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Re: [ts-7000] Bad eraseblock on nand flash

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Subject: Re: [ts-7000] Bad eraseblock on nand flash
From: "Eddie Dawydiuk" <>
Date: Mon, 12 Sep 2005 11:02:23 -0700 (MST)
Hello,

>> I'm using TS7250 with onboard 128MB Nand Flash.
>>
>> When i'm running from nand flash, i get this kernel warning as follows:
>>
>> ***********
>> Searching for NAND flash...
>> NAND device: Manufacturer ID: 0x20, Chip ID: 0x79 (ST Micro NAND 128MiB
>> 3,3V 8-bit)
>> Scanning device for bad blocks
>> Bad eraseblock 245 at 0x003d4000
>> Bad eraseblock 279 at 0x0045c000
>> Bad eraseblock 281 at 0x00464000
>> ***********
>
> Just FYI, I also ran into this problem... Actually I have *many* more
> "Bad eraseblocks" warnings. I've searched the internet a lot on how to
> fix it, but I couldn't find either. I read it somewhere it *could* be
> related to the yaffs2 filesystem on the NAND flash, but I'm not sure
> about this.

The TS-7250 uses Nand flash, Nand flash is much different than Nor
flash(if you are interested there is a pretty good write up here
http://support.gateway.com/s/Manuals/Desktops/5502664/NOR_vs_NANDwhitepaper.pdf).
Basically Nand flash is sometimes shipped from the manufacturer with bad
blocks, in addition blocks will become bad over time. The general
consensus is  not to worry if your flash consists of 1% or less bad
blocks. Nand flash has out of band data which basically stores meta data,
this is where a block is marked bad. The filesystem(Yaffs) handles this
and will ensure data is not written to any block marked as bad. The
bottom line is the messages your are seeing are benign, unless the number
of bad blocks exceeds 1%.

//Eddie



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