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