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<base href="https://bugs.freedesktop.org/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [Bisected] Linux 3.17+ defaults to low resolution on Thinkpad T440p"
href="https://bugs.freedesktop.org/show_bug.cgi?id=87124">87124</a>
</td>
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<th>Summary</th>
<td>[Bisected] Linux 3.17+ defaults to low resolution on Thinkpad T440p
</td>
</tr>
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<th>Product</th>
<td>DRI
</td>
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<th>Version</th>
<td>XOrg git
</td>
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<th>Hardware</th>
<td>Other
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
</td>
</tr>
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<th>Component</th>
<td>DRM/Intel
</td>
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<th>Assignee</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr>
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<th>Reporter</th>
<td>proski@gnu.org
</td>
</tr>
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<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=110588" name="attach_110588" title="Output of lspci -vvvnnxxx">attachment 110588</a> <a href="attachment.cgi?id=110588&action=edit" title="Output of lspci -vvvnnxxx">[details]</a></span>
Output of lspci -vvvnnxxx
I'm using Lenovo Thinkpad T440p with a dock. A monitor with 2560x1600
resolution is connected to a DP port on the dock. The lib panel resolution is
1366x768.
Linux 3.16 starts with the native resolution of the external monitor. Linux
3.17 and newer starts with the resolution of the dock (actually, a few pixels
less than that, 1360x768). It can be set to the native resolution by running
xrandr --output DP4 --auto
Bisection gives the first bad commit: 0e32b39ceed665bfa4a77a4bc307b6652b991632
by
Dave Airlie - drm/i915: add DP 1.2 MST support (v0.7)
Unlike other bugs introduced by that commit, this bug is not fixed in Linux
3.18 and in the current commit on intel-drm/drm-intel-nightly,
97416b3589be60c5ece051784aa6bf34c31d86bc.
xrandr shows that the new kernels recognize more DP ports. The port connected
to the monitor is seen as DP2 by the old kernels and DP4 by the new kernels.</pre>
</div>
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