嵌入式Linux之我行——u-boot-2009.08在2440上的移植详解（五）

嵌入式Linux之我行，主要讲述和总结了本人在学习嵌入式linux中的每个步骤。一为总结经验，二希望能给想入门嵌入式Linux的朋友提供方便。如有错误之处，谢请指正。

• 共享资源，欢迎转载：http://hbhuanggang.cublog.cn

一、移植环境

• 主  机：VMWare--Fedora 9
• 开发板：Mini2440--64MB Nand,Kernel:2.6.30.4
• 编译器：arm-linux-gcc-4.3.2.tgz
• u-boot：u-boot-2009.08.tar.bz2

二、移植步骤

上接：u-boot-2009.08在2440上的移植详解（四）

9）实现u-boot对yaffs/yaffs2文件系统下载的支持。

 

    注意：此篇对Nand的操作是基于MTD架构方式，在“u-boot-2009.08在2440上的移植详解（三）”中讲到过。

 

    通常一个Nnad Flash存储设备由若干块组成，1个块由若干页组成。一般128MB以下容量的Nand Flash芯片，一页大小为528B，被依次分为2个256B的主数据区和16B的额外空间；128MB以上容量的Nand Flash芯片，一页大小通常为2KB。由于Nand Flash出现位反转的概率较大，一般在读写时需要使用ECC进行错误检验和恢复。

 

    Yaffs/yaffs2文件系统的设计充分考虑到Nand Flash以页为存取单位等的特点，将文件组织成固定大小的段(Chunk)。以528B的页为例，Yaffs/yaffs2文件系统使用前512B存储数据和16B的额外空间存放数据的ECC和文件系统的组织信息等(称为OOB数据)。通过OOB数据，不但能实现错误检测和坏块处理，同时还可以避免加载时对整个存储介质的扫描，加快了文件系统的加载速度。以下是Yaffs/yaffs2文件系统页的结构说明：

Yaffs页结构说明 ==============================================    字节                   用途 ==============================================  0 - 511                存储数据(分为两个半部) 512 - 515               系统信息    516                  数据状态字    517                  块状态字 518 - 519               系统信息 520 - 522               后半部256字节的ECC 523 - 524               系统信息 525 - 527               前半部256字节的ECC ==============================================

    好了，在了解Nand Flash组成和Yaffs/yaffs2文件系统结构后，我们再回到u-boot中。目前，在u-boot中已经有对Cramfs、Jffs2等文件系统的读写支持，但与带有数据校验等功能的OOB区的Yaffs/Yaffs2文件系统相比，他们是将所有文件数据简单的以线性表形式组织的。所以，我们只要在此基础上通过修改u-boot的Nand Flash读写命令，增加处理00B区域数据的功能，即可以实现对Yaffs/Yaffs2文件系统的读写支持。

实现对Yaffs或者Yaffs2文件系统的读写支持步骤如下：

①、 在include/configs/my2440.h头文件中定义一个管理对Yaffs2支持的宏和开启u-boot中对Nand Flash默认分区的宏，如下：

#gedit include/configs/my2440.h  //添加到文件末尾即可

#define CONFIG_MTD_NAND_YAFFS2   1 //定义一个管理对Yaffs2支持的宏 //开启Nand Flash默认分区，注意此处的分区要和你的内核中的分区保持一致 #define MTDIDS_DEFAULT "nand0=nandflash0" #define MTDPARTS_DEFAULT "mtdparts=nandflash0:192k(bootloader)," \                      "64k(params)," \                      "2m(kernel)," \                      "-(root)"

②、在原来对Nand操作的命令集列表中添加Yaffs2对Nand的写命令，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 devices\n"     "nand device [dev] - show or set current device\n"     "nand read - addr off|partition size\n"     "nand write - addr off|partition size\n"     " read/write 'size' bytes starting at offset 'off'\n"     " to/from memory address 'addr', skipping bad blocks.\n" //注意：这里只添加了yaffs2的写命令，因为我们只用u-boot下载(即写)功能，所以我们没有添加yaffs2读的命令 #if defined(CONFIG_MTD_NAND_YAFFS2)     "nand write[.yaffs2] - addr off|partition size - write `size' byte yaffs image\n"     " starting at offset off' from memory address addr' (.yaffs2 for 512+16 NAND)\n" #endif     "nand erase [clean] [off size] - erase 'size' bytes from\n"     " offset 'off' (entire device if not specified)\n"     "nand bad - show bad blocks\n"     "nand dump[.oob] off - dump page\n"     "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 pages\n"     "nand unlock [offset] [size] - unlock section" #endif );

接着，在该文件中对nand操作的do_nand函数中添加yaffs2对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; /* 1 = read, 0 = write */         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相关操作，注意该处又关联到nand_write_skip_bad函数 #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"))         {             /* out-of-band data */             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: %s\n", size, read ? "read" : "written", ret ? "ERROR" : "OK");         return ret == 0 ? 0 : 1;     }

③、 在include/linux/mtd/mtd.h头文件的mtd_info结构体中添加上面用到rw_oob和skipfirstblk数据成员，如下：

#gedit include/linux/mtd/mtd.h   //在mtd_info结构体中添加

#if defined(CONFIG_MTD_NAND_YAFFS2)     u_char rw_oob;     u_char skipfirstblk; #endif

④、 在第二步关联的nand_write_skip_bad函数中添加对Nand OOB的相关操作，如下：

#gedit drivers/mtd/nand/nand_util.c  //在nand_write_skip_bad函数中添加

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     /* Reject writes, which are not page aligned */     if ((offset & (nand->writesize - 1)) != 0 ||      (*length & (nand->writesize - 1)) != 0) {         printf ("Attempt to write non page aligned data\n");         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 area\n");         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 %d\n",                 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 0x%08llx\n",                 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 %llx\n", 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 %d\n",                 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函数中我们看到又对nand_write函数进行了访问，所以这一步是到nand_write函数中添加对yaffs2的支持，如下：

#gedit drivers/mtd/nand/nand_base.c  //在nand_write函数中添加

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       /* Do not allow reads past end of device */     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，对yaffs2支持的代码已修改完毕，重新编译u-boot并下载到nand中，启动开发板，在u-boot的命令行输入:nand help查看nand的命令，可以看到多了一个 nand write[.yaffs2]的命令，这个就是用来下载yaffs2文件系统到nand中的命令了。

⑥、使用nand write[.yaffs2]命令把事前制作好的yaffs2文件系统下载到Nand Flash中(yaffs2文件系统的制作请参考：Linux-2.6.30.4在2440上的移植之文件系统)，下载操作步骤和效果图如下：

tftp 0x30000000 root-2.6.30.4.bin //用tftp将yaffs2文件系统下载到内存的0x30000000位置 nand erase 0x250000 0x3dac000 //擦除Nand的文件系统分区 nand write.yaffs2 0x30000000 0x250000 0x658170 //将内存中的yaffs2文件系统写入Nand的文件系统分区，注意这里的0x658170是yaffs2文件系统的实际大小(可以在tftp传送完后可以看到)，要写正确，否则会形成假坏块

⑦、结合u-boot和内核来测试启动下载的yaffs2文件系统
设置u-boot启动参数bootargs，注意：这一长串参数要与内核配置里面的Boot options-->Default kernel command string的设置要一致。特别是mtdblock3要根据内核具体的分区来设，在上一篇中讲到了内核中Nand的分区情况，u-boot属于mtdblock0，param属于mtdblock1，kernel属于mtdblock2，root就属于mtdblock3，所以这里要设置成root=/dev/mtdblock3，否则文件系统无法启动成功，会出现一些什么I/O之类的错误

好了，最后重启开发板，内核引导成功，yaffs2文件系统也挂载成功，效果图如下：