arm9之MMU_Init()

#include "def.h"
#include "option.h"
#include "2410addr.h"
#include "2410lib.h"
#include "2410slib.h"
#include "mmu.h"

// 1) Only the section table is used. 
// 2) The cachable/non-cachable area can be changed by MMT_DEFAULT value.
//    The section size is 1MB.

void MMU_Init(void)
{
    int i,j;
    //========================== IMPORTANT NOTE =========================
    //The current stack and code area can't be re-mapped in this routine.
    //If you want memory map mapped freely, your own sophiscated MMU
    //initialization code is needed.
    //===================================================================

    MMU_DisableDCache();//关闭数据Cache
    MMU_DisableICache();//关闭指令Cache

    //If write-back is used,the DCache should be cleared.
    for(i=0;i<64;i++)    //16K的Cache由512条Cache Line组成
     for(j=0;j<8;j++)    //ARM920T的一个Cache Line是32字节
         MMU_CleanInvalidateDCacheIndex((i<<26)|(j<<5));//清除无效的数据cache内的列表
    MMU_InvalidateICache();  //无效指令cache
    
    #if 0
    //To complete MMU_Init() fast, Icache may be turned on here.
    MMU_EnableICache(); 
    #endif
    
    MMU_DisableMMU();  //关闭MMU
    MMU_InvalidateTLB();   //无效整个TLB

    //MMU_SetMTT(int vaddrStart,int vaddrEnd,int paddrStart,int attr) 虚拟地址与物理地址映射规则函数
    MMU_SetMTT(0x00000000,0x07f00000,0x00000000,RW_CNB);  //bank0 //attr为访问权限，页缓冲等属性配置
    MMU_SetMTT(0x08000000,0x0ff00000,0x08000000,RW_CNB);  //bank1  //此处皆为平行相等映射
    MMU_SetMTT(0x10000000,0x17f00000,0x10000000,RW_NCNB); //bank2
    MMU_SetMTT(0x18000000,0x1ff00000,0x18000000,RW_NCNB); //bank3
    MMU_SetMTT(0x20000000,0x27f00000,0x20000000,RW_NCNB); //bank4
    MMU_SetMTT(0x28000000,0x2ff00000,0x28000000,RW_NCNB); //bank5
    MMU_SetMTT(0x30000000,0x30f00000,0x30000000,RW_CB);   //bank6-1
    MMU_SetMTT(0x31000000,0x33e00000,0x31000000,RW_NCNB); //bank6-2
    MMU_SetMTT(0x33f00000,0x33f00000,0x33f00000,RW_CB);   //bank6-3
    MMU_SetMTT(0x38000000,0x3ff00000,0x38000000,RW_NCNB); //bank7
    
    MMU_SetMTT(0x40000000,0x5af00000,0x40000000,RW_NCNB);//SFR+StepSram    
    MMU_SetMTT(0x5b000000,0xfff00000,0x5b000000,RW_FAULT);//not used

    MMU_SetTTBase(_MMUTT_STARTADDRESS);   //设置基地址：C2用于保存页表的在内存中的基地址,
    MMU_SetDomain(0x55555550|DOMAIN1_ATTR|DOMAIN0_ATTR);   ////MMU将整个存储空间分成16个域
     //DOMAIN1: no_access, DOMAIN0,2~15=client(AP is checked)
    MMU_SetProcessId(0x0);
    MMU_EnableAlignFault();
     
    MMU_EnableMMU();
    MMU_EnableICache();
    MMU_EnableDCache(); //DCache should be turned on after MMU is turned on.
}   

// attr=RW_CB,RW_CNB,RW_NCNB,RW_FAULT
void ChangeRomCacheStatus(int attr)
{
    int i,j;
    MMU_DisableDCache();
    MMU_DisableICache();
    //If write-back is used,the DCache should be cleared.
    for(i=0;i<64;i++)
     for(j=0;j<8;j++)
         MMU_CleanInvalidateDCacheIndex((i<<26)|(j<<5));
    MMU_InvalidateICache();
    MMU_DisableMMU();
    MMU_InvalidateTLB();
    MMU_SetMTT(0x00000000,0x07f00000,0x00000000,attr); //bank0
    MMU_SetMTT(0x08000000,0x0ff00000,0x08000000,attr); //bank1
    MMU_EnableMMU();
    MMU_EnableICache();
    MMU_EnableDCache();
}    
   

//void MMU_SetMTT（虚拟地址首地址，虚拟地址末地址，物理地址首地址，相关属性）

void MMU_SetMTT(int vaddrStart,int vaddrEnd,int paddrStart,int attr)
{
    U32 *pTT;
    int i,nSec;      
    pTT=(U32 *)_MMUTT_STARTADDRESS+(vaddrStart>>20);//基址加VA高12位得到该描述符在页表中的地址
                                  // 页表中每一行对应一个虚地址页对应的实地址页的地址、该位的方位权限和该页的缓冲特性
    nSec=(vaddrEnd>>20)-(vaddrStart>>20);//段大小
    for(i=0;i<=nSec;i++)*pTT++=attr |(((paddrStart>>20)+i)<<20);//映射规则:在映射页表中条目中写上相应的要映射的物理地址及相关属性。由虚拟地址可以找到在映射页表中的相应条目，再由条目中的内容找到相应的物理地址。注：条目中的内容：高12为物理地址段基址，映射规则的根本之处；低12位为相应的访问属性等
}