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      <base href="https://bugs.freedesktop.org/">
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Dell XPS 15 (9550) External Monitor not waking"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=99438">99438</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Dell XPS 15 (9550) External Monitor not waking
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>DRI
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>DRI git
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Other
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>medium
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>DRM/Intel
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>intel-gfx-bugs@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>ernstp@gmail.com
          </td>
        </tr>

        <tr>
          <th>QA Contact</th>
          <td>intel-gfx-bugs@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>intel-gfx-bugs@lists.freedesktop.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>After a longer period of DPMS (haven't tested exactly where the threshold is) I
can no longer wake my external monitor.
The monitor is connected with a HDMI-DVI cable directly to the HDMI port of my 
Dell XPS 15 9550.
The monitor, a HP LA2405x, has a number of settings for source/auto-detect but
none of them help.

Tested with kernel 4.9.3, both with Xorg and Wayland.

I see the same problem here:

<a href="http://askubuntu.com/questions/699649/15-10-dell-xps-15-9550-external-monitor-not-waking">http://askubuntu.com/questions/699649/15-10-dell-xps-15-9550-external-monitor-not-waking</a>

and here:

<a href="http://en.community.dell.com/support-forums/laptop/f/3519/t/19679539">http://en.community.dell.com/support-forums/laptop/f/3519/t/19679539</a>

Note this is with DPMS, doing a full suspend-resume usually fixes the problem.
Another workaround is to unplug the cable and put it back.</pre>
        </div>
      </p>


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