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

[Alex Deucher]

On Thu, Aug 15, 2019 at 10:15 AM Karol Herbst <kherbst@xxxxxxxxxx> wrote:
>
> On Thu, Aug 15, 2019 at 4:13 PM Alex Deucher <alexdeucher@xxxxxxxxx> wrote:
> >
> > On Thu, Aug 15, 2019 at 10:04 AM Karol Herbst <kherbst@xxxxxxxxxx> wrote:
> > >
> > > On Thu, Aug 15, 2019 at 3:56 PM <Mario.Limonciello@xxxxxxxx> wrote:
> > > >
> > > > > -----Original Message-----
> > > > > From: linux-acpi-owner@xxxxxxxxxxxxxxx <linux-acpi-owner@xxxxxxxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > > > 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
> >
>
> thanks for clarifying. But that still means that we won't need such
> workarounds for AMD users, right? amdgpu handles hybrid graphics just
> fine, right?

Yeah it should, assuming you have a new enough kernel which supports
HG, which has been several years at this point IIRC.

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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