Dear Michael Trimarchi,
In message CAOf5uw=hCkwPaqogCO3KvM1erhS-dvC5BRT4USU3uqKETtTQ7A@mail.gmail.com you wrote:
This does not answer Stefano's question: why do it in SPL, what's wrong with loading the real U-Boot for this purpose?
Because it's not possible, internal memory size of some cpus. You need to have a way to load the second stage and I'm discussing a general way to do.
I'm not sure that there are many use cases where you have sufficient room for all that is needed for DFU (including I/O buffers); and if you move to RAM early, you have other options as well.
What is your alternative way?
Depending on your hardware there is a zillion ways to do this. For low to medium volumes good old JTAG is still a very powerful tool; for high volumes you will probably just fit pre-programmed NAND on your board. And of course there is the growing number of systems that can just boot and install from a SDCard or USB MSD.
Best regards,
Wolfgang Denk