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

Alex Deucher
2019-08-15T14:37:05Z

On Thu, Aug 15, 2019 at 10:25 AM Karol Herbst <kherbst at redhat.com>
wrote:
>
> On Thu, Aug 15, 2019 at 4:20 PM <Mario.Limonciello at dell.com>
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?

There was an issue with hpd events not making it to the audio side
when things were powered down that was fixed with this patch set:
https://patchwork.freedesktop.org/patch/316793/
Those patches depended on a bunch of alsa changes as well which may
have not been available in the distro used for a particular OEM
program.

>
> > >
> > > 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?

I'm not familiar with this patches in particular, but I know we've
done things with OEM programs to support Linux on platforms where
Linux support is lacking for in new features for the target distros.
E.g., when the first hybrid graphics laptops were coming out, Linux
didn't support it too well or at all depending on the timing, so the
bios exposed power express which was working well at the time if the
OS told ACPI it was Linux.

Alex