ARM笔记: MMU单元控制器

.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
    bl    disable_watch_dog    @关闭WATCHDOG，否则CPU会不断重启
    bl    memsetup        @设置好存储控制器以使用SDRAM
    bl    copy_2th_to_sdram    @将第二部分代码复制到SDRAM
    bl    create_page_table    @设置页表
    bl    mmu_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中继续执行第二部份代码
halt_loop:
    b    halt_loop




#define WTCON    (*(volatile unsigned long *)0x53000000)


#define MEM_CTL_BASE    0X48000000



void disable_watch_dog(void)
{
    WTCON=0;    //关闭WATCHDOG，WATCHDOG寄存器设为0
}


void memsetup(void)
{
   
    unsigned long 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;
    volatile unsigned 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)
{
//用于段描述符的一些宏定义
#define    MMU_FULL_ACCESS    (3<<10)        //访问权限
#define MMU_DOMAIN    (0<<5)        //属于那个域
#define MMU_SPECIAL    (1<<4)        //必须是1
#define MMU_CACHEABLE    (1<<3)       
#define MMU_BUFFERABLE    (1<<2)       
#define MMU_SECTION    (2)       
#define MMU_SECDESC    (MMU_FULL_ACCESS|MMU_DOMAIN|MMU_SPECIAL|MMU_SECTION)
#define MMU_SECDESC_WB   (MMU_FULL_ACCESS|MMU_DOMAIN|MMU_SPECIAL|MMU_CACHEABLE|\
             MMU_BUFFERABLE|MMU_SECTION)
#define MMU_SECTION_SIZE 0x00100000

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

   
    virtuladdr=0;
    physicaladdr=0;
    *(mmu_tlb_base+(virtuladdr>>20))=(physicaladdr&0xfff00000)|MMU_SECDESC_WB;

   
    virtuladdr=0xa0000000;
    physicaladdr=0x56000000;
    *(mmu_tlb_base+(virtuladdr>>20))=(physicaladdr&0xfff00000)|MMU_SECDESC;

   
    virtuladdr=0xb0000000;
    physicaladdr=0x30000000;
    while(virtuladdr<0xb4000000)
    {
        *(mmu_tlb_base+(virtuladdr>>20))=(physicaladdr&0xfff00000)|MMU_SECDESC_WB;
        virtuladdr+=0x100000;
        physicaladdr+=0x100000;
    }
}


void mmu_init(void)
{
    unsigned long ttb=0x30000000;
__asm__(
    "mov    r0,#0\n"
    "mcr    p15,0,r0,c7,c7,0\n"    //使无效ICches和DCaches
   
    "mcr    p15,0,r0,c7,c10,4\n"    //drain write buffer on v4
    "mcr    p15,0,r0,c8,c7,0\n"    //使无效指令,数据TLB

    "mov    r4,%0\n"        //r4=页表基址
    "mcr    p15,0,r4,c2,c0,0\n"    //设置页表基址寄存器
   
    "mvn    r0,#0\n"
    "mcr    p15,0,r0,c3,c0,0\n"   
   
    //对控制寄存器，先读出其值，在这基础上修改位，然后在写入
    "mrc    p15,0,r0,c1,c0,0\n"    //读出控制就能器的值
   
   

    //先清除不需要的位,往下若需要则重新设置
   
    "bic    r0,r0,#0x3000\n"    //.RVI ..RS B... .CAM
    "bic    r0,r0,#0x0300\n"    //..11 ..... .... ....清除V.I位
    "bic    r0,r0,#0x0087\n"    //.... .... 1... .111清除B/C/A/M

    //设置需要的位
    "orr    r0,r0,#0x0002\n"    //开启对其检查
    "orr    r0,r0,#0x0004\n"    //开启DCaches
    "orr    r0,r0,#0x1000\n"    //开启ICaches
    "orr    r0,r0,#0x0001\n"    //使能MMU

    "mcr    p15,0,r0,c1,c0,0\n"    //将修改的值写入控制寄存器
    :    //无输出
    :"r"(ttb) );
}



#define GPFCON    (*(volatile unsigned long *)0xa0000050)
#define GPFDAT    (*(volatile unsigned long *)0xa0000054)

#define GPF4_OUT    (1<<(2*4))
#define GPF5_OUT    (1<<(2*5))
#define GPF6_OUT    (1<<(2*6))


static inline void wait(volatile unsigned long dly)
{
    for(;dly>0;dly--);
}
int main(void)
{
    unsigned long i=0;
    GPFCON=GPF4_OUT|GPF5_OUT|GPF6_OUT;
   
    while(1)
    {
        wait(30000);
        GPFDAT=(~(i<<4));
        if(++i==8)
            i=0;
    }
    return 0;
}
mmu.lds:
SECTIONS{
    firtst 0x00000000 : { head.o init.o}
    second 0xb0004000 : AT(2048) { leds.o }
}
Makefile:
objs := head.o init.o leds.o

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

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

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

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