Nouveau - Aug 2019 - [PATCH v3 5/7] drm/nouveau: utilize subconnector property for DP

On Wed, Aug 28, 2019 at 10:47:08AM -0400, Ilia Mirkin
wrote:
> On Wed, Aug 28, 2019 at 10:38 AM Ville Syrjälä
> <ville.syrjala at linux.intel.com> wrote:
> >
> > On Mon, Aug 26, 2019 at 09:36:50AM -0400, Ilia Mirkin wrote:
> > > This should probably be fixed to account for the scenario where
an
> > > HDMI connector is plugged directly into the DP++ port. I
don't think
> > > the dp.subconnector property will be valid in that case.
> > > (Unfortunately I don't remember how one detects that
particular
> > > situation.)
> >
> > One may or may not be able to detect it very well. I've seen
dongles
> > that automagically change the DFP type from DP++ to DP/HDMI depending
> > on what's plugged in, and I've also seen dongles that leave
the DFP
> > type to DP++.
> 
> Well, our internal logic certainly knows if it's driving DP or TMDS. I
> just don't remember how it knows this.
You'll be driving DP in this case. The DFP will be the one driving
DP or TMDS depending on what's plugged in.

-- 
Ville Syrjälä
Intel

On Wed, Aug 28, 2019 at 10:54 AM Ville Syrjälä
<ville.syrjala at linux.intel.com> wrote:
>
> On Wed, Aug 28, 2019 at 10:47:08AM -0400, Ilia Mirkin wrote:
> > On Wed, Aug 28, 2019 at 10:38 AM Ville Syrjälä
> > <ville.syrjala at linux.intel.com> wrote:
> > >
> > > On Mon, Aug 26, 2019 at 09:36:50AM -0400, Ilia Mirkin wrote:
> > > > This should probably be fixed to account for the scenario
where an
> > > > HDMI connector is plugged directly into the DP++ port. I
don't think
> > > > the dp.subconnector property will be valid in that case.
> > > > (Unfortunately I don't remember how one detects that
particular
> > > > situation.)
> > >
> > > One may or may not be able to detect it very well. I've seen
dongles
> > > that automagically change the DFP type from DP++ to DP/HDMI
depending
> > > on what's plugged in, and I've also seen dongles that
leave the DFP
> > > type to DP++.
> >
> > Well, our internal logic certainly knows if it's driving DP or
TMDS. I
> > just don't remember how it knows this.
>
> You'll be driving DP in this case. The DFP will be the one driving
> DP or TMDS depending on what's plugged in.
OK. That's not the case I was worried about though :)

I'm worried about the case where you plug a true HDMI thing into the
DP port, which will then be driven by HDMI and none of the dp.* things
will be set (I don't remember, but they might even be in a union). I
think Intel multiplies connectors for this, but nouveau/amd just have
a single connector that handles both.

  -ilia

On Wed, Aug 28, 2019 at 11:11:41AM -0400, Ilia Mirkin
wrote:
> On Wed, Aug 28, 2019 at 10:54 AM Ville Syrjälä
> <ville.syrjala at linux.intel.com> wrote:
> >
> > On Wed, Aug 28, 2019 at 10:47:08AM -0400, Ilia Mirkin wrote:
> > > On Wed, Aug 28, 2019 at 10:38 AM Ville Syrjälä
> > > <ville.syrjala at linux.intel.com> wrote:
> > > >
> > > > On Mon, Aug 26, 2019 at 09:36:50AM -0400, Ilia Mirkin wrote:
> > > > > This should probably be fixed to account for the
scenario where an
> > > > > HDMI connector is plugged directly into the DP++ port.
I don't think
> > > > > the dp.subconnector property will be valid in that
case.
> > > > > (Unfortunately I don't remember how one detects
that particular
> > > > > situation.)
> > > >
> > > > One may or may not be able to detect it very well. I've
seen dongles
> > > > that automagically change the DFP type from DP++ to DP/HDMI
depending
> > > > on what's plugged in, and I've also seen dongles
that leave the DFP
> > > > type to DP++.
> > >
> > > Well, our internal logic certainly knows if it's driving DP
or TMDS. I
> > > just don't remember how it knows this.
> >
> > You'll be driving DP in this case. The DFP will be the one driving
> > DP or TMDS depending on what's plugged in.
> 
> OK. That's not the case I was worried about though :)
> 
> I'm worried about the case where you plug a true HDMI thing into the
> DP port, which will then be driven by HDMI and none of the dp.* things
> will be set (I don't remember, but they might even be in a union). I
> think Intel multiplies connectors for this, but nouveau/amd just have
> a single connector that handles both.
Ah. Yeah, that's a bit more confusing since you kinda now have two
levels of subconnectors. Not sure how to deal with that tbh.

-- 
Ville Syrjälä
Intel