Hi, I'm looking at the am335x cpu, and have a few questions that I hope the community can answer:
(1) It seems that the ROM code does not support booting from eMMC boot partitions; I can't find anything about it in the reference manual, and this ancient thread suggests that it indeed not supported: https://u-boot.denx.narkive.com/S8U7Z3Wr/dra7xx-booting-from-emmc-raw-boot-partition (2) The cpu does support looking at a sequence of offsets (0, 128K, 256K, 384K) for a proper header/image, and will read MLO from the first such offset. So it is possible to do a safe update of MLO. However, it seems that MLO will always load U-Boot proper from some fixed offset (or partition), independent of which offset MLO was loaded from. So in order to implement an update mechanism for the whole bootloader which is safe against power failures, one would need to teach the SPL phase to pick an offset depending on the offset SPL itself was loaded from. But that in turn requires that the ROM code exposes that information. Does it? Poking around the reference manual, it seems there are some "tracing vectors" (0x4030ce40 ..), of which word 2, bits 12-15 are "memory boot trial 0-3". So perhaps those bits can be used to figure out which offset the ROM code eventually ended up using? But is there some more direct/documented approach? [Alternatively, one would have to build two distinct copies of U-Boot merely differing in their value of CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR, but that's not a very attractive option]. Rasmus
