Dual monitors with DP1.2 are duplicating instead of extending

[aczer]

I have a desktop with 2 monitors. They are connected with DP 1.2 (daisy-chain) so cables are desktop -> monitor 1 via a DP cable -> monitor 2 via a DP cable from monitor 1 output to monitor 2 input.

This works well in Windows 10 (I have dual boot) so I know the hardware is properly connected and DP 1.2 is supported by the desktop and both monitors.

But in Linux Mint both monitors display the same image (duplicate the display instead of extending them).

How do I configure monitor 2 to extend the desktop instead of duplicating the monitors (which is useful for projectors but not for extending monitors)?

Thank in advance!

[ClixTrix]

Please run the following command from Terminal and post back the results.

Code: Select all

inxi -Fxz

I'm assuming you've checked Preferences - Displays for options (including Mirror displays is unchecked).

I do see some discussion at ubuntu on minimum Kernel necessary for chaining DP.

https://askubuntu.com/questions/766931/ ... 032#772032

[aczer]

Yes, the display option only shows one monitor but both monitors work and show the same image (but I want them to extend, not duplicate the display). See the attached 2 images.

Here is the result of inxi -Fxz:

System: Host: Z200 Kernel: 4.13.0-32-generic x86_64 (64 bit gcc: 5.4.0)
Desktop: Cinnamon 3.6.7 (Gtk 3.18.9-1ubuntu3.3) Distro: Linux Mint 18.3 Sylvia
Machine: System: Hewlett-Packard product: HP Z200 SFF Workstation
Mobo: Hewlett-Packard model: 0B48h Bios: Hewlett-Packard v: 786H4 v01.18 date: 09/09/2013
CPU: Quad core Intel Core i7 870 (-HT-MCP-) cache: 8192 KB
flags: (lm nx sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx) bmips: 23410
clock speeds: max: 3066 MHz 1: 1199 MHz 2: 1199 MHz 3: 1199 MHz 4: 1199 MHz 5: 1199 MHz 6: 1199 MHz
7: 1199 MHz 8: 1733 MHz
Graphics: Card: Advanced Micro Devices [AMD/ATI] Caicos XTX [Radeon HD 8490 / R5 235X OEM] bus-ID: 01:00.0
Display Server: X.Org 1.18.4 drivers: ati,radeon (unloaded: fbdev,vesa) Resolution: 1920x1200@59.95hz
GLX Renderer: AMD CAICOS (DRM 2.50.0 / 4.13.0-32-generic, LLVM 5.0.0)
GLX Version: 3.0 Mesa 17.2.8 Direct Rendering: Yes
Audio: Card-1 Intel 5 Series/3400 Series High Definition Audio driver: snd_hda_intel bus-ID: 00:1b.0
Card-2 Advanced Micro Devices [AMD/ATI] Caicos HDMI Audio [Radeon HD 6400 Series]
driver: snd_hda_intel bus-ID: 01:00.1
Sound: Advanced Linux Sound Architecture v: k4.13.0-32-generic
Network: Card: Intel 82578DM Gigabit Network Connection driver: e1000e v: 3.2.6-k port: 2100 bus-ID: 00:19.0
IF: enp0s25 state: up speed: 1000 Mbps duplex: full mac: <filter>
Drives: HDD Total Size: 250.1GB (8.9% used) ID-1: /dev/sda model: WDC_WD2500AAKX size: 250.1GB
Partition: ID-1: / size: 86G used: 14G (17%) fs: ext4 dev: /dev/sda6
ID-2: swap-1 size: 8.19GB used: 0.00GB (0%) fs: swap dev: /dev/sda5
RAID: No RAID devices: /proc/mdstat, md_mod kernel module present
Sensors: System Temperatures: cpu: 33.0C mobo: N/A gpu: 46.5
Fan Speeds (in rpm): cpu: N/A
Info: Processes: 259 Uptime: 2 min Memory: 1823.1/20008.2MB Init: systemd runlevel: 5 Gcc sys: 5.4.0
Client: Shell (bash 4.3.481) inxi: 2.2.35

Screenshot of the monitor

Monitor1.png

Picture of both monitors with the same image

IMG_0814.JPG

[ClixTrix]

Is there a setting on Monitor #1 (first in chain) for DP 1.2 mode or enable MT?

Also, what does xrandr show when run from Terminal.

I am a little concerned that the AMD open source xorg driver may not yet support DP 1.2 chaining, i.e. still "a work in progress".

[aczer]

Yes, both monitors have a DP 1.2 setting and are both enabled. When I boot on Windows this is working perfectly, with both monitors working and extending the desktop instead of duplicating.

What is interesting to me is that on Mint both monitors DO work and I can see the image on both, which I think means that DP 1.2 is working, but as you can see in the image above both monitors are duplicating the image instead of extending.

Given that both monitors work on Windows and Mint it does feel like there is a missing setting somewhere that would make Mint extend the desktop instead of duplicating it. But I have no idea where/what that could be.

Below is the output of xrandr.

Screen 0: minimum 320 x 200, current 1920 x 1200, maximum 16384 x 16384
DisplayPort-0 connected primary 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
1920x1200 59.95*+
1920x1080 60.00 50.00 59.94 30.00 25.00 24.00 29.97 23.98
1920x1080i 60.00 50.00 59.94
1600x1200 60.00
1280x1024 75.02 60.02
1152x864 75.00
1280x720 60.00 50.00 59.94
1024x768 75.03 60.00
800x600 75.00 60.32
720x576 50.00
720x576i 50.00
720x480 60.00 59.94
720x480i 60.00 59.94
640x480 75.00 60.00 59.94
720x400 70.08
DVI-0 disconnected (normal left inverted right x axis y axis)

Any ideas?

Thanks!

[ClixTrix]

Yep, maybe. Read this post at arch. Yes, I see the second monitor becomes "black screen", but it's worth a shot. They're also attempting 3 monitors, so maybe that's a monitor too many.

https://bbs.archlinux.org/viewtopic.php?id=210338

So, the Radeon folks said you need to pass a parm to the Kernel.

radeon.mst=1

To see if it works, use the "e" key at the Grub boot menu, and modify the line with "quiet splash", like you do with nomodeset. That's a good way to test without changing system grub file for permanent. (per article)

After you're up, try xrandr again, and check Displays menu. Fingers crossed.

[aczer]

I just tried and yes, got the black screen. For me, both monitors were black, not just the 2nd one. I did use the "e" at Grub boot so restarting brought everything back (both monitors on, but the same image on both) so I'm back at square one. Not sure what else I could really try.

[ClixTrix]

In further checking, that should be the correct parm. However, it appears to be "experimental".

If you run this command from Terminal, you'll get a list of available Kernel parameters.

Code: Select all

modinfo -p radeon

Here is the line from my check.

mst:DisplayPort MST experimental support (1 = enable, 0 = disable) (int)

This is where I found discussion.

https://www.x.org/wiki/RadeonFeature/#L ... parameters

Go to page 36 in this PDF and look at the last bullet on Ubuntu-MST and note the date at page bottom. Remember, Mint 18 is based upon Ubuntu 16.04.

https://www.x.org/wiki/Events/XDC2016/P ... md_dal.pdf

Edit:

If you really want the latest X.Org drivers, here's discussion and the PPA.

https://www.epicgames.com/unrealtournam ... -in-ubuntu

https://launchpad.net/~ubuntu-x-swat/+a ... /+packages

I have no clue whether the latest will fix the problem, or break your system. Proceed with caution and backup.

[aczer]

I tried but wasn't able to get DP 1.2 to work at all. No matter what I did the screens would always duplicate instead of extend.

In the end I purchased and installed a $35 video card (details below in case anyone wants a reference) and it came with 2 ports so with the new card both monitors extend as expected. The video card I purchased is this:
product: G98 [Quadro NVS 295]
vendor: NVIDIA Corporation
width: 64 bits
clock: 33MHz
capabilities: vga_controller bus_master cap_list rom
configuration: driver=nouveau latency=0

While this doesn't solve the DP1.2 issue it at least gets me able to use both monitors. Now back to my day job

THANK YOU for all the guidance above. Much appreciated!