colleague just asked me how to (if possible) chain-load a modified u-boot from a u-boot currently stored in flash, and from having done this once *years* ago, i'm fairly sure i can make this happen, i just want to confirm my plan. (the current running version is based off of u-boot v2015.07 -- i have no freedom to change that.)
the newer u-boot will do nothing more than add a couple commands ("mii" and "mdio"), and i've already tweaked the configuration to add those commands to the configuration, compiled and verified that those commands are now listed in the u-boot.map file, so that part seems fine.
at this point, i've been told that there is a proprietary pre-boot loader in ROM which, among other things, loads u-boot from flash into RAM and jumps to that address -- i assume, at that point, i just need to download my new u-boot binary from the server to some address in RAM currently *not* occupied by u-boot, and "go" to that new address.
my only question is, what do i change in the configuration to identify where i will load the enhanced u-boot? i vaguely recall that i need to change the text base, and load the new binary at precisely that address, is that correct?
finally (as an aside), i've read a number of pieces online that describe how the second u-boot should try to avoid doing low-level H/W initialization that the first has already done, but for now, i'm just going to assume idempotency for all of that early initialization unless proven wrong.
so ... what must i change in the config to support loading the new version of u-boot at a different address? thanks.
rday