嵌入式学习笔记101-uboot_1.1.6移植（1）

1. 根据前篇博文（嵌入式学习笔记100-uboot1.1.6初体验）最后的结论，现在开始将其实现：
   a. 修改makefile的CROSS_COMPILE指定编译器

   1. arm-linux-gcc -v –> gcc version 3.4.5
   2. CROSS_COMPILE = /opt/EmbedSky/crosstools_3.4.5_softfloat/gcc-3.4.5-glibc-2.3.6/arm-linux/bin/arm-linux-
   3. chmod -R 777 u-boot-1.1.6/

   b. 在makefile里增加类似该配置
   1.tq2440_config : unconfig
   @(MKCONFIG)(@:_config=) arm arm920t tq2440 NULL s3c24x0

   c. 在board目录下新增板子的名称为目录

   1. cd board/
   2. cp -ar smdk2410/ tq2440
   3. mv smdk2410.c tq2440.c
   4. Makefile smdk2410.o –> tq2440.o

   d. 在include/configs下新增板子的头文件，文件名是配置第一个参数名

   1. cd include/configs/
   2. cp smdk2410.h tq2440.h

   e. make xxx_config 配置板子

   1. make tq2440_config –> Configuring for tq2440 board…

   f. make all 编译配置信息

   1. make all –> 会在跟目录生成bin等文件

2. 启动流程分析：
   a.删除不必要的文件以免干扰
   根目录下lib开头的库，其中保留lib_arm lib_generic
   删除board下除smdk2410 和tq2440 外所有文件
   删除include下除asm-arm外的asm-xx目录 include下configs下除smdk2410.h 和tq2440.h外的所有头文件
   删除cpu下除arm920t外所有的cpu
   重新建立一个新的project或者在原有的project sync

   b.第一阶段code分析

/* *  armboot - Startup Code for ARM920 CPU-core * *  Copyright (c) 2001  Marius Gr鰃er <[e-mail]> *  Copyright (c) 2002  Alex Z黳ke <[e-mail]> *  Copyright (c) 2002  Gary Jennejohn <[e-mail]> * * 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>/*============ ===  代码分析======================**还记得P28的config.h怎么来的么，前篇博文有提到*mkconfig 会在include下生成config.h，最终里面指向*#include <configs/tq2440.h>，所以接下来的很多宏定义都是*在include/configs/tq2440.h里定义的**=================================================*//* ************************************************************************* * * Jump vector table as in table 3.1 in [1] * ************************************************************************* */.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/*============ ===  代码分析======================**P41-P57 主要设置了中断和异常的向量*对应的处理函数其实除了IRQ,FIQ其他并没有做啥**=================================================*//* ************************************************************************* * * 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#ifdef CONFIG_USE_IRQ/* IRQ stack memory (calculated at run-time) */.globl IRQ_STACK_STARTIRQ_STACK_START:    .word   0x0badc0de/* IRQ stack memory (calculated at run-time) */.globl FIQ_STACK_STARTFIQ_STACK_START:    .word 0x0badc0de#endif/*============ ===  代码分析======================**很明显想要使能IRQ/FIQ的话要在tq2440.h里*定义这个CONFIG_USE_IRQ，不过stack的值就不是*这个0x0badc0de，要更改成合适的**=================================================*//* * 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 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    /* FCLK:HCLK:PCLK = 1:2:4 */    /* default FCLK is 120 MHz ! */    ldr r0, =CLKDIVN    mov r1, #3    str r1, [r0]#endif  /* CONFIG_S3C2400 || CONFIG_S3C2410 *//*============ ===  代码分析======================**P131-P174无非就是跟之前裸奔程序一样*关闭看门狗，设置时钟和中断**=================================================*/    /*     * we do sys-critical inits only at reboot,     * not when booting from ram!     */#ifndef CONFIG_SKIP_LOWLEVEL_INIT    bl  cpu_init_crit#endif/*============ ===  代码分析======================**P188-P190会做一次系统更基本的初始化*根据上面的注释可知如果是直接从RAM*启动的话不能调用cpu_init_crit 因为他会对RAM做*清零的动作，code download到RAM结果自己清自己*明显不行，否则程序跑到cpu_init_crit就挂了**=================================================*/#ifndef CONFIG_SKIP_RELOCATE_UBOOTrelocate:               /* 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     stack_setup    ldr r2, _armboot_start    ldr r3, _bss_start    sub r2, r3, r2      /* r2 <- size of armboot            */    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  /* CONFIG_SKIP_RELOCATE_UBOOT *//*============ ===  代码分析======================**P202-P219会判断此时正在跑的code是否就是指定的地址*其中adr  r0, _start的用法就是获得真正的运行地址*比如_start会等于board/tq2440/config.mk * TEXT_BASE = 0x33F80000*但是程序刚跑是前面的博文讲过PC是从0开始+4的，所以*地址无关的PC减去_start偏移最后_start=0,而*_TEXT_BASE = 0x33F80000，所以会执行后面的copy动作，*如果我们直接将code download到RAM的0x33F80000处，这部分的*code则相当于无效**=================================================*/    /* 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    *//*============ ===  代码分析======================**P237-P245跟之前的裸奔一样设置好栈，为第二阶段的C准备*这里需要注意的是，由于栈是对_TEXT_BASE往下偏移的，这就*要求_TEXT_BASE不能为RAM的基址，如果将_TEXT_BASE设置成*0x30000000，那再往下就不是RAM了! 这是要注意的，同时_TEXT_BASE*下还作为CFG_MALLOC_LEN的buffer，CFG_GBL_DATA_SIZE等用于*传给linux的参数**=================================================*/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#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/*============ ===  代码分析======================**设置好栈后直接调用_start_armboot，由于采用的是*ldr    pc, _start_armboot ldr是赋值绝对地址，最终导致*跑到运行地址处**=================================================*//* ************************************************************************* * * CPU_init_critical registers * * setup important registers * setup memory timing * ************************************************************************* */#ifndef CONFIG_SKIP_LOWLEVEL_INITcpu_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  5undefined_instruction:    get_bad_stack    bad_save_user_regs    bl  do_undefined_instruction    .align  5software_interrupt:    get_bad_stack    bad_save_user_regs    bl  do_software_interrupt    .align  5prefetch_abort:    get_bad_stack    bad_save_user_regs    bl  do_prefetch_abort    .align  5data_abort:    get_bad_stack    bad_save_user_regs    bl  do_data_abort    .align  5not_used:    get_bad_stack    bad_save_user_regs    bl  do_not_used#ifdef CONFIG_USE_IRQ    .align  5irq:    get_irq_stack    irq_save_user_regs    bl  do_irq    irq_restore_user_regs    .align  5fiq:    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  5irq:    get_bad_stack    bad_save_user_regs    bl  do_irq    .align  5fiq:    get_bad_stack    bad_save_user_regs    bl  do_fiq#endif