Hello Scott,
For the kmp204x boards, UBI is used to take care of the volumes created and deleted on our NAND Flash. I am currently using a 3.10 kernel and when UBI attaches mtd0, this works fine:
UBI: attaching mtd0 to ubi0 UBI: scanning is finished UBI: attached mtd0 (name "ubi0", size 128 MiB) to ubi0 UBI: PEB size: 131072 bytes (128 KiB), LEB size: 129024 bytes UBI: min./max. I/O unit sizes: 2048/2048, sub-page size 512 UBI: VID header offset: 512 (aligned 512), data offset: 2048 UBI: good PEBs: 1024, bad PEBs: 0, corrupted PEBs: 0 UBI: user volume: 0, internal volumes: 1, max. volumes count: 128 UBI: max/mean erase counter: 2/2, WL threshold: 4096, image sequence number: 598317289 UBI: available PEBs: 980, total reserved PEBs: 44, PEBs reserved for bad PEB handling: 40
It is interesting to notice that with the kernel's MTD subsystem, subpage access is supported (we don't use HW ECC but SOFT_BCH) and thus the VID header offset is going to be 512 thanks to this subpage support.
Now, when I try to access the same NAND flash ubi partition in u-boot 2013.10, this fails:
=> ubi part ubi0 UBI: attaching mtd1 to ubi0 UBI: physical eraseblock size: 131072 bytes (128 KiB) UBI: logical eraseblock size: 126976 bytes UBI: smallest flash I/O unit: 2048 UBI: VID header offset: 2048 (aligned 2048) UBI: data offset: 4096 UBI error: validate_ec_hdr: bad VID header offset 512, expected 2048 UBI error: validate_ec_hdr: bad EC header UBI error: ubi_io_read_ec_hdr: validation failed for PEB 0 UBI error: ubi_init: cannot attach mtd1 UBI error: ubi_init: UBI error: cannot initialize UBI, error -22 UBI init error 22 =>
Since u-boot does not support subpage access with the fsl_elbc_nand driver, it choses a VID offset that is as big as a page and here we have an incompatibility...
I know that I could give an argument to the kernel (ubi.mtd=0,2048) so that it also ignores the subpages, but that feels like a not optimal workaround (that I am currently using but I would like to get rid of if), and our other systems (kirkwood and 83xx based) support NAND subpage access in u-boot nicely.
Is there a reason why fsl_elbc_nand does not allow subpage access in the case of SOFT_(BCH_)ECC ?
Best Regards
Valentin