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Problem with LVDS interface for GMA3150

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Daniel Sosa's picture
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Daniel Sosa

Dec 16, 2014 - 01:25pm

  • I am running Ubuntu 14.04.1 LTS on a SBC equipped with the Intel Atom N450 chipset (which uses the integrated Graphics Media Accelerator 3150). The GMA3150 supports both VGA & LVDS interfaces. I am trying to set up a touchscreen display that runs at 640x480 over the LVDS interface.

    I have already downloaded and run the Intel Graphics Installer 1.0.7. I was able to complete the installer process with no errors. Afterwards, when looking under the system hardware information I see the Intel 'i915' driver is running in the kernel.

    However, when running under this configuration only the upper-left hand portion of the video output is viewable on the LVDS display. Furthermore, when running a mirrored dual monitor setup (VGA & LVDS) at 640x480 the VGA displays correctly but the LVDS still only shows a portion of the display.

    I'm a relative noobie to Linux and have exhausted my troubleshooting capabilities. Any ideas how I might fix this problem?

    Dec 16, 2014 - 01:25pm
  • Hi there. A followup question:

    - Do you know if this problem occurred before the upgrade?
    - with the LVDS connected, what does `xrandr' show?

    Jan 06, 2015 - 07:34am
  • The display problem was occurring even before I ran the Intel Graphics Installer.

    Here is the terminal output after running 'xrandr':

    ms3@ms3-desktop:~$ xrandr
    Screen 0: minimum 8 x 8, current 1024 x 768, maximum 32767 x 32767
    LVDS1 connected primary 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
       1024x768       60.0*+
       800x600        60.3     56.2 
       640x480        59.9 
    VGA1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 443mm x 249mm
       640x480        75.0+   72.8     66.7     60.0 
       1600x900       60.0 +
       1280x800       59.8 
       1152x864       75.0 
       1280x720       60.0 
       1024x768       75.1*     70.1     60.0 
       832x624        74.6 
       800x600        72.2     75.0     60.3     56.2 
       720x400        70.1 
    VIRTUAL1 disconnected (normal left inverted right x axis y axis)

     

    Jan 06, 2015 - 02:06pm
  • Sorry for the confusion - the 'xrandr' output posted above was from my last test configuration when troubleshooting. I found that when configured at 1024x768, the desired output (640x480) becomes viewable on the LVDS touchscreen.

    Here is the actual terminal output when running mirrored displays at 640x480 resolution:

    ms3@ms3-desktop:~$ xrandr
    Screen 0: minimum 8 x 8, current 640 x 480, maximum 32767 x 32767
    LVDS1 connected primary 640x480+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
       1024x768       60.0 +
       800x600        60.3     56.2 
       640x480        59.9*
    VGA1 connected 640x480+0+0 (normal left inverted right x axis y axis) 443mm x 249mm
       640x480        75.0*+   72.8     66.7     60.0 
       1600x900       60.0 +
       1280x800       59.8 
       1152x864       75.0 
       1280x720       60.0 
       1024x768       75.1     70.1     60.0 
       832x624        74.6 
       800x600        72.2     75.0     60.3     56.2 
       720x400        70.1 
    VIRTUAL1 disconnected (normal left inverted right x axis y axis)

     

    Jan 07, 2015 - 06:43am
  • Does that mean you found a working setup?

    If I've understood correctly:

    - mirroring a 640x480 display to a 640x480 external doesn't work
    you get only part of the display on the LVDS
    - mirroring an 1024x768 display to 640x480 works as expected?

    Jan 12, 2015 - 09:45am
  • As I said in a previous post, this resolution output problem only affects the LVDS port. For the VGA port, the configured resolution always matches the output seen on the VGA display (for all resolution options).

    In order to get the desired resolution to output on the LVDS display, I have to "trick" the system. Since it appears that only the upper-lefthand section of the output is viewable on the LVDS display, I tried configuring the LVDS port for 1024x768. Under this resolution configuration the viewable area on the LVDS display appears to match my target resolution of 640x480. However, this is not an ideal solution since a significant portion of the screen is still cut off (e.g., toolbars, desktop space, etc.).

    I would be happy to provide photos of the LVDS display under if that would be helpful.

    Jan 12, 2015 - 10:39am
  • I see - my advice to you would be to take the information presented here
    (and a photo of the symptoms) and file a bug either with your distro or
    directly with freedesktop.org - that's probably the fastest way to get the
    attention of the people who actually write the parts of your system that
    appear to be flaking out.

    Jan 19, 2015 - 08:01am