From: Jarkko Lavinen
To: jeanwelly
Cc: yaffs@stoneboat.aleph1.co.uk ;linux-mtd@lists.infradead.org ;Balloon@balloonboard.org
Subject: [Balloon] Re: Real bad blocks of nand flash?
Sent: Tue May 17 18:38:06 CST 2005
Thanks for your comments.
Some people told me that using nandflash without ecc will easily cause the bad block. I will use the soft ecc in yaffs.
But any other suggestions are welcome. Thanks.
>
> On Tue, May 17, 2005 at 10:46:52AM +0800, ext jeanwelly wrote:
> > Why occured so many bad blocks of nand. Are these blocks real bad? How
> > can I take a test in another way?
>
> I have seen few test boards with JFFS2 partitions and more bad blcoks
> than there should be. More than the manyfactures suggests the should
> be at maximum.
>
> When investigating one board I found something had been write garbage
> to OOB. I found for example word "driv" at the end of one OOB and "er"
> at the beginning of next. It looked just as if somebody had written
> kernel memory at random point to flash. This is not reproducinle but
> now I have garbage check in nand_base.c:write_oob() to hopefully catch
> this if it ever repeats.
>
> With one boatd with with lots of presumably incorrectly marked bad
> blocks board I broke the rules and simply disabled the bad block check
> from nand_base.c and from flash_eraseall.c. I ran flash_eraseall and
> the flash erased nicely except for few, obviously real bad blocks
> which refused ot be erased. I wouldn't recommed the procedure because
> one end up with no bad blocks at all but in my case it worked nice and
> test board has performed flawlessly since then.
>
> I think we would need a simple test program that would be similar to
> badblocks program, writing patterns of 0x00, 0x55, 0xAA etc. to flash
> and trying to find if some block fails when erasing, writing or in
> verify read.
>
> Jarkko Lavinen
>
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