Adding AMD GPU support via Linux ATOM BIOS emulator port

[BogDan Vatra]

Hello there,

  I'd like to *try* to port the Linux ATOM BIOS emulator to U-Boot to
enable AMD GPU initialization and basic display support across all
platforms, eliminating the dependency on option ROMs.
  Linux already successfully uses this approach on platforms without option
ROM support. Newer AMD GPUs work on older PowerPC Macs (like the G5) that
lack OpenFirmware GPU support, demonstrating the viability of ATOM BIOS
emulation for cross-platform GPU initialization.

The goal would be to provide:
 - basic AMD GPU detection and initialization.
 - simple framebuffer/display output capability.

Before starting this effort, I'd like to get your input on:
 - feasibility: Does U-Boot's current PCI subsystem provide sufficient
support for tasks like mapping and reading the VBIOS from an AMD GPU, and
accessing its BARs for register I/O, which would be essential for an ATOM
BIOS interpreter? Are there any architectural limitations that would
prevent this integration?

 - prior work: Has anyone already started working on AMD GPU support in
U-Boot? If so, what's the current status and are there opportunities to
collaborate?


Any guidance, concerns, or suggestions would be greatly appreciated before
I dive into the implementation.

Best regards,
BogDan.