beq wakeup_reset_pre
cmp r1, #0x80000
beq wakeup_reset_from_didle
/* IO Retention release */
ldr r0, =(ELFIN_CLOCK_POWER_BASE + OTHERS_OFFSET)
ldr r1, [r0]
ldr r2, =IO_RET_REL
orr r1, r1, r2
str r1, [r0]
/* Disable Watchdog */
ldr r0, =ELFIN_WATCHDOG_BASE /* 0xE2700000 */
mov r1, #0
str r1, [r0]
/* SRAM(2MB) init for SMDKC110 */
/* GPJ1 SROM_ADDR_16to21 */
ldr r0, =ELFIN_GPIO_BASE
ldr r1, [r0, #GPJ1CON_OFFSET]
bic r1, r1, #0xFFFFFF
ldr r2, =0x444444
orr r1, r1, r2
str r1, [r0, #GPJ1CON_OFFSET]
ldr r1, [r0, #GPJ1PUD_OFFSET]
ldr r2, =0x3ff
bic r1, r1, r2
str r1, [r0, #GPJ1PUD_OFFSET]
/* GPJ4 SROM_ADDR_16to21 */
ldr r1, [r0, #GPJ4CON_OFFSET]
bic r1, r1, #(0xf<<16)
ldr r2, =(0x4<<16)
orr r1, r1, r2
str r1, [r0, #GPJ4CON_OFFSET]
ldr r1, [r0, #GPJ4PUD_OFFSET]
ldr r2, =(0x3<<8)
bic r1, r1, r2
str r1, [r0, #GPJ4PUD_OFFSET]
/* CS0 - 16bit sram, enable nBE, Byte base address */
ldr r0, =ELFIN_SROM_BASE /* 0xE8000000 */
mov r1, #0x1
str r1, [r0]
/* PS_HOLD pin(GPH0_0) set to high */
ldr r0, =(ELFIN_CLOCK_POWER_BASE + PS_HOLD_CONTROL_OFFSET)
ldr r1, [r0]
orr r1, r1, #0x300
orr r1, r1, #0x1
str r1, [r0]
/* when we already run in ram, we don't need to relocate U-Boot.
* and actually, memory controller must be configured before U-Boot
* is running in ram.
*/
ldr r0, =0x00ffffff
bic r1, pc, r0 /* r0 <- current base addr of code */
ldr r2, _TEXT_BASE /* r1 <- original base addr in ram */
bic r2, r2, r0 /* r0 <- current base addr of code */
cmp r1, r2 /* compare r0, r1 */
beq 1f /* r0 == r1 then skip sdram init */
/* init system clock */
bl system_clock_init
/* Memory initialize */
bl mem_ctrl_asm_init
1:
/* for UART */
bl uart_asm_init
bl tzpc_init
#if defined(CONFIG_ONENAND)
bl onenandcon_init
#endif
#if defined(CONFIG_NAND)
/* simple init for NAND */
bl nand_asm_init
#endif
/* check reset status */
ldr r0, =(ELFIN_CLOCK_POWER_BASE+RST_STAT_OFFSET)
ldr r1, [r0]
bic r1, r1, #0xfffeffff
cmp r1, #0x10000
beq wakeup_reset_pre
/* ABB disable */
ldr r0, =0xE010C300
orr r1, r1, #(0x1<<23)
str r1, [r0]
/* Print 'K' */
ldr r0, =ELFIN_UART_CONSOLE_BASE
ldr r1, =0x4b4b4b4b
str r1, [r0, #UTXH_OFFSET]
pop {pc}
关看门狗,初始化 SRAM,初始化 SROM,初始化电源保持控制器,初始化系统时钟,内存初始化
初始化串口,Nand Flash 早期初始化等.
接下来我们继续回到start.S里,看call_board_init_f这个函数.
/* Set stackpointer in internal RAM to call board_init_f */
call_board_init_f:
/* 为待会要执行的 C 函数设置栈 */
ldr sp, =(CONFIG_SYS_INIT_SP_ADDR)
bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
ldr r0,=0x00000000
#if defined(CONFIG_TINY210) || defined(CONFIG_WEBEE210)
adr r4, _start
ldr r5,_TEXT_BASE
/* 判断当前代码是否已在 RAM 上运行(DDR2) */
/* 因为现在还在第一阶段,还在代码 SRAM 上运行,
* 所以不会直接跳到 board_init_in_ram*/
cmp r5,r4
beq board_init_in_ram
/* PRO_ID_BASE 是判断启动方式的寄存器 */
ldr r0, =PRO_ID_BASE
ldr r1, [r0,#OMR_OFFSET]
bic r2, r1, #0xffffffc1
/* NAND BOOT ,判断是否通过 Nand Flash 方式启动 */
cmp r2, #0x0 @ 512B 4-cycle
moveq r3, #BOOT_NAND
cmp r2, #0x2 @ 2KB 5-cycle
moveq r3, #BOOT_NAND
cmp r2, #0x4 @ 4KB 5-cycle 8-bit ECC
moveq r3, #BOOT_NAND
cmp r2, #0x6 @ 4KB 5-cycle 16-bit ECC
moveq r3, #BOOT_NAND
cmp r2, #0x8 @ OneNAND Mux
moveq r3, #BOOT_ONENAND
/* SD/MMC BOOT */
cmp r2, #0xc
moveq r3, #BOOT_MMCSD
/* NOR BOOT */
cmp r2, #0x14
moveq r3, #BOOT_NOR
/* Uart BOOTONG failed */
cmp r2, #(0x1<<4)
moveq r3, #BOOT_SEC_DEV
ldr r0, =INF_REG_BASE
str r3, [r0, #INF_REG3_OFFSET]
ldr r1, [r0, #INF_REG3_OFFSET]
cmp r1, #BOOT_NAND /* 0x0 => boot device is nand */
beq nand_boot_210
cmp r1, #BOOT_MMCSD
beq mmcsd_boot_210
nand_boot_210:
bl board_init_f_nand
mmcsd_boot_210:
bl board_init_f
board_init_in_ram:
#endif
bl board_init_f
假如是nand启动,`arch\arm\cpu\armv7\s5pc1xx/nand_cp.c`
void board_init_f_nand(unsigned long bootflag)
{
__attribute__((noreturn)) void (*uboot)(void);
copy_uboot_to_ram_nand();
/* Jump to U-Boot image */
uboot = (void *)CONFIG_SYS_TEXT_BASE;
(*uboot)();
/* Never returns Here */
}
假如是sd卡启动 ,`arch\arm\cpu\armv7\s5pc1xx/mmc_boot.c`
void board_init_f(unsigned long bootflag)
{
__attribute__((noreturn)) void (*uboot)(void);
/*把第二阶段的 U-Boot 从 sd 拷贝到内存的函数*/
copy_uboot_to_ram();
/* Jump to U-Boot image */
uboot = (void *)CONFIG_SYS_TEXT_BASE;
/* 跳转到第二阶段所在的内存(DDR2)地址处 */
(*uboot)();
/* Never returns Here */
}
到此为止,上面的内容为第一阶段所做的工作,即bl1,接下来是bl2,完成全面的硬件初始化和加载OS到内存中，接着运行OS
看回start.S里的call_board_init_f函数,在我们进行是在nand flash启动还是sd卡启动之前有一段代码如下,这段代码是判断当前的代码是否运行于RAM上的.假如不是则根据PRO_ID_BASE判断是哪种启动方式,然后调用board_init_f()或board_init_f_nand(),在他们里面有调用了copy_uboot_to_ram()0或copy_uboot_to_ram_nand(),所以uboot将会被copy到ram中,即代码开始从ram上运行.当代码已经在ram上运行了,则执行board_init_in_ram()函数.我看看接下来看看这个函数都做了什么.
#if defined(CONFIG_TINY210) || defined(CONFIG_WEBEE210)
adr r4, _start
ldr r5,_TEXT_BASE
/* 判断当前代码是否已在 RAM 上运行(DDR2) */
/* 因为现在还在第一阶段,还在代码 SRAM 上运行,
* 所以不会直接跳到 board_init_in_ram*/
cmp r5,r4
beq board_init_in_ram
/* PRO_ID_BASE 是判断启动方式的寄存器 */
ldr r0, =PRO_ID_BASE
ldr r1, [r0,#OMR_OFFSET]
bic r2, r1, #0xffffffc1
board_init_in_ram执行的也是board_init_f()这个函数,这个函数在前也出现过,当我们搜索board_init_f函数时,我们将发现在`arch\arm\cpu\armv7\s5pc1xx/mmc_boot.c`和`arch\arm\lib\board.c`中都有出现过.那么系统是如何判断是执行哪个board_init_f的呢.我觉得应该是与程序执行的内存地址不同有关.在没有判断进入ram之前,board_init_f在一个内存里,当进入ram之后,board_init_f则在另外的地址里.
这里使用相同的函数名,不知道通过什么连接方式实现不冲突,令人疑惑.网上搜到大多数的board_init_f函数都指的是`arch\arm\lib\board.c`里的这个board_init_f.
board_init_in_ram:
#endif
bl board_init_f
下面看看这个board_init_f都做了什么工作.
void board_init_f(ulong bootflag)
{
bd_t *bd;
init_fnc_t **init_fnc_ptr;
gd_t *id;
ulong addr, addr_sp;
/* Pointer is writable since we allocated a register for it */
gd = (gd_t *) ((CONFIG_SYS_INIT_SP_ADDR) & ~0x07);
/* compiler optimization barrier needed for GCC >= 3.4 */
__asm__ __volatile__("": : :"memory");
memset((void *)gd, 0, sizeof(gd_t));
gd->mon_len = _bss_end_ofs;
/* 依次调用 init_fnc_ptr 指针数组里的每个函数 */
for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
if ((*init_fnc_ptr)() != 0) {
hang ();
}
}
涉及到两个重要的数据结构：1）bd_t结构体，关于开发板信息（波特率，ip, 平台号，启动参数）。2）gd_t结构体成员主要是一些全局的系统初始化参数
`gd=(gd_t *)(CONFIG_SYS_INIT_SP_ADDR) &~0x07)`
CONFIG_SYS_INIT_SP_ADDR的定义如下：
`#define CONFIG_SYS_INIT_SP_ADDR (0x22000)`
0x22000 & ~0x07，为了保证结果八字节对齐。
查芯片手册，可知0x0002_0000----0x0003_8000范围，为96K,是IRAM的空间。即gd指向IRAM的一个地址。
在本文中前面有声明DECLARE_GLOBAL_DATA_PTR
跟踪定义可看到下面形式：
`#define DECLARE_GLOBAL_DATA_PTR register volatile gd_t *gd asm ("r8")`这个声明告诉编译器使用寄存器r8来存储gd_t类型的指针gd，即这个定义声明了一个指针，并且指明了它的存储位置。（即gd值放在寄存器r8中)
- register表示变量放在机器的寄存器
- volatile用于指定变量的值可以由外部过程异步修改
- 并且这个指针现在被赋值为CONFIG_SYS_INIT_SP_ADDR) &~0x07， __asm__ __volatile__("": : :"memory"); memset((void *)gd, 0, sizeof(gd_t));
- memory 强制gcc编译器假设RAM所有内存单元均被汇编指令修改，这样cpu中的registers和cache中已缓存的内存单元中的数据将作废。cpu将不得不在需要的时候重新读取内存中的数据。这就阻止了cpu又将registers，cache中的数据用于去优化指令，而避免去访问内存。
- __asm__用于指示编译器在此插入汇编语句。
- volatile 用于告诉编译器，严禁将此处的汇编语句与其它的语句重组合优化。即：原原本本按原来的样子处理这这里的汇编。 memory强制gcc编译器假设RAM所有内存单元均被汇编指令修改，这样cpu中的registers和cache中已缓存的内存单元中的数据将作废。cpu将不得不在需要的时候重新读取内存中的数据。这就阻止了cpu又将registers，cache中的数据用于去优化指令，而避免去访问内存。
- "":::表示这是个空指令。
`gd->mon_len = _bss_end_ofs; `
_bss_end_ofs的定义在start.S中： .globl _bss_end_ofs
_bss_end_ofs:
.word __bss_end__ - _start
.word就是在当前地址_bss_end_ofs放值 __bss-end__ - _start。看到是所以段的大小，此时，新开终端。打开u-boot.lds，找__bss_end__ Gd->mon_len存的值就是u-boot的实际大小。
init_fnc_ptr是一个函数指针,而init_sequence是一个函数队列,定义如下:
init_fnc_t *init_sequence[] = {
#if defined(CONFIG_ARCH_CPU_INIT)
arch_cpu_init, /* basic arch cpu dependent setup */
#endif
#if defined(CONFIG_BOARD_EARLY_INIT_F)
board_early_init_f,
#endif
timer_init, /* initialize timer */
#ifdef CONFIG_FSL_ESDHC
get_clocks,
#endif
env_init, /* initialize environment */
init_baudrate, /* initialze baudrate settings */
serial_init, /* serial communications setup */
console_init_f, /* stage 1 init of console */
display_banner, /* say that we are here */
#if defined(CONFIG_DISPLAY_CPUINFO)
print_cpuinfo, /* display cpu info (and speed) */
#endif
#if defined(CONFIG_DISPLAY_BOARDINFO)
checkboard, /* display board info */
#endif
#if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)
init_func_i2c,
#endif
dram_init, /* configure available RAM banks */
NULL,
};所以通过循环，调用了函数指针数组中的一系列初始化函数：arch_cpu_init，timer_init，env_int，init_baudrate， serial_init，console_init_f， display_banner， dram_init。
接下是board_init_f的后半段函数内容:
debug("monitor len: %08lX\n", gd->mon_len);
/*
* Ram is setup, size stored in gd !!
*/
debug("ramsize: %08lX\n", gd->ram_size);
#if defined(CONFIG_SYS_MEM_TOP_HIDE)
/*
* Subtract specified amount of memory to hide so that it won't
* get "touched" at all by U-Boot. By fixing up gd->ram_size
* the Linux kernel should now get passed the now "corrected"
* memory size and won't touch it either. This should work
* for arch/ppc and arch/powerpc. Only Linux board ports in
* arch/powerpc with bootwrapper support, that recalculate the
* memory size from the SDRAM controller setup will have to
* get fixed.
*/
gd->ram_size -= CONFIG_SYS_MEM_TOP_HIDE;
#endif
/*这里addr是内存的高地址，0x20000000+256M
关于gd->ram_size,在初始化函数dram_init中，已经给过值了 */
addr = CONFIG_SYS_SDRAM_BASE + gd->ram_size;
#ifdef CONFIG_LOGBUFFER
#ifndef CONFIG_ALT_LB_ADDR
/* reserve kernel log buffer */
addr -= (LOGBUFF_RESERVE);
debug("Reserving %dk for kernel logbuffer at %08lx\n", LOGBUFF_LEN,
addr);
#endif
#endif
#ifdef CONFIG_PRAM
/*
* reserve protected RAM
*/
i = getenv_r("pram", (char *)tmp, sizeof(tmp));
reg = (i > 0) ? simple_strtoul((const char *)tmp, NULL, 10) :
CONFIG_PRAM;
addr -= (reg << 10); /* size is in kB */
debug("Reserving %ldk for protected RAM at %08lx\n", reg, addr);
#endif /* CONFIG_PRAM */
#if !(defined(CONFIG_SYS_ICACHE_OFF) && defined(CONFIG_SYS_DCACHE_OFF))
/* reserve TLB table */
addr -= (4096 * 4);
/* round down to next 64 kB limit */
addr &= ~(0x10000 - 1);
gd->tlb_addr = addr;
debug("TLB table at: %08lx\n", addr);
#endif
/* round down to next 4 kB limit */
addr &= ~(4096 - 1);
debug("Top of RAM usable for U-Boot at: %08lx\n", addr);
#ifdef CONFIG_LCD
#ifdef CONFIG_FB_ADDR
gd->fb_base = CONFIG_FB_ADDR;
#else
/* reserve memory for LCD display (always full pages) */
addr = lcd_setmem(addr);
gd->fb_base = addr;
#endif /* CONFIG_FB_ADDR */
#endif /* CONFIG_LCD */
/*
* reserve memory for U-Boot code, data & bss
* round down to next 4 kB limit
*/
addr -= gd->mon_len;
addr &= ~(4096 - 1);
debug("Reserving %ldk for U-Boot at: %08lx\n", gd->mon_len >> 10, addr);
/*宏CONFIG_SPL_BUILD,用ctags找，在spl/Makefile中能找到，如下：
CONFIG_SPL_BUILD := y
export CONFIG_SPL_BUILD
但是从u-boot根目录的Makefile中，可以看到，ALL-$(CONFIG_SPL)，如下：
ALL-$(CONFIG_SPL) += $(obj)spl/u-boot-spl.bin
CONFIG_SPL没有定义（include/configs/fsc100.h中没这个宏），因此，相当于spl/Makefile没有执行。*/
#ifndef CONFIG_SPL_BUILD
/*
* reserve memory for malloc() arena
*/
addr_sp = addr - TOTAL_MALLOC_LEN;
debug("Reserving %dk for malloc() at: %08lx\n",
TOTAL_MALLOC_LEN >> 10, addr_sp);
/*
* (permanently) allocate a Board Info struct
* and a permanent copy of the "global" data
*/
addr_sp -= sizeof (bd_t);
bd = (bd_t *) addr_sp;
gd->bd = bd;
debug("Reserving %zu Bytes for Board Info at: %08lx\n",
sizeof (bd_t), addr_sp);
#ifdef CONFIG_MACH_TYPE
gd->bd->bi_arch_number = CONFIG_MACH_TYPE; /* board id for Linux */
#endif
addr_sp -= sizeof (gd_t);
id = (gd_t *) addr_sp;
debug("Reserving %zu Bytes for Global Data at: %08lx\n",
sizeof (gd_t), addr_sp);
/* setup stackpointer for exeptions */
gd->irq_sp = addr_sp;
#ifdef CONFIG_USE_IRQ
addr_sp -= (CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ);
debug("Reserving %zu Bytes for IRQ stack at: %08lx\n",
CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ, addr_sp);
#endif
/* leave 3 words for abort-stack */
addr_sp -= 12;
/* 8-byte alignment for ABI compliance */
addr_sp &= ~0x07;
#else
addr_sp += 128; /* leave 32 words for abort-stack */
gd->irq_sp = addr_sp;
#endif
debug("New Stack Pointer is: %08lx\n", addr_sp);
#ifdef CONFIG_POST
post_bootmode_init();
post_run(NULL, POST_ROM | post_bootmode_get(0));
#endif
gd->bd->bi_baudrate = gd->baudrate;
/* Ram ist board specific, so move it to board code ... */
dram_init_banksize();
display_dram_config(); /* and display it */
gd->relocaddr = addr;
gd->start_addr_sp = addr_sp;
gd->reloc_off = addr - _TEXT_BASE;
debug("relocation Offset is: %08lx\n", gd->reloc_off);
memcpy(id, (void *)gd, sizeof(gd_t));
/* 跳去执行重定位代码 */
relocate_code(addr_sp, id, addr);
/* NOTREACHED - relocate_code() does not return */
}
relocate_code(addr_sp, id, addr)；在start.S中定义，C又回到了汇编
（栈指针，全局数据的地方, 搬后起始地址）
完成了第二次搬运过程，把u-boot从27e00000搬到了addr．
/*
* void relocate_code (addr_sp, gd, addr_moni)
*
* This "function" does not return, instead it continues in RAM
* after relocating the monitor code.
*
*/
.globl relocate_code
relocate_code:
mov r4, r0 /* save addr_sp */
mov r5, r1 /* save addr of gd */
mov r6, r2 /* save addr of destination */
……
/* Set up the stack */
stack_setup:
mov sp, r4
adr r0, _start
//得到u-boot的链接地址
cmp r0, r6
//判断u-boot是否已经搬移到最终地址
moveq r9, #0 /* no relocation. relocation offset(r9) = 0 */
beq clear_bss /* skip relocation */
//若不需要再次搬移，直接清bss段。
mov r1, r6 /* r1 <- scratch for copy_loop */
ldr r3, _image_copy_end_ofs
//需要搬移的u-boot的大小。
add r2, r0, r3 /* r2 <- source end address */
//r0和r2之间的内容全部搬走。
copy_loop:
ldmia r0!, {r9-r10} /* copy from source address [r0] */
stmia r1!, {r9-r10} /* copy to target address [r1] */
cmp r0, r2 /* until source end address [r2] */
blo copy_loop
//若u-boot需要自搬移，即不在最终地址运行，把u-boot复制到了SDRAM的高端地址
.....
jump_2_ram:
/*
* If I-cache is enabled invalidate it
*/
#ifndef CONFIG_SYS_ICACHE_OFF
mcr p15, 0, r0, c7, c5, 0 @ invalidate icache
mcr p15, 0, r0, c7, c10, 4 @ DSB
mcr p15, 0, r0, c7, c5, 4 @ ISB
#endif
//程序从_board_init_r_ofs开始执行,目的是为了跳到board_init_r
ldr r0, _board_init_r_ofs
adr r1, _start
/* _board_init_r_ofs + _start = board_init_r */
add lr, r0, r1
add lr, lr, r9
/* setup parameters for board_init_r */
mov r0, r5 /* gd_t */
mov r1, r6 /* dest_addr */
/* jump to it ... */
mov pc, lr /* 跳转到 board_init_r */
/* board_init_r - _start = _board_init_r_ofs */
_board_init_r_ofs:
.word board_init_r - _start
在board_init_r函数中,主要针对开发板自身的外设资源进行初始化,包括串口,网卡,sd卡等
/*
************************************************************************
*
* This is the next part if the initialization sequence: we are now
* running from RAM and have a "normal" C environment, i. e. global
* data can be written, BSS has been cleared, the stack size in not
* that critical any more, etc.
*
************************************************************************
*/
void board_init_r(gd_t *id, ulong dest_addr)
{
char *s;
bd_t *bd;
ulong malloc_start;
#if !defined(CONFIG_SYS_NO_FLASH)
ulong flash_size;
#endif
gd = id;
bd = gd->bd;
gd->flags |= GD_FLG_RELOC; /* tell others: relocation done */
monitor_flash_len = _end_ofs;
/* Enable caches */
enable_caches();
debug("monitor flash len: %08lX\n", monitor_flash_len);
board_init(); /* Setup chipselects */
#ifdef CONFIG_SERIAL_MULTI
serial_initialize();
#endif
debug("Now running in RAM - U-Boot at: %08lx\n", dest_addr);
#ifdef CONFIG_LOGBUFFER
logbuff_init_ptrs();
#endif
#ifdef CONFIG_POST
post_output_backlog();
#endif
/* The Malloc area is immediately below the monitor copy in DRAM */
malloc_start = dest_addr - TOTAL_MALLOC_LEN;
mem_malloc_init (malloc_start, TOTAL_MALLOC_LEN);
#if !defined(CONFIG_SYS_NO_FLASH)
puts("Flash: ");
flash_size = flash_init();
if (flash_size > 0) {
# ifdef CONFIG_SYS_FLASH_CHECKSUM
print_size(flash_size, "");
/*
* Compute and print flash CRC if flashchecksum is set to 'y'
*
* NOTE: Maybe we should add some WATCHDOG_RESET()? XXX
*/
s = getenv("flashchecksum");
if (s && (*s == 'y')) {
printf(" CRC: %08X", crc32(0,
(const unsigned char *) CONFIG_SYS_FLASH_BASE,
flash_size));
}
putc('\n');
# else /* !CONFIG_SYS_FLASH_CHECKSUM */
print_size(flash_size, "\n");
# endif /* CONFIG_SYS_FLASH_CHECKSUM */
} else {
puts(failed);
hang();
}
#endif
#if defined(CONFIG_CMD_NAND)
puts("NAND: ");
nand_init(); /* go init the NAND */
#endif
#if defined(CONFIG_CMD_ONENAND)
onenand_init();
#endif
#ifdef CONFIG_GENERIC_MMC
puts("MMC: ");
mmc_initialize(bd);
#endif
#ifdef CONFIG_HAS_DATAFLASH
AT91F_DataflashInit();
dataflash_print_info();
#endif
/* initialize environment */
env_relocate();
#if defined(CONFIG_CMD_PCI) || defined(CONFIG_PCI)
arm_pci_init();
#endif
/* IP Address */
gd->bd->bi_ip_addr = getenv_IPaddr("ipaddr");
stdio_init(); /* get the devices list going. */
jumptable_init();
#if defined(CONFIG_API)
/* Initialize API */
api_init();
#endif
console_init_r(); /* fully init console as a device */
#if defined(CONFIG_ARCH_MISC_INIT)
/* miscellaneous arch dependent initialisations */
arch_misc_init();
#endif
#if defined(CONFIG_MISC_INIT_R)
/* miscellaneous platform dependent initialisations */
misc_init_r();
#endif
/* set up exceptions */
interrupt_init();
/* enable exceptions */
enable_interrupts();
/* Perform network card initialisation if necessary */
#if defined(CONFIG_DRIVER_SMC91111) || defined (CONFIG_DRIVER_LAN91C96)
/* XXX: this needs to be moved to board init */
if (getenv("ethaddr")) {
uchar enetaddr[6];
eth_getenv_enetaddr("ethaddr", enetaddr);
smc_set_mac_addr(enetaddr);
}
#endif /* CONFIG_DRIVER_SMC91111 || CONFIG_DRIVER_LAN91C96 */
/* Initialize from environment */
s = getenv("loadaddr");
if (s != NULL)
load_addr = simple_strtoul(s, NULL, 16);
#if defined(CONFIG_CMD_NET)
s = getenv("bootfile");
if (s != NULL)
copy_filename(BootFile, s, sizeof(BootFile));
#endif
#ifdef BOARD_LATE_INIT
board_late_init();
#endif
#ifdef CONFIG_BITBANGMII
bb_miiphy_init();
#endif
#if defined(CONFIG_CMD_NET)
#if defined(CONFIG_NET_MULTI)
puts("Net: ");
#endif
eth_initialize(gd->bd);
puts("\n ");
puts("\n");
#if defined(CONFIG_RESET_PHY_R)
debug("Reset Ethernet PHY\n");
reset_phy();
#endif
#endif
#ifdef CONFIG_POST
post_run(NULL, POST_RAM | post_bootmode_get(0));
#endif
#if defined(CONFIG_PRAM) || defined(CONFIG_LOGBUFFER)
/*
* Export available size of memory for Linux,
* taking into account the protected RAM at top of memory
*/
{
ulong pram;
uchar memsz[32];
#ifdef CONFIG_PRAM
char *s;
s = getenv("pram");
if (s != NULL)
pram = simple_strtoul(s, NULL, 10);
else
pram = CONFIG_PRAM;
#else
pram = 0;
#endif
#ifdef CONFIG_LOGBUFFER
#ifndef CONFIG_ALT_LB_ADDR
/* Also take the logbuffer into account (pram is in kB) */
pram += (LOGBUFF_LEN + LOGBUFF_OVERHEAD) / 1024;
#endif
#endif
sprintf((char *)memsz, "%ldk", (gd->ram_size / 1024) - pram);
setenv("mem", (char *)memsz);
}
#endif
/*
* 进入主循环,也就说,U-Boot 的命令状态,
* 其实就是个死循环状态,它会不断地检测用户
* 是否有命令输入,然后分析输入的命令是什么,
* 最后执行输入命令对应的函数,之后又再继续地循环
*/
/* main_loop() can return to retry autoboot, if so just run it again. */
for (;;) {
main_loop();
}
/* NOTREACHED - no way out of command loop except booting */
}这个main_loop函数定义于`common/main.c`
void main_loop (void)
{
#ifndef CONFIG_SYS_HUSH_PARSER
static char lastcommand[CONFIG_SYS_CBSIZE] = { 0, };
int len;
int rc = 1;
int flag;
#endif
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
char *s;
int bootdelay;
#endif
#ifdef CONFIG_PREBOOT
char *p;
#endif
#ifdef CONFIG_BOOTCOUNT_LIMIT
unsigned long bootcount = 0;
unsigned long bootlimit = 0;
char *bcs;
char bcs_set[16];
#endif /* CONFIG_BOOTCOUNT_LIMIT */
#ifdef CONFIG_BOOTCOUNT_LIMIT
bootcount = bootcount_load();
bootcount++;
bootcount_store (bootcount);
sprintf (bcs_set, "%lu", bootcount);
setenv ("bootcount", bcs_set);
bcs = getenv ("bootlimit");
bootlimit = bcs ? simple_strtoul (bcs, NULL, 10) : 0;
#endif /* CONFIG_BOOTCOUNT_LIMIT */
#ifdef CONFIG_MODEM_SUPPORT
debug ("DEBUG: main_loop: do_mdm_init=%d\n", do_mdm_init);
if (do_mdm_init) {
char *str = strdup(getenv("mdm_cmd"));
setenv ("preboot", str); /* set or delete definition */
if (str != NULL)
free (str);
mdm_init(); /* wait for modem connection */
}
#endif /* CONFIG_MODEM_SUPPORT */
#ifdef CONFIG_VERSION_VARIABLE
{
setenv ("ver", version_string); /* set version variable */
}
#endif /* CONFIG_VERSION_VARIABLE */
#ifdef CONFIG_SYS_HUSH_PARSER
u_boot_hush_start ();
#endif
#if defined(CONFIG_HUSH_INIT_VAR)
hush_init_var ();
#endif
#ifdef CONFIG_PREBOOT
if ((p = getenv ("preboot")) != NULL) {
# ifdef CONFIG_AUTOBOOT_KEYED
int prev = disable_ctrlc(1); /* disable Control C checking */
# endif
# ifndef CONFIG_SYS_HUSH_PARSER
run_command (p, 0);
# else
parse_string_outer(p, FLAG_PARSE_SEMICOLON |
FLAG_EXIT_FROM_LOOP);
# endif
# ifdef CONFIG_AUTOBOOT_KEYED
disable_ctrlc(prev); /* restore Control C checking */
# endif
}
#endif /* CONFIG_PREBOOT */
#if defined(CONFIG_UPDATE_TFTP)
update_tftp (0UL);
#endif /* CONFIG_UPDATE_TFTP */
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
s = getenv ("bootdelay");
bootdelay = s ? (int)simple_strtol(s, NULL, 10) : CONFIG_BOOTDELAY;
debug ("### main_loop entered: bootdelay=%d\n\n", bootdelay);
# ifdef CONFIG_BOOT_RETRY_TIME
init_cmd_timeout ();
# endif /* CONFIG_BOOT_RETRY_TIME */
#ifdef CONFIG_POST
if (gd->flags & GD_FLG_POSTFAIL) {
s = getenv("failbootcmd");
}
else
#endif /* CONFIG_POST */
#ifdef CONFIG_BOOTCOUNT_LIMIT
if (bootlimit && (bootcount > bootlimit)) {
printf ("Warning: Bootlimit (%u) exceeded. Using altbootcmd.\n",
(unsigned)bootlimit);
s = getenv ("altbootcmd");
}
else
#endif /* CONFIG_BOOTCOUNT_LIMIT */
s = getenv ("bootcmd");
debug ("### main_loop: bootcmd=\"%s\"\n", s ? s : "");
if (bootdelay >= 0 && s && !abortboot (bootdelay)) {
# ifdef CONFIG_AUTOBOOT_KEYED
int prev = disable_ctrlc(1); /* disable Control C checking */
# endif
# ifndef CONFIG_SYS_HUSH_PARSER
run_command (s, 0);
# else
parse_string_outer(s, FLAG_PARSE_SEMICOLON |
FLAG_EXIT_FROM_LOOP);
# endif
# ifdef CONFIG_AUTOBOOT_KEYED
disable_ctrlc(prev); /* restore Control C checking */
# endif
}
# ifdef CONFIG_MENUKEY
if (menukey == CONFIG_MENUKEY) {
s = getenv("menucmd");
if (s) {
# ifndef CONFIG_SYS_HUSH_PARSER
run_command(s, 0);
# else
parse_string_outer(s, FLAG_PARSE_SEMICOLON |
FLAG_EXIT_FROM_LOOP);
# endif
}
}
#endif /* CONFIG_MENUKEY */
#endif /* CONFIG_BOOTDELAY */
/*添加MENU菜单 make by nietao email: [email protected] */
#ifdef CONFIG_CMD_MENU
run_command("menu", 0);
#endif
/*
* Main Loop for Monitor Command Processing
*/
#ifdef CONFIG_SYS_HUSH_PARSER
parse_file_outer();
/* This point is never reached */
for (;;);
#else
for (;;) {
#ifdef CONFIG_BOOT_RETRY_TIME
if (rc >= 0) {
/* Saw enough of a valid command to
* restart the timeout.
*/
reset_cmd_timeout();
}
#endif
len = readline (CONFIG_SYS_PROMPT);
flag = 0; /* assume no special flags for now */
if (len > 0)
strcpy (lastcommand, console_buffer);
else if (len == 0)
flag |= CMD_FLAG_REPEAT;
#ifdef CONFIG_BOOT_RETRY_TIME
else if (len == -2) {
/* -2 means timed out, retry autoboot
*/
puts ("\nTimed out waiting for command\n");
# ifdef CONFIG_RESET_TO_RETRY
/* Reinit board to run initialization code again */
do_reset (NULL, 0, 0, NULL);
# else
return; /* retry autoboot */
# endif
}
#endif
if (len == -1)
puts ("\n");
else
rc = run_command (lastcommand, flag);
if (rc <= 0) {
/* invalid command or not repeatable, forget it */
lastcommand[0] = 0;
}
}
#endif /*CONFIG_SYS_HUSH_PARSER*/
}