移植环境
1，主机环境：VMare下CentOS 5.5 ，1G内存。
2，集成开发环境：Elipse IDE
3，编译编译环境：arm-linux-gcc v4.4.3，arm-none-eabi-gcc v4.5.1。
4，开发板：mini2440，2M nor flash，128M nand flash。
5，u-boot版本：u-boot-2009.08
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由于现在很多使用Nand Flash 的系统，在Linux 下都用Yaffs2作为存储数据的文件系统，甚至是根文件系统。所以在BootLoader 下能够烧写Yaffs2 映像文件变得很必要。对于Yaffs2 映像烧写的支持其实就是在烧写时，写入数据的同时，将镜像文件中的oob数据也写入到Nand Flash 的Spare 区。这和Yaffs 文件系统原理以及Nand Flash 的结构有关，注意：这里对Nand的操作是基于MTD架构方式。
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u-boot对Yaffs或者Yaffs2文件系统的读写支持步骤如下：
【1】下面是需要修改的 4 个文件的补丁：
(1)打开/common/cmd_nand.c，定位到392行，在nand操作的do_nand函数中，修改如下：
?? if (read)
??? ret = nand_read_skip_bad(nand,off,&size,
??????? (u_char *)addr);
?? else
??? ret = nand_write_skip_bad(nand,
???????? (u_char *)addr);
}
#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
?? };
... ...
定位到509行附近，在Nand操作的命令集列表中添加Yaffs2对Nand的读写命令，修改如下
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 'off'n"
?"??? to/from memory address 'addr',skipping bad blocks.n"
?"nand erase [clean] [off size] - erase 'size' bytes fromn"
?"??? offset 'off' (entire device if not specified)n"
#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 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
);
注意：这里只添加了yaffs2的写命令，u-boot下载用的是写功能。
(2)打开include/linux/mtd/mtd.h头文件，定位到131行，在mtd_info结构体中添加上面用到rw_oob和skipfirstblk数据成员，修改如下：
u_int32_t writesize;
#if defined(CONFIG_MTD_NAND_YAFFS2)
? /*Thanks for hugerat's code*/
?u_char rw_oob;
?u_char skipfirstblk;
#endif
?u_int32_t oobsize;?? /* Amount of OOB data per block (e.g. 16) */
?u_int32_t oobavail;? /* Available OOB bytes per block */
(3)在第一步关联的nand_write_skip_bad函数中添加对Nand OOB的相关操作，修改如下：
打开/drivers/mtd/nand/nand_util.c，定位到483行，在nand_write_skip_bad函数中添加代码，修改如下：
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)
?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 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,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 0x%08llxn",
??? 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,&write_size,p_buffer);
? if (rval != 0) {
?? printf ("NAND write to offset %llx failed %dn",rval);
?? *length -= left_to_write;
?? return rval;
? }
? left_to_write -= write_size;
? printf("%d%% is complete.",100-(left_to_write/(*length/100)));/*Thanks for hugerat's code*/
? offset??????? += write_size;
#if defined(CONFIG_MTD_NAND_YAFFS2)
? /*Thanks for hugerat's code*/
? 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;
}
(4)在第三步的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。
打开/drivers/mtd/nand/nand_base.c，定位到1961行，修改如下：
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)
?/*Thanks for hugerat's code!*/
?? 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;
?//chip->ops.oobbuf = NULL;
#if defined(CONFIG_MTD_NAND_YAFFS2)//add yaffs2 file system support
?/*Thanks for hugerat's code!*/
?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
?/*Thanks for hugerat's code!*/
?chip->ops.mode = oldopsmode;
#endif
?return ret;
}
【2】在mini2440.h里添加yaffs2相关宏定义
打开include/configs/mini2440.h，定位到98行附近，加入下列代码：
/*
?* Command line configuration.
?*/
#include <config_cmd_default.h>
#define CONFIG_CMD_CACHE
#define CONFIG_CMD_DATE
#define CONFIG_CMD_ELF
#define CONFIG_CMD_NAND
#define CONFIG_CMD_JFFS2? /* JFFS2 Support*/
... ...
在文件末尾处加入下列代码：
/*-----------------------------------------------------------------------
?* NAND flash settings
?*/
#if defined(CONFIG_CMD_NAND)
#define CONFIG_NAND_S3C2410
#define CONFIG_SYS_NAND_BASE 0x4E000000
#define CONFIG_SYS_MAX_NAND_DEVICE 1 /* Max number of NAND devices? */
#define SECTORSIZE 512
#define SECTORSIZE_2K 2048
#define NAND_SECTOR_SIZE SECTORSIZE
#define NAND_SECTOR_SIZE_2K SECTORSIZE_2K
#define NAND_BLOCK_MASK 511
#define NAND_BLOCK_MASK_2K 2047
#define NAND_MAX_CHIPS 1
#define CONFIG_MTD_NAND_VERIFY_WRITE
#define CONFIG_SYS_64BIT_VSPRINTF? /* needed for nand_util.c */
#endif /* CONFIG_CMD_NAND */
?
#define CONFIG_JFFS2_NAND 1
//#undef CONFIG_JFFS2_CMDLINE
#define CONFIG_JFFS2_DEV "nand0"
#define CONFIG_JFFS2_PART_SIZE 0x480000
#define CONFIG_JFFS2_PART_OFFSET 0x80000
#define CONFIG_JFFS2_CMDLINE 1
#define MTDIDS_DEFAULT "nand0=nandflash0"
#define MTDPARTS_DEFAULT "mtdparts=nandflash0:384k(bootloader),"
?????????? "128k(params),"
?????????? "5m(kernel),"
?????????? "-(root)"
#define CONFIG_MTD_NAND_YAFFS2?? 1
#define ENABLE_CMD_LOADB_X 1
?
5.2，?烧录yaffs2文件系统测试
重新编译后下载，nand方式启动，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：
[u-boot@MINI2440]# nand help
nand - NAND sub-system
Usage:
nand info - show available NAND devices
nand device [dev] - show or set current device
nand read - addr off|partition size
nand write - addr off|partition size
??? read/write 'size' bytes starting at offset 'off'
??? to/from memory address 'addr',skipping bad blocks.
nand erase [clean] [off size] - erase 'size' bytes from
??? offset 'off' (entire device if not specified)
nand write[.yaffs2] - addr off|partition size - write `size' byte yaffs image
?starting at offset off' from memory address addr' (.yaffs2 for 512+16 NAND)
nand bad - show bad blocks
nand dump[.oob] off - dump page
nand scrub - really clean NAND erasing bad blocks (UNSAFE)
nand markbad off [...] - mark bad block(s) at offset (UNSAFE)
nand biterr off - make a bit error at offset (UNSAFE)
[u-boot@MINI2440]#
这个就是用来下载yaffs2文件系统到nand中的命令了。首先需要将友善官方提供的有关mini2440的yaffs2文件系统文件root_qtopia-128M.img复制到linux宿主机的/tftpboot目录下，然后执行：
tf[u-boot@MINI2440]# tp 0x30000000 root_qtopia-128M.img
Filename 'root_qtopia-128M.img'.
Load address: 0x30000000
Loading: T ##########T T #####################################################T
##T T
???????? #T T T T ######
Retry count exceeded; starting again
dm9000 i/o: 0x20000300,id: 0x90000a46
DM9000: running in 16 bit mode
MAC: 12:34:56:78:9a:bc
operating at 100M full duplex mode
Using dm9000 device
TFTP from server 10.1.0.128; our IP address is 10.1.0.129
Filename 'root_qtopia-128M.img'.
Load address: 0x30000000
Loading: T ###T ###T T ########
一直无休止循环，经网上搜索得知Uboot 端 tftp 程序传过来的Timeout参数不符合服务器端定义引起的，原文链接地址
Retry count exceeded; starting again 解决方法：tftp客户端传过来的timeout是7810，而服务器端定义的范围在1-255秒之间，不是服务器的问题，而是uboot中tftp参数设置的问题，参见TFTP Unsupported option(s) requested 问题详细分析及解决。
打开/net/net.c，定位到104行附近，修改如下：
#if defined(CONFIG_CMD_NET)
DECLARE_GLOBAL_DATA_PTR;
#ifndef?CONFIG_ARP_TIMEOUT
# define ARP_TIMEOUT??10000UL*CONFIG_SYS_HZ/1000 //5000UL?/* Milliseconds before trying ARP again */
#else
# define ARP_TIMEOUT??CONFIG_ARP_TIMEOUT
#endif
定位到573行附近，修改如下：
#ifndef CONFIG_NET_MULTI
?//NetSetTimeout (10000UL,startAgainTimeout);
?NetSetTimeout (10000UL*CONFIG_SYS_HZ/1000,startAgainTimeout);
?NetSetHandler (startAgainHandler);
#else?/* !CONFIG_NET_MULTI*/
定位到585行附近，修改如下：
eth_init (gd->bd);
?if (NetRestartWrap) {
??NetRestartWrap = 0;
??if (NetDevExists && !once) {
???//NetSetTimeout (10000UL,startAgainTimeout);
???NetSetTimeout (10000UL*CONFIG_SYS_HZ/1000,startAgainTimeout);
???NetSetHandler (startAgainHandler);
??} else {
???NetState = NETLOOP_FAIL;
??}
定位到779行附近，修改如下：
#define CDP_SYSOBJECT_TLV??0x0015
#define CDP_MANAGEMENT_ADDRESS_TLV?0x0016
#define CDP_TIMEOUT???(250UL*CONFIG_SYS_HZ/1000) //250UL?/* one packet every 250ms */
static int CDPSeq;
static int CDPOK;
打开/net/tftp.c，定位到16行，修改如下：
#define TIMEOUT??60000UL?//5000UL?/* Millisecs to timeout for lost pkt */
然后重新编译后下载测试：
[u-boot@MINI2440]# tftp 0x30000000 root_qtopia-128M.img
dm9000 i/o: 0x20000300,id: 0x90000a46
DM9000: running in 16 bit mode
MAC: 12:34:56:78:9a:bc
operating at 100M full duplex mode
Using dm9000 device
TFTP from server 10.1.0.128; our IP address is 10.1.0.129
Filename 'root_qtopia-128M.img'.
Load address: 0x30000000
Loading: T T T T T T T T T T
Retry count exceeded; starting again
dm9000 i/o: 0x20000300,id: 0x90000a46
DM9000: running in 16 bit mode
MAC: 12:34:56:78:9a:bc
operating at 100M full duplex mode
Using dm9000 device
TFTP from server 10.1.0.128; our IP address is 10.1.0.129
Filename 'root_qtopia-128M.img'.
Load address: 0x30000000
Loading: #################################################################
???????? #################################################################?
?? ????? ... ...
???????? #################################################################
???????? ####################
done
Bytes transferred = 58487616 (37c7340 hex)
[u-boot@MINI2440]#
在yaffs2文件系统镜像下载到内存后:
[u-boot@MINI2440]# nand erase 0 0x40000
NAND erase: device 0 offset 0x0,size 0x40000
Erasing at 0x2000000000004 --?? 0% complete.
OK
[u-boot@MINI2440]# nand write 0x30000000 0 0x40000
NAND write: device 0 offset 0x0,size 0x40000
Writing at 0x2000000020000 -- 100% is complete. 262144 bytes written: OK
[u-boot@MINI2440]#
?可以看到，yaffs2文件系统烧录成功。下一步需要加载内核来挂载yaffs2文件系统。
接下来将进入u-boot的第六阶段，为u-boot-2009.08 增加引导内核功能。