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<base href="https://bugs.freedesktop.org/" />
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<th>Priority</th>
<td>medium
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Vertical sync (vsync) broken on Radeon Zaphod mode"
href="https://bugs.freedesktop.org/show_bug.cgi?id=78713">78713</a>
</td>
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<th>Assignee</th>
<td>xorg-driver-ati@lists.x.org
</td>
</tr>
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<th>Summary</th>
<td>Vertical sync (vsync) broken on Radeon Zaphod mode
</td>
</tr>
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<th>QA Contact</th>
<td>xorg-team@lists.x.org
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr>
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<th>OS</th>
<td>Linux (All)
</td>
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<th>Reporter</th>
<td>chewi@aura-online.co.uk
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<th>Hardware</th>
<td>x86-64 (AMD64)
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Version</th>
<td>git
</td>
</tr>
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<th>Component</th>
<td>Driver/Radeon
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<th>Product</th>
<td>xorg
</td>
</tr></table>
<p>
<div>
<pre>I know that vsync worked on Radeon Zaphod mode when <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - New CRTC ID query breaks Radeon DRM in Zaphod mode"
href="show_bug.cgi?id=29726">bug #29726</a> was fixed but it
has broken at some point since. I am now observing tearing in glxgears even
when it reports that vsync is enabled. Unfortunately I have no idea exactly
when it broke. The good news is I have a very strong clue as to what the
problem is. If you remove this line...
<a href="http://cgit.freedesktop.org/xorg/driver/xf86-video-ati/tree/src/radeon_dri2.c?id=be1469cc23aba46daf3293b3d09c5f2e792e7f42#n480">http://cgit.freedesktop.org/xorg/driver/xf86-video-ati/tree/src/radeon_dri2.c?id=be1469cc23aba46daf3293b3d09c5f2e792e7f42#n480</a>
...then it works. Why? I wish I knew. It was just a very lucky stab in the
dark. This line was around a good deal before <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - New CRTC ID query breaks Radeon DRM in Zaphod mode"
href="show_bug.cgi?id=29726">bug #29726</a> was fixed so
presumably its interaction with something else must have changed in the
meantime. SwapbuffersWait is definitely enabled.</pre>
</div>
</p>
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