GMUX

[Redecorating]

Graphics Multiplexer on dual GPU models.

• Read and Write to gmux ports
• Backlight control
• Switching Display between GPUs
  • To preserve state after resume (so you can resume properly when using the igpu!)
  • At runtime with vga_switcheroo
    • Make amdgpu register with vga_switcheroo
    • Make intel card register with vga_switcheroo
  • Get the switched to GPU to output to the display
• Interrupts
• Power up/down dGPU
  • Power Down
  • GMUX: dGPU Power Up #3
    • mbp15,x
    • mbp16,x
  • ACPI PWRD, PWG1
• Update internal documentation
• Test on other T2 models once everything should be working
• Ensure these changes don't cause regressions for pio and indexed models.

https://lore.kernel.org/platform-driver-x86/20230218132007.3350-1-orlandoch.dev@gmail.com/

[Redecorating]

v4: https://lore.kernel.org/platform-driver-x86/20230303112842.3094-1-orlandoch.dev@gmail.com/