Hi Simon, As I've mentioned in my comments to several patches related to coreboot support in U-Boot, I would like to discuss how to formally support the execution of U-Boot as a coreboot payload.
Looking at the code in arch/x86/cpu/coreboot, I think the cleanest approach will be to move the coreboot code into arch/x86/lib/. We could either prefix coreboot related source files with cb_ or create a coreboot directory under arch/x86/lib (there would be no reason not to pull in the coreboot lib through the existing lib/Makefile) Every x86 board would then have it's own board config file which define CONFIG_X86_COREBOOT. As discussed previously CONFIG_X86_COREBOOT should result in the exclusion of all 16-bit code The next item to discuss is the passing of data from coreboot to U-Boot (and ultimately to Linux) including: - Physical memory map (E820) - List of initialised devices - Pointer to the coreboot filesystem (or multiple pointers if multiple such filesystems exist) - etc. I know you have mentioned that coreboot has data structure used to maintain such data and that this will be preferred in future over FTD. Considering that U-Boot already has extensive FDT support, I'm loath to add yet another data passing mechanism. Add to this rumours I have heard that FDT support is 'coming to an x86 kernel near you', I think FDT is the most appropriate way forward. Last but not least, we need to have a closer look at how coreboot loads and launches U-Boot. I can't say for sure, but I am assuming U-Boot is built to some fixed RAM address (0xfc0000) and U-Boot relocates based on memory information passed by U-Boot. What I would like to see is one of two possible approaches implemented: 1) Have coreboot load U-Boot to the final RAM location 2) If U-Boot is stored in cbfs as a single linear chunk, execute U-Boot in-place from cbfs Both of these will eliminate a redundant memory copy. If option 1) is chosen, we have two sub-options: 1) Tweak U-Boot's relocation code for x86 to allow relocation from an arbitrary load address (al-la how the Linux kernel works) 2) Have coreboot perform the relocation adjustments I think sub-option 1) is probably the way to go Regards, Graeme _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
