[Yaffs-archive] Re: corrupt my NAND flash device

[Charles Manning]

On Tuesday 22 April 2003 19:51, Paul Wong wrote:
>  Hi all!
>      i installed the YAFFS file system in the NAND flash (samsung 16MB).
> And test the reliability. I tried to copy a 5 MB file to the mounted yaffs
> (spare 8MB) directory ( i separated the device to 3 partition - 4MB 4MB and
>   8MB) . and then check the disk space, it is shown that it has 3 MB spare.
>   Next step, I erased the file and copied another 5 MB file to it. The
> device
>   said " no enough spare. Then I use the "mkyaffs" to format it, it is
> shown many bad block in the device. I checked the OOB[5] ( bad block flag)
> it is set to 0x00. Why? Why the yaffs set the health block to the bad block
> after
>   erase file? Is the YAFFS not support big file ?  any ideal?


Can you send the output of /proc/yaffs?

YAFFS certianly supports large files and you should not be seeing problems 
like these.

As YAFFS writes data to the NAND it checks the results. If it encounters data 
errors then it marks the block for retirement and you get ""**>>Block %d 
marked for retirement" messages. Later on, during garbage collection, these 
blocks will be marked as bad blocks.

I suggest that while you figure the problem out you first disable the bad 
block marking.  You can do this by commenting out the two lines in 
yaffs_RetireBlock() that write to NAND. Now the software will think these 
blocks have been retired, but the NAND will not be marked. 

I have seen this problem before where the NAND read/write algorithms were not 
working properly and YAFFS was thus seeing bad data and thought the blocks 
were bad.

You might, of course, really have a bad chip or bad soldering etc. You should 
not have more than approx 1-2% bad blocks.

-- Charles


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