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u-boot-2011.03在TQ2440上的移植(8)--支持下载yaffs2文件系统

2011-03-21 15:11 561 查看
参考文章http://blog.chinaunix.net/u3/101649/showart.php?id=2134240，第2步修改分区大小后经过测试可以在TQ2440上使用，TQ2440分区如下：

0~0x40000 u-boot （256K）

0x200000~0x500000 kernel (3M)

0x500000~~ (剩余的)

1、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。TQ2440上的Nandflash型号是K9F2G08，页面大小为page = 2K + 64Byte。

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。

2、在include/configs/smdk2440.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：
vi include/configs/smdk2440.h
//定义一个管理对Yaffs2支持的宏
#define CONFIG_MTD_NAND_YAFFS2 1
//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=nandflash0:256k(bootloader)," /
"3m(kernel)," /
"-(root)"

3、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：
vi common/cmd_nand.c
在函数U_BOOT_CMD中添加如下：
//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

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;
}

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： 

#vi 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

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： 

#vi 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;
}

在上一步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。



                                            

                                        

                        
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