[Nouveau] support for dp 1.2

[Ilia Mirkin]

On Tue, Jun 16, 2015 at 3:53 PM, Stephen Adler <adler at stephenadler.com> wrote:
> On Tue, 2015-06-16 at 15:47 -0400, Ilia Mirkin wrote:
>> On Tue, Jun 16, 2015 at 3:33 PM, Stephen Adler <
>> adler at stephenadler.com> wrote:
>> > Guys,
>> >
>> > Is there support for display port 1.2 with the nouveau driver and
>> > GTX
>> > 970?
>> >
>> > I have a dell 4K monitor and to run it in 4K mode at 60Hz I need to
>> > configure the monitor to run version 1.2 of the display port
>> > protocol.
>> > the nouveau driver works well with display port 1.1 but I only get
>> > a
>> > 30Hz refresh rate at 4K resolution.
>>
>> The DP 1.2 540MHz rate should be supported. However there is
>> presently
>> no MST support, so if the monitor has 2 internal panels, that won't
>> pan out so well (yet).
>>
>> Also note that the GTX 970 requires signed firmware from NVIDIA to
>> use
>> any acceleration, and we haven't quite yet figured out how to get
>> that
>> going. This means that all you get is modesetting, no acceleration.
>> Esp with a 4K screen, using llvmpipe may feel slow if you use a GL
>> compositor, as many modern desktops do.
>>
>>   -ilia
>>
>
> Thanks for the quick response. I'm having a hell of a time with the
> nvidia driver since I have three 4K monitors which hook up to the GTX
> 970 card, but in linux it will only drive two of the 3 monitors. The
> monitors do have the dual internal panels each running at 1920x2160 or
> something like that. For some reason nvidia only drives 4 of the panels
> (two monitors) per GPU...

Kepler+ GPUs only have 4 CRTC's, so you can only scan out 4 things at
a time [pre-Kepler have only 2 CRTC's]. However perhaps you can have a
single CRTC split an image up into 2 encoders, I don't really know how
that works, esp in the context of DP-MST, where it's really a single
encoder.

>
> Is the MST support imminent? or off into the future?

It's on the horizon... a horizon, of course, being an imaginary line
that keeps moving further away as you attempt to approach it :) Here's
Ben's tree from a year ago (which BTW has no support for your GPU at
all):

http://cgit.freedesktop.org/~darktama/nouveau/log/?h=devel-mst

AFAIK he's been putting it off, trying to combine it with a conversion
to atomic modesetting.

  -ilia