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	 > 嵌入式系統(tǒng) > 設(shè)計應(yīng)用 > 嵌入式Linux之我行——u-boot-2009.08在2440上的移植詳解（五）
          
    
          

          

          


	
	
	

          
	
          
		
          
			
          嵌入式Linux之我行——u-boot-2009.08在2440上的移植詳解（五）
          
						
          
				作者：
				時間：2016-11-20
				來源：網(wǎng)絡(luò)

							
				
				
				
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			一、移植環(huán)境
          • 主 機：VMWare--Fedora 9
          • 開發(fā)板：Mini2440--64MB Nand,Kernel:2.6.30.4
          • 編譯器：arm123.com.cn/linux/arm-linux-gcc-4.3.2.tgz" target="_blank">arm-linux-gcc-4.3.2.tgz
          • u-boot：u-boot-2009.08.tar.bz2
          二、移植步驟
          本文引用地址：http://yuyingmama.com.cn/article/201611/319003.htm
          9）實現(xiàn)u-boot對yaffs/yaffs2文件系統(tǒng)下載的支持。
          注意：此篇對Nand的操作是基于MTD架構(gòu)方式，在“u-boot-2009.08在2440上的移植詳解（三）”中講到過。
           通常一個Nnad Flash存儲設(shè)備由若干塊組成，1個塊由若干頁組成。一般128MB以下容量的Nand Flash芯片，一頁大小為528B，被依次分為2個256B的主數(shù)據(jù)區(qū)和16B的額外空間；128MB以上容量的Nand Flash芯片，一頁大小通常為2KB。由于Nand Flash出現(xiàn)位反轉(zhuǎn)的概率較大，一般在讀寫時需要使用ECC進(jìn)行錯誤檢驗和恢復(fù)。
           Yaffs/yaffs2文件系統(tǒng)的設(shè)計充分考慮到Nand Flash以頁為存取單位等的特點，將文件組織成固定大小的段(Chunk)。以528B的頁為例，Yaffs/yaffs2文件系統(tǒng)使用前512B存儲數(shù)據(jù)和16B的額外空間存放數(shù)據(jù)的ECC和文件系統(tǒng)的組織信息等(稱為OOB數(shù)據(jù))。通過OOB數(shù)據(jù)，不但能實現(xiàn)錯誤檢測和壞塊處理，同時還可以避免加載時對整個存儲介質(zhì)的掃描，加快了文件系統(tǒng)的加載速度。以下是Yaffs/yaffs2文件系統(tǒng)頁的結(jié)構(gòu)說明：
           Yaffs頁結(jié)構(gòu)說明
          ==============================================
          字節(jié) 用途
          ==============================================
          0 - 511 存儲數(shù)據(jù)(分為兩個半部)
          512 - 515 系統(tǒng)信息
          516 數(shù)據(jù)狀態(tài)字
          517 塊狀態(tài)字
          518 - 519 系統(tǒng)信息
          520 - 522 后半部256字節(jié)的ECC
          523 - 524 系統(tǒng)信息
          525 - 527 前半部256字節(jié)的ECC
          ==============================================

          好了，在了解Nand Flash組成和Yaffs/yaffs2文件系統(tǒng)結(jié)構(gòu)后，我們再回到u-boot中。目前，在u-boot中已經(jīng)有對Cramfs、Jffs2等文件系統(tǒng)的讀寫支持，但與帶有數(shù)據(jù)校驗等功能的OOB區(qū)的Yaffs/Yaffs2文件系統(tǒng)相比，他們是將所有文件數(shù)據(jù)簡單的以線性表形式組織的。所以，我們只要在此基礎(chǔ)上通過修改u-boot的Nand Flash讀寫命令，增加處理00B區(qū)域數(shù)據(jù)的功能，即可以實現(xiàn)對Yaffs/Yaffs2文件系統(tǒng)的讀寫支持。

          實現(xiàn)對Yaffs或者Yaffs2文件系統(tǒng)的讀寫支持步驟如下：
          ①、在include/configs/my2440.h頭文件中定義一個管理對Yaffs2支持的宏和開啟u-boot中對Nand Flash默認(rèn)分區(qū)的宏，如下：
          #gedit include/configs/my2440.h//添加到文件末尾即可
          #define CONFIG_MTD_NAND_YAFFS21//定義一個管理對Yaffs2支持的宏
          //開啟Nand Flash默認(rèn)分區(qū)，注意此處的分區(qū)要和你的內(nèi)核中的分區(qū)保持一致
          #define MTDIDS_DEFAULT"nand0=nandflash0"
          #define MTDPARTS_DEFAULT"mtdparts=nandflash0:192k(bootloader),"
          "64k(params),"
          "2m(kernel),"
          "-(root)"
          ②、在原來對Nand操作的命令集列表中添加Yaffs2對Nand的寫命令，如下：
          #gedit common/cmd_nand.c//在U_BOOT_CMD中添加
          U_BOOT_CMD(nand, CONFIG_SYS_MAXARGS, 1, do_nand,
           "NAND sub-system",
           "info - show available NAND devicesn"
           "nand device [dev] - show or set current devicen"
           "nand read - addr off|partition sizen"
           "nand write - addr off|partition sizen"
           " read/write size bytes starting at offset offn"
           " to/from memory address addr, skipping bad blocks.n"
          //注意：這里只添加了yaffs2的寫命令，因為我們只用u-boot下載(即寫)功能，所以我們沒有添加yaffs2讀的命令
          #if defined(CONFIG_MTD_NAND_YAFFS2)
           "nand write[.yaffs2] - addr off|partition size - write `size byte yaffs imagen"
           "starting at offset off from memory address addr (.yaffs2 for 512+16 NAND)n"
          #endif

           "nand erase [clean] [off size] - erase size bytes fromn"
           " offset off (entire device if not specified)n"
           "nand bad - show bad blocksn"
           "nand dump[.oob] off - dump pagen"
           "nand scrub - really clean NAND erasing bad blocks (UNSAFE)n"
           "nand markbad off [...] - mark bad block(s) at offset (UNSAFE)n"
           "nand biterr off - make a bit error at offset (UNSAFE)"
          #ifdef CONFIG_CMD_NAND_LOCK_UNLOCK
           "n"
           "nand lock [tight] [status]n"
           " bring nand to lock state or display locked pagesn"
           "nand unlock [offset] [size] - unlock section"
          #endif
          );

          接著，在該文件中對nand操作的do_nand函數(shù)中添加yaffs2對nand的操作，如下：
           if (strncmp(cmd, "read", 4) == 0 || strncmp(cmd, "write", 5) == 0)
           {
           int read;
           if (argc < 4)
           goto usage;
           addr = (ulong)simple_strtoul(argv[2], NULL, 16);
           read = strncmp(cmd, "read", 4) == 0;
           printf("nNAND %s: ", read ? "read" : "write");
           if (arg_off_size(argc - 3, argv + 3, nand, &off, &size) != 0)
           return 1;
           s = strchr(cmd, .);
           if (!s || !strcmp(s, ".jffs2") || !strcmp(s, ".e") || !strcmp(s, ".i"))
           {
           if (read)
           ret = nand_read_skip_bad(nand, off, &size, (u_char *)addr);
           else
           ret = nand_write_skip_bad(nand, off, &size, (u_char *)addr);
           }
          //添加yaffs2相關(guān)操作，注意該處又關(guān)聯(lián)到nand_write_skip_bad函數(shù)
          #if defined(CONFIG_MTD_NAND_YAFFS2)
           else if (s != NULL && (!strcmp(s, ".yaffs2")))
           {
           nand->rw_oob = 1;
           nand->skipfirstblk = 1;
           ret = nand_write_skip_bad(nand,off,&size,(u_char *)addr);
           nand->skipfirstblk = 0;
           nand->rw_oob = 0;
           }
          #endif
           else if (!strcmp(s, ".oob"))
           {

           mtd_oob_ops_t ops =
           {
           .oobbuf = (u8 *)addr,
           .ooblen = size,
           .mode = MTD_OOB_RAW
           };
           if (read)
           ret = nand->read_oob(nand, off, &ops);
           else
           ret = nand->write_oob(nand, off, &ops);
           }
           else
           {
           printf("Unknown nand command suffix %s.n", s);
           return 1;
           }
           printf(" %zu bytes %s: %sn", size, read ? "read" : "written", ret ? "ERROR" : "OK");
           return ret == 0 ? 0 : 1;
           }

          ③、在include/linux/mtd/mtd.h頭文件的mtd_info結(jié)構(gòu)體中添加上面用到rw_oob和skipfirstblk數(shù)據(jù)成員，如下：
          #gedit include/linux/mtd/mtd.h//在mtd_info結(jié)構(gòu)體中添加
          #if defined(CONFIG_MTD_NAND_YAFFS2)
          u_char rw_oob;
          u_char skipfirstblk;
          #endif

          ④、在第二步關(guān)聯(lián)的nand_write_skip_bad函數(shù)中添加對Nand OOB的相關(guān)操作，如下：
          #gedit drivers/mtd/nand/nand_util.c//在nand_write_skip_bad函數(shù)中添加
          int nand_write_skip_bad(nand_info_t *nand, loff_t offset, size_t *length, u_char *buffer)
          {
           int rval;
           size_t left_to_write = *length;
           size_t len_incl_bad;
           u_char *p_buffer = buffer;
          #if defined(CONFIG_MTD_NAND_YAFFS2)//add yaffs2 file system support
           if(nand->rw_oob==1)
           {
           size_t oobsize = nand->oobsize;
           size_t datasize = nand->writesize;
           int datapages = 0;
           if (((*length)%(nand->oobsize+nand->writesize)) != 0)
           {
           printf ("Attempt to write error length data!n");
           return -EINVAL;
           }
           datapages = *length/(datasize+oobsize);
           *length = datapages*datasize;
           left_to_write = *length;
           }
          #endif

           if ((offset & (nand->writesize - 1)) != 0 ||
           (*length & (nand->writesize - 1)) != 0) {
           printf ("Attempt to write non page aligned datan");
           return -EINVAL;
           }
           len_incl_bad = get_len_incl_bad (nand, offset, *length);
           if ((offset + len_incl_bad) >= nand->size) {
           printf ("Attempt to write outside the flash arean");
           return -EINVAL;
           }
          #if !defined(CONFIG_MTD_NAND_YAFFS2)//add yaffs2 file system support
           if (len_incl_bad == *length) {
           rval = nand_write (nand, offset, length, buffer);
           if (rval != 0)
           printf ("NAND write to offset %llx failed %dn",
           offset, rval);
           return rval;
           }
          #endif
           while (left_to_write > 0) {
           size_t block_offset = offset & (nand->erasesize - 1);
           size_t write_size;
           WATCHDOG_RESET ();
           if (nand_block_isbad (nand, offset & ~(nand->erasesize - 1))) {
           printf ("Skip bad block 0xllxn",
           offset & ~(nand->erasesize - 1));
           offset += nand->erasesize - block_offset;
           continue;
           }
          #if defined(CONFIG_MTD_NAND_YAFFS2)//add yaffs2 file system support
           if(nand->skipfirstblk==1)
           {
           nand->skipfirstblk=0;
           printf ("Skip the first good block %llxn", offset & ~(nand->erasesize - 1));
           offset += nand->erasesize - block_offset;
           continue;
           }
          #endif
           if (left_to_write < (nand->erasesize - block_offset))
           write_size = left_to_write;
           else
           write_size = nand->erasesize - block_offset;
          printf("rWriting at 0x%llx -- ",offset);//add yaffs2 file system support

           rval = nand_write (nand, offset, &write_size, p_buffer);
           if (rval != 0) {
           printf ("NAND write to offset %llx failed %dn",
           offset, rval);
           *length -= left_to_write;
           return rval;
           }
           left_to_write -= write_size;
           printf("%d%% is complete.",100-(left_to_write/(*length/100)));
           offset += write_size;
          #if defined(CONFIG_MTD_NAND_YAFFS2)//add yaffs2 file system support
           if(nand->rw_oob==1)
           {
           p_buffer += write_size+(write_size/nand->writesize*nand->oobsize);
           }
           else
           {
           p_buffer += write_size;
           }
          #else
           p_buffer += write_size;
          #endif
           }
           return 0;
          }

          ⑤、在第四步nand_write_skip_bad函數(shù)中我們看到又對nand_write函數(shù)進(jìn)行了訪問，所以這一步是到nand_write函數(shù)中添加對yaffs2的支持，如下：
          #gedit drivers/mtd/nand/nand_base.c//在nand_write函數(shù)中添加
          static int nand_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const uint8_t *buf)
          {
           struct nand_chip *chip = mtd->priv;
           int ret;
          #if defined(CONFIG_MTD_NAND_YAFFS2)//add yaffs2 file system support
           int oldopsmode = 0;
           if(mtd->rw_oob==1)
           {
           int i = 0;
           int datapages = 0;
           size_t oobsize = mtd->oobsize;
           size_t datasize = mtd->writesize;
           uint8_t oobtemp[oobsize];
           datapages = len / (datasize);
           for(i = 0; i < (datapages); i++)
           {
           memcpy((void *)oobtemp, (void *)(buf + datasize * (i + 1)), oobsize);
           memmove((void *)(buf + datasize * (i + 1)), (void *)(buf + datasize * (i + 1) + oobsize), (datapages - (i + 1)) * (datasize) + (datapages - 1) * oobsize);
           memcpy((void *)(buf+(datapages) * (datasize + oobsize) - oobsize), (void *)(oobtemp), oobsize);
           }
           }
          #endif

           if ((to + len) > mtd->size)
           return -EINVAL;
           if (!len)
           return 0;
           nand_get_device(chip, mtd, FL_WRITING);
           chip->ops.len = len;
           chip->ops.datbuf = (uint8_t *)buf;
          #if defined(CONFIG_MTD_NAND_YAFFS2)//add yaffs2 file system support
           if(mtd->rw_oob!=1)
           {
           chip->ops.oobbuf = NULL;
           }
           else
           {
           chip->ops.oobbuf = (uint8_t *)(buf + len);
           chip->ops.ooblen = mtd->oobsize;
           oldopsmode = chip->ops.mode;
           chip->ops.mode = MTD_OOB_RAW;
           }
          #else
           chip->ops.oobbuf = NULL;
          #endif
           ret = nand_do_write_ops(mtd, to, &chip->ops);
           *retlen = chip->ops.retlen;
           nand_release_device(mtd);
          #if defined(CONFIG_MTD_NAND_YAFFS2)//add yaffs2 file system support
           chip->ops.mode = oldopsmode;
          #endif
           return ret;
          }

          OK，對yaffs2支持的代碼已修改完畢，重新編譯u-boot并下載到nand中，啟動開發(fā)板，在u-boot的命令行輸入:nand help查看nand的命令，可以看到多了一個nand write[.yaffs2]的命令，這個就是用來下載yaffs2文件系統(tǒng)到nand中的命令了。
          ⑥、使用nand write[.yaffs2]命令把事前制作好的yaffs2文件系統(tǒng)下載到Nand Flash中(yaffs2文件系統(tǒng)的制作請參考：Linux-2.6.30.4在2440上的移植之文件系統(tǒng))，下載操作步驟和效果圖如下：
          tftp 0x30000000 root-2.6.30.4.bin//用tftp將yaffs2文件系統(tǒng)下載到內(nèi)存的0x30000000位置

          nand erase 0x250000 0x3dac000//擦除Nand的文件系統(tǒng)分區(qū)

          nand write.yaffs2 0x30000000 0x250000 0x658170//將內(nèi)存中的yaffs2文件系統(tǒng)寫入Nand的文件系統(tǒng)分區(qū)，注意這里的0x658170是yaffs2文件系統(tǒng)的實際大小(可以在tftp傳送完后可以看到)，要寫正確，否則會形成假壞塊



          ⑦、結(jié)合u-boot和內(nèi)核來測試啟動下載的yaffs2文件系統(tǒng)
          設(shè)置u-boot啟動參數(shù)bootargs，注意：這一長串參數(shù)要與內(nèi)核配置里面的Boot options-->Default kernel command string的設(shè)置要一致。特別是mtdblock3要根據(jù)內(nèi)核具體的分區(qū)來設(shè)，在上一篇中講到了內(nèi)核中Nand的分區(qū)情況，u-boot屬于mtdblock0，param屬于mtdblock1，kernel屬于mtdblock2，root就屬于mtdblock3，所以這里要設(shè)置成root=/dev/mtdblock3，否則文件系統(tǒng)無法啟動成功，會出現(xiàn)一些什么I/O之類的錯誤
          好了，最后重啟開發(fā)板，內(nèi)核引導(dǎo)成功，yaffs2文件系統(tǒng)也掛載成功，效果圖如下：
          
				
            
                
			
							
          
                
			              
              
            
          
		
          
		
          
		
          
		
          
		
          
			
            
				
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