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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 - [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe B FIFO underrun"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=94898">94898</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>[drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe B FIFO underrun
          </td>
        </tr>

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

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>x86-64 (AMD64)
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux (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>garrettn@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>Created <span class=""><a href="attachment.cgi?id=122868" name="attach_122868" title="Full Dmesg with debug (a lockup occured at 11:02AM-ish)">attachment 122868</a> <a href="attachment.cgi?id=122868&action=edit" title="Full Dmesg with debug (a lockup occured at 11:02AM-ish)">[details]</a></span>
Full Dmesg with debug (a lockup occured at 11:02AM-ish)

I running Manjaro (Arch based) (4.4.6-1 kernel) on a Dell XPS 13" (9343) with
an external displayport (v1.2) 4K@60Hz monitor.

I'm getting several hard lockups per day but this only occurs when I use an
external 4K monitor through the display port (i.e. internal laptop display is
100% stable)

I've turned on drm.debug=14 to try to see what is going on, but I do not catch
anything on the hard lockups.  

I get quite a bit of display flickering and see these messages in my logs
frequently:

Apr 08 12:13:44 station kernel: [drm:intel_cpu_fifo_underrun_irq_handler
[i915]] *ERROR* CPU pipe B FIFO underrun
Apr 09 09:49:56 station kernel: [drm:intel_cpu_fifo_underrun_irq_handler
[i915]] *ERROR* CPU pipe B FIFO underrun
Apr 09 20:55:13 station kernel: [drm:intel_cpu_fifo_underrun_irq_handler
[i915]] *ERROR* CPU pipe B FIFO underrun
Apr 10 16:02:29 station kernel: [drm:intel_cpu_fifo_underrun_irq_handler
[i915]] *ERROR* CPU pipe B FIFO underrun
Apr 11 07:40:40 station kernel: [drm:intel_cpu_fifo_underrun_irq_handler
[i915]] *ERROR* CPU pipe B FIFO underrun
Apr 11 10:12:11 station kernel: [drm:intel_cpu_fifo_underrun_irq_handler
[i915]] *ERROR* CPU pipe B FIFO underrun

Eventually, my machine hard locks right while I'm using it.

I've tried different kernel versions and also set i915.enable_ips=0. I've also
tried different 4K monitors and also swapped out my displayport cable.

I'm attaching some files:
* Full dmesg with drm.debug=14 from boot (one lockup occurred at 11:03AM)
* xrandr --verbose
* Xorg.log
* /sys/class/drm/card0/error contains "no error state collected"

Appreciate any ideas.</pre>
        </div>
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