Nouveau - Aug 2022 - [RFC 0/2] Stop the abuse of Linux-* _OSI strings

On Fri, 2022-08-19 at 17:44 +0200, Karol Herbst wrote:
> On Fri, Aug 19, 2022 at 4:25 PM Mario Limonciello
> <mario.limonciello at amd.com> wrote:
> > 
> > 3 _OSI strings were introduced in recent years that were intended
> > to workaround very specific problems found on specific systems.
> > 
> > The idea was supposed to be that these quirks were only used on
> > those systems, but this proved to be a bad assumption.  I've found
> > at least one system in the wild where the vendor using the _OSI
> > string doesn't match the _OSI string and the neither does the use.
> > 
> > So this brings a good time to review keeping those strings in the
kernel.
> > There are 3 strings that were introduced:
> > 
> > Linux-Dell-Video
> > -> Intended for systems with NVIDIA cards that didn't support
RTD3
> > Linux-Lenovo-NV-HDMI-Audio
> > -> Intended for powering on NVIDIA HDMI device
> > Linux-HPI-Hybrid-Graphics
> > -> Intended for changing dGPU output
> > 
> > AFAIK the first string is no longer relevant as nouveau now supports
> > RTD3.  If that's wrong, this can be changed for the series.
> > 
> 
> Nouveau always supported RTD3, because that's mainly a kernel feature.
> When those were introduced we simply had a bug only hit on a few
> systems. And instead of helping us to debug this, this workaround was
> added :( We were not even asked about this.
> 
> I am a bit curious about the other two though as I am not even sure
> they are needed at all as we put other work arounds in place. @Lyude
> Paul might know more about these.
Some of the _OSI strings are totally fine. From my recollection:

[    0.242993] ACPI: Added _OSI(Linux-Lenovo-NV-HDMI-Audio)
^ this one is needed to do a couple of ACPI tricks at startup to get the PCIe
device for audio on nvidia's GPU to be detected properly

[    0.242993] ACPI: Added _OSI(Linux-HPI-Hybrid-Graphics)

I don't actually know how necessary this is, but I'm hesistant to call
this
one bad as it may be related to the funny mux configurations that I'm
learning
may exist on HP machines.
> 
-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat

[+Cc Aaron]

On Tue, Aug 23, 2022 at 5:18 AM Lyude Paul <lyude at redhat.com>
wrote:
>
> On Fri, 2022-08-19 at 17:44 +0200, Karol Herbst wrote:
> > On Fri, Aug 19, 2022 at 4:25 PM Mario Limonciello
> > <mario.limonciello at amd.com> wrote:
> > >
> > > 3 _OSI strings were introduced in recent years that were intended
> > > to workaround very specific problems found on specific systems.
> > >
> > > The idea was supposed to be that these quirks were only used on
> > > those systems, but this proved to be a bad assumption.  I've
found
> > > at least one system in the wild where the vendor using the _OSI
> > > string doesn't match the _OSI string and the neither does the
use.
> > >
> > > So this brings a good time to review keeping those strings in the
kernel.
> > > There are 3 strings that were introduced:
> > >
> > > Linux-Dell-Video
> > > -> Intended for systems with NVIDIA cards that didn't
support RTD3
> > > Linux-Lenovo-NV-HDMI-Audio
> > > -> Intended for powering on NVIDIA HDMI device
> > > Linux-HPI-Hybrid-Graphics
> > > -> Intended for changing dGPU output
> > >
> > > AFAIK the first string is no longer relevant as nouveau now
supports
> > > RTD3.  If that's wrong, this can be changed for the series.
> > >
> >
> > Nouveau always supported RTD3, because that's mainly a kernel
feature.
> > When those were introduced we simply had a bug only hit on a few
> > systems. And instead of helping us to debug this, this workaround was
> > added :( We were not even asked about this.
> >
> > I am a bit curious about the other two though as I am not even sure
> > they are needed at all as we put other work arounds in place. @Lyude
> > Paul might know more about these.
>
> Some of the _OSI strings are totally fine. From my recollection:
>
> [    0.242993] ACPI: Added _OSI(Linux-Lenovo-NV-HDMI-Audio)
> ^ this one is needed to do a couple of ACPI tricks at startup to get the
PCIe
> device for audio on nvidia's GPU to be detected properly
This should be fixed by commit b516ea586d71 ("PCI: Enable NVIDIA HDA
controllers").
Aaron worked on more Lenovo systems than me, so he may be more sure of it.
>
> [    0.242993] ACPI: Added _OSI(Linux-HPI-Hybrid-Graphics)
>
> I don't actually know how necessary this is, but I'm hesistant to
call this
> one bad as it may be related to the funny mux configurations that I'm
learning
> may exist on HP machines.
Should be fixed by commit 8e55f99c510f ("drm/i915: Invoke another _DSM
to enable MUX on HP Workstation laptops").

And for "Linux-Dell-Video", it should be fixed by 5775b843a619
("PCI:
Restore config space on runtime resume despite being unbound").

So actually I am in favor of removing them all.

Kai-Heng
>
> >
>
> --
> Cheers,
>  Lyude Paul (she/her)
>  Software Engineer at Red Hat
>