Bug 107668

Summary: Blank screen (Cannot find any crtc or sizes) since Kernel 4.17 (AMDGPU.DC) on Amd Radeon RX460 on HDMI LG Ultrawidescreen Monitor
Product: DRI Reporter: Naheem Zaffar <naheemzaffar>
Component: DRM/AMDgpuAssignee: Default DRI bug account <dri-devel>
Status: RESOLVED MOVED QA Contact:
Severity: normal    
Priority: medium CC: buckh, fkmclane, harry.wentland, nicholas.kazlauskas, sunpeng.li, xavierb
Version: DRI git   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
Dmesg from boot with Kernel 4.19 prerelease
none
Dmesg output with amdgpu.dc=0
none
Log messages from Gnome Logs for boot with blank screen
none
Dmesg outut with latest build from Kernel 4.21 pre-release series none

Description Naheem Zaffar 2018-08-23 23:11:54 UTC 
Created attachment 141265 [details]
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
Comment 1 Naheem Zaffar 2018-08-23 23:12:58 UTC 
Created attachment 141266 [details]
Dmesg output with amdgpu.dc=0

Taken when booting with Vanilla Mainline kernel 4.19.0-0.rc0.git8.1.vanilla.knurd.1.fc28.x86_64 with argument amdgpu.dc=0
Comment 2 Naheem Zaffar 2018-08-27 15:39:23 UTC 
Having a look online I can see the same bug reported on Ubuntu where attempted triage has provided more results that may help track this issue down:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1761751
Comment 3 Naheem Zaffar 2018-08-27 17:14:04 UTC 
Created attachment 141299 [details]
Log messages from Gnome Logs for boot with blank screen

Taken from kernel 4.19.0-0.rc0.git12.1.vanilla.knurd.1.fc28.x86_64
Comment 4 Naheem Zaffar 2019-01-05 16:24:28 UTC 
Created attachment 142982 [details]
Dmesg outut with latest build from Kernel 4.21 pre-release series

The same error occurs with kernel 4.21 after the merging of the DRM feature updates. Dmesg output attached.
Comment 5 Naheem Zaffar 2019-02-23 16:35:36 UTC 
I have just tried using an older 3m long HDMI cable I had at home that I presume cannot support the latest HDMI version and with that I got a display at full resolution.

The problem may be with HDMI handling, there seem to be others experiencing some problems with HDMI 2, which I dont think this card supports.

is there a way to confirm the HDMI versions I was using that failed and the version that succeeded?
Comment 6 Martin Peres 2019-11-19 08:48:54 UTC 
-- GitLab Migration Automatic Message --

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