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    <head>
      <base href="https://bugs.freedesktop.org/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - [IVB] switching to tty1 causes fifo underrun on pipe B and pipe C (bisected)"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=93802">93802</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>[IVB] switching to tty1 causes fifo underrun on pipe B and pipe C (bisected)
          </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>chris.bainbridge@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=121163" name="attach_121163" title="dmesg with drm.debug">attachment 121163</a> <a href="attachment.cgi?id=121163&action=edit" title="dmesg with drm.debug">[details]</a></span>
dmesg with drm.debug

Reproduce: Connect 3 displays, boot to Xorg, press ctrl-alt-f1
Result: fifo underrun, both displays power off

dmesg:

[    9.755511] [drm:intel_check_cpu_fifo_underruns] *ERROR* fifo underrun on
pipe B
[    9.755513] [drm:intel_check_cpu_fifo_underruns] *ERROR* fifo underrun on
pipe C
[    9.755519] [drm:intel_check_pch_fifo_underruns] *ERROR* pch fifo underrun
on pch transcoder B
[    9.755523] [drm:intel_check_pch_fifo_underruns] *ERROR* pch fifo underrun
on pch transcoder C
[    9.761398] [drm:intel_check_cpu_fifo_underruns] *ERROR* fifo underrun on
pipe B
[    9.761400] [drm:intel_check_cpu_fifo_underruns] *ERROR* fifo underrun on
pipe C
[    9.761407] [drm:intel_check_pch_fifo_underruns] *ERROR* pch fifo underrun
on pch transcoder B
[    9.761411] [drm:intel_check_pch_fifo_underruns] *ERROR* pch fifo underrun
on pch transcoder C
[    9.774117] [drm:intel_check_cpu_fifo_underruns] *ERROR* fifo underrun on
pipe C
[    9.774125] [drm:intel_check_pch_fifo_underruns] *ERROR* pch fifo underrun
on pch transcoder C


bisect result (commit was merged in to the Linus tree 3 days ago in
984065055e6e):


92826fcdfc147a7d16766e987c12a9dfe1860c3f is the first bad commit
commit 92826fcdfc147a7d16766e987c12a9dfe1860c3f
Author: Maarten Lankhorst <<a href="mailto:maarten.lankhorst@linux.intel.com">maarten.lankhorst@linux.intel.com</a>>
Date:   Thu Dec 3 13:49:13 2015 +0100

    drm/i915: Calculate watermark related members in the crtc_state, v4.

    This removes pre/post_wm_update from intel_crtc->atomic, and
    creates atomic state for it in intel_crtc.

    Changes since v1:
    - Rebase on top of wm changes.
    Changes since v2:
    - Split disable_cxsr into a separate patch.
    Changes since v3:
    - Move some of the changes to intel_wm_need_update.

    Signed-off-by: Maarten Lankhorst <<a href="mailto:maarten.lankhorst@linux.intel.com">maarten.lankhorst@linux.intel.com</a>>
    Link:
<a href="http://patchwork.freedesktop.org/patch/msgid/56603A49.5000507@linux.intel.com">http://patchwork.freedesktop.org/patch/msgid/56603A49.5000507@linux.intel.com</a>
    Reviewed-by: Daniel Vetter <<a href="mailto:daniel.vetter@ffwll.ch">daniel.vetter@ffwll.ch</a>>

:040000 040000 b97b4b2338e1da2ee9e93791154b4deb2ecaf8b6
ae91735a668b6785e55122c646dbca93b54eb8c9 M    drivers</pre>
        </div>
      </p>
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