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<body><span class="vcard"><a class="email" href="mailto:matthew.d.roper@intel.com" title="Matt Roper <matthew.d.roper@intel.com>"> <span class="fn">Matt Roper</span></a>
</span> changed
<a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED - [CI] igt@kms_ccs@pipe-[a|b]-crc-sprite-planes-basic - fail - Test assertion failure function try_config, Failed assertion: ret == 0"
href="https://bugs.freedesktop.org/show_bug.cgi?id=105458">bug 105458</a>
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<th>What</th>
<th>Removed</th>
<th>Added</th>
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<td style="text-align:right;">CC</td>
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<td>matthew.d.roper@intel.com
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<td style="text-align:right;">Assignee</td>
<td>juhapekka.heikkila@gmail.com
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<td>matthew.d.roper@intel.com
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<b><a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED - [CI] igt@kms_ccs@pipe-[a|b]-crc-sprite-planes-basic - fail - Test assertion failure function try_config, Failed assertion: ret == 0"
href="https://bugs.freedesktop.org/show_bug.cgi?id=105458#c10">Comment # 10</a>
on <a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED - [CI] igt@kms_ccs@pipe-[a|b]-crc-sprite-planes-basic - fail - Test assertion failure function try_config, Failed assertion: ret == 0"
href="https://bugs.freedesktop.org/show_bug.cgi?id=105458">bug 105458</a>
from <span class="vcard"><a class="email" href="mailto:matthew.d.roper@intel.com" title="Matt Roper <matthew.d.roper@intel.com>"> <span class="fn">Matt Roper</span></a>
</span></b>
<pre>The problem here is the DDB algorithm that was initially proposed by the bspec.
A pipe's DDB allocation is divided up between its active planes according to
the % of the total data rate that they contribute. That's usually a reasonable
heuristic, but breaks down when you have a large difference in the size (data
rate) of your planes. If you divide the DDB proportionally, the very small
plane will get such a small allocation that it will fail to even achieve it's
level 0 watermark requirements. This problems pops up most often on APL (due
to its smaller DDB size in general) and/or on systems with high display
resolutions (due to the greater size disparity between "full-screen plane" and
"256x256 plane".
I've posted a patch series here:
<a href="https://patchwork.freedesktop.org/series/53682/">https://patchwork.freedesktop.org/series/53682/</a>
which switches to an alternate DDB algorithm aimed at avoiding these kinds of
problems.</pre>
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