Eraseall will not try to erase blocks marked bad. Anyway, the mtd will
also not allow this.

If I understand the thread properly, you want to erase blocks that were
marked bad by YAFFS but were not marked bad by manufacturing.

Attempting to erase a factory marked bad block **might** destroy the
flash and make is unusable.

To do this, I suggest doing the following:
* Modify eraseall to skip the check, as Thomas suggests. Instead of
checking for bad blocks, check for some other pattern to distinguish
between YAFFS-marked and factory-marked bad blocks. The actual patterns
used by factories depends on the make, part number etc but most often
the whole OOB area of a bad block will be zero. A YAFFS-marked bad block
will be zero only in the bad-block byte and only then in the first two
pages. 

* You will also need to bypass the check in mtd.

-- Charles


-----Original Message-----
From: yaffs-admin@stoneboat.aleph1.co.uk
[mailto:yaffs-admin@stoneboat.aleph1.co.uk] On Behalf Of Timofei V.
Bondarenko
Sent: Tuesday, 7 December 2004 2:20 a.m.
To: Aras Vaichas
Cc: yaffs@stoneboat.aleph1.co.uk
Subject: Re: [Yaffs] cvs YAFFS + MTD cvs + 2.4.27-vrs1 problems


Hi.

Aras Vaichas wrote:
> Thomas Gleixner wrote:

>>>Surely it's not the easy to "break" a NAND chip? Can my original NAND

>>>be recovered?
>>>
>> It's quite easy, if the timing is wrong or if the rdy/busy check is 
>> not reliable.
> 
> Is there a utility that writes to every single page, reads back the 
> data and then marks the pages correctly? Or are those "bad 
> eraseblocks" permanently lost?
> 

AFAIK, the eraseall can't erase blocks already marked bad.

To do it i'm just comment out a 'goto' near "attempt to erase bad block"

warning in drivers/mtd/nand/nand_base.c
Not the best way, though there were no appropriate ioctl to do it else.
You'll have to reboot after eraseall, since bad block list still reside 
in memory.

Regards.
	Timofei.




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