MMU 裸机程序

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我是靠谱客的博主温婉缘分，最近开发中收集的这篇文章主要介绍MMU 裸机程序，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

来自：http://blog.sina.com.cn/s/blog_49d9a0820100e37l.html

一级页表

head.S//

@*************************************************************************
@ File：head.S
@ 功能：设置SDRAM，将第二部分代码复制到SDRAM，设置页表，启动MMU，
@

     然后跳到SDRAM继续执行
@*************************************************************************

.text
.global _start
_start:
    ldr sp,=4096                      @ 设置栈指针，以下都是C函数，调用前需要设好栈
    bldisable_watch_dog              @ 关闭WATCHDOG，否则CPU会不断重启
    blmemsetup                       @ 设置存储控制器以使用SDRAM
    blcopy_2th_to_sdram              @ 将第二部分代码复制到SDRAM
    blcreate_page_table              @ 设置页表
    blmmu_init                       @ 启动MMU
    ldr sp,=0xB4000000                @ 重设栈指针，指向SDRAM顶端(使用虚拟地址)
    ldr pc,=0xB0004000                @ 跳到SDRAM中继续执行第二部分代码
halt_loop:
   b   halt_loop

//init.c//

#defineWTCON          (*(volatile unsigned long *)0x53000000)

#defineMEM_CTL_BASE   0x48000000

void disable_watch_dog(void)
{
    WTCON = 0;// 关闭WATCHDOG很简单，往这个寄存器写0即可
}

void memsetup(void)
{

    unsignedlong const   mem_cfg_val[]={0x22011110,    //BWSCON
                                           0x00000700,    //BANKCON0
                                           0x00000700,    //BANKCON1
                                           0x00000700,    //BANKCON2
                                           0x00000700,    //BANKCON3
                                           0x00000700,    //BANKCON4
                                           0x00000700,    //BANKCON5
                                           0x00018005,    //BANKCON6
                                           0x00018005,    //BANKCON7
                                           0x008C07A3,    //REFRESH
                                           0x000000B1,    //BANKSIZE
                                           0x00000030,    //MRSRB6
                                           0x00000030,    //MRSRB7
                                   };
   int    i = 0;
    volatileunsigned long *p = (volatile unsigned long *)MEM_CTL_BASE;
    for(; i< 13; i++)
       p[i] = mem_cfg_val[i];
}

void copy_2th_to_sdram(void)
{
    unsigned int*pdwSrc = (unsigned int *)2048;
    unsigned int*pdwDest = (unsigned int *)0x30004000;

    while(pdwSrc < (unsigned int *)4096)
    {
       *pdwDest = *pdwSrc;
       pdwDest++;
       pdwSrc++;
    }
}

void create_page_table(void)
{

#defineMMU_FULL_ACCESS    (3 <<10)
#defineMMU_DOMAIN         (0 <<5)
#defineMMU_SPECIAL        (1 <<4)
#defineMMU_CACHEABLE      (1 <<3)
#defineMMU_BUFFERABLE     (1 <<2)
#defineMMU_SECTION        (2)
#defineMMU_SECDESC        (MMU_FULL_ACCESS | MMU_DOMAIN | MMU_SPECIAL |
                            MMU_SECTION)
#defineMMU_SECDESC_WB     (MMU_FULL_ACCESS | MMU_DOMAIN | MMU_SPECIAL |
                            MMU_CACHEABLE | MMU_BUFFERABLE | MMU_SECTION)
#defineMMU_SECTION_SIZE   0x00100000

    unsignedlong virtuladdr, physicaladdr;
    unsignedlong *mmu_tlb_base = (unsigned long *)0x30000000;


    virtuladdr =0;
    physicaladdr= 0;
   *(mmu_tlb_base + (virtuladdr >> 20))= (physicaladdr & 0xFFF00000) |
                                           MMU_SECDESC_WB;

//从SDRAM的开始存放页表，将虚拟地址0对应的物理地址0的页表创建好，当我们以后对这个虚拟地址操作的时候，MMU可以为我们在这个页表也找到相应的物理地址。

    virtuladdr =0xA0000000;
    physicaladdr= 0x56000000;
   *(mmu_tlb_base + (virtuladdr >> 20))= (physicaladdr & 0xFFF00000) |
                                           MMU_SECDESC;


    virtuladdr =0xB0000000;
    physicaladdr= 0x30000000;
    while(virtuladdr < 0xB4000000)
   {创建好了页表以后
       *(mmu_tlb_base + (virtuladdr >> 20))= (physicaladdr & 0xFFF00000) |
                                               MMU_SECDESC_WB;
       virtuladdr += 0x100000;
       physicaladdr += 0x100000;
    }
}

void mmu_init(void)
{
    unsignedlong ttb = 0x30000000;

__asm__(
   "mov    r0,#0n"
   "mcr    p15, 0,r0, c7, c7,0n"

   "mcr    p15, 0,r0, c7, c10, 4n"
   "mcr    p15, 0,r0, c8, c7,0n"

   "mov    r4,%0n"
   "mcr    p15, 0,r4, c2, c0,0n"

   "mvn    r0,#0n"
   "mcr    p15, 0,r0, c3, c0,0n"

   "mrc    p15, 0,r0, c1, c0,0n"





   "bic    r0, r0,#0x3000n"
   "bic    r0, r0,#0x0300n"
   "bic    r0, r0,#0x0087n"


   "orr    r0, r0,#0x0002n"
   "orr    r0, r0,#0x0004n"
   "orr    r0, r0,#0x1000n"
   "orr    r0, r0,#0x0001n"

   "mcr    p15, 0,r0, c1, c0,0n"
    :
    : "r" (ttb));
}

/mmu.lds/
SECTIONS
{
       first0x00000000 : {head.o init.o} #first
       second0xB0004000 : AT(2048) {leds.o}#指定这个段在编译出来的映像文件中的地址－加载地址。如果不使用这个选项，并且不指定0xB0004000，则加载地址等于运行地址，否则指定了 0xB0004000是不相同的。通过这个选项。可以控制各段分别保存输出文件中不同的位置。这里指定leds.o保存在映像文件的2048这个起始地址，而0xB0000000这个是段重定位地址，也称为运行地址，它是个虚拟地址。
}

///Makefile/
objs := head.o init.o leds.o

mmu.bin : $(objs)
   arm-softfloat-linux-gnu-ld -Tmmu.lds -o mmu_elf $^
   arm-softfloat-linux-gnu-objcopy -O binary -S mmu_elf $@
   arm-softfloat-linux-gnu-objdump -D -m arm mmu_elf >mmu.dis

%.o:%.c
   arm-softfloat-linux-gnu-gcc -Wall -O2 -c -o $@$<

%.o:%.S
   arm-softfloat-linux-gnu-gcc -Wall -O2 -c -o $@$<

clean:
    rm -fmmu.bin mmu_elf mmu.dis*.o

leds.c///

#defineGPFCON     (*(volatile unsigned long*)0xA0000050)    // 物理地址0x56000050
#defineGPFDAT     (*(volatile unsigned long*)0xA0000054)    // 物理地址0x56000054

#defineGPF4_out   (1<<(4*2))
#defineGPF5_out   (1<<(5*2))
#defineGPF6_out   (1<<(6*2))
#defineGPF7_out   (1<<(7*2))

static inline void wait(unsigned long dly)
{
    for(; dly> 0; dly--);
}

int main(void)
{
    unsignedlong i = 0;

    //将LED1-4对应的GPF4/5/6/7四个引脚设为输出
    GPBCON =GPF4_out|GPF5_out|GPF6_out|GPF7_out;

   while(1){
       wait(300000);
       GPBDAT =(~(i<<4));    // 根据i的值，点亮LED1-4
       if(++i == 16)
           i = 0;
    }

    return0;
}