UBI文件系统 nand驱动子页支持问题

我在用TI的dm368开发板，kernel是2.6.32.17，默认的flash文件系统是jffs2，但是jffs2在大分区下，mount速度很慢，而且占用ram较多，因此，我想使用ubifs看看性能是否会更好些。

ubifs的原理和配置过程，很多网页都有介绍的，我给一个链接，大家可以看看，我就不转载了，我重点说我移植过程中遇到并解决的问题。

http://bbs.chinaunix.net/thread-1954881-1-1.html

kerne的配置很简单，2.6.32里面都有，选上并重新编译就好了。

ubiattach、ubimkvol等工具，TI的dvsdk里面自带了，能用，我就偷了个懒，没有重新编译。

很轻松的照着网页说明操作了下，mount 分区也成功了，复制文件也成功了，很高兴：）

ubiattach /dev/ubi_ctrl -m 3

ubimkvol /dev/ubi0 -N rootfs -s 480MiB

mount -t ubifs ubi0_0 /mnt/nand/ -o sync

但很快就遇到麻烦了，开发板关机重新启动，我再mout ubi文件系统就出错了，提示了一堆错误，而且分区是空的，之前复制的文件不见了。

问题如下：

ubiattach /dev/ubi_ctrl -m 3

UBI error: ubi_io_read: error -74while reading 64 bytes from PEB 1662:0, read 64 bytes

UBI error: ubi_io_read: error -74while reading 64 bytes from PEB 1663:0, read 64 bytes

为了分析问题，我把mtd和ubifs的debug log都打开了，看到了一些信息；

#define EBADMSG 74 /* Not a data message */

/*Nand returns -EBADMSG on ecc errors, but it returns

* the data. For our userspace tools it isimportant

* to dump areas with ecc errors !

* For kernel internal usage it also mightreturn -EUCLEAN

* to signal the caller that a bitflip hasoccured and has

* been corrected by the ECC algorithm.

* Userspace software which accesses NAND thisway

* must be aware of the fact that it deals withNAND

*/

nand_do_read_ops

stats= mtd->ecc_stats;

if(mtd->ecc_stats.failed - stats.failed)

return-EBADMSG;

nand_read_page_hwecc

stat= chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);

if(stat < 0)

mtd->ecc_stats.failed++;

else

mtd->ecc_stats.corrected+= stat;

看样子，应该是ECC出错了，可是我用的是硬件ECC校验，怎么可能几乎全部的page都出现ecc校验错误了呢？

root@dm368-evm:~#flash_eraseall /dev/mtd3

root@dm368-evm:~# ubiattach/dev/ubi_ctrl -m 3

UBI: attaching mtd3 to ubi0

UBI: physical eraseblock size: 131072 bytes (128 KiB)

UBI: logical eraseblock size: 129024 bytes

UBI: smallest flash I/O unit: 2048

UBI: sub-page size: 512

UBI: VID header offset: 512 (aligned 512)

UBI: data offset: 2048

分析下UBI写数据的过程，

UBI DBG (pid 1484): ubi_io_write:write 512 bytes to PEB 57:0

int ubi_io_write(struct ubi_device*ubi, const void *buf, int pnum, int offset,

int len)

addr= (loff_t)pnum * ubi->peb_size + offset;

err= ubi->mtd->write(ubi->mtd, addr, len, &written, buf);

在io_init函数中可以看到几个变量的赋值；

ubi->peb_size = ubi->mtd->erasesize;

ubi->peb_count = mtd_div_by_eb(ubi->mtd->size,ubi->mtd);

ubi->flash_size= ubi->mtd->size;

从debug log来看，这里一次写了512字节，从某个block的起始page开始，offset是0；

那么到了nand mtd底层驱动，行为就是；

nand_write->nand_do_write_ops:

subpage= column || (writelen & (mtd->writesize - 1));

这里，subpage就是writelen，512；

也可以得知一点，ubifs没有使用oob，这跟jffs2和yaffs2是不同的；

/*Partial page write ? */

if(unlikely(column || writelen < (mtd->writesize - 1))) {

cached= 0;

bytes= min_t(int, bytes - column, (int) writelen);

chip->pagebuf= -1;

memset(chip->buffers->databuf,0xff, mtd->writesize);

memcpy(&chip->buffers->databuf[column],buf, bytes);

wbuf= chip->buffers->databuf;

}

ret= chip->write_page(mtd, chip, wbuf, page, cached,

(ops->mode == MTD_OOB_RAW));

下面是write_page函数的代码；

static int nand_write_page(structmtd_info *mtd, struct nand_chip *chip,

const uint8_t *buf, int page, int cached,int raw)

{

intstatus;

chip->cmdfunc(mtd,NAND_CMD_SEQIN, 0x00, page);

if(unlikely(raw))

chip->ecc.write_page_raw(mtd,chip, buf);

else

chip->ecc.write_page(mtd,chip, buf);

/*

* Cached progamming disabled for now, Not sureif its worth the

* trouble. The speed gain is not veryimpressive. (2.3->2.6Mib/s)

*/

cached= 0;

这里需要注意的就是raw，如果是MTD_OOB_RAW，那么不会做ECC校验，也不会把ECC码写入OOB；

如果是这样，在read的时候也必须指定是MTD_OOB_RAW，不需要ECC校验；否则，就会出现我们最开始看到的错误；

if(mtd->ecc_stats.failed - stats.failed)

return-EBADMSG;

那么，从这里的情况来看，我们可能已经找到出错的原因了；ubi使用了subpage write，而底层nand flash驱动实际上是不支持subpage write的，尽管ubi一次只写了512字节，但这个page的其他部分已经不能再次写入新的数据了。

从Nand_base.c(drivers\mtd\nand)来看，large page的nand flash，对subpage write的支持是不完善的，限制条件比较多，比如，不能是MLC的nand flash，不能用硬件ECC；

更严重的问题是代码存在缺陷，在写入部分data的时候，将其他部分的数据填充为0xff了，然后write整个page，并写入全部ecc码到oob，也许这就是前面ecc校验出错的原因吧。

nand_do_write_ops()

/*Partial page write ? */

memset(chip->buffers->databuf, 0xff, mtd->writesize);

memcpy(&chip->buffers->databuf[column],buf, bytes);

因此，我想到的解决办法就是在nand驱动中禁止subpage write。

第一步，在chip options中增加NAND_NO_SUBPAGE_WRITE；

static struct davinci_nand_pdatadavinci_nand_data = {

.options = NAND_USE_FLASH_BBT|NAND_NO_SUBPAGE_WRITE,

然后重新编译下载kernel，但问题依旧；

root@dm368-evm:~# ubiattach/dev/ubi_ctrl -m 3

UBI: attaching mtd3 to ubi0

UBI: physical eraseblock size: 131072 bytes (128 KiB)

UBI: logical eraseblock size: 129024 bytes

UBI: smallest flash I/O unit: 2048

UBI: sub-page size: 512

UBI: VID header offset: 512 (aligned 512)

心想很奇怪，为什么 sub-page size还是512？

回头查看代码，想看看sub page size是怎样计算出来的，

if (!(chip->options & NAND_NO_SUBPAGE_WRITE) &&

!(chip->cellinfo & NAND_CI_CELLTYPE_MSK)) {

switch(chip->ecc.steps) {

case 2:

mtd->subpage_sft = 1;

break;

case 4:

case 8:

case 16:

mtd->subpage_sft = 2;

break;

}

}

chip->subpagesize = mtd->writesize >> mtd->subpage_sft;

可是我已经给options增加了NAND_NO_SUBPAGE_WRITE啊？有些怀疑，我就在此处加了打印log，果然是这里出了问题，

chip->options = 0x10101.

mtd->subpage_sft = 0.

chip->subpagesize = 512.

#define NAND_NO_SUBPAGE_WRITE 0x00000200

可是，这里的options 明明是不对的！那我设置的NAND_NO_SUBPAGE_WRITE在哪里丢掉了？

在下面的函数中有对chip->options赋值改变；

nand_get_flash_type()

printk(KERN_INFO"nand_get_flash_type 1, chip->options = 0x%x.\n",chip->options);

/*Get chip options, preserve non chip based options */

chip->options &= ~NAND_CHIPOPTIONS_MSK;

printk(KERN_INFO"nand_get_flash_type 2, chip->options = 0x%x.\n",chip->options);

chip->options|= type->options & NAND_CHIPOPTIONS_MSK;

printk(KERN_INFO"nand_get_flash_type 3, chip->options = 0x%x.\n",chip->options);

/*

* Set chip as a default. Board drivers canoverride it, if necessary

*/

chip->options|= NAND_NO_AUTOINCR;

/*Check if chip is a not a samsung device. Do not clear the

* options for chips which are not having anextended id.

*/

if(*maf_id != NAND_MFR_SAMSUNG && !type->pagesize)

chip->options&= ~NAND_SAMSUNG_LP_OPTIONS;

printk(KERN_INFO"nand_get_flash_type 4, chip->options = 0x%x.\n",chip->options);

nand_get_flash_type 1,chip->options = 0x10200.

nand_get_flash_type 2,chip->options = 0x10000.

nand_get_flash_type 3,chip->options = 0x1011c.

nand_get_flash_type 4,chip->options = 0x10101.

问题出在这里，红色的代码！

/* Mask to zero out thechip options, which come from the id table */

#defineNAND_CHIPOPTIONS_MSK (0x0000ffff &~NAND_NO_AUTOINCR)

/* Chip can not autoincrement pages */

#define NAND_NO_AUTOINCR 0x00000001

找到问题了，解决办法就有了，注释掉红色的那行代码，就是他把NAND_NO_SUBPAGE_WRITE给丢掉了。

//chip->options &=~NAND_CHIPOPTIONS_MSK;

再重新编译下载kernel，问题搞定了！

再次启动开发板，加载ubi，一切正常了。

root@dm368-evm:/# ubiattach/dev/ubi_ctrl -m 3

UBI: attaching mtd3 to ubi0

UBI: physical eraseblock size: 131072 bytes (128 KiB)

UBI: logical eraseblock size: 126976 bytes

UBI: smallest flash I/O unit: 2048

UBI: VID header offset: 2048 (aligned 2048)

UBI: data offset: 4096

UBI: attached mtd3 to ubi0

UBI: MTD device name: "filesystem1"

UBI: MTD device size: 512 MiB

UBI: number of good PEBs: 4096

UBI: number of bad PEBs: 0

UBI: max. allowed volumes: 128

UBI: wear-leveling threshold: 4096

UBI: number of internal volumes: 1

UBI: number of user volumes: 1

UBI: available PEBs: 3639

UBI: total number of reserved PEBs:457

UBI: number of PEBs reserved for badPEB handling: 40

UBI: max/mean erase counter: 2/1

UBI: image sequence number: 0

UBI: background thread"ubi_bgt0d" started, PID 1483

UBI device number 0, total 4096 LEBs(520093696 bytes, 496.0 MiB), available 3639 LEBs (462065664 bytes, 440.7 MiB),LEB size 126976 bytes (124.0 KiB)

root@dm368-evm:/# mount -tubifs ubi0_0 /mnt/nand/ -o sync

UBIFS: mounted UBI device 0, volume0, name "rootfs"

UBIFS: file system size: 51171328 bytes (49972 KiB, 48 MiB, 403 LEBs)

UBIFS: journal size: 2539520 bytes (2480 KiB, 2 MiB, 20 LEBs)

UBIFS: media format: w4/r0 (latest is w4/r0)

UBIFS: default compressor: lzo

UBIFS: reserved for root: 2416947 bytes (2360 KiB)

root@dm368-evm:/# df

Filesystem 1K-blocks Used Available Use% Mounted on

/dev/root 39544232 16239820 21295632 43% /

none 1024 24 1000 2% /dev

tmpfs 16384 20 16364 0% /var/volatile

tmpfs 21760 0 21760 0% /dev/shm

tmpfs 16384 0 16384 0% /media/ram

ubi0_0 45528 1528 41640 4% /mnt/nand

最后，总结下，就是要禁止nand flash驱动里面的subpage write，让 chip->subpagesize == mtd->writesize 就好了。

这是我的解决办法。如果有人要使用subpage write，那么一定要保证你的读写逻辑是正确的，要么不用ecc，要么各个subpage的ecc都应是正确的。