I need some help related to u-boot and linux kernel’s use of NAND ECC schemes on the AM335x. It looks like 8-bit BCH ECC scheme is used across ROM, u-boot, Kernel and File System, but 1-bit ECC Hamming scheme is used on the u-boot environment. That mixed ECC scheme is a problem in the kernel because it expects only one scheme, 8-bit BCH ECC, to be used across the whole NAND flash. My u-boot environment is on the NAND flash and I sometimes require it to be modified with the fw_setenv user space application. Fw_setenv utilizes the kernel’s MTD device driver to modify the u-boot environment. But since the kernel uses 8-bit BCH ECC, instead of the 1-bit ECC Hamming scheme across all of NAND flash, it writes ECC data that u-boot sees as invalid the next time it runs.
I tried modifying u-boot to use 8-bit BCH ECC scheme on the u-boot environment in NAND, but I get “ECC: uncorrectable” errors. The following comments are in the u-boot code where that “ECC: uncorrectable” errors occurs:
/* This currently sees all pages as being completely full of
* uncorrectable errors. The suspicion is that this is due
* to limitations in the elm support we have in U-Boot today
*/
I also see a comment in the u-boot code that says “For undocumented reasons we need to currently keep our environment in 1-bit ECC so we configure ourself thusly.” Since the kernel is set to use 8-bit BCH ECC scheme and mixed ECC schemes are not supported, I’d like to get some help with enabling the 8-bit BCH ECC scheme on the u-boot environment.
Thank you,
Peggy
