[christina_b]

Yeah I looked at it, my firmware mostly just aims at bringing up enough stuff to be able to boot ARM, which is essentially just:

  - Setting up exception vectors and enabling exceptions
  - Reclocking VPU from PLLC
  - UART initialization
  - SDRAM initialization
  - Copying an ARM blinker stub to 0x0
  - ARM power domain initialization
  - PLLB initialization
  - Enabling passthrough mapping for ARM
  - ARM AXI interface initilaization

I'm still trying to figure out what I'm missing in order to get it to work but I suspect it's related to not properly setting up the ARM PLL. I was going to port the RPi clock management driver from Linux but I don't have the time at the moment.

As far as the compiler goes, I think it works reasonably well, though I only tested it by compiling my own code with it, there may be things that cause it to error out (anything that involves the frame pointer like VLAs/some C++ features). Also code quality is not ideal since it still doesn't make use of conditional instructions (aside from conditional branches) and doesn't implement AnalyzeBranch to eliminate redundant branches.

I started cleaning up TableGen to turn multi-instruction asm prints into glue DAG in SelDAGtoDAG but I still have to do it for like 4 instructions, which is pretty much a requirement to have MC code emission.

[david-given]

It's been too long and I've forgotten too much about how LLVM works. The gcc port I linked to, BTW, claims to have VC4 binutils.

Random question: how did you do 64 bit arithmetic? I couldn't find any kind of add-with-carry or subtract-with-carry instruction. I was semi-resigning myself to have to do a compare-and-test as well as the add, which would have more than doubled the amount of work.

Also, nice work reverse engineering the ARM controller --- how did you get the info?