Uboot 启动流程简介

SECTIONS
{
????. = 0x00000000;

????. = ALIGN(4);
????.text :
????{
???? cpu/arm920t/start.o????(.text)
???? cpu/arm920t/s3c24x0/nand_read.o (.text)
???? *(.text)
????}

????. = ALIGN(4);
????.rodata : { *(.rodata) }

????. = ALIGN(4);
????.data : { *(.data) }

????. = ALIGN(4);
????.got : { *(.got) }

????. = .;
????__u_boot_cmd_start = .;
????.u_boot_cmd : { *(.u_boot_cmd) }
????__u_boot_cmd_end = .;

????. = ALIGN(4);
????__bss_start = .;
????.bss : { *(.bss) }
????_end = .;
}

cpu/arm920t/start.o(.text)
?.text 0x33f80000 0x4e0 cpu/arm920t/start.o
????????????????0x33f80050 IRQ_STACK_START
????????????????0x33f80048 _bss_start
????????????????0x33f8004c _bss_end
????????????????0x33f80044 _armboot_start
????????????????0x33f80000 _start
????????????????0x33f80054 FIQ_STACK_START
?cpu/arm920t/s3c24x0/nand_read.o(.text)
?.text 0x33f804e0 0x1b8 cpu/arm920t/s3c24x0/nand_read.o
????????????????0x33f804e0 nand_read_ll
?*(.text)
?.text 0x33f80698 0x64 board/smdk2440/libsmdk2440.a(lowlevel_init.o)
????????????????0x33f8069c lowlevel_init
?.text 0x33f806fc 0x280 cpu/arm920t/libarm920t.a(interrupts.o)
????????????????0x33f80934 do_fiq
????????????????0x33f80880 do_undefined_instruction
????????????????0x33f80744 show_regs
????????????????0x33f80958 do_irq
????????????????0x33f80728 bad_mode
????????????????0x33f808c8 do_prefetch_abort
????????????????0x33f8070c disable_interrupts
????????????????0x33f80910 do_not_used
????????????????0x33f808ec do_data_abort
????????????????0x33f808a4 do_software_interrupt
????????????????0x33f806fc enable_interrupts
?.text 0x33f8097c 0x250 cpu/arm920t/s3c24x0/libs3c24x0.a(interrupts.o)
????????????????0x33f80aa4 set_timer
????????????????0x33f80a20 reset_timer
????????????????0x33f8097c interrupt_init
????????????????0x33f80ba0 get_tbclk
????????????????0x33f80a90 get_timer
????????????????0x33f809f0 reset_timer_masked
????????????????0x33f80a24 get_timer_masked
????????????????0x33f80ab4 udelay
????????????????0x33f80b10 udelay_masked
????????????????0x33f80bac reset_cpu
????????????????0x33f80b8c get_ticks
?.text 0x33f80bcc 0x150 cpu/arm920t/s3c24x0/libs3c24x0.a(speed.o)
????????????????0x33f80c4c get_HCLK
????????????????0x33f80cec get_PCLK
????????????????0x33f80c44 get_FCLK
????????????????0x33f80d14 get_UCLK
?.text 0x33f80d1c 0x1e8 cpu/arm920t/s3c24x0/libs3c24x0.a(cmd_s3c24xx.o)
????????????????0x33f80d8c do_s3c24xx
?.text 0x33f80f04 0xdc cpu/arm920t/s3c24x0/libs3c24x0.a(serial.o)
????????????????0x33f80f04 serial_setbrg
????????????????0x33f80fa8 serial_tstc
????????????????0x33f80f80 serial_putc
????????????????0x33f80f58 serial_init
????????????????0x33f80fb8 serial_puts
????????????????0x33f80f68 serial_getc
?.text 0x33f80fe0 0x140 lib_arm/libarm.a(_divsi3.o)
????????????????0x33f80fe0 __divsi3

_start:????
????b start_code
????ldr????pc, _undefined_instruction
????ldr????pc, _software_interrupt
????ldr????pc, _prefetch_abort
????ldr????pc, _data_abort
????ldr????pc, _not_used
????ldr????pc, _irq
????ldr????pc, _fiq

????//读取CPSR寄存器的内容到R0
????mrs????r0,cpsr
????//清除R0中的0 - 4 这5个位后保存到R0中
????//也就是清除用户模式位
????bic????r0,r0,#0x1f
????//置R0的0 1 4 6 7 位为真
????//也就是选择SVC模式
????//关闭中断和快速中断
????orr????r0,#0xd3
????//将R0中的值保存到CPSR上
????msr????cpsr,r0
# define pWTCON????????0x53000000
# define INTMSK????????0x4A000008????/* Interupt-Controller base addresses */
# define INTSUBMSK????0x4A00001C
# define LOCKTIME????0x4c000000
# define MPLLCON ????0x4c000004
# define UPLLCON ????0x4c000008
# define CLKDIVN????0x4C000014????/* clock divisor register */

# define INTSUBMSK_val????0xffff
# define MPLLCON_val????((184 << 12) + (2 << 4) + 2)????/*406M*/
# define UPLLCON_val ????((60 << 12) + (4 << 4) + 2) /* 47M */
# define CLKDIVN_val????7 /* FCLK:HCLK:PCLK = 1:3:6 */
# define CAMDIVN????0x4C000018
????//取得看门狗寄存器的地址
????ldr r0, =pWTCON
????//将R1寄存器清0
????mov r1, #0x0
????//将看门狗寄存器清0
????str r1, [r0]
????/*
???? * mask all IRQs by setting all bits in the INTMR - default
???? */
????//设R1寄存器为0xFFFF FFFF
????mov????r1, #0xffffffff
????//读取中断屏蔽寄存器的地址
????ldr????r0, =INTMSK
????//将中断屏蔽寄存器中的位全设1,屏蔽所有中断
????str????r1, [r0]
????//# define INTSUBMSK_val????0xffff
????//设R1寄存器为0xFFFF
????ldr????r1, =INTSUBMSK_val
????//读取辅助中断屏蔽寄存器的地址
????ldr????r0, =INTSUBMSK
????//将辅助中断屏蔽寄中的11个中断信号屏蔽掉
????str????r1, [r0]
????//# define LOCKTIME????0x4c000000
????//读取PLL锁频计数器寄存器地址到R0中
????ldr r0,=LOCKTIME
????//将R1设为0x00FF FFFF
????ldr r1,=0xffffff
????//M_LTIME为0xFFFF
????//U_LTIME为0x00FF
????str r1,[r0]????
????/* FCLK:HCLK:PCLK = 1:2:4 */
????/* default FCLK is 120 MHz ! */
????//# define CLKDIVN????0x4C000014????/* clock divisor register */
????//读取时钟分频寄存器的地址
????ldr????r0, =CLKDIVN
????//# define CLKDIVN_val????7 /* FCLK:HCLK:PCLK = 1:3:6 */
????//将R1设为0x7
????mov????r1, #CLKDIVN_va
????//PDIVN - 1: PCLK has the clock same as the HCLK/2.
????//HDIVN - 11 : HCLK = FCLK/3 when CAMDIVN[8] = 0.
????// HCLK = FCLK/6 when CAMDIVN[8] = 1.
????str????r1, [r0]
????/* Make sure we get FCLK:HCLK:PCLK = 1:3:6 */
????//# define CAMDIVN????0x4C000018
????//读取摄像头时钟分频寄存器的地址
????ldr r0, =CAMDIVN
????//将R1设为0
????mov r1, #0
????//将摄像头时钟分频寄存器清0
????str r1, [r0]
????/* Clock asynchronous mode */
????//MRC p15,Rd,c1,c0,0 ; read control register
????//读取控制寄存器中的值到R1中
????mrc p15, 0, r1, c1, c0, 0
????//31 iA bit Asynchronous clock select
????//30 nF bit notFastBus select
????orr r1, #0xc0000000
????//MCR p15,0 ; write control register

????//将R1中的值写到控制寄存器中
????mcr p15, 0
????//# define UPLLCON ????0x4c000008
????//读取UPLL设置寄存器的地址到R0中
????ldr????r0,=UPLLCON
????//# define UPLLCON_val ????((60 << 12) + (4 << 4) + 2) /* 47M */
????ldr????r1,=UPLLCON_val
????//将R1中的值写入UPLL设置寄存器中
????str????r1,[r0]
????//ARM920T为5级流水线,需要至少5个周期来让指令生效
????nop????
????nop
????nop
????nop
????nop
????nop
????nop
????nop
????//读取MPLL设置寄存器的地址到R0中????
????ldr????r0,=MPLLCON
????//# define MPLLCON_val????((184 << 12) + (2 << 4) + 2)????/*406M*/
????ldr????r1,=MPLLCON_val
????//将R1中的值写入MPLL设置寄存器中
????str????r1,[r0]
#define GPJCON 0x560000D0
#define GPJDAT 0x560000D4
#define GPJUP???????????? 0x560000D8
????//跳转到cpu_init_crit处执行
????//并将下一条指令的地址写入LR寄存器中
????bl????cpu_init_crit

cpu_init_crit:
????/*
???? * flush v4 I/D caches
???? */
????//将R0寄存器置0
????mov????r0, #0
????//Invalidate ICache and DCache SBZ MCR p15,c7,0
????//禁止指令和数据cache
????mcr????p15, r0, c7, 0????/* flush v3/v4 cache */
????//Invalidate TLB(s) SBZ MCR p15,c8,0
????mcr????p15, c8, 0????/* flush v4 TLB */
????/*
???? * disable MMU stuff and caches
???? */
????//MRC p15,0 ; read control register
????mrc????p15, 0
????//清除[8] [9] [13] 这3个位
????//8 - System protection
????//9 - ROM protection
????//13 - Base location of exception registers - 0 = Low addresses = 0x00000000.
????bic????r0, #0x00002300????// clear bits 13,9:8 (--V- --RS)
????//清除[0] [1] [2] [7] 这4个位
????// 0 - MMU enable - 0 = MMU disabled.
????// 1 - Alignment fault enable - 0 = Fault checking disabled.
????// 2 - DCache enable - 0 = DCache disabled.
????// 7 - Endianness - 0 = Little-endian operation.
????bic????r0, #0x00000087????// clear bits 7,2:0 (B--- -CAM)
????//设置位[1]为真
????// 1 - Alignment fault enable - 1 = Fault checking enabled.
????orr????r0, #0x00000002????// set bit 2 (A) Align
????//设置位[12]为真
????//12 - ICache enable - 1 = ICache enabled.
????orr????r0, #0x00001000????// set bit 12 (I) I-Cache
????//MCR p15,0 ; write control register
????mcr????p15, 0
????//将返回地址保存到IP中
????mov????ip, lr
????//跳转到lowlevel_init中执行
????bl????lowlevel_init

.globl lowlevel_init
????//读取下面标号为SMRDATA处的地址到R0中
????ldr r0, =SMRDATA
????//读取上面标号为_TEXT_BASE处的地址内容到R1中
????//也就是取得TEXT_BASE的值到R1中
????ldr????r1, _TEXT_BASE
????//计算SMRDATA的相对地址保存到R0中
????//SMRDATA为虚拟地址,而TEXT_BASE为虚拟地址的起始地址
????//而现在Uboot的起始地址并不为虚拟地址
????//TEXT_BASE为0x33F8 0000,SMRDATA为0x33F8 06C8
????//而现在程序运行在起始地址为0x0000 0000的地方
????//所以需要计算以0x0000 0000为标准的相对地址
????sub????r0, r1
????//取得带宽与等待状态控制寄存器地址到R1中
????ldr????r1, =BWSCON????/* Bus Width Status Controller */
????//一共需要设置13个寄存器,每个寄存器4字节
????add r2, #13*4
0:
????//读取R0所指的项的值到R3中后R0自加4字节
????ldr r3, [r0], #4
????//将R3中的值保存到R1所指的地址中后R1自加4字节
????str r3, [r1], #4
????//比较R0和R2是否相等,相等则说明13个寄存器全部设置完毕
????cmp r2, r0
????//不等则跳转到上面标号为0处的地址继续执行
????bne 0b
????//跳回到返回地址中继续执行
????mov????pc, lr
????.ltorg
/* the literal pools origin */
SMRDATA:
????.word (0+(B1_BWSCON<<4)+(B2_BWSCON<<8)+(B3_BWSCON<<12)+(B4_BWSCON<<16)+(B5_BWSCON<<20)+(B6_BWSCON<<24)+(B7_BWSCON<<28))
????.word ((B0_Tacs<<13)+(B0_Tcos<<11)+(B0_Tacc<<8)+(B0_Tcoh<<6)+(B0_Tah<<4)+(B0_Tacp<<2)+(B0_PMC))
????.word ((B1_Tacs<<13)+(B1_Tcos<<11)+(B1_Tacc<<8)+(B1_Tcoh<<6)+(B1_Tah<<4)+(B1_Tacp<<2)+(B1_PMC))
????.word ((B2_Tacs<<13)+(B2_Tcos<<11)+(B2_Tacc<<8)+(B2_Tcoh<<6)+(B2_Tah<<4)+(B2_Tacp<<2)+(B2_PMC))
????.word ((B3_Tacs<<13)+(B3_Tcos<<11)+(B3_Tacc<<8)+(B3_Tcoh<<6)+(B3_Tah<<4)+(B3_Tacp<<2)+(B3_PMC))
????.word ((B4_Tacs<<13)+(B4_Tcos<<11)+(B4_Tacc<<8)+(B4_Tcoh<<6)+(B4_Tah<<4)+(B4_Tacp<<2)+(B4_PMC))
????.word ((B5_Tacs<<13)+(B5_Tcos<<11)+(B5_Tacc<<8)+(B5_Tcoh<<6)+(B5_Tah<<4)+(B5_Tacp<<2)+(B5_PMC))
????.word ((B6_MT<<15)+(B6_Trcd<<2)+(B6_SCAN))
????.word ((B7_MT<<15)+(B7_Trcd<<2)+(B7_SCAN))
????.word ((REFEN<<23)+(TREFMD<<22)+(Trp<<20)+(Trc<<18)+(Tchr<<16)+REFCNT)
????.word 0x32
????.word 0x30
??? .word 0x30

????//恢复返回地址到LR
????mov????lr, ip
????//跳转到返回地址
????mov????pc, lr

??????? //#define GPJCON 0x560000D0
??????? //取得J端口控制寄存器的地址到R0中
????????LDR R0, = GPJCON
????????//将R1设置为0x1 5555
????????LDR R1, = 0x15555
????????//将R1中的值保存到J端口控制寄存器
????????//GPJ0 - 01 - Output
????????//GPJ1 - 01 - Output
????????//GPJ2 - 01 - Output
????????//GPJ3 - 01 - Output
????????//GPJ4 - 01 - Output
????????STR R1, [R0]
????????//#define GPJUP????????0x560000D8
??????? //取得J端口上拉功能寄存器的地址到R0中
????????LDR R0, = GPJUP
????????//将R1设置为0x1F
????????LDR R1, = 0x1f
????????//将R1中的值保存到J端口上拉功能寄存器
????????//禁止GPJ0 - GPJ4的上拉功能
????????STR R1, [R0]
????????//#define GPJDAT 0x560000D4
??????? //取得J端口数据寄存器的地址到R0中
????????LDR R0, = GPJDAT
????????//将R1设为0x0
????????LDR R1, = 0x00
????????//将R1中的值保存到J端口数据寄存器
????????//将J端口数据寄存器清0
????????STR R1, [R0]

//下面是NAND数据拷贝过程

//relocate:
copy_myself:
????//#define S3C2440_NAND_BASE????????0x4E000000
????//取得Nand Flash设置寄存器的地址
????mov????r1, #S3C2440_NAND_BASE
????//将R2设为0xFFF0
????ldr????r2, =0xfff0????????// initial value tacls=3,rph0=7,rph1=7
????//#define oNFCONF????????????0x00
????//读取Nand Flash设置寄存器中的值到R3中
????ldr????r3, [r1, #oNFCONF]
????//将R3或上R2后保存到R3中
????orr????r3, r3, r2
????//将R3中的值保存到Nand Flash设置寄存器中
????//TWRPH0 - 111 - Duration = HCLK * (TWRPH0 + 1)
????//TACLS - 11 - Duration = HCLK * TACLS
????str????r3, #oNFCONF]
????//#define oNFCONT????????????0x04
????//读取Nand Flash控制寄存器中的值到R3中
????ldr????r3, #oNFCONT]
????//将R3的[0]位置1
????orr????r3, #1????????// enable nand controller
????//将R3中的值保存到Nand Flash控制寄存器中
????//Mode - 1:Nand Flash Controller Enable
????str????r3, #oNFCONT]
????//读取虚拟起始地址到R0中
????ldr????r0, _TEXT_BASE????????/* upper 128 KiB: relocated uboot */
????//预留malloc所需要的空间
????sub????r0, #CFG_MALLOC_LEN????/* malloc area */
????//预留bdinfo所需要的空间
????sub????r0, #CFG_GBL_DATA_SIZE /* bdinfo */
????//预留中断和快速中断向量表空间
????sub????r0, #(CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ)
????//预留12字节给中断栈
????sub????sp, #12????????/* leave 3 words for abort-stack */
????// copy u-boot to RAM
????//读取虚拟起始地址到R0中,作为目标地址
????ldr????r0, _TEXT_BASE
????//将R1设为0,作为源地址
????mov r1, #0x0
????//将UBOOT大小的值保存在R2中,作为数据大小
????mov????r2, #CFG_UBOOT_SIZE
????//跳转到nand_read_ll处执行
????//并将下一条指令的地址保存在LR中
????bl????nand_read_ll

int nand_read_ll(unsigned char *buf, unsigned long start_addr, int size)
{
????int i, j;
????//检测源地址和大小是否在NandFlash的边界上
????if ((start_addr & NAND_BLOCK_MASK) || (size & NAND_BLOCK_MASK))
????????//不在边界上则返回-1表示出错
????????return -1;????/* invalid alignment */
????/* chip Enable */
????// #define nand_select()????(NFCONT &= ~(1 << 1))
????//置NAND Flash控制寄存器中除Reg_nCE外所有的位为1
????//Reg_nCE - NAND FLASH Memory nFCE signal control
????//0 - Force nFCE to low (Enable chip select)
????nand_select();
????// #define nand_clear_RnB()????(NFSTAT |= (1 << 2))
????//置NAND Flash操作状态寄存器中的RnB_TransDetect位为1
????//When RnB low to high transition is occurred,this value set and issue interrupt if enabled.?
????//To clear this value write '1'
????//1: RnB transition is detected
????nand_clear_RnB();
????for (i=0; i<10; i++);
????//从源地址的首地址开始历便所要拷贝的数据大小
????for (i=start_addr; i < (start_addr + size);)
????{
????????//检测地址是否在NAND Flash的边界上
????????if (start_addr % NAND_BLOCK_SIZE == 0)
????????{
????????????//检测是否为坏块
????????????if (is_bad_block(i))
????????????{
????????????????/* Bad block */
????????????????//向后延伸一个存储块
????????????????i += NAND_BLOCK_SIZE;
????????????????size += NAND_BLOCK_SIZE;
????????????????//跳到下一块
????????????????continue;
????????????}
????????}
????????j = nand_read_page_ll(buf, i);
????????//指向下一块
????????i += j;
????????buf += j;
????//????LED_FLASH();
????}
????/* chip Disable */
????// #define nand_deselect()????(NFCONT |= (1 << 1))
????//置Reg_nCE位为1
????//NAND Flash Memory nFCE signal control
????//1: Force nFCE to High(Disable chip select)
????nand_deselect();
????return 0;
}

????//检测R0是否为0,R0为nand_read_ll的返回值
????tst????r0, #0x0
????//为0则说明无错,跳转到ok_nand_read处执行
????beq????ok_nand_read
ok_nand_read:
????//将R0设为0
????mov????r0, #0
????//ldr????r1,=0x33f00000
????//将R1设为虚拟地址起始处
????ldr????r1, _TEXT_BASE
????//检测0x400个字节
????mov????r2, #0x400????// 4 bytes * 1024 = 4K-bytes
go_next:
????//读取R0处地址的数据到R3中
????//然后R0自加4字节
????ldr????r3, #4
????//读取R1处地址的数据到R4中
????//然后R1自加4字节
????ldr????r4, #4
????//比较R3和R4的数据是否相等
????//也就是检测Boot Internal SRAM和RAM中的数据是否相等
????//以保证数据无错
????teq????r3, r4
????//不等则跳转到notmatch
????bne????notmatch
????//相等则R2自减4
????subs????r2, r2, #4
????//当R2为0则跳转到done_nand_read
????beq????done_nand_read
????//R2不为0则跳转回go_next继续检测
????bne????go_next
done_nand_read:
??? LDR R0, = GPJDAT
??? LDR R1, = 0x2
??? STR R1, [R0]
stack_setup:
????//读取虚拟起始地址到R0中
????ldr????r0, #12????????/* leave 3 words for abort-stack */
clear_bss:
????//读取BSS段的起始地址
????ldr????r0, _bss_start????????/* find start of bss segment */
????//读取BSS段的结束地址
????ldr????r1, _bss_end????????/* stop here */
????//将R2设为0x0
????mov ????r2, #0x00000000????????/* clear */
clbss_l:
????//将R2中的值保存在R0所指的地址
????str????r2, [r0]????????/* clear loop... */
????//R0自加4字节
????add????r0, #4
????//比较R0和R1是否相等
????cmp????r0, r1
????//不等则说明清0还没结束
????ble????clbss_l
??? LDR R0, = 0x1
??? STR R1, [R0]
????//跳转到start_armboot处执行
????ldr????pc, _start_armboot


_start_armboot:????.word start_armboot