Hello Hans,
Sorry for ignoring the second half of your question so far. Here's what's on my mind. Op 21-05-15 om 20:08 schreef Hans de Goede:
Hi Roy,
- What is the plan to add support for loading files from nand in
u-boot proper, so that we can get (e.g.) extlinux.conf + kernel +dtb from a /boot on nand ?
For the full U-boot I agree we want both MMC and NAND support, regardless of where it was loaded from. From what I can tell U-boot already has UBI support. It sounds like a logical step to try and construct a proper NAND driver for U-boot that either co-exists with this SPL driver or, even better, shares code. That way, I only assume that the UBI and UBIFS layers will take care of all the rest. The NAND framework in u-boot resembles Linux in many ways. I'm currently in doubt whether we should take Boris' driver as a starting point, or rather use something heavily reduced that re-uses this SPL code. Either way, in U-boot we can perform a clean NAND-chip detection, preferably based on DT definitions as we also use on Linux, and take care of everything proper like PLL settings and a bunch of parameters which are now hard-coded or a configuration option in sunxi-common.h.
SPL is a different story. I don't know the exact size restriction, but for A10 I've heard it might be as little as 30KB. Current SPL with my patches and without MMC is already 23KiB. I personally think we can reduce it slightly by taking out support for reading everything other than the bootloader partition from SPL (so remove non-syndrome mode, remove the random seeds table...), but it certainly doesn't leave any room for the full NAND framework to do ID-based NAND chip detection. I personally think it's acceptable if NAND-SPL does not have MMC support and vice-versa. For NAND, SPL is only loaded when there is no first-level bootloader found on the MMC, so I safely dare to assume U-boot isn't there. MMCs are generally not so tiny that SPL fits but U-boot doesn't.
Questions, comments? Cheers,
Roy
Regards,
Hans