https://bugs.freedesktop.org/show_bug.cgi?id=107668

Bug ID: 107668 Summary: Blank screen since Kernel 4.17 (AMDGPU.DC) on Amd Radeon RX460 and RX380 on HDMI Ultrawidescreen Monitor Product: DRI Version: XOrg git Hardware: Other OS: All Status: NEW Severity: normal Priority: medium Component: DRM/AMDgpu Assignee: dri-devel@lists.freedesktop.org Reporter: naheemzaffar@gmail.com

Created attachment 141265 --> https://bugs.freedesktop.org/attachment.cgi?id=141265&action=edit 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: https://bugzilla.redhat.com/show_bug.cgi?id=1594488

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 https://bugs.freedesktop.org/show_bug.cgi?id=105880 but that is for laptop panels on LVDS while this issue is with a discrete RX460 graphics card on HDMI