Re: [PATCH] ARM: dts: omap3-igep00x0: Fix nand ECC to maintain backward compatibility.

[Tom Rini <trini@ti.com>]

On 12/02/2013 10:51 AM, Thomas Petazzoni wrote:
> Dear Enric Balletbo Serra,
> 
> On Mon, 2 Dec 2013 16:39:09 +0100, Enric Balletbo Serra wrote:
> 
>> Thanks for the explanations to all.
>>
>> Although the new ECC schema breaks the compatibility between the board
>> files and new DT based kernel, I think we should use BCH8 scheme.
>> Sorry, because I had not realized that this was configurable in
>> u-boot, so I think, if Thomas is also agree, the better fix in that
>> case is change CONFIG_NAND_OMAP_ECCSCHEME to
>> OMAP_ECC_BCH8_CODE_HW_DETECTION_SW in u-boot. If this works we can
>> discard this patch.
> 
> I theoretically don't have anything against that, but if I do this
> change in U-Boot, and then use U-Boot to reflash to NAND the SPL and
> U-Boot itself, will the OMAP ROM code still be able to read the SPL
> from NAND ? I'm not sure which ECC scheme does the OMAP ROM code
> support, and how it detects (or not) which ECC scheme to use to read
> the SPL.

Yes, this brings us back to one of the old and long-standing problems.
The ROM on these devices will generally speak one format and that means
using NAND chips that say for the first block (or N blocks or whatever)
you only need 1bit ECC but for the rest 4/8/16/whatever.  And then
informing the kernel (and anything else) that "partitions" N need this
format and the rest need that.

-- 
Tom