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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 - option to disable deep color (or set HDMI bandwidth limit)"
href="https://bugs.freedesktop.org/show_bug.cgi?id=101166">101166</a>
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<th>Summary</th>
<td>option to disable deep color (or set HDMI bandwidth limit)
</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>All
</td>
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<th>OS</th>
<td>Linux (All)
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>minor
</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
</td>
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<th>Reporter</th>
<td>axkibe@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>Steps to reproduce the problem:
* have a kernel (~> 4.6 ) where drm is able to do deep color
* have an chip that uses i915
* have a deep color able TV screen (1080p)
* connect them via a CAT5-bridge (as in our meeting rooms be done) that can
handle 1060p only on 8bit.
Happens all the time.
This setup breaks with and only with Linux laptops with recent kernels, due to
them turning on deep color which seemingly overloads the CAT5 bridge and thus
the screen starts flickering (turning to black every 10-20 seconds for half a
second).
Following "patch" solves the issue for me, since it forcefully disables all
deep color ability for this notebook:
----
linux-4.11.2$ diff -u drivers/gpu/drm/drm_edid.c.org drivers/gpu/drm/drm_edid.c
--- drivers/gpu/drm/drm_edid.c.org 2017-05-24 14:08:19.162452768 +0200
+++ drivers/gpu/drm/drm_edid.c 2017-05-24 14:10:33.149417356 +0200
@@ -3803,6 +3803,7 @@
if (cea_db_payload_len(hdmi) < 6)
return;
+ return;
if (hdmi[6] & DRM_EDID_HDMI_DC_30) {
dc_bpc = 10;
------
I'd wish there was a module parameter to force this off, other than hacking the
source. (Or I kept overlooking an existing one)
PS: As far I realize, unless this is a more sophisticated EDID bug, at fault
here is that stupid CAT5-bridge that is supposed to modify the EDID to
something it can handle, which it doesn't.</pre>
</div>
</p>
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