[U-Boot] [PATCH 3/3] mtd/nand : workaround for Freescale FCM to support large-page Nand chip

[Scott Wood]

On 01/03/2012 04:43 PM, Matthew L. Creech wrote:
> On Tue, Jan 3, 2012 at 5:08 PM, Scott Wood <scottwood at freescale.com> wrote:
>>
>> Even on SLC chips, when using an ECC block size of 512 bytes?  Or are
>> you only able to find MLC?
>>
>> I looked for a datasheet for a 4K NAND chip, but couldn't find one
>> readily available from a Google search.  Hopefully someone internally
>> can provide me with the one for the chip we're using.
>>
> 
> Yes, this is SLC.  The Micron MT29F8G08ABABAWP is one example.  The
> datasheet is here (sign-up required, unfortunately - I can send a copy
> if you want):
> 
> https://www.micron.com/parts/nand-flash/mass-storage/mt29f8g08ababawp

The sign-up terms say:

> Use License
> Permission is granted to download one (1) copy of the materials on Micron's websites for personal, non-commercial transitory viewing only. This is the grant of a limited and non-exclusive license, not a transfer of title, and under this license you may not:
> 
> (a) modify or further copy the materials;
> (b) use the materials for any commercial purpose, or for any public display (commercial or noncommercial);
> (c) attempt to decompile or reverse engineer any software contained on Micron's websites;
> (d) remove any copyright or other proprietary notices on the materials;
> (e) transfer the materials to another person or "mirror" or "frame" the materials on any other website or server. 

It could be argued that my "purpose" is commercial, since I'm trying to
gain information to help support NAND controller hardware that my
employer sells (even though it's to Micron's benefit to maximize the
number of systems their NAND chips can interoperate with...).

Of course, that logic also applies to anyone using the information to
build a product for sale, that includes a Micron chip -- which seems to
be exactly who they'd be wanting to access these documents -- so it's
probably not what they meant (unless they give customers access via some
other terms).  It's not obvious what they *do* mean, though.

> On page 93, it says "Minimum required ECC: 4-bit ECC per 540 bytes of data".

OK.  Is booting from a source other than NAND (at least enough to fit
software BCH support) an option?

> Maybe there are some 4k parts around that don't have this limitation,
> but our hardware guy informed me that all of the common (high
> availability) 4k parts he saw were similar.

I found this after some more searching, but I've no idea if it (or
related chips) are highly available:

http://www.samsung.com/global/system/business/semiconductor/product/2007/6/11/NANDFlash/SLC_LargeBlock/8Gbit/K9F8G08U0M/ds_k9f8g08x0m_rev10.pdf

>> There's also the issue of ECC on the boot page itself -- that has to be
>> hardware ECC, because there's no software running yet.
>>
> 
> True.  I guess for random bit-flips, maybe that's just as much a
> problem as the other blocks/pages?  I know that the first block is
> somewhat "special", in that it's guaranteed not to be bad for some
> minimum # of P/E cycles; will ECC errors still accumulate the same as
> any other block?

The datasheets I checked say things like "guaranteed to be a valid block
up to 1K program/erase cycles with 1bit/512Byte ECC" (this is on a chip
that wants 1bit ECC normally) -- so it looks like it's just guaranteed
to not be an official "bad block", not guaranteed to not have any bit flips.

You could check your datasheet to see what its specific claim is.

-Scott