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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 - Screen is frozen on second connection of DP MST dock"
href="https://bugs.freedesktop.org/show_bug.cgi?id=107546">107546</a>
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<th>Summary</th>
<td>Screen is frozen on second connection of DP MST dock
</td>
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<th>Product</th>
<td>DRI
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>x86-64 (AMD64)
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<th>OS</th>
<td>Linux (All)
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
</td>
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<th>Component</th>
<td>DRM/Intel
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<th>Assignee</th>
<td>intel-gfx-bugs@lists.freedesktop.org
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<th>Reporter</th>
<td>sergey.menshikov@gmail.com
</td>
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<th>QA Contact</th>
<td>intel-gfx-bugs@lists.freedesktop.org
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<th>CC</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr></table>
<p>
<div>
<pre>Kernel 4.15.0.30 Ubuntu 18.04.1 Xorg/Gnome Lenovo 4th gen X1 20FBxxx Skylake i7
Intel built-in video, Lenovo OneLink+ DP MST dock with dual dell 24" displays
Error messages upon dock disconnect:
[drm:intel_dp_start_link_train [i915]] *ERROR* failed to enable link training
[drm:intel_mst_pre_enable_dp [i915]] *ERROR* failed to allocate vcpi
Next connection leads to frozen screen on laptop, no change on exterenal
monitors.
[drm:intel_wait_ddi_buf_idle [i915]] *ERROR* Timeout waiting for DDI BUF C idle
bit
Disconnecting the dock restores laptop screen functionality, but subsequent
connection of the dock has the same symptoms repeating. Reboot fixes the issue
until first dock disconnect.
My workaround is to enable GuC firmware loading and boot without the dock
attached.
sudo vi /etc/modprobe.d/i915.conf
options i915 enable_guc_loading=1 enable_guc_submission=1
sudo update-initramfs -u
sudo reboot
(reboot while not connected to dock)</pre>
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