Re: [Nouveau] [PATCH 1/7] Revert "ACPI / OSI: Add OEM _OSI string to enable dGPU direct output"

[Karol Herbst]

On Thu, Aug 15, 2019 at 4:20 PM <Mario.Limonciello@xxxxxxxx> wrote:
>
> > > There are definitely going to be regressions on machines in the field with the
> > > in tree drivers by reverting this.  I think we should have an answer for all of
> > those
> > > before this revert is accepted.
> > >
> > > Regarding systems with Intel+NVIDIA, we'll have to work with partners to
> > collect
> > > some information on the impact of reverting this.
> > >
> > > When this is used on a system with Intel+AMD the ASL configures AMD GPU to
> > use
> > > "Hybrid Graphics" when on Windows and "Power Express" and "Switchable
> > Graphics"
> > > when on Linux.
> >
> > and what's exactly the difference between those? And what's the actual
> > issue here?
>
> DP/HDMI is not detected unless plugged in at bootup.  It's due to missing HPD
> events.
>

afaik Lyude was working on fixing all that, at least for some drivers.
If there is something wrong, we still should fix the drivers, not
adding ACPI workarounds.

Alex: do you know if there are remaining issues regarding that with amdgpu?

> >
> > We already have the PRIME offloading in place and if that's not
> > enough, we should work on extending it, not adding some ACPI based
> > workarounds, because that's exactly how that looks like.
> >
> > Also, was this discussed with anybody involved in the drm subsystem?
> >
> > >
> > > I feel we need a knob and/or DMI detection to affect the changes that the ASL
> > > normally performs.
> >
> > Why do we have to do that on a firmware level at all?
>
> Folks from AMD Graphics team recommended this approach.  From their perspective
> it's not a workaround.  They view this as a different architecture for AMD graphics driver on
> Windows and AMD graphics w/ amdgpu driver.  They have different ASL paths used for
> each.

@alex: is this true?