Maxim Polyakov has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/32044 )
Change subject: soc/intel/skylake: Update GFX devtree options ......................................................................
Patch Set 8:
Patch Set 7: Code-Review-1
IMO, this patch does too much at once to keep track of everything...
Open questions:
- Why change the PrimaryDisplay setting of h110m?
- Why would we ever set `PrimaryDisplay = Display_Auto` together with `SkipExtGfxScan`?
- If I didn't miss it, the `SkipExtGfxScan` UPD wasn't set before? So this change changes all boards without mentioning it?
- What does `SkipExtGfxScan` do anyway?
1) "Why change the PrimaryDisplay setting of h110m?" - This board has a PEG port. The Primary_PEG value gives a higher priority to an external graphics card. This means that if I inserted a GPU into this port, then this device outputs information from the coreboot and linux on the display that is connected to this device. But, if there is no external GPU, then another device is used for output, for example, a gfx card connected to the PCH via a PCIe, or an internal iGPU.
In the case when PrimaryDisplay = Auto, I do not know how the priorities in the device sequence are distributed: - iGPU - PEG_GPU - PCH_PCIe_GPU.
Maybe the "Switchable Graphics" mode will be used. I don't know what "Auto" means:)
In case with h110m mb, I want to be sure that the main gfx device is PEG_GPU, as in the AMI BIOS.