[coreboot] Powersavings: 8W of difference between bios and coreboot

[Felix Held]

Hi!

> I don't know if Charlotte has added the ID of the dGPU to 
> src/drivers/lenovo/hybrid_graphics.c. Does the dGPU consume power 
> after hybrid_graphics.c disable the dGPU?
OPTIMUS_ENABLE is a PCH GPIO and controls the muxes that select if the 
internal display is connected to the iGPU or the dGPU; that's done in 
hybrid_graphics.c.
GFXCORE_ON_D (and another signal that controls the power supply of the 
VRAM) are driven by the Thinker-1 chip; those switch on/off the power 
supply of the GPU. So to really disable the GPU you probably have to ask 
the EC to make that chip turn off the voltage for the GPU and VRAM.

Regards
Felix