嵌入式学习笔记101-uboot_1.1.6移植（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- arm-linux-gcc -v –> gcc version 3.4.5
- CROSS_COMPILE = /opt/EmbedSky/crosstools_3.4.5_softfloat/gcc-3.4.5-glibc-2.3.6/arm-linux/bin/arm-linux-
- 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 s3c24x0c. 在board目录下新增板子的名称为目录
- cd board/
- cp -ar smdk2410/ tq2440
- mv smdk2410.c tq2440.c
- 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
- cd include/configs/
- cp smdk2410.h tq2440.h
e. make xxx_config 配置板子
- make tq2440_config –> Configuring for tq2440 board…
f. make all 编译配置信息
- make all –> 会在跟目录生成bin等文件
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 syncb.第一阶段code分析
/* * armboot - Startup Code for ARM920 CPU-core * * Copyright (c) 2001 Marius Gr鰃er <[email protected]> * Copyright (c) 2002 Alex Z黳ke <[email protected]> * Copyright (c) 2002 Gary Jennejohn <[email protected]> * * 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_START
IRQ_STACK_START:
.word 0x0badc0de
/* IRQ stack memory (calculated at run-time) */
.globl FIQ_STACK_START
FIQ_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_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 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_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
#ifdef CONFIG_USE_IRQ
.align 5
irq:
get_irq_stack
irq_save_user_regs
bl do_irq
irq_restore_user_regs
.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