Hi,
I'm trying to figure out what my options are for booting a system completely from NAND flash. Googling around hasn't yielded much info, but browsing "drivers/nand/" I've gathered that U-Boot handles bad blocks (factory or worn-out) & bit-flips to some degree. It's not entirely clear how things work by glancing at the code, though, so I have a few questions:
1. How does U-Boot handle a bad block in the area where the environment is stored? I can create a second environment via CFG_ENV_OFFSET_REDUND, but that's not very flexible (what if the primary and the backup are both bad blocks?) I also need to write to the environment from within Linux via the "fw_setenv" utility, but it doesn't seem to have any NAND awareness.
2. It's not obvious to me how U-Boot reacts when it encounters a bad block. If I'm copying a kernel image out of NAND, and a bad block is encountered, does it skip to the next block? If so, do I need to compensate by padding each partition with unused blocks, or how else does addressing work? Similarly for writes - if I do "nand write <memaddr> <location> 100000", and the first block is bad, will U-Boot write all 0x100000 bytes _after_ that block?
3. Can Linux handle bad blocks in the same manner? Specifically, I need to use 'nandwrite' to copy a kernel image to an MTD partition from within Linux, and have U-Boot read the image correctly on bootup, both in the presence of bad blocks and bit-flips.
The only references I found were at the openmoko site, but I'm not sure how much of what they discuss is native in U-Boot & Linux, vs. being added on for openmoko. Thanks in advance for the help!