Eclipse开发调试ARM裸机程序(五)MMU调试

@*@ File：head.S@ 功能：设置SDRAM，将第二部分代码到SDRAM，设置页表，启动MMU，@       然后跳到SDRAM继续执行@*@head.S.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                        @ 设置存储控制器以使用SDRAMbl  copy_2th_to_sdram               @ 将第二部分代码到SDRAMbl  create_page_table               @ 设置页表bl  mmu_init                        @ 启动MMUldr 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: 进行一些初始化，在Steppingstone中运行* 它和head.S同属第一部分程序，此时MMU未开启，使用物理地址*/ /* WATCHDOG寄存器 */#define WTCON           (*(volatile unsigned long *)0x53000000)/* 存储控制器的寄存器起始地址 */#define MEM_CTL_BASE    0x48000000/** 关闭WATCHDOG，否则CPU会不断重启*/void disable_watch_dog(void){WTCON = 0;  // 关闭WATCHDOG很简单，往这个寄存器写0即可}/** 设置存储控制器以使用SDRAM*/void memsetup(void){/* SDRAM 13个寄存器的值 */unsigned long  const    mem_cfg_val[]={ 0x22011110,     //BWSCON0x00000700,     //BANKCON00x00000700,     //BANKCON10x00000700,     //BANKCON20x00000700,     //BANKCON3  0x00000700,     //BANKCON40x00000700,     //BANKCON50x00018005,     //BANKCON60x00018005,     //BANKCON70x008C07A3,     //REFRESH0x000000B1,     //BANKSIZE0x00000030,     //MRSRB60x00000030,     //MRSRB7};int     i = 0;volatile unsigned long *p = (volatile unsigned long *)MEM_CTL_BASE;for(; i < 13; i++)p[i] = mem_cfg_val[i];}/** 将第二部分代码到SDRAM*/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++;}}/** 设置页表*/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)    /* 属于哪个域 */#define MMU_SPECIAL         (1 < 4)    /* 必须是1 */#define MMU_CACHEABLE       (1 < 3)    /* cacheable */#define MMU_BUFFERABLE      (1 < 2)    /* bufferable */#define MMU_SECTION         (2)         /* 表示这是段描述符 */#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    0x00100000unsigned long virtuladdr, physicaladdr;unsigned long *mmu_tlb_base = (unsigned long *)0x30000000;/** Steppingstone的起始物理地址为0，第一部分程序的起始运行地址也是0，* 为了在开启MMU后仍能运行第一部分的程序，* 将0～1M的虚拟地址映射到同样的物理地址*/virtuladdr = 0;physicaladdr = 0;*(mmu_tlb_base + (virtuladdr >> 20)) = (physicaladdr & 0xFFF00000) | \MMU_SECDESC_WB;/** 0x56000000是GPIO寄存器的起始物理地址，* GPBCON和GPBDAT这两个寄存器的物理地址0x56000010、0x56000014，* 为了在第二部分程序中能以地址0xA0000010、0xA0000014来操作GPBCON、GPBDAT，* 把从0xA0000000开始的1M虚拟地址空间映射到从0x56000000开始的1M物理地址空间*/virtuladdr = 0xA0000000;physicaladdr = 0x56000000;*(mmu_tlb_base + (virtuladdr >> 20)) = (physicaladdr & 0xFFF00000) | \MMU_SECDESC;/** SDRAM的物理地址范围是0x30000000～0x33FFFFFF，* 将虚拟地址0xB0000000～0xB3FFFFFF映射到物理地址0x30000000～0x33FFFFFF上，* 总共64M，涉及64个段描述符*/virtuladdr = 0xB0000000;physicaladdr = 0x30000000;while (virtuladdr < 0xB4000000){*(mmu_tlb_base + (virtuladdr >> 20)) = (physicaladdr & 0xFFF00000) | \MMU_SECDESC_WB;virtuladdr += 0x100000;physicaladdr += 0x100000;}}/** 启动MMU*/void mmu_init(void){unsigned long ttb = 0x30000000;__asm__("mov    r0, #0\n""mcr    p15, 0, r0, c7, c7, 0\n"    /* 使无效ICaches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"    /* 域访问控制寄存器设为0xFFFFFFFF，* 不进行权限检查*/    /* * 对于控制寄存器，先读出其值，在这基础上修改感兴趣的位，* 然后再写入*/"mrc    p15, 0, r0, c1, c0, 0\n"    /* 读出控制寄存器的值 *//* 控制寄存器的低16位含义为：.RVI ..RS B... .CAM* R : 表示换出Cache中的条目时使用的算法，*     0 = Random replacement；1 = Round robin replacement* V : 表示异常向量表所在的位置，*     0 = Low addresses = 0x00000000；1 = High addresses = 0xFFFF0000* I : 0 = 关闭ICaches；1 = 开启ICaches* R、S : 用来与页表中的描述符一起确定内存的访问权限* B : 0 = CPU为小字节序；1 = CPU为大字节序* C : 0 = 关闭DCaches；1 = 开启DCaches* A : 0 = 数据访问时不进行地址对齐检查；1 = 数据访问时进行地址对齐检查* M : 0 = 关闭MMU；1 = 开启MMU*//*  * 先清除不需要的位，往下若需要则重新设置它们*//* .RVI ..RS B... .CAM */ "bic    r0, r0, #0x3000\n"          /* ..11 .... .... .... 清除V、I位 */"bic    r0, r0, #0x0300\n"          /* .... ..11 .... .... 清除R、S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"          /* .... .... .... ..1. 开启对齐检查 */"orr    r0, r0, #0x0004\n"          /* .... .... .... .1.. 开启DCaches */"orr    r0, r0, #0x1000\n"          /* ...1 .... .... .... 开启ICaches */"orr    r0, r0, #0x0001\n"          /* .... .... .... ...1 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) );}

/**