>From: Thomas Petazzoni [mailto:thomas.petazzoni@xxxxxxxxxxxxxxxxxx] > >On Mon, 2 Dec 2013 11:00:35 -0500, Tom Rini wrote: > >> >> 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. > >As long as U-Boot provides separate commands, or a "nandecc" command >that allows to switch between ECC scheme, and select the ECC scheme >expected by the ROM code when flashing the SPL, and then the ECC scheme >expected by the SPL and the kernel to flash U-Boot itself, the kernel >image, and the various filesystem images, then it's all fine, we can >leave with different ECC schemes used for different things on the NAND >flash. > Yes, at-least OMAP3 arch u-boot should still supports 'nandecc'. The infrastructure is still in place, however the command 'nandecc' is deprecated in newer versions. References in mainline u-boot: arch/arm/cpu/armv7/omap3/board.c @@do_switch_ecc() driver/mtd/nand/omap_gpmc.c @@omap_nand_switch_ecc() So with minor hacks, you should be able to bring-back 'nandecc'. But for all these, images need to be flashed from u-boot. As kernel cannot switch ecc-schemes on-the-fly. with regards, pekon -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
