Change in coreboot[master]: soc/intel/alderlake: Skip IGD initialziation if DGPU_VGA_IS_PRIMARY e...

[Nico Huber (Code Review)]

Attention is currently required from: Furquan Shaikh, Paul Menzel, Subrata Banik, Patrick Rudolph.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/49291 )

Change subject: soc/intel/alderlake: Skip IGD initialziation if DGPU_VGA_IS_PRIMARY enable
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Patch Set 6:

(4 comments)

Patchset:

PS5:
> > NB. I learned just yesterday (the hard way, wasting an hour […]

I didn't say anything about hardware availability. I'm talking
about coreboot code. And the code in src/soc/intel/alderlake/
was neither written nor adapted nor reviewed for actual Alder
Lake hardware, AFAICS. For instance the pad macros don't seem
to match the actual pads of the hardware. I guess one of many
left overs from the initial copy-paste. And I wonder how people
intend to keep track of it.

Patchset:

PS6: 
Sorry for asking again, I must have forgotten to untick `Resolved`.
> Is this about onboard DGPU or cards with DGPU?

File src/soc/intel/alderlake/romstage/fsp_params.c:

https://review.coreboot.org/c/coreboot/+/49291/comment/c77bb498_2968e751 
PS5, Line 26: 		m_cfg->InternalGfx = 0;
> > Isn't that possible with ADL anymore?
> Not required on ADL anymore

Can you provide some details? What exactly changed? The EDS still
lists the classic IVD bit in GGC.
> Also one more reason, if we don't disable IGD then there are 2 nodes getting created for VGA, one for IGD and another for DGPU and looks like OS is always binding with IGD first hence no display using DGPU

Are you referring to the i915 driver in Linux, maybe? IIRC, it can indeed
control only a single GPU (while it supports both IGD and DG1). If so,
please always mention it if you implement a workaround. Otherwise people
can't clean things up when the issue is resolved.

File src/soc/intel/alderlake/romstage/fsp_params.c:

https://review.coreboot.org/c/coreboot/+/49291/comment/12db635c_98a1a015 
PS6, Line 25: 	if (CONFIG(DGPU_VGA_IS_PRIMARY)) {
Primary usually refers to the order in which software, e.g. the OS, considers
GPUs for display. It's not supposed to decide which GPUs get enabled. Sorry
for the confusion.