[U-Boot-Users] AT91 NAND om AT91SAM9260EK

[Michel Benoit <murpme@gmail.com>]

Good morning!

What version of the AT91SAM9260EK u-boot code are you referring to?

I am using u-boot-1.1.5_atmel_1.2  from the Atmel ftp site.
Is there a more recent version available?  Are there any plans to add
the at91sam9260ek support to the main branch of u-boot (latest version
1.2).

In looking through the 1.1.5 Atmel u-boot code I see that nand_bbt.c
is used to map out bad blocks marked by the manufacturer.  I can write
my code to nand from external SAM-BA tool and boot without any
problems.  Has anyone tried booting from JFFS2 nand within u-boot?

The problem that I was having with the NAND flash on my AT91SAM9260EK
board is related to the fact that the hw ECC controller in the 9260
uses the first four bytes of out of bounds space after each page to
store an error correction/verification number.  The Samsung flash on
my board uses the first byte of oob space in the first two pages of a
block to mark that it is bad. If the byte is not FF then the mfg has
marked the block as bad and it should never be used.  When linux mtd
starts up it looks for mfg bad blocks and removes them from the
available list of nand blocks.  Thus any page which contains data is
excluded.  Looking around at other nand flash devices I found that
some use both offsets 0 and 5 in the oob space to mark bad blocks.  We
plan to use such a nand flash on our custom board.  I hope that Atmel
will do the same on future revisions of its AT91SAM9260EK board.

My work around for now is to ignore mfg bad blocks and hope that they
get caught by the ECC verification code.  Mfg bad block info has
already been overwritten on my flash chip by the ECC data.  Does
anyone know if the Atmel SAMBA tool does any bad block verification
when programming nand flash?  It seems to be writing the 4 byte ECC
code in the oob space.  Is it also marking mfg bad blocks?  If so, at
which offset into the oob space?


Michel


On 2/8/07, Stefan Roese <sr@denx.de> wrote:
> On Thursday 08 February 2007 00:17, Ulf Samuelsson wrote:
> > > Has anyone used the at91_nand driver on the AT91SAM9260EK?
> > >
> > > I get bad erase blocks on every block that contaions data (written to
> > > nand flash with SAM-BA).  Seems like the read_oob (read out of bounds
> > > area) function is returning data from the in bounds area.
> > >
> > > U-boot configs the nand flash to use hw ecc (syndrome) whereas the
> > > at91_nand seems to be setup to use soft ecc.
> >
> > According to recent conversations on U-Boot mailing list
> > U-boot can do a raw copy of a flash file system, but nothing more.
> > (Correct me if I have misunderstood)
>
> Yes. But this copy is bad block aware.
>
> > This means that if there are faulty pages in the NAND flash, you are dead.
>
> No. Bad blocks are handled correctly.
>
> Best regards,
> Stefan
>
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