GTX 980 and K4200 3D Linux Woes

So I’ve been trying to get a setup with 2 G-SYNC mointors (one 4K @ 60
Hz and one 1920x1080 @ 120 Hz) working under Linux. I’ve run into a
few issues, but nothing that seemed like a show stopper, until now. I
should mention that one additional requirement is that I’d like use a
set of 3D VISION 2 glasses with the 120 Hz display. My initial
approach was to try to get this all working with the GTX 980
card. Then I discovered that the GTX 980 only supports the 3d sync
signal over USB, not 3-pin mini DIN, and that there is no Linux
support for the USB 3D stuff (that’s another issue, see footnote
below). So I bought a K4200 which does (supposedly) support 3d-sync
over 3-pin mini-DIN.

Now I have a GTX 980 driving a 4K display and the K4200 driving a
1920x1080 display at 120 MHz. Unfortuately, I’m actually worse off
than I was before buying the fancy workstation graphics card. Both
displays off of a single graphics card actually worked reasonably well
(but for the fact that I couldn’t drive the 3D sync stuff over USB).

For background, I’m using Ubuntu 14.10 and am using the 343.22 drivers
as these are the only ones that support the GTX 980, AFAICT.

So, I plug in the two cards and the two monitors, boot things up and
… I’ve only got a display on one monitor. The Ubuntu “Displays”
System Settings panel only sees one monitor, unlike the default
configuration when both monitors were on the GTX 980. So, I go to Nvidia
Settings and start trying to figure how to get both monitors to show
up. It seems there are a couple of options for multiple monitor support in X:

Multiple X Screens

I have tried each of these with unsatisfying results.

  • BaseMosaic

When I try to use BaseMosaic, things fall apart. Even if I check the
“Use BaseMosaic” tick box and save my settings, the setting doesn’t
get properly saved to my xorg.conf file. It’s not clear to me if there
is some way to manually specify that the Driver should use BaseMosaic
and to make things work. I’ve tried turning it to “On”, but I was
unable to make things work properly. This is probably compounded by
the fact that changing each of these settings requires an X server
restart. Makes for a frustrating debugging process.

  • Xinerama

So this sort of seems to work, minus the 3d stuff. I’ve got xinerama
working, which means no XRandR, and no ability to set different zoom
factors for the different monitors. I could probably live with that if
I could get the 3d stuff working, but, try as I may, I can’t get the
3d sync box light to go green. Should this be supported?

  • Multiple X Screens

This seemed like an interesting approach, but I couldn’t figure out
how to have a window manager work with both screens, so I abandoned
this path. If folks think this is the way to go, I could try harder,
but it still wasn’t clear to me that the 3d stuff would work even if I
got this going.

In order to minimize the number of variables, I tried unpluigging the
4K display and trying to get 3d working on the 120 Hz display alone,
but even here I was unable to get things working. Is the 343.22 driver
compatible with the 3d support for the K4200?

So, so far some of the issues/questions I’ve run into are:

  1. NVIDIA driver 343.22 breaks under 3.18 kernel. (Resolution: Ignored
    for the moment, sticking with a 3.16.0 kernel)

  2. No 3D-sync-support over USB for Linux. Is Nvidia ever going to
    support 3d on the GTX 970/980 cards? This would be great, but if the
    answer is no, not much I can doi about it and I’m back to using the
    K4200. I hope there are plans for continued K4200 support (including
    full 3d support) under Linux!

  3. Nvidia Settings GUI doesn’t save the “BaseMosaic” setting.

  4. In general the multiple monitors stuff in the Nvidia Settings GUI
    doesn’t seem to work to well. The GUI options are nicely presented,
    but, upon saving, most of the good bits never seem to get written out
    (no, this isn’t a permission issue – some stuff in the file is
    changed, but not the options I want usually).

  5. How does one test/debug the 3d support stuff? Are there any
    utilities for querying the card to see that things are set up
    properly, or that there is a successful connection to the 3D Vision

  6. What happened to the GSYNC options in Nvidia Settings? Once I went
    to multiple cards, the GSYNC check boxes disappeared from the Nvidia
    Settings panel.

This is rather length post to say “K4200 and GTX 980 don’t play well
together” under Linux, but I think there are other, deeper, issues in
play here. I’m planning on trying this setup with Windows too
(something I would have preferred to avoid), but it will be nice to
rule out hardware failure/incompatibility here.

If anyone has a recipe for getting this stuff working under Linux, I’d
love to hear it.