从主函数跳到ReqHandler，在ReqHandler内先初始化SSD--InitNandReset，然后建立映射表InitFtlMapTable
void InitNandReset()
{
// reset SSD
int i, j;
for(i=; i<CHANNEL_NUM; ++i)
{
for(j=; j<WAY_NUM; ++j)
{
WaitWayFree(i, j);
SsdReset(i, j);
}
} // change SSD mode
for(i=; i<CHANNEL_NUM; ++i)
{
for(j=; j<WAY_NUM; ++j)
{
WaitWayFree(i, j);
SsdModeChange(i, j);
}
} print("\n[ ssd NAND device reset complete. ]\r\n");
}
InitNandReset
遍历每条channel每条way来重启，change mode
接下来来看怎么建立映射表InitFtlMapTable
void InitFtlMapTable()
{
InitPageMap();
InitBlockMap();
InitDieBlock(); InitGcMap();
}
这里有四步，我们一步一步来分析
首先是页表建立，InitPageMap
#define RAM_DISK_BASE_ADDR 0x10000000
#define PAGE_MAP_ADDR (RAM_DISK_BASE_ADDR + (0x1 << 27)) //PAGE_MAP_ADDR =0x18000000
#define PAGE_NUM_PER_DIE (PAGE_NUM_PER_BLOCK * BLOCK_NUM_PER_DIE)
struct pmEntry {
u32 ppn; // Physical Page Number (PPN) to which a logical page is mapped
u32 valid : 1; // validity of a physical page
u32 lpn : 31; // Logical Page Number (LPN) of a physical page
};
每个entry页表构造如下图
每个入口8Byte
struct pmArray {
struct pmEntry pmEntry[DIE_NUM][PAGE_NUM_PER_DIE]; //页表entry个数为DIE_NUM * PAGE_NUM_PER_DIE = 16*4096*256 = 224
};
这样页表大小就为 224 * 8Byte = 128MB
void InitPageMap()
{
pageMap = (struct pmArray*)(PAGE_MAP_ADDR); // page status initialization, allows lpn, ppn access
int i, j;
for(i= ; i<DIE_NUM ; i++)
{
for(j= ; j<PAGE_NUM_PER_DIE ; j++)
{
pageMap->pmEntry[i][j].ppn = 0xffffffff; pageMap->pmEntry[i][j].valid = ;
pageMap->pmEntry[i][j].lpn = 0x7fffffff;
}
} xil_printf("[ ssd page map initialized. ]\r\n");
}
这里将设置每个页表entry的初始值，
接下来分析InitBlockMap
#define BLOCK_MAP_ADDR (PAGE_MAP_ADDR + sizeof(struct pmEntry) * PAGE_NUM_PER_SSD) //块表是在页表之后继续建立
struct bmEntry {
u32 bad : 1;
u32 free : 1;
u32 eraseCnt : 30;
u32 invalidPageCnt : 16;
u32 currentPage : 16;
u32 prevBlock;
u32 nextBlock;
};
每个块entry构造图如下，占据16Byte
struct bmArray {
struct bmEntry bmEntry[DIE_NUM][BLOCK_NUM_PER_DIE]; //块表入口数为 16 * 4096 = 216，所以块表大小为216 * 16Byte = 1MB
};
分配块表之后，首先先检测坏块--CheckBadBlock
blockMap = (struct bmArray*)(BLOCK_MAP_ADDR);
u32 dieNo, diePpn, blockNo, tempBuffer, badBlockCount;
u8* shifter;
u8* markPointer;
int loop; markPointer = (u8*)(RAM_DISK_BASE_ADDR + BAD_BLOCK_MARK_POSITION);
#define BAD_BLOCK_MARK_POSITION (7972) //代表着坏块标记的偏移量
//read badblock marks
loop = DIE_NUM *BLOCK_NUM_PER_DIE;
dieNo = METADATA_BLOCK_PPN % DIE_NUM;
diePpn = METADATA_BLOCK_PPN / DIE_NUM; tempBuffer = RAM_DISK_BASE_ADDR;
while(loop > )
{
SsdRead(dieNo % CHANNEL_NUM, dieNo / CHANNEL_NUM, diePpn, tempBuffer);
WaitWayFree(dieNo % CHANNEL_NUM, dieNo / CHANNEL_NUM); diePpn++;
tempBuffer += PAGE_SIZE;
loop -= PAGE_SIZE;
}
疑问：dieNo =0，diePpn=0，进入循环之后，读取channel0，way0的第01234567页存在tempbuffer里面，8页大小为64KB，一个字节记录一个块的信息的话，那么大小也为1Byte*16*4096=64KB，其中因为第一个块厂家保证是好的，所以不需要保存是否为坏块，所以里面可以存一个标记位，表示是否有现成的坏块信息表
if(*shifter == EMPTY_BYTE) //check whether badblock marks exist
{
// static bad block management
for(blockNo=; blockNo < BLOCK_NUM_PER_DIE; blockNo++)
for(dieNo=; dieNo < DIE_NUM; dieNo++)
{
blockMap->bmEntry[dieNo][blockNo].bad = ; SsdRead(dieNo % CHANNEL_NUM, dieNo / CHANNEL_NUM, (blockNo*PAGE_NUM_PER_BLOCK+), RAM_DISK_BASE_ADDR);
WaitWayFree(dieNo % CHANNEL_NUM, dieNo / CHANNEL_NUM); if(CountBits(*markPointer)<)
{
xil_printf("Bad block is detected on: Ch %d Way %d Block %d \r\n",dieNo%CHANNEL_NUM, dieNo/CHANNEL_NUM, blockNo);
blockMap->bmEntry[dieNo][blockNo].bad = ;
badBlockCount++;
}
shifter= (u8*)(GC_BUFFER_ADDR + blockNo + dieNo *BLOCK_NUM_PER_DIE );//gather badblock mark at GC buffer
*shifter = blockMap->bmEntry[dieNo][blockNo].bad;
} // save bad block mark
loop = DIE_NUM *BLOCK_NUM_PER_DIE;
dieNo = METADATA_BLOCK_PPN % DIE_NUM;
diePpn = METADATA_BLOCK_PPN / DIE_NUM;
blockNo = diePpn / PAGE_NUM_PER_BLOCK; SsdErase(dieNo % CHANNEL_NUM, dieNo / CHANNEL_NUM, blockNo);
WaitWayFree(dieNo % CHANNEL_NUM, dieNo / CHANNEL_NUM); tempBuffer = GC_BUFFER_ADDR;
while(loop>)
{
WaitWayFree(dieNo % CHANNEL_NUM, dieNo / CHANNEL_NUM);
SsdProgram(dieNo % CHANNEL_NUM, dieNo / CHANNEL_NUM, diePpn, tempBuffer);
diePpn++;
tempBuffer += PAGE_SIZE;
loop -= PAGE_SIZE;
}
xil_printf("[ Bad block Marks are saved. ]\r\n");
}
第九行为什么是读取每个块第一页的内容而不是第零页的内容？
12行位数小于4位就是坏块？
else //read existing bad block marks
{
for(blockNo=; blockNo<BLOCK_NUM_PER_DIE; blockNo++)
for(dieNo=; dieNo<DIE_NUM; dieNo++)
{
shifter = (u8*)(RAM_DISK_BASE_ADDR + blockNo + dieNo *BLOCK_NUM_PER_DIE );
blockMap->bmEntry[dieNo][blockNo].bad = *shifter;
if(blockMap->bmEntry[dieNo][blockNo].bad)
{
xil_printf("Bad block mark is checked at: Ch %d Way %d Block %d \r\n",dieNo % CHANNEL_NUM, dieNo / CHANNEL_NUM, blockNo );
badBlockCount++;
}
} xil_printf("[ Bad blocks are checked. ]\r\n");
} // save bad block size
BAD_BLOCK_SIZE = badBlockCount * BLOCK_SIZE_MB;
接下来是InitBlockMap的代码
blockMap = (struct bmArray*)(BLOCK_MAP_ADDR);
CheckBadBlock();
// block status initialization except bad block marks, allows only physical access
int i, j;
for(i= ; i<BLOCK_NUM_PER_DIE ; i++)
{
for(j= ; j<DIE_NUM ; j++)
{
blockMap->bmEntry[j][i].free = ;
blockMap->bmEntry[j][i].eraseCnt = ;
blockMap->bmEntry[j][i].invalidPageCnt = ;
blockMap->bmEntry[j][i].currentPage = 0x0;
blockMap->bmEntry[j][i].prevBlock = 0xffffffff;
blockMap->bmEntry[j][i].nextBlock = 0xffffffff;
}
}
初始化块表的一些值
for (i = ; i < BLOCK_NUM_PER_DIE; ++i)
for (j = ; j < DIE_NUM; ++j)
if (!blockMap->bmEntry[j][i].bad && ((i != METADATA_BLOCK_PPN % DIE_NUM)|| (j != (METADATA_BLOCK_PPN / DIE_NUM) / PAGE_NUM_PER_BLOCK)))
{
// initial block erase
WaitWayFree(j % CHANNEL_NUM, j / CHANNEL_NUM);
SsdErase(j % CHANNEL_NUM, j / CHANNEL_NUM, i);
}
xil_printf("[ ssd entire block erasure completed. ]\r\n");
除了die0的block0之外，全部擦除
for(i= ; i<DIE_NUM ; i++)
{
// initially, 0th block of each die is allocated for storage start point
blockMap->bmEntry[i][].free = ;
blockMap->bmEntry[i][].currentPage = 0xffff;
// initially, the last block of each die is reserved as free block for GC migration
blockMap->bmEntry[i][BLOCK_NUM_PER_DIE-].free = ;
}
//block0 of die0 is metadata block
blockMap->bmEntry[][].free = ;
blockMap->bmEntry[][].currentPage = 0xffff; xil_printf("[ ssd block map initialized. ]\r\n");
因为die0的第一个block是用来存储元数据，所以他开始的块指针为第一块
每个die的开始和最后一块都不能用，die0的第一块也不让用
#define DIE_MAP_ADDR (BLOCK_MAP_ADDR + sizeof(struct bmEntry) * BLOCK_NUM_PER_SSD)
struct dieEntry {
u32 currentBlock;
u32 freeBlock;
};
struct dieArray {
struct dieEntry dieEntry[DIE_NUM];
};
void InitDieBlock()
{
dieBlock = (struct dieArray*)(DIE_MAP_ADDR); // xil_printf("DIE_MAP_ADDR : %8x\r\n", DIE_MAP_ADDR); int i;
for(i= ; i<DIE_NUM ; i++)
{
if(i==) // prevent to write at meta data block
dieBlock->dieEntry[i].currentBlock = ;
else
dieBlock->dieEntry[i].currentBlock = ;
dieBlock->dieEntry[i].freeBlock = BLOCK_NUM_PER_DIE - ;
} xil_printf("[ ssd die map initialized. ]\r\n");
}
freeblock用作垃圾回收
struct gcEntry {
u32 head;
u32 tail;
};
struct gcArray {
struct gcEntry gcEntry[DIE_NUM][PAGE_NUM_PER_BLOCK+1];
};
void InitGcMap()
{
gcMap = (struct gcArray*)(GC_MAP_ADDR); // xil_printf("GC_MAP_ADDR : %8x\r\n", GC_MAP_ADDR); // gc table status initialization
int i, j;
for(i= ; i<DIE_NUM ; i++)
{
for(j= ; j<PAGE_NUM_PER_BLOCK+ ; j++)
{
gcMap->gcEntry[i][j].head = 0xffffffff;
gcMap->gcEntry[i][j].tail = 0xffffffff;
}
} xil_printf("[ ssd gc map initialized. ]\r\n");
}