u-boot_smdkv210 分析二：启动代码start.s分析

u-boot_smdkv210 分析二：启动代码start.s分析

1.链接文件
. = 0x00000000;

. = ALIGN(4);
.text      :
{
  cpu/s5pc11x/start.o    (.text)
  cpu/s5pc11x/s5pc110/cpu_init.o  (.text)

又链接文件可知，首先启动的是start.o，现在从start.s开始分析。

2.启动阶段
u-boot的启动分为两个阶段：
stage1: 系统上电后执行的汇编代码，完成系统初始化、代码搬移等操作。
stage2:搭建c环境，进入c语言执行。

3.start.s

#if defined(CONFIG_EVT1) && !defined(CONFIG_FUSED)    阶段启动相关配置
 .word 0x2000
 .word 0x0
 .word 0x0
 .word 0x0
#endif

.globl _start
_start: b reset                                 复位入口，此处使用b指令为相对调整，不依赖运行地址
 ldr pc, _undefined_instruction            以下进入异常处理函数
 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                   定义异常处理函数地址
_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
_pad:
 .word 0x12345678 /* now 16*4=64 */           保证16字节对齐
.global _end_vect
_end_vect:

 .balignl 16,0xdeadbeef                       同样是保证16字节对齐，详见.align实验文章
/*
 *************************************************************************
 *
 * Startup Code (reset vector)                       启动代码（复位向量）此处仅进行重要的初始化操作，搬移代码和建立堆栈
 *
 * 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                            TEST_BASE为根目录下Makefile传递进来的参数，具体为0xc3e00000

/*
 * Below variable is very important because we use MMU in U-Boot.
 * Without it, we cannot run code correctly before MMU is ON.
 * by scsuh.                                        下面的代码非常重要，因为我们使用了MMU，没有这段代码，在MMC开启前我们将不能正确的运行代码
 */
_TEXT_PHY_BASE:
 .word CFG_PHY_UBOOT_BASE                  由dram的物理地址0x20000000加上0x3e00000而得，即0x23e00000.这个地址为MMU开启前的物理地址

.globl _armboot_start
_armboot_start:
 .word _start                                复位地址，具体为0xc3e00010

/*
 * These are defined in the board-specific linker script.
 */
.globl _bss_start
_bss_start:
 .word __bss_start                           __bss_start在链接脚本文件中的bss段开始，_end在bss段结尾，用于清零bss端，这两个值在链接时才确定

.globl _bss_end
_bss_end:
 .word _end

#if defined(CONFIG_USE_IRQ)                         如果使用中断，定义中断栈地址
/* 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 and IRQ & FIQ disable
  */
 @;mrs r0,cpsr
 @;bic r0,r0,#0x1f
 @;orr r0,r0,#0xd3
 @;msr cpsr,r0
 msr cpsr_c, #0xd3  @ I & F disable, Mode: 0x13 - SVC  1.进入svc模式，中断禁止

/*
 *************************************************************************
 *
 * CPU_init_critical registers
 *
 * setup important registers
 * setup memory timing
 *
 *************************************************************************
 */
         /*
         * we do sys-critical inits only at reboot, 仅在关键初始化时执行，而不是在从ram复位时执行
         * not when booting from ram!
         */
cpu_init_crit:

#ifndef CONFIG_EVT1
#if 0 
 bl v7_flush_dcache_all
#else
 bl disable_l2cache                  2.禁止l2cache

 mov r0, #0x0 @ 
 mov r1, #0x0 @ i 
 mov r3, #0x0
 mov r4, #0x0
lp1:
 mov r2, #0x0 @ j
lp2: 
 mov r3, r1, LSL #29  @ r3 = r1(i) <<29
 mov r4, r2, LSL #6  @ r4 = r2(j) <<6
 orr r4, r4, #0x2  @ r3 = (i<<29)|(j<<6)|(1<<1)
 orr r3, r3, r4
 mov r0, r3   @ r0 = r3
 bl CoInvalidateDCacheIndex                        3.清除数据缓存 8 * 1024
 add r2, #0x1  @ r2(j)++
 cmp r2, #1024  @ r2 < 1024
 bne lp2   @ jump to lp2
 add r1, #0x1  @ r1(i)++
 cmp r1, #8   @ r1(i) < 8
 bne lp1   @ jump to lp1

 bl set_l2cache_auxctrl                            4.锁定l2cache
 
 bl enable_l2cache                                 5.使能l2cache地址对齐
#endif
#endif
 
 bl disable_l2cache                                6.禁止l2cache

 bl set_l2cache_auxctrl_cycle                      7.锁定l2cache

 bl enable_l2cache                                 8.使能l2cache
 
       /*
        * Invalidate L1 I/D
        */
        mov r0, #0                  @ set up for MCR
        mcr p15, 0, r0, c8, c7, 0   @ invalidate TLBs      9.禁止TLB
        mcr p15, 0, r0, c7, c5, 0   @ invalidate icache    10.禁止指令缓存

       /*
        * disable MMU stuff and caches
        */
        mrc p15, 0, r0, c1, c0, 0
        bic r0, r0, #0x00002000     @ clear bits 13 (--V-)
        bic r0, r0, #0x00000007     @ clear bits 2:0 (-CAM)
        orr r0, r0, #0x00000002     @ set bit 1 (--A-) Align
        orr r0, r0, #0x00000800     @ set bit 12 (Z---) BTB
        mcr  p15, 0, r0, c1, c0, 0                         11.禁止MMC和cache

        /* Read booting information */
        ldr r0, =PRO_ID_BASE
        ldr r1, [r0,#OMR_OFFSET]
        bic r2, r1, #0xffffffc1                           12.读取启动信息

#ifdef CONFIG_VOGUES
 /* PS_HOLD(GPH0_0) set to output high */
 ldr r0, =ELFIN_GPIO_BASE
 ldr r1, =0x00000001
 str r1, [r0, #GPH0CON_OFFSET]

 ldr r1, =0x5500
 str r1, [r0, #GPH0PUD_OFFSET]

 ldr r1, =0x01
 str r1, [r0, #GPH0DAT_OFFSET]
#endif

 /* NAND BOOT */
 cmp r2, #0x0  @ 512B 4-cycle      13.识别各种启动方式，并将识别到的启动识别码写入R3中
 moveq r3, #BOOT_NAND

 cmp r2, #0x2  @ 2KB 5-cycle
 moveq r3, #BOOT_NAND

 cmp r2, #0x4  @ 4KB 5-cycle 8-bit ECC
 moveq r3, #BOOT_NAND

 cmp r2, #0x6  @ 4KB 5-cycle 16-bit ECC
 moveq r3, #BOOT_NAND

 cmp r2, #0x8  @ OneNAND Mux
 moveq r3, #BOOT_ONENAND

 /* SD/MMC BOOT */
 cmp     r2, #0xc
 moveq   r3, #BOOT_MMCSD 

 /* NOR BOOT */
 cmp     r2, #0x14
 moveq   r3, #BOOT_NOR 

#if 0 /* Android C110 BSP uses OneNAND booting! */
 /* For second device booting */
 /* OneNAND BOOTONG failed */
 cmp     r2, #0x8
 moveq   r3, #BOOT_SEC_DEV
#endif

 /* Uart BOOTONG failed */
 cmp     r2, #(0x1<<4)
 moveq   r3, #BOOT_SEC_DEV
 
 ldr r0, =INF_REG_BASE
 str r3, [r0, #INF_REG3_OFFSET]                                 14.将启动标识码写入INF_REG3中

 /*
  * Go setup Memory and board specific bits prior to relocation.    15.重定位前初始化存储器和板特殊位
  */

 ldr sp, =0xd0036000 /* end of sram dedicated to u-boot */      16.分配给u-boot的sram的结尾 sram为0xd0020000-d003ffff 分配大小为90k
 sub sp, sp, #12 /* set stack */
 mov fp, #0
 
 bl lowlevel_init /* go setup pll,mux,memory */              17.调用lowlevel_init函数初始化pll memory等与板子相关的内容 函数位于board目录下
 /* To hold max8698 output before releasing power on switch,
  * set PS_HOLD signal to high
  */
 ldr r0, =0xE010E81C  /* PS_HOLD_CONTROL register */            18.PS_HOLD输出高电平，PS_HOLD使能。PMIC相关
 ldr r1, =0x00005301  /* PS_HOLD output high */
 str r1, [r0]

 /* get ready to call C functions */
 ldr sp, _TEXT_PHY_BASE /* setup temp stack pointer */     19.建立临时栈指针，内容为0x23e00000
 sub sp, sp, #12
 mov fp, #0   /* no previous frame, so fp=0 */

 /* when we already run in ram, we don't need to relocate U-Boot.
  * and actually, memory controller must be configured before U-Boot   20.如果程序已经在ram中运行，我们不需要重新定位u-boot。
  * is running in ram.                                                    实际上存储器一定在u-boot在ram中运行前被初始化了
  */
 ldr r0, =0xff000fff
 bic r1, pc, r0  /* r0 <- current base addr of code */  21.r1=当前PC
 ldr r2, _TEXT_BASE  /* r1 <- original base addr in ram */
 bic r2, r2, r0  /* r0 <- current base addr of code */  22.r2=定位后运行地址
 cmp     r1, r2                  /* compare r0, r1                  */
 beq     after_copy  /* r0 == r1 then skip flash copy   */  23.如果r1=r2，跳过复制部分

#if defined(CONFIG_EVT1)
 /* If BL1 was copied from SD/MMC CH2 */
 ldr r0, =0xD0037488
 ldr r1, [r0]                          24.取0xd0037488地址的值
 ldr r2, =0xEB200000
 cmp r1, r2
 beq     mmcsd_boot                        25.如果等于0xEB200000,跳转到mmcsd_boot
#endif

 ldr r0, =INF_REG_BASE                 26.读取存储的INF_REG3中的启动类型
 ldr r1, [r0, #INF_REG3_OFFSET] 
 cmp r1, #BOOT_NAND  /* 0x0 => boot device is nand */
 beq nand_boot
 cmp r1, #BOOT_ONENAND /* 0x1 => boot device is onenand */
 beq onenand_boot
 cmp     r1, #BOOT_MMCSD
 beq     mmcsd_boot
 cmp     r1, #BOOT_NOR
 beq     nor_boot
 cmp     r1, #BOOT_SEC_DEV
 beq     mmcsd_boot

nand_boot:
 mov r0, #0x1000                       27.以下函数实现代码的搬移
 bl copy_from_nand
 b after_copy

onenand_boot:
 bl onenand_bl2_copy
 b after_copy

mmcsd_boot:
#if DELETE
 ldr     sp, _TEXT_PHY_BASE      
 sub     sp, sp, #12
 mov     fp, #0
#endif
 bl      movi_bl2_copy
 b       after_copy

nor_boot:
 bl      read_hword
 b       after_copy

after_copy:

#if defined(CONFIG_ENABLE_MMU)
enable_mmu:
 /* enable domain access */
 ldr r5, =0x0000ffff                 28.定义使能域的访问权限
 mcr p15, 0, r5, c3, c0, 0  @load domain access register

 /* Set the TTB register */
 ldr r0, _mmu_table_base
 ldr r1, =CFG_PHY_UBOOT_BASE
 ldr r2, =0xfff00000
 bic r0, r0, r2
 orr r1, r0, r1
 mcr p15, 0, r1, c2, c0, 0           29.将MMU启用前的的mmu_table_base转成sdram中的地址，并写入cp15的c2中

 /* Enable the MMU */
mmu_on:
 mrc p15, 0, r0, c1, c0, 0           30.启用mmu
 orr r0, r0, #1
 mcr p15, 0, r0, c1, c0, 0
 nop
 nop
 nop
 nop
#endif

skip_hw_init:
 /* Set up the stack          */
stack_setup:
#if defined(CONFIG_MEMORY_UPPER_CODE)
 ldr sp, =(CFG_UBOOT_BASE + CFG_UBOOT_SIZE - 0x1000)
#else
 ldr r0, _TEXT_BASE  /* upper 128 KiB: relocated uboot   */      0xc3e00000
 sub r0, r0, #CFG_MALLOC_LEN /* malloc area                      */      0x4000
 sub r0, r0, #CFG_GBL_DATA_SIZE /* bdinfo                        */      128
#if defined(CONFIG_USE_IRQ)
 sub r0, r0, #(CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ)                2*4*1024
#endif
 sub sp, r0, #12  /* leave 3 words for abort-stack    */      31.为取址终止异常预留3个字空间

#endif

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...                    */      32.清除bss端内存
 add r0, r0, #4
 cmp r0, r1
 ble clbss_l
 
 ldr pc, _start_armboot                                                  33.第一阶段结束，进入c程序阶段

_start_armboot:
 .word start_armboot

#if defined(CONFIG_ENABLE_MMU)
_mmu_table_base:
 .word mmu_table
#endif

/*
 * copy U-Boot to SDRAM and jump to ram (from NAND or OneNAND)
 * r0: size to be compared
 * Load 1'st 2blocks to RAM because U-boot's size is larger than 1block(128k) size
 */
 .globl copy_from_nand
copy_from_nand:
 push {lr}  /* save return address */

 mov r9, r0
 
 mov r9, #0x100  /* Compare about 8KB */
 bl copy_uboot_to_ram                                 35.从nandflash中读取512k到0x23e00000中
 tst  r0, #0x0
 bne copy_failed

#if defined(CONFIG_EVT1)
 ldr r0, =0xd0020000                                   36.iram的起始地址
#else 
 ldr r0, =0xd0030000                                   37.iram的中间地址
#endif
 ldr r1, _TEXT_PHY_BASE /* 0x23e00000 */

#if !defined(CONFIG_SECURE_BOOT)
1: ldr r3, [r0], #4                                      38.取r0+4地址的值到r3中
 ldr r4, [r1], #4                                      39.取r1+4地址的值到r4中
 teq r3, r4
 bne compare_failed /* not matched */                 40.如果r3和r4不相等，比较失败
 subs r9, r9, #4
 bne 1b
#endif
 pop {pc}  /* all is OK */                   41.复制成功，返回

copy_failed:
 nop   /* copy from nand failed */
 b copy_failed

compare_failed:
 nop   /* compare failed */
 b compare_failed

/*
 * we assume that cache operation is done before. (eg. cleanup_before_linux())
 * actually, we don't need to do anything about cache if not use d-cache in U-Boot
 * So, in this function we clean only MMU. by scsuh
 *
 * void theLastJump(void *kernel, int arch_num, uint boot_params);
 */
#if defined(CONFIG_ENABLE_MMU)
 .globl theLastJump
theLastJump:
 mov r9, r0                    保存内核地址
 ldr r3, =0xfff00000
 ldr r4, _TEXT_PHY_BASE
 adr r5, phy_last_jump
 bic r5, r5, r3
 orr r5, r5, r4
 mov pc, r5
phy_last_jump:
 /*
  * disable MMU stuff             关闭MMU
  */
 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

 mcr p15, 0, r0, c8, c7, 0 /* flush v4 TLB */

 mov r0, #0
 mov pc, r9                      跳转到内核地址
#endif
/*
 *************************************************************************
 *
 * 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

/*                                                     定义异常时保存寄存器的宏
 * 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  @ carve out a frame on current user stack
 stmia sp, {r0 - r12}   @ Save user registers (now in svc mode) r0-r12

 ldr r2, _armboot_start
 sub r2, r2, #(CFG_MALLOC_LEN)
 sub r2, r2, #(CFG_GBL_DATA_SIZE+8) @ set base 2 words into abort stack
 ldmia r2, {r2 - r3}   @ get values for "aborted" pc and cpsr (into parm regs)
 add r0, sp, #S_FRAME_SIZE  @ grab pointer to old stack

 add r5, sp, #S_SP
 mov r1, lr
 stmia r5, {r0 - r3}   @ save sp_SVC, lr_SVC, pc, cpsr
 mov r0, sp    @ save current stack into r0 (param register)
 .endm

 .macro irq_save_user_regs
 sub sp, sp, #S_FRAME_SIZE
 stmia sp, {r0 - r12}   @ Calling r0-r12
 add r8, sp, #S_PC   @ !!!! R8 NEEDS to be saved !!!! a reserved stack spot would be good.
 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 (enter in banked mode)
 sub r13, r13, #(CFG_MALLOC_LEN) @ move past malloc pool
 sub r13, r13, #(CFG_GBL_DATA_SIZE+8) @ move to reserved a couple spots for abort stack

 str lr, [r13]   @ save caller lr in position 0 of saved stack
 mrs lr, spsr   @ get the spsr
 str lr, [r13, #4]   @ save spsr in position 1 of saved stack

 mov r13, #MODE_SVC   @ prepare SVC-Mode
 @ msr spsr_c, r13
 msr spsr, r13   @ switch modes, make sure moves will execute
 mov lr, pc    @ capture return pc
 movs pc, lr    @ jump to next instruction & switch modes.
 .endm

 .macro get_bad_stack_swi
 sub r13, r13, #4   @ space on current stack for scratch reg.
 str r0, [r13]   @ save R0's value.
 ldr r0, _armboot_start  @ get data regions start
 sub r0, r0, #(CFG_MALLOC_LEN) @ move past malloc pool
 sub r0, r0, #(CFG_GBL_DATA_SIZE+8) @ move past gbl and a couple spots for abort stack
 str lr, [r0]   @ save caller lr in position 0 of saved stack
 mrs r0, spsr   @ get the spsr
 str lr, [r0, #4]   @ save spsr in position 1 of saved stack
 ldr r0, [r13]   @ restore r0
 add r13, r13, #4   @ pop stack entry
 .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                         异常处理句柄
 */
 .align 5
undefined_instruction:
 get_bad_stack
 bad_save_user_regs
 bl do_undefined_instruction

 .align 5
software_interrupt:
 get_bad_stack_swi
 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

#if defined(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
 .align 5
.global arm_cache_flush
arm_cache_flush:
       mcr     p15, 0, r1, c7, c5, 0           @ invalidate I cache
       mov     pc, lr                          @ back to caller

/*
 *     v7_flush_dcache_all()
 *
 *     Flush the whole D-cache.
 *
 *     Corrupted registers: r0-r5, r7, r9-r11
 *
 *     - mm    - mm_struct describing address space
 */
       .align 5
.global v7_flush_dcache_all
v7_flush_dcache_all:

 ldr r0, =0xffffffff
 mrc p15, 1, r0, c0, c0, 1   @ Read CLIDR
 ands r3, r0, #0x7000000
 mov r3, r3, LSR #23         @ Cache level value (naturally aligned)
 beq  Finished
 mov r10, #0
Loop1:         
 add r2, r10, r10, LSR #1    @ Work out 3xcachelevel
 mov r1, r0, LSR r2          @ bottom 3 bits are the Ctype for this level
 and r1, r1, #7              @ get those 3 bits alone
 cmp r1, #2
 blt Skip                     @ no cache or only instruction cache at this level
 mcr p15, 2, r10, c0, c0, 0   @ write the Cache Size selection register
 mov r1, #0
 mcr p15, 0, r1, c7, c5, 4   @ PrefetchFlush to sync the change to the CacheSizeID reg
 mrc p15, 1, r1, c0, c0, 0   @ reads current Cache Size ID register
 and r2, r1, #0x7             @ extract the line length field
 add r2, r2, #4              @ add 4 for the line length offset (log2 16 bytes)
 ldr r4, =0x3FF
 ands r4, r4, r1, LSR #3     @ R4 is the max number on the way size (right aligned)
 clz r5, r4                  @ R5 is the bit position of the way size increment
 ldr r7, =0x00007FFF
 ands r7, r7, r1, LSR #13    @ R7 is the max number of the index size (right aligned)
Loop2:         
 mov r9, r4                       @ R9 working copy of the max way size (right aligned)
Loop3:         
 orr r11, r10, r9, LSL r5         @ factor in the way number and cache number into R11
 orr r11, r11, r7, LSL r2         @ factor in the index number
 mcr p15, 0, r11, c7, c6, 2   @ invalidate by set/way
 subs r9, r9, #1                  @ decrement the way number
 bge Loop3
 subs r7, r7, #1                  @ decrement the index
 bge Loop2
Skip:          
 add r10, r10, #2                 @ increment the cache number
 cmp r3, r10
 bgt Loop1
Finished:
 mov pc, lr
 
       .align  5
.global disable_l2cache
disable_l2cache:
 mrc     p15, 0, r0, c1, c0, 1
 bic     r0, r0, #(1<<1)
 mcr     p15, 0, r0, c1, c0, 1
 mov pc, lr

       .align  5
.global enable_l2cache
enable_l2cache:
 mrc     p15, 0, r0, c1, c0, 1
 orr     r0, r0, #(1<<1)
 mcr     p15, 0, r0, c1, c0, 1
 mov     pc, lr

       .align  5
.global set_l2cache_auxctrl
set_l2cache_auxctrl:
 mov r0, #0x0
 mcr     p15, 1, r0, c9, c0, 2
 mov     pc, lr

       .align  5
.global set_l2cache_auxctrl_cycle
set_l2cache_auxctrl_cycle:
 mrc  p15, 1, r0, c9, c0, 2                   值0010_0000_0010_0000_0001_1100_0111？
 bic  r0, r0, #(0x1<<29)
 bic  r0, r0, #(0x1<<21)
 bic  r0, r0, #(0x7<<6)
 bic  r0, r0, #(0x7<<0)
 mcr  p15, 1, r0, c9, c0, 2
 mov     pc,lr

 .align 5
CoInvalidateDCacheIndex:
 ;/* r0 = index */
 mcr     p15, 0, r0, c7, c6, 2
 mov     pc,lr

#if defined(CONFIG_INTEGRATOR) && defined(CONFIG_ARCH_CINTEGRATOR)
/* Use the IntegratorCP function from board/integratorcp/platform.S */
#elif defined(CONFIG_S5PC11X)
/* For future usage of S3C64XX*/
#else
 .align 5
.globl reset_cpu
reset_cpu:
 ldr r1, rstctl /* get addr for global reset reg */
 mov r3, #0x2 /* full reset pll+mpu */
 str r3, [r1] /* force reset */              复位CPU
 mov r0, r0
_loop_forever:
 b _loop_forever
rstctl:
 .word PM_RSTCTRL_WKUP

#endif