[U-Boot] NAND on Davinci boards

[Nick Thompson]

On 16/03/11 08:22, Stefano Babic wrote:
> Hi all,
> 
> I have seen an incompatibility between the NAND driver in u-boot for the
> davinci boards and the linux driver (kernel 2.6.38, mainline).
> 
> I think it is not related to the specific board I use. In any case, I am
> using the ea20 board (OMAP-L138 based, in u-boot mainline), and I have
> added NAND support setting for the driver:

I'm using da830evm (OMAP-L137) with more or less up-to-date U-Boot, but
quite old 2.6.18+ kernel from Montavista.

> 
> #define CONFIG_SYS_NAND_4BIT_HW_ECC_OOBFIRST
> #define CONFIG_SYS_NAND_USE_FLASH_BBT

I don't have BBT enabled.

> 
> This is done in the linux driver, too. Both drivers are using ECC in
> Hardware, the number of bits for ECC is set to 4, the OOB is set first,
> and the oob layout is the same.
> 
> The NAND driver under u-boot works flawless. The kernel is stored on
> NAND (the board boots from a SPI-Flash), and everything seems correct.
> 
> The same thing under linux. In Linux I am able to set up a root
> filesystem with UBIfs, everything ok. Problems arises when u-boot tries
> to access to data written from Linux and viceversa. It seems to me that
> the management of ECC is different in u-boot and in kernel.

I almost always update my NAND kernel image from within Linux. U-Boot reads
this with no errors and can reboot the system correctly.

> 
> If I write under Linux a kernel Image in a NAND partition, after a reset
> I am not able to read that partition from u-boot.
> Setting MTDDEBUG and a couple of printf, I see that nand_do_read_ops()
> report an error:
> 
> 	 if (mtd->ecc_stats.failed - stats.failed)
>                  return -EBADMSG;
> 
> This is the output of my board:
> 
> nboot aKernel
> 
>  Loading from nand0, offset 0x0
>  Bad block table found at page 262080, version 0x01
>  Bad block table found at page 262016, version 0x01
>  Returning error 4 0
>  nand_bbt: ECC error while reading bad block table
>  nand_read_bbt: Bad block at 0x000002220000
>  nand_read_bbt: Bad block at 0x00000b120000
>  nand_read_bbt: Bad block at 0x00001f100000
>  nand_isbad_bbt(): bbt info for offs 0x00000000: (block 0) 0x00
>  Returning error 8 4
>  NAND read from offset 0 failed -74
>  ** Read error
> 
> Checking the two drivers, it seems to me that they are doing different
> things. However, I do not know which one is correct. I would think that
> the driver in u-boot is old and must be synchronized with the Linux's
> driver, but after checking how u-boot gets the ecc's error from Hardware
> it seems to me it is correct.
> 
> Has anyone seen the same issue or have proposal, which driver should be
> modified ?

Neither ;)

I think the U-Boot NAND driver for davinci has always been setup to be
compatible with the TI & Montavista Kernels. What I'm not sure about is if
those Kernels are compatible with mainline Linux and in particular the
very latest mainline kernels. In fact I'm not sure if it is compatible with
the very latest TI Kernels.

Have you tried "nand dump" of a Linux programmed Kernel and compared it with
"nand dump" of a U-Boot programmed Kernel? You would be able to see
identical data in each case, but you will be able to compare the differences
in the OOB. You only need to look at the first page to see if the OOB data
or position of the OOB data differs.

You errors all seem to be in the BBT handling. I don't use BBT here.

Nick.