u-boot-2009.08在2440上的移植详解（五）

发布时间：2020-12-15 18:30:25 所属栏目：百科来源：网络整理

导读：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 F

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),0)">"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,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,(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,(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,&ops);
??????????? else
??????????????? ret = nand->write_oob(nand,&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,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,&write_size,p_buffer);
??????? if (rval != 0) {
??????????? printf ("NAND write to offset %llx failed %d/n",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??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;

//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：

（编辑：李大同）

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