<html>
    <head>
      <base href="https://bugs.freedesktop.org/" />
    </head>
    <body>
      <p>
        <div>
            <b><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - [drm:intel_dp_start_link_train] error on connecting an external monitor on VGA"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=82763#c3">Comment # 3</a>
              on <a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - [drm:intel_dp_start_link_train] error on connecting an external monitor on VGA"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=82763">bug 82763</a>
              from <span class="vcard"><a class="email" href="mailto:daniele.pizzolli@create-net.org" title="Daniele Pizzolli <daniele.pizzolli@create-net.org>"> <span class="fn">Daniele Pizzolli</span></a>
</span></b>
        <pre>Additional test on 3.17.0-rc3

This is worse than 3.16.  The screen remains black for all modes.

I used the following snippet:

MODES="1920x1200 1920x1080 1600x1200 1680x1050 1280x1024 1440x900 1280x960
1024x768 800x600 640x480"

sudo dmesg -c
for MODE in $MODES;
do
    printf "Trying mode: %s\n" "$MODE"
    xrandr --output DP4 --mode $MODE
    sudo dmesg -c
    sleep 2
done

To get the following output:

Trying mode: 1920x1200
[33982.971039] [drm:ivybridge_set_fifo_underrun_reporting] *ERROR* uncleared
fifo underrun on pipe B
[33982.971043] [drm:ivb_err_int_handler] *ERROR* Pipe B FIFO underrun
Trying mode: 1920x1080
Trying mode: 1600x1200
[33987.636507] [drm:ivybridge_set_fifo_underrun_reporting] *ERROR* uncleared
fifo underrun on pipe B
[33987.636512] [drm:ivb_err_int_handler] *ERROR* Pipe B FIFO underrun
Trying mode: 1680x1050
Trying mode: 1280x1024
[33992.076803] [drm:ivybridge_set_fifo_underrun_reporting] *ERROR* uncleared
fifo underrun on pipe B
[33992.076807] [drm:ivb_err_int_handler] *ERROR* Pipe B FIFO underrun
[33992.235904] [drm:ivybridge_set_fifo_underrun_reporting] *ERROR* uncleared
fifo underrun on pipe B
[33992.235908] [drm:ivb_err_int_handler] *ERROR* Pipe B FIFO underrun
Trying mode: 1440x900
Trying mode: 1280x960
[33996.655649] [drm:ivybridge_set_fifo_underrun_reporting] *ERROR* uncleared
fifo underrun on pipe B
[33996.655656] [drm:ivb_err_int_handler] *ERROR* Pipe B FIFO underrun
[33996.819414] [drm:ivybridge_set_fifo_underrun_reporting] *ERROR* uncleared
fifo underrun on pipe B
[33996.819418] [drm:ivb_err_int_handler] *ERROR* Pipe B FIFO underrun
Trying mode: 1024x768
[33999.101794] [drm:ivybridge_set_fifo_underrun_reporting] *ERROR* uncleared
fifo underrun on pipe B
[33999.101798] [drm:ivb_err_int_handler] *ERROR* Pipe B FIFO underrun
Trying mode: 800x600
[34001.302311] [drm:ivybridge_set_fifo_underrun_reporting] *ERROR* uncleared
fifo underrun on pipe B
[34001.302315] [drm:ivb_err_int_handler] *ERROR* Pipe B FIFO underrun
Trying mode: 640x480
[34003.634664] [drm:ivybridge_set_fifo_underrun_reporting] *ERROR* uncleared
fifo underrun on pipe B
[34003.634668] [drm:ivb_err_int_handler] *ERROR* Pipe B FIFO underrun

Maybe now the problem is a duplicate of 83180</pre>
        </div>
      </p>
      <hr>
      <span>You are receiving this mail because:</span>
      
      <ul>
          <li>You are the QA Contact for the bug.</li>
          <li>You are on the CC list for the bug.</li>
      </ul>
    </body>
</html>