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#include <config.h>
#include <version.h>
#if defined(CONFIG_OMAP1610)
#include <./configs/omap1510.h>
#elif defined(CONFIG_OMAP730)
#include <./configs/omap730.h>
#elif defined(CONFIG_HISILICON)
#include <asm/arch/platform.h>
#endif
/*
?*************************************************************************
?*
?* 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
/*
?*************************************************************************
?*
?* 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
?*
?*************************************************************************
?*/
_TEXT_BASE:
?.word?TEXT_BASE? /*应该表示在当前位置定义一个字的变量，变量的内容紧跟其后，.word为GCC汇编伪指令*/
.globl _armboot_start
_armboot_start:
?.word _start
.globl _img_end
_img_end:
?.word __img_end
/*
?* 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
#ifdef CONFIG_HISILICON
_clr_remap_rom_entry:
?.word?? ROM_TEXT_ADRS + do_clr_remap - TEXT_BASE
_clr_remap_nand_entry:
?.word?? NAND_TEXT_ADRS + do_clr_remap - TEXT_BASE
#endif
/*
?* the actual reset code
?*/
reset:
?/*
? * set the cpu to SVC32 mode
? */
?mrs?r0,cpsr
?bic?r0,r0,#0x1f
?orr?r0,#0xd3
?msr?cpsr,r0
??/*
? * we do sys-critical inits only at reboot,
? * not when booting from ram!
? */
#ifndef CONFIG_SKIP_LOWLEVEL_INIT
?/*
? * flush v4 I/D caches
? */
?mov?r0,#0
?mcr?p15,c7,0?/* flush v3/v4 cache */
?mcr?p15,c8,0?/* flush v4 TLB */
?/*
? * disable MMU stuff and caches
? */
?mrc?p15,c1,c0,0
?bic?r0,#0x00002300?/* clear bits 13,9:8 (--V- --RS) */
?bic?r0,#0x00000087?/* clear bits 7,2:0 (B--- -CAM) */
?orr?r0,#0x00000002?/* set bit 2 (A) Align */
?mcr?p15,0
?
?ldr?r0,=REG_BASE_SCTL
?ldr???? r1,[r0,#0x8c]
?and???? r1,r1,#0x60
?lsr?r4,#5?? /*以上获取BOOT状态到R4*/
?@Check if I need jump to rom
?@movs?r0,pc,lsr#24????????? /* Z flag if r0 == 0 then 1 else 0 */
?@bne???? do_clr_remap
?mov ?r0,lsr#24
?cmp ?r0,#0x0
?bne?do_clr_remap? /*检测是否需要跳转，PC的高八位如果不为0（已经在ram中运行了）则跳转*/
?
?cmp???? r4,#2 ??/* boot from nand flash*/
?ldreq?? pc,_clr_remap_nand_entry
?cmp ?r4,#0??/* boot from nor flash */
?ldreq?? pc,_clr_remap_rom_entry
do_clr_remap:
?ldr???? r4,=REG_BASE_SCTL
?@ldr?r0,=REG_VALUE_SC_NOLOCK
?@str?r0,[r4,#REG_VALUE_SC_LOCKED]
?ldr?r0,#REG_SC_CTRL]
?@Set clear remap bit.
?orr?r0,#(1<<8)
?str?r0,#REG_SC_CTRL]
?@Setup ITCM (ENABLED,2KB)
?ldr?r0,=( 1 | (MEM_CONF_ITCM_SIZE<<2) | MEM_BASE_ITCM)
?mcr???? p15,c9,1?/*以上清除重映射，清除重映射后地址0x000000处安排为ITCM，
既然还运行在flash里面那么清重映射后就会运行在ITCM里面?@enable I-Cache now
?mrc?p15,0
?orr?r0,#0x00001000?/* set bit 12 (I) I-Cache */
?mcr?p15,0
?@Setup lowlevel sp
?ldr?sp,=(MEM_BASE_ITCM + MEM_SIZE_ITCM)
?@Check if I'm running in static mem bank
?mov?r0,lsr#28
?cmp?r0,#(TEXT_BASE>>28)
?/*
? * Go setup Memory and board specific bits prior to relocation.
? */
?beq?relocate
?bl?lowlevel_init?/* go setup pll,mux,memory */
#endif
#ifndef CONFIG_SKIP_RELOCATE_UBOOT
relocate:????/* relocate U-Boot to RAM???? */? /* 将U-Boot复制到RAM中 */
?ldr???? r0,=REG_BASE_SCTL??
?ldr???? r6,#0x8c]
?and???? r6,#0x60
?lsr ?r4,r6,#5
?
?adr?r0,_start????? /* r0 <- current position of code???? r0 = 当前代码的开始地址 */
?ldr?r1,_TEXT_BASE??/* test if we run from flash or RAM?? r1 = 代码段的连接地址 */
?cmp???? r0,r1????????? /* don't reloc during debug? ?? 测试现在是在Flash中还是在RAM中? */
?beq???? stack_setup??/* 如果已经在RAM中(这通常是调试时，直接下载到RAM中)， * 则不需要复制 */
?ldr?r2,_armboot_start??/* _armboot_start在前面定义，是第一条指令的运行地址 */
?ldr?r3,_img_end??? /* 在连接脚本u-boot.lds中定义，是代码段的结束地址 */
?sub?r2,r3,r2??/* r2 <- size of armboot??????????? */?/* r2 = 代码段长度 */
?cmp ?r4,#2
?ldreq?? r2,=(CFG_NAND_U_BOOT_ONE_PART)
?add?r2,r2??/* r2 <- source end address???????? */?/* r2 = NOR Flash上代码段的结束地址 */
copy_loop:
?ldmia?r0!,{r3-r10}??/* copy from source address [r0]??? */? }/* 从地址[r0]处获得数据 */
?stmia?r1!,{r3-r10}??/* copy to?? target address [r1] 复制到地址[r1]处?? */
?cmp?r0,r2???/* until source end addreee [r2]? 判断是否复制完毕? */
?ble?copy_loop?? /* 没复制完，则继续 */
#endif?/* CONFIG_SKIP_RELOCATE_UBOOT */
/*以上重定位代码，既把代码段复制到ram空间里面*/
?/* Set up the stack????????? */
stack_setup:
?ldr?r0,_TEXT_BASE??/* upper 128 KiB: relocated uboot?? */?/* _TEXT_BASE为代码段的开始地址，值为 */
?sub?r0,#CFG_MALLOC_LEN?/* malloc area???? 代码段下面，留出一段内存以实现malloc???????? */
?sub?r0,#CFG_GBL_DATA_SIZE /* bdinfo????? 再留出一段内存，存一些全局参数????????????????? */
#ifdef CONFIG_USE_IRQ
?sub?r0,#(CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ)? /* IRQ、FIQ模式的栈 */
#endif
?sub?sp,#12??/* leave 3 words for abort-stack?? 最后，留出12字节的内存给abort异常， * 往下的内存就都是栈了? */
/*以上设置堆栈*/
clear_bss:
?ldr?r0,_bss_start??/* find start of bss segment? BSS段的开始地址，它的值在连接脚本u-boot.lds中确定????? */
?ldr?r1,_bss_end??/* stop here???? BSS段的结束地址，它的值在连接脚本u-boot.lds中确定?????????????????? */
?mov?r2,#0x00000000??/* clear??????????????????????????? */
clbss_l:str?r2,[r0]??/* clear loop...?????? 往BSS段中写入0值???????????? */
?add?r0,#4
?cmp?r0,r1
?ble?clbss_l
/*以上清除BSS*/
?ldr?pc,_start_armboot
_start_armboot: ?.word start_armboot /*以上跳转到第二段*/
待续……
