arm9_uboot_分析源码

/*
 *  armboot - Startup Code for ARM920 CPU-core
 *
 *  Copyright (c) 2001    Marius Gr鰃er <mag@sysgo.de>
 *  Copyright (c) 2002    Alex Z黳ke <azu@sysgo.de>
 *  Copyright (c) 2002    Gary Jennejohn <gj@denx.de>
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */


#include <config.h>
#include <version.h>


/*
 *************************************************************************
 *
 * Jump vector table as in table 3.1 in [1]
 *
 *************************************************************************
 */
#define GSTATUS2       (0x560000B4)
#define GSTATUS3       (0x560000B8)
#define GSTATUS4       (0x560000BC)

#define REFRESH        (0x48000024)
#define MISCCR         (0x56000080)

#define LOCKTIME    0x4C000000    /* R/W, PLL lock time count register */
#define MPLLCON        0x4C000004    /* R/W, MPLL configuration register */
#define UPLLCON        0x4C000008    /* R/W, UPLL configuration register */
#define CLKCON        0x4C00000C    /* R/W, Clock generator control reg. */
#define CLKSLOW        0x4C000010    /* R/W, Slow clock control register */
#define CLKDIVN        0x4C000014    /* R/W, Clock divider control */


.globl _start
_start:    b       reset
    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

_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

    .balignl 16,0xdeadbeef


/*
 *************************************************************************
 *
 * Startup Code (reset vector)
 *
 * do important init only if we don't start from memory!
 * relocate armboot to ram
 * setup stack
 * jump to second stage
 *
 *************************************************************************
 */

_TEXT_BASE:
    .word    TEXT_BASE

.globl _armboot_start
_armboot_start:
    .word _start

/*
 * These are defined in the board-specific linker script.
 */
.globl _bss_start
_bss_start:
    .word __bss_start

.globl _bss_end
_bss_end:
    .word _end

.globl FREE_RAM_END
FREE_RAM_END:
    .word    0x0badc0de

.globl FREE_RAM_SIZE
FREE_RAM_SIZE:
    .word    0x0badc0de

.globl PreLoadedONRAM
PreLoadedONRAM:
    .word    0

#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


/*
 * the actual reset code
 */

reset:
    /*
     * set the cpu to SVC32 mode
     */
    mrs    r0,cpsr
    bic    r0,r0,#0x1f
    orr    r0,r0,#0xd3
    msr    cpsr,r0

/* turn off the watchdog */
#if defined(CONFIG_S3C2400)
# define pWTCON        0x15300000
# define INTMSK        0x14400008    /* Interupt-Controller base addresses */
# define CLKDIVN    0x14800014    /* clock divisor register */
#elif defined(CONFIG_S3C2410)
# define pWTCON        0x53000000
# define INTMOD     0X4A000004
# define INTMSK        0x4A000008    /* Interupt-Controller base addresses */
# define INTSUBMSK    0x4A00001C
# define CLKDIVN    0x4C000014    /* clock divisor register */
#endif

#if defined(CONFIG_S3C2400) || defined(CONFIG_S3C2410)
    ldr     r0, =pWTCON
    mov     r1, #0x0
    str     r1, [r0]

    /*
     * mask all IRQs by setting all bits in the INTMR - default
     */
    mov    r1, #0xffffffff
    ldr    r0, =INTMSK
    str    r1, [r0]
# if defined(CONFIG_S3C2410)
    ldr    r1, =0x3ff
    ldr    r0, =INTSUBMSK
    str    r1, [r0]
# endif

#if 0
    /* FCLK:HCLK:PCLK = 1:2:4 */
    /* default FCLK is 120 MHz ! */
    ldr    r0, =CLKDIVN
    mov    r1, #3
    str    r1, [r0]
#endif
#endif    /* CONFIG_S3C2400 || CONFIG_S3C2410 */

#ifndef CONFIG_SKIP_LOWLEVEL_INIT
#if 0
        /* 这些代码会使用SP,在NAND启动时会破坏片内内存的部分代码
         * 导致NAND启动时无法使用休眠-唤醒功能
         */
        /* 设置SP指向片内内存 */
        ldr sp, =4092
        ldr r0, =0x12345678
        str r0, [sp]
        ldr r1, [sp]
        cmp r0, r1
        ldrne sp, =0x40000000+4096
        bl clock_init
#else
    /* 设置时钟, 使用汇编 */
#define S3C2440_MPLL_400MHZ     ((0x5c<<12)|(0x01<<4)|(0x01))
#define S3C2440_UPLL_48MHZ      ((0x38<<12)|(0x02<<4)|(0x02))
#define S3C2440_CLKDIV          (0x05) // | (1<<3))    /* FCLK:HCLK:PCLK = 1:4:8, UCLK = UPLL/2 */

    ldr r1, =CLKDIVN
    mov r2, #S3C2440_CLKDIV
    str r2, [r1]

    mrc p15, 0, r1, c1, c0, 0        // read ctrl register 
    orr r1, r1, #0xc0000000         // Asynchronous    
    mcr p15, 0, r1, c1, c0, 0        // write ctrl register

    ldr r0,=LOCKTIME
    ldr r1,=0xffffff
    str r1,[r0]
    // delay
    mov     r0, #0x200
1:  subs    r0, r0, #1
    bne     1b

    // Configure MPLL
    ldr r0,=MPLLCON          
    ldr r1,=S3C2440_MPLL_400MHZ
    str r1,[r0]
    // delay
    mov     r0, #0x200
1:  subs    r0, r0, #1
    bne     1b

    //Configure UPLL
    ldr     r0, =UPLLCON          
    ldr     r1, =S3C2440_UPLL_48MHZ
    str     r1, [r0]
    // delay
    mov     r0, #0x200
1:  subs    r0, r0, #1
    bne     1b


#endif
#endif    

    /* 2. 根据 GSTATUS2[1]判断是复位还是唤醒 */    
    ldr r0, =GSTATUS2
    ldr r1, [r0]
    tst r1, #(1<<1)  /* r1 & (1<<1) */
    bne wake_up    

    /*
     * we do sys-critical inits only at reboot,
     * not when booting from ram!
     */
#ifndef CONFIG_SKIP_LOWLEVEL_INIT
    adr    r0, _start        /* r0 <- current position of code   */
    ldr    r1, _TEXT_BASE        /* test if we run from flash or RAM */
    cmp     r0, r1                  /* don't reloc during debug         */
    blne    cpu_init_crit
#endif

    /* Set up the stack                            */
stack_setup:
    ldr    r0, _TEXT_BASE        /* upper 128 KiB: relocated uboot   */
    sub    r0, r0, #CFG_MALLOC_LEN    /* malloc area                      */
    sub    r0, r0, #CFG_GBL_DATA_SIZE /* bdinfo                        */

#ifdef CONFIG_USE_IRQ
    sub    r0, r0, #(CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ)
#endif
    sub    sp, r0, #12        /* leave 3 words for abort-stack    */

#ifndef CONFIG_SKIP_RELOCATE_UBOOT
relocate:                /* relocate U-Boot to RAM        */
    adr    r0, _start        /* r0 <- current position of code   */
    ldr    r1, _TEXT_BASE        /* test if we run from flash or RAM */
    cmp     r0, r1                  /* don't reloc during debug         */
    beq     clear_bss
    
    ldr    r2, _armboot_start
    ldr    r3, _bss_start
    sub    r2, r3, r2        /* r2 <- size of armboot            */
#if 1
    bl  CopyCode2Ram    /* r0: source, r1: dest, r2: size */
#else
    add    r2, r0, r2        /* r2 <- source end address         */

copy_loop:
    ldmia    r0!, {r3-r10}        /* copy from source address [r0]    */
    stmia    r1!, {r3-r10}        /* copy to   target address [r1]    */
    cmp    r0, r2            /* until source end addreee [r2]    */
    ble    copy_loop
#endif
#endif    /* CONFIG_SKIP_RELOCATE_UBOOT */

clear_bss:
    ldr    r0, _bss_start        /* find start of bss segment        */
    ldr    r1, _bss_end        /* stop here                        */
    mov     r2, #0x00000000        /* clear                            */

clbss_l:str    r2, [r0]        /* clear loop...                    */
    add    r0, r0, #4
    cmp    r0, r1
    ble    clbss_l

SetLoadFlag:
    /* Set a global flag, PreLoadedONRAM */
    adr    r0, _start        /* r0 <- current position of code   */
    ldr    r1, _TEXT_BASE        /* test if we run from flash or RAM */
    cmp     r0, r1                  /* don't reloc during debug         */
    ldr r2, =PreLoadedONRAM
    mov r3, #1
    streq r3, [r2]

#if 0
    /* try doing this stuff after the relocation */
    ldr     r0, =pWTCON
    mov     r1, #0x0
    str     r1, [r0]

    /*
     * mask all IRQs by setting all bits in the INTMR - default
     */
    mov    r1, #0xffffffff
    ldr    r0, =INTMR
    str    r1, [r0]

    /* FCLK:HCLK:PCLK = 1:2:4 */
    /* default FCLK is 120 MHz ! */
    ldr    r0, =CLKDIVN
    mov    r1, #3
    str    r1, [r0]
    /* END stuff after relocation */
#endif

    ldr    pc, _start_armboot

_start_armboot:    .word start_armboot

/* 1. 按下按键 */
wake_up:
    str r1, [r0]  /* clear GSTATUS2 */
    /* 3. 设置 MISCCR[19:17]=000b, 以释放SDRAM信号 */
    ldr r0, =MISCCR
    ldr r1, [r0]
    bic r1, r1, #(7<<17)
    str r1, [r0]
        
    /* 4. 配置s3c2440的memory controller */
    bl    cpu_init_crit
    
    /* 5. 等待SDRAM退出self-refresh mode */
    mov r0, #1000
1:    subs r0, r0, #1
    cmp r0, #0
    bne 1b
    
    /* 6. 根据GSTATUS[3:4]的值来运行休眠前的函数 */
    ldr r0, =GSTATUS3
    ldr r1, [r0]
    mov pc, r1
    

/*
 *************************************************************************
 *
 * CPU_init_critical registers
 *
 * setup important registers
 * setup memory timing
 *
 *************************************************************************
 */


#ifndef CONFIG_SKIP_LOWLEVEL_INIT
cpu_init_crit:
    /*
     * flush v4 I/D caches
     */
    mov    r0, #0
    mcr    p15, 0, r0, c7, c7, 0    /* flush v3/v4 cache */
    mcr    p15, 0, r0, c8, c7, 0    /* flush v4 TLB */

    /*
     * disable MMU stuff and caches
     */
    mrc    p15, 0, r0, c1, c0, 0
    bic    r0, r0, #0x00002300    @ clear bits 13, 9:8 (--V- --RS)
    bic    r0, r0, #0x00000087    @ clear bits 7, 2:0 (B--- -CAM)
    orr    r0, r0, #0x00000002    @ set bit 2 (A) Align
    orr    r0, r0, #0x00001000    @ set bit 12 (I) I-Cache
    mcr    p15, 0, r0, c1, c0, 0

    /*
     * before relocating, we have to setup RAM timing
     * because memory timing is board-dependend, you will
     * find a lowlevel_init.S in your board directory.
     */
    mov    ip, lr
    bl    lowlevel_init
    mov    lr, ip
    mov    pc, lr
#endif /* CONFIG_SKIP_LOWLEVEL_INIT */

/*
 *************************************************************************
 *
 * Interrupt handling
 *
 *************************************************************************
 */

@
@ IRQ stack frame.
@
#define S_FRAME_SIZE    72

#define S_OLD_R0    68
#define S_PSR        64
#define S_PC        60
#define S_LR        56
#define S_SP        52

#define S_IP        48
#define S_FP        44
#define S_R10        40
#define S_R9        36
#define S_R8        32
#define S_R7        28
#define S_R6        24
#define S_R5        20
#define S_R4        16
#define S_R3        12
#define S_R2        8
#define S_R1        4
#define S_R0        0

#define MODE_SVC 0x13
#define I_BIT     0x80

/*
 * use bad_save_user_regs for abort/prefetch/undef/swi ...
 * use irq_save_user_regs / irq_restore_user_regs for IRQ/FIQ handling
 */

    .macro    bad_save_user_regs
    sub    sp, sp, #S_FRAME_SIZE
    stmia    sp, {r0 - r12}            @ Calling r0-r12
    ldr    r2, _armboot_start
    sub    r2, r2, #(CONFIG_STACKSIZE+CFG_MALLOC_LEN)
    sub    r2, r2, #(CFG_GBL_DATA_SIZE+8)  @ set base 2 words into abort stack
    ldmia    r2, {r2 - r3}            @ get pc, cpsr
    add    r0, sp, #S_FRAME_SIZE        @ restore sp_SVC

    add    r5, sp, #S_SP
    mov    r1, lr
    stmia    r5, {r0 - r3}            @ save sp_SVC, lr_SVC, pc, cpsr
    mov    r0, sp
    .endm

    .macro    irq_save_user_regs
    sub    sp, sp, #S_FRAME_SIZE
    stmia    sp, {r0 - r12}            @ Calling r0-r12
    add     r8, sp, #S_PC
    stmdb   r8, {sp, lr}^                   @ Calling SP, LR
    str     lr, [r8, #0]                    @ Save calling PC
    mrs     r6, spsr
    str     r6, [r8, #4]                    @ Save CPSR
    str     r0, [r8, #8]                    @ Save OLD_R0
    mov    r0, sp
    .endm

    .macro    irq_restore_user_regs
    ldmia    sp, {r0 - lr}^            @ Calling r0 - lr
    mov    r0, r0
    ldr    lr, [sp, #S_PC]            @ Get PC
    add    sp, sp, #S_FRAME_SIZE
    subs    pc, lr, #4            @ return & move spsr_svc into cpsr
    .endm

    .macro get_bad_stack
    ldr    r13, _armboot_start        @ setup our mode stack
    sub    r13, r13, #(CONFIG_STACKSIZE+CFG_MALLOC_LEN)
    sub    r13, r13, #(CFG_GBL_DATA_SIZE+8) @ reserved a couple spots in abort stack

    str    lr, [r13]            @ save caller lr / spsr
    mrs    lr, spsr
    str     lr, [r13, #4]

    mov    r13, #MODE_SVC            @ prepare SVC-Mode
    @ msr    spsr_c, r13
    msr    spsr, r13
    mov    lr, pc
    movs    pc, lr
    .endm

    .macro get_irq_stack            @ setup IRQ stack
    ldr    sp, IRQ_STACK_START
    .endm

    .macro get_fiq_stack            @ setup FIQ stack
    ldr    sp, FIQ_STACK_START
    .endm

/*
 * exception handlers
 */
    .align  5
undefined_instruction:
    get_bad_stack
    bad_save_user_regs
    bl     do_undefined_instruction

    .align    5
software_interrupt:
    get_bad_stack
    bad_save_user_regs
    bl     do_software_interrupt

    .align    5
prefetch_abort:
    get_bad_stack
    bad_save_user_regs
    bl     do_prefetch_abort

    .align    5
data_abort:
    get_bad_stack
    bad_save_user_regs
    bl     do_data_abort

    .align    5
not_used:
    get_bad_stack
    bad_save_user_regs
    bl     do_not_used

@ thisway.diy, 2006.06.24
.globl Launch
    .align    4
Launch:    
    mov r7, r0
    @ diable interrupt
    @ disable watch dog timer
    mov    r1, #0x53000000
    mov    r2, #0x0
    str    r2, [r1]

    ldr r1,=INTMSK
    ldr r2,=0xffffffff  @ all interrupt disable
    str r2,[r1]

    ldr r1,=INTSUBMSK
    ldr r2,=0x7ff       @ all sub interrupt disable
    str r2,[r1]

    ldr     r1, = INTMOD
    mov r2, #0x0        @ set all interrupt as IRQ (not FIQ)
    str     r2, [r1]

    @ 
    mov    ip, #0
    mcr    p15, 0, ip, c13, c0, 0      @    /* zero PID */
    mcr    p15, 0, ip, c7, c7, 0       @    /* invalidate I,D caches */
    mcr    p15, 0, ip, c7, c10, 4      @    /* drain write buffer */
    mcr    p15, 0, ip, c8, c7, 0       @    /* invalidate I,D TLBs */
    mrc    p15, 0, ip, c1, c0, 0       @    /* get control register */
    bic    ip, ip, #0x0001             @    /* disable MMU */
    mcr    p15, 0, ip, c1, c0, 0       @    /* write control register */

    @ MMU_EnableICache
    @mrc p15,0,r1,c1,c0,0
    @orr r1,r1,#(1<<12)
    @mcr p15,0,r1,c1,c0,0

    @ clear SDRAM: the end of free mem(has wince on it now) to the end of SDRAM
    ldr     r3, FREE_RAM_END
    ldr     r4, =PHYS_SDRAM_1+PHYS_SDRAM_1_SIZE    @ must clear all the memory unused to zero
    mov     r5, #0

    ldr     r1, _armboot_start
    ldr     r2, =On_Steppingstone
    sub     r2, r2, r1
    mov     pc, r2
On_Steppingstone:
2:  stmia   r3!, {r5}
    cmp     r3, r4
    bne     2b

    @ set sp = 0 on sys mode
    mov sp, #0

    @ add by thisway.diy 2006.06.26, switch to SVC mode
    msr    cpsr_c,    #0xdf    @ set the I-bit = 1, diable the IRQ interrupt
    msr    cpsr_c,    #0xd3    @ set the I-bit = 1, diable the IRQ interrupt
    ldr sp, =0x31ff5800    
    
    nop
    nop
    nop
    nop

    mov     pc, r7  @ Jump to PhysicalAddress
    nop
    mov pc, lr

#ifdef CONFIG_USE_IRQ

    .align    5
irq:
/* add by www.100ask.net to use IRQ for USB and DMA */
    sub    lr, lr, #4                    @ the return address
    ldr    sp, IRQ_STACK_START            @ the stack for irq
    stmdb    sp!,     { r0-r12,lr }    @ save registers
    
    ldr    lr,    =int_return                @ set the return addr
    ldr    pc, =IRQ_Handle                @ call the isr
int_return:
    ldmia    sp!,     { r0-r12,pc }^    @ return from interrupt

    .align    5
fiq:
    get_fiq_stack
    /* someone ought to write a more effiction fiq_save_user_regs */
    irq_save_user_regs
    bl     do_fiq
    irq_restore_user_regs

#else

    .align    5
irq:
    get_bad_stack
    bad_save_user_regs
    bl     do_irq

    .align    5
fiq:
    get_bad_stack
    bad_save_user_regs
    bl     do_fiq

#endif

以上就是boot第一阶段:

1.硬件设备初始化:将CPU设为SVC模式,关闭开门狗,设置时钟,关闭MMU,Cache

2.准备ram:设置存储控制器

3.复制boot的第二阶段的代码到ram

4.设置好栈

5.跳转到第二阶段的C入口:先清理bss段,再调用arm_lib/board.c的start_armboot函数进入第二阶段

第二阶段:

1.初始化本阶段用到的硬件:改变时钟,配置串口等

2.检测内存映射:板子的内存其实地址和大小

3.uboot命令的格式

4.为内核设置启动参数:对于arm架构,通过lib_arm/armlinux.c的do_bootm_linux函数来启动内核,这个函数设置标记列表,最后通过

theKernel (0, bd->bi_arch_number, bd->bi_boot_params);调用内核

下图为uboot内存使用情况

arm9_uboot_分析源码

 

 

 辨别是否从nor启动:

int bBootFrmNORFlash(void)
{
    volatile unsigned int *pdw = (volatile unsigned int *)0;
    unsigned int dwVal;
    
    /*
     * 无论是从NOR Flash还是从NAND Flash启动,
     * 地址0处为指令"b    Reset", 机器码为0xEA00000B,
     * 对于从NAND Flash启动的情况,其开始4KB的代码会复制到CPU内部4K内存中,
     * 对于从NOR Flash启动的情况,NOR Flash的开始地址即为0。
     * 对于NOR Flash,必须通过一定的命令序列才能写数据,
     * 所以可以根据这点差别来分辨是从NAND Flash还是NOR Flash启动:
     * 向地址0写入一个数据,然后读出来,如果没有改变的话就是NOR Flash
     */

    dwVal = *pdw;       
    *pdw = 0x12345678;
    if (*pdw != 0x12345678)
    {
        return 1;
    }
    else
    {
        *pdw = dwVal;
        return 0;
    }
}

 

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