一、介紹
Nand flash K9GAG08U0D (2G Byte)
在u-boot的shell里面執(zhí)行如下命令: 把 rootfs.yaffs從SD卡的第一個分區(qū)讀取出來,并寫到nand flash中去.
SMDK6401>fatload mmc 0:1 50008000 rootfs.yaffs
SMDK6401>nand erase 600000 $(filesize)
SMDK6401>nand write.yaffs2 50008000 600000 $(filesize)
這兒分析一下最后一條命令：將數(shù)據(jù)寫入到y(tǒng)affs2分區(qū)的過程

二、 過程分析
1.1 u-boot/common/cmd_nand.c中

1. intdo_nand(cmd_tbl_t*cmdtp,intflag,intargc,char*argv[])
   

2. {
   

3. if(strncmp(cmd,"read",4)==0||strncmp(cmd,"write",5)==0){
   

4. addr=(ulong)simple_strtoul(argv[2],NULL,16);

5. read=strncmp(cmd,"read",4)==0;/*1=read,0=write*/
   

6. 
   

7. if(arg_off_size(argc-3,argv+3,nand,&off,&size)!=0)
   

8. return 1;
   

9. 
   

10. s=strchr(cmd,'.');
    

11. if(!read&&s!=NULL&&+(!strcmp(s,".yaffs2")||!strcmp(s,".yaffs1")))
    

12. {
    

13. nand_write_options_t opts;
    

14. memset(&opts,0,sizeof(opts));
    

15. opts.buffer=(u_char*)addr;//addr=0x50008000內(nèi)存
    

16. opts.length=size;// length是文件長度
    

17. opts.offset=off;// offset 是要寫到nand flash的地址0x600000
    

18. opts.pad=0;
    

19. opts.blockalign=1;
    

20. opts.quiet=quiet;
    

21. opts.writeoob=1;
    

22. opts.autoplace=1;
    

23. ret=nand_write_opts(nand,&opts);
    

24. }
    

25. }

argv[0] argv[1] argv[2] argv[3] argv[4]
nand write.yaffs2 50008000 600000 $(filesize)
addr off size=0x420000

1.2 在文件driver/nand/nand_utils.c中

1. intnand_write_opts(nand_info_t*meminfo,constnand_write_options_t*opts)
   

2. {
   

3. ulong mtdoffset=opts->offset;//mtdoffset=nand_flash中的偏移0x600000
   

4. ulong erasesize_blockalign;
   

5. u_char*buffer=opts->buffer;//buffer=(u_char*)0x500080
   

6. imglen=opts->length;//imglen是rootfs.yaffs2這個文件的長度
   

7. while(imglen&&(mtdoffsetsize)){

8. 
   

9. //下面這個 while判斷要寫入的塊是不是壞塊，如果是壞塊繼續(xù)查找直到找到一個好塊
   

10. while(blockstart!=(mtdoffset&(~erasesize_blockalign+1))){
    

11. blockstart=mtdoffset&(~erasesize_blockalign+1);
    

12. offs=blockstart;
    

13. baderaseblock=0;
    

14. 
    

15. do{
    

16. intret=meminfo->block_isbad(meminfo,offs);//判斷是不是塊壞
    

17. 
    

18. if(ret<0){
    

19. printf("Bad block check failedn");
    

20. goto restoreoob;
    

21. }
    

22. if(ret==1){//ret=1是壞塊
    

23. baderaseblock=1;//這個地方還要設個標志，直接do_something不就得了？
    

24. if(!opts->quiet)
    

25. printf("rBad block at 0x%lx "
    

26. "in erase block from "
    

27. "0x%x will be skippedn",
    

28. (long)offs,
    

29. blockstart);
    

30. }
    

31. 
    

32. if(baderaseblock){
    

33. mtdoffset=blockstart+erasesize_blockalign;//如果ret=1是壞塊，要寫入的起始位置指向下一個塊
    

34. }
    

35. offs+= erasesize_blockalign
    

36. /opts->blockalign;
    

37. }while(offs

38. }
    

39. 
    

40. readlen=meminfo->writesize;
    

41. memcpy(data_buf,buffer,readlen); //初始時:buffer=(u_char*)0x50008000
    

42. buffer+=readlen;//meminfo->writesize= 4096
    

43. 
    

44. if (opts->writeoob) {