On Fri, May 17, 2013 at 08:06:07PM +0200, Henrik Nordstr?m wrote:
I am looking into reusing the SPL system initialization part for a very minimalistic "SPL" which only initializes the board.
To give a bit of context, on the Allwinner CPUs there is a recovery boot mode where data can be copied over USB and executed by the CPU. But most of the board including DRAM controller is not initialized by default so the very first thing you need to do is to upload & execute board initialization code (but excluding CPU initialization).
Note: It is not really an SPL as all it does is initializing the board and then returning control to the USB loader so additional code (u-boot.bin) can be uploaded to DRAM and executed.
I have this implemented today partially out-of-tree leaching objects from an u-boot build to build a binary with the initialization code. My question is if it would make sense to try integrate this into the u-boot tree somehow. Have something similar been done for any other board?
The current "code" is at https://github.com/linux-sunxi/sunxi-tools/tree/master/felboot mainly main.c (entry + stubs), the rest is only for a small printf and is not needed.
I would say you want to hypothetically add a _felboot build target for the allwinner boards that instead of building out a regular CONFIG_SPL_FRAMEWORK (I hope!) SPL spits out just a very tiny one that does what you need for this use case. Having different builds for different SPL cases is a normal thing that we do on a few boards, but none are quite so drastically different sounding as this.