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

[Alex Deucher]

On Thu, Aug 15, 2019 at 10:04 AM Karol Herbst <kherbst at redhat.com> wrote:
>
> On Thu, Aug 15, 2019 at 3:56 PM <Mario.Limonciello at dell.com> wrote:
> >
> > > -----Original Message-----
> > > From: linux-acpi-owner at vger.kernel.org <linux-acpi-owner at vger.kernel.org> On
> > > Behalf Of Dave Airlie
> > > Sent: Wednesday, August 14, 2019 5:48 PM
> > > To: Karol Herbst
> > > Cc: LKML; Linux ACPI; dri-devel; nouveau; Rafael J . Wysocki; Alex Hung; Ben
> > > Skeggs; Dave Airlie
> > > Subject: Re: [Nouveau] [PATCH 1/7] Revert "ACPI / OSI: Add OEM _OSI string to
> > > enable dGPU direct output"
> > >
> > > On Thu, 15 Aug 2019 at 07:31, Karol Herbst <kherbst at redhat.com> wrote:
> > > >
> > > > This reverts commit 28586a51eea666d5531bcaef2f68e4abbd87242c.
> > > >
> > > > The original commit message didn't even make sense. AMD _does_ support it and
> > > > it works with Nouveau as well.
> > > >
> > > > Also what was the issue being solved here? No references to any bugs and not
> > > > even explaining any issue at all isn't the way we do things.
> > > >
> > > > And even if it means a muxed design, then the fix is to make it work inside the
> > > > driver, not adding some hacky workaround through ACPI tricks.
> > > >
> > > > And what out of tree drivers do or do not support we don't care one bit anyway.
> > > >
> > >
> > > I think the reverts should be merged via Rafael's tree as the original
> > > patches went in via there, and we should get them in asap.
> > >
> > > Acked-by: Dave Airlie <airlied at redhat.com>
> > > Dave.
> >
> > 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?

Hybrid Graphics is the new "standard" way of handling these laptops.
It uses the standard _PR3 APCI method to handle dGPU power.  Support
for this was added to Linux relatively later compared to when the
laptops were launched.  "Power Express" used the other AMD specific
ATPX ACPI method to handle dGPU power.  The driver supports both so
either method will work.

Alex

>
> 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?
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