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#1 2016-11-29 21:04:55

stupidus
Member
Registered: 2012-02-27
Posts: 124

[solved] DisplayPort on Thinkpad T420 using Reverse PRIME

Hello,

I have a Thinkpad T420 with an integrated intel card and an discrete Nvidia card, meaning it is an optimus setup. I have nouveau installed and PRIME GPU offloading works as expected.
In this laptop the Displayport is hardwired to the Nvidia card. Using reverse PRIME, an output that is connected to the Displayport will show up correctly in xrandr, and the possible resolutions are shown correctly. However, when I activate the output, nothing is actually send to the screen, it just stays in standby mode. This is not an hardware issue, as I have tried it with different screens over the last few months.
I am not using an xorg.conf, everything is detected automatically.

# xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x95 cap: 0xb, Source Output, Sink Output, Sink Offload crtcs: 2 outputs: 2 associated providers: 1 name:Intel
Provider 1: id: 0x66 cap: 0x7, Source Output, Sink Output, Source Offload crtcs: 2 outputs: 5 associated providers: 1 name:nouveau
# xrandr
Screen 0: minimum 320 x 200, current 5200 x 1200, maximum 8192 x 8192
LVDS1 connected primary 1600x900+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
   1600x900      60.01*+  40.00  
   1024x768      60.00  
   800x600       60.32    56.25  
   640x480       59.94  
VGA1 connected 1920x1200+1600+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200     59.95*+
   1920x1080     60.00  
   1600x1200     60.00  
   1680x1050     59.95  
   1600x900      60.00  
   1280x1024     60.02  
   1440x900      59.89  
   1280x800      59.81  
   1280x720      60.00  
   1024x768      60.00  
   800x600       60.32  
   640x480       59.94  
LVDS-1-2 disconnected (normal left inverted right x axis y axis)
VGA-1-2 disconnected (normal left inverted right x axis y axis)
DP-1-1 connected 1680x1050+3520+0 (normal left inverted right x axis y axis) 474mm x 296mm
   1680x1050     59.88*+
   1280x1024     75.02    60.02  
   1152x864      75.00  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   640x480       75.00    59.94  
   720x400       70.08  
DP-1-2 disconnected (normal left inverted right x axis y axis)
DP-1-3 disconnected (normal left inverted right x axis y axis)
  1280x1024 (0x69) 108.000MHz +HSync +VSync
        h: width  1280 start 1328 end 1440 total 1688 skew    0 clock  63.98KHz
        v: height 1024 start 1025 end 1028 total 1066           clock  60.02Hz
  1024x768 (0x6c) 65.000MHz -HSync -VSync
        h: width  1024 start 1048 end 1184 total 1344 skew    0 clock  48.36KHz
        v: height  768 start  771 end  777 total  806           clock  60.00Hz
  800x600 (0x6e) 40.000MHz +HSync +VSync
        h: width   800 start  840 end  968 total 1056 skew    0 clock  37.88KHz
        v: height  600 start  601 end  605 total  628           clock  60.32Hz
  640x480 (0x70) 25.175MHz -HSync -VSync
        h: width   640 start  656 end  752 total  800 skew    0 clock  31.47KHz
        v: height  480 start  490 end  492 total  525           clock  59.94Hz

I don't actually understand what the lines after DP-1-3 mean. Also note, that the behaviour is the same if there is something connected to VGA1 or not.

On some nouveau bug reports, I found that I should try to run the system with the parameters "nouveau.debug=trace drm.debug=0xe".
I uploaded the output of "dmesg | grep nouveau" here: http://pastebin.com/gef4ZWWx

Did anyone who uses a Thinkpad T420 get the Displayport to work with nouveau?

Last edited by stupidus (2016-11-30 17:58:01)

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#2 2016-11-30 16:14:54

stupidus
Member
Registered: 2012-02-27
Posts: 124

Re: [solved] DisplayPort on Thinkpad T420 using Reverse PRIME

Ok, I managed to get it sort of working. I just updated the BIOS. I had not thought of that before, because to me it seemed unlikely that Lenovo would still release BIOS updates for a 5 year old computer. Turns out, there have been lots of BIOS updates in between.

The only remaining problem that I have are serious graphical glitches on the screen that is connected to the Displayport (using nouveau). The mouse cursor leaves traces of itself on the screen.
I will look into this, if there is maybe a fix for this.

EDIT: I still had a file in /etc/X11/xorg.conf.d/. After deleting/moving it, the graphics glitches are gone, however, the initial setup of the screens is a bit screwed up (Screen on VGA being a clone of the laptop display with all the wrong resolutions)

# 20-intel.conf
Section "Device"
        Identifier  "Intel Graphics"
        Driver      "intel"
        Option      "AccelMethod"  "uxa"
	Option	    "DRI"   "3"
EndSection

Section "Device"
        Identifier  "Nvidia Graphics"
        Driver      "nouveau"
EndSection

I guess it is one of the options for the intel chip, that caused the problems before.

EDIT2: It was the uxa option. Using sna it works. The only issue is the automatic configuration of the screens, but I guess I can fix that with some script.

Last edited by stupidus (2016-11-30 17:57:37)

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#3 2017-02-20 22:06:06

sebkoller
Member
Registered: 2017-02-19
Posts: 1

Re: [solved] DisplayPort on Thinkpad T420 using Reverse PRIME

Sorry to hijack your thread, I'm also using a T420 with a nvida card.

I was wondering if hardware acceleration (chromium, glxgears,...) is working on your display port powered monitor (extended mode, not mirror mode).

Because it is working fine on the internal screen (rendered by the intel card) but not on the external monitor.
Also: is xrandr --output DP-1-1  --rotate right working for you?

Thanks in advance

Last edited by sebkoller (2017-02-20 22:10:03)

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#4 2017-02-22 23:41:44

stupidus
Member
Registered: 2012-02-27
Posts: 124

Re: [solved] DisplayPort on Thinkpad T420 using Reverse PRIME

I am currently at home, where I don't have a monitor with a display port. I can test it tomorrow at work.

EDIT: I tested it now. glxgears seems to run just fine on the display port connected monitor. I can also rotate the monitor without any issues. What kind of issues do you have?

Last edited by stupidus (2017-02-23 15:48:39)

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