"Andreas" == Andreas Bießmann andreas.devel@googlemail.com writes:
Hi,
Please note that these patches are AM33XX-specific (as we are using ELM that, I think, just isn't available on OMAP3) so we use OOB layout that is compatible with AM33xx ROM boot code.
Andreas> You are right, ELM is not available in OMAP3 devices. It seems Andreas> the ROM loader of these devices only support the 1-Bit Andreas> Hamming, but is also different to the OOB layout used for the Andreas> SW 1-bit hamming provided by the Kernel. So we get here a lot Andreas> of different OOB layouts ... I wonder if we can stick to Andreas> e.g. the generic SW BCH layout (of linux kernel) for all but Andreas> the ROM partition (where the SPL is placed). So the SPL need Andreas> to know just one mechanism but software modifying that place Andreas> needs to know about the 'special' ROM layout.
No, please not. Having more than 1 OOB layout on the same NAND device leads to all kind of complications. There has also been kernel patches posted for the ELM, so IMHO the only sane option for am33xx is BCH8 everywhere (with the ROM layout).
It's likely that this layout doesn't match with the current kernel layout as RBL uses strange 14th byte for BCH8 while only 13 bytes are needed.
Andreas> Sorry, what does RBL mean in that context?
The ROM boot loader, E.G. the part loading the spl.
Actually, the only assumption the code does about the OOB layout is that ECC code occupies continuous area in the OOB.
Andreas> Well, but you have defined that for example it is written in Andreas> big endian.
Andreas> I'm currently working on a omap3 enabled device that requires Andreas> 4-bit ECC for all but the first block. And I'm searching for a Andreas> clean solution that would be accepted mainline. I think it Andreas> would be best to have the same OOB layout for the whole device Andreas> but the SPL space (cause that needs to be read by ROM). The Andreas> layout should be chosen at compile time of the SPL. What do Andreas> you think about?
So the only reason to not have the same OOB layout everywhere is because of ROM restrictions and that 1bit ECC isn't good enough anymore? E.G. you actually would have prefered to use the ROM layout if it would have used something better like the am33xx ROM does.