ADS下bootloader之MMU研究

如下是ADS下的boot的MMU.c的MMU初始化代碼。在2440init.S中跳入Main，這個Main函數在U2440mom.c中實現，這個Main函數包括了對端口，中斷服務，MMU，VGA等的初始化函數的調用。MMU.c中進行了MMU的初始化，其中調用了很多初始化函數，使用匯編寫的，確切的說是用協處理指令寫的。這些函數的聲明部分在2440slib.h，實現在2440slib.c中。在MMU的初始化程序MMU_Init中，首先禁止了Dcache,Icache，清除了Dcache和Icache。禁止了MMU，TLB。然后對存儲系統進行了虛擬地址到物理地址的映射。然后設置了轉化表的基地址，設置了域，開啟了MMU，Icache,Dcache。

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();
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();

#if 0
//To complete MMU_Init() fast, Icache may be turned on here.
MMU_EnableICache();
#endif

MMU_DisableMMU();
MMU_InvalidateTLB();
//MMU_SetMTT(int vaddrStart,int vaddrEnd,int paddrStart,int attr)
//MMU_SetMTT(0x00000000,0x07f00000,0x00000000,RW_CNB);//bank0
if(rBWSCON0x6)//nor啟動
MMU_SetMTT(0x00000000,0x07f00000,0x00000000,RW_NCNB); //bank0
else//nand 啟動
MMU_SetMTT(0x00000000,0x00001000,0/*(int)__ENTRY*/,RW_CB); //bank0
//MMU_SetMTT(0x04000000,0x07f00000,0,RW_NCNB); //bank0
MMU_SetMTT(0x08000000,0x0ff00000,0x08000000,RW_NCNB);//bank1
MMU_SetMTT(0x10000000,0x17f00000,0x10000000,RW_NCNB); //bank2
MMU_SetMTT(0x18000000,0x1ff00000,0x18000000,RW_NCNB); //bank3
//MMU_SetMTT(0x20000000,0x27f00000,0x20000000,RW_CB); //bank4
MMU_SetMTT(0x20000000,0x27f00000,0x20000000,RW_NCNB); //bank4 for STRATA Flash
MMU_SetMTT(0x28000000,0x2ff00000,0x28000000,RW_NCNB); //bank5
MMU_SetMTT(0x30000000,0x30100000,0x30000000,RW_CB); //bank6-1 1
MMU_SetMTT(0x30200000,0x33e00000,0x30200000,RW_NCNB); //bank6-2 60
//
MMU_SetMTT(0x33f00000,0x33f00000,0x33f00000,RW_CB); //bank6-3
MMU_SetMTT(0x38000000,0x3ff00000,0x38000000,RW_NCNB); //bank7

MMU_SetMTT(0x40000000,0x47f00000,0x40000000,RW_NCNB); //SFR 127
MMU_SetMTT(0x48000000,0x5af00000,0x48000000,RW_NCNB); //SFR 303
MMU_SetMTT(0x5b000000,0x5b000000,0x5b000000,RW_NCNB); //SFR
MMU_SetMTT(0x5b100000,0xfff00000,0x5b100000,RW_FAULT);//not used

MMU_SetTTBase(_MMUTT_STARTADDRESS);
MMU_SetDomain(0x55555550|DOMAIN1_ATTR|DOMAIN0_ATTR);
//DOMAIN1: no_access, DOMAIN0,215=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.
}

for(i=0;i＜64;i++)
for(j=0;j＜8;j++)
MMU_CleanInvalidateDCacheIndex((i＜＜26)|(j＜＜5));
MMU_InvalidateICache();

這里是因為ARM920T有64路，每路有8個組。所以。。。為什么要i＜＜26,j＜＜5呢，看下圖便知