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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Blank screen since Kernel 4.17 (AMDGPU.DC) on Amd Radeon RX460 and RX380 on HDMI Ultrawidescreen Monitor"
href="https://bugs.freedesktop.org/show_bug.cgi?id=107668">107668</a>
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<th>Summary</th>
<td>Blank screen since Kernel 4.17 (AMDGPU.DC) on Amd Radeon RX460 and RX380 on HDMI Ultrawidescreen Monitor
</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>
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<th>OS</th>
<td>All
</td>
</tr>
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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/AMDgpu
</td>
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<tr>
<th>Assignee</th>
<td>dri-devel@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>naheemzaffar@gmail.com
</td>
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<pre>Created <span class=""><a href="attachment.cgi?id=141265" name="attach_141265" title="Dmesg from boot with Kernel 4.19 prerelease">attachment 141265</a> <a href="attachment.cgi?id=141265&action=edit" title="Dmesg from boot with Kernel 4.19 prerelease">[details]</a></span>
Dmesg from boot with Kernel 4.19 prerelease
I have already reported this on Redhat Bugzilla, so if more information is
needed, that may be a good place to look at comments:
<a href="https://bugzilla.redhat.com/show_bug.cgi?id=1594488">https://bugzilla.redhat.com/show_bug.cgi?id=1594488</a>
Since the change to using dc in the kernel I am getting a blank screen with
trying to boot my ultrawidescreen monitor.
As a workaround I can use amdgpu.dc=0, but this hits al earlier big where at
native resolution the display output is garbled (links in Redhat Bugzilla
attach to another big report, youtube video of the same).
I am attaching dmesg output from
4.19.0-0.rc0.git8.1.vanilla.knurd.1.fc28.x86_64 with and without amdgpu.dc=0
I have noticed a couple of entries in the dmesg without the amdgpu.dc=0:
kernel: [drm] add ip block number 4 <dm>
with amdgpu.dc=0 it is:
kernel: [drm] add ip block number 4 <dce_v11_0>
The other ip address block entries are identical.
with amdgpu.dc=0 I get this section:
Aug 22 23:46:22 kernel: [drm] PCIE GART of 256M enabled (table at
0x000000F400900000).
Aug 22 23:46:22 kernel: [drm] Supports vblank timestamp caching Rev 2
(21.10.2013).
Aug 22 23:46:22 kernel: [drm] Driver supports precise vblank timestamp query.
Aug 22 23:46:22 kernel: [drm] AMDGPU Display Connectors
Aug 22 23:46:22 kernel: [drm] Connector 0:
Aug 22 23:46:22 kernel: [drm] DP-1
Aug 22 23:46:22 kernel: [drm] HPD5
Aug 22 23:46:22 kernel: [drm] DDC: 0x4868 0x4868 0x4869 0x4869 0x486a 0x486a
0x486b 0x486b
Aug 22 23:46:22 kernel: [drm] Encoders:
Aug 22 23:46:22 kernel: [drm] DFP1: INTERNAL_UNIPHY1
Aug 22 23:46:22 kernel: [drm] Connector 1:
Aug 22 23:46:22 kernel: [drm] HDMI-A-1
Aug 22 23:46:22 kernel: [drm] HPD3
Aug 22 23:46:22 kernel: [drm] DDC: 0x4874 0x4874 0x4875 0x4875 0x4876 0x4876
0x4877 0x4877
Aug 22 23:46:22 kernel: [drm] Encoders:
Aug 22 23:46:22 kernel: [drm] DFP2: INTERNAL_UNIPHY1
Aug 22 23:46:22 kernel: [drm] Connector 2:
Aug 22 23:46:22 kernel: [drm] DVI-D-1
Aug 22 23:46:22 kernel: [drm] HPD4
Aug 22 23:46:22 kernel: [drm] DDC: 0x4878 0x4878 0x4879 0x4879 0x487a 0x487a
0x487b 0x487b
Aug 22 23:46:22 kernel: [drm] Encoders:
Aug 22 23:46:22 kernel: [drm] DFP3: INTERNAL_UNIPHY
Aug 22 23:46:22 kernel: [drm] Chained IB support enabled!
but without amdgpu.dc=0 only the first and last line of that section appear.
Later down without the amdgpu.dc=0 I also get the following message:
kernel: [drm] Cannot find any crtc or sizes
This may also be similar to bug
<a class="bz_bug_link
bz_status_NEW "
title="NEW - [dc] No support for LVDS or VGA connectors (Cannot find any crtc or sizes)"
href="show_bug.cgi?id=105880">https://bugs.freedesktop.org/show_bug.cgi?id=105880</a> but that is for laptop
panels on LVDS while this issue is with a discrete RX460 graphics card on HDMI</pre>
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