Bug 104248

Summary: Black screen after switching refresh rate from 144 Hz
Product: DRI Reporter: Thomas Lange <thomas-lange2>
Component: DRM/AMDgpuAssignee: Default DRI bug account <dri-devel>
Status: RESOLVED FIXED QA Contact:
Severity: normal    
Priority: medium    
Version: XOrg git   
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
Output of dmesg
none
Output of xrandr
none
Xorg log none

Description Thomas Lange 2017-12-13 19:26:07 UTC 
Created attachment 136148 [details]
Output of dmesg

My monitor supports 144 Hz as refresh rate which works fine. But switching from 144 Hz to a lower value (like 120 Hz) always results in a black screen with no signal.

The intention is to use 144 Hz for games and 120 Hz on the desktop. PowerPlay doesn't work with 144 Hz, so the GPU wastes energy and gets hotter than necessary.

Switching between other rates (like 120 -> 60 -> 100 -> 60 -> 120) works fine. It also worked correctly with previous cards (HD4830 and HD6850).

The workaround is to stay on 120 Hz all the time. When the screen shows no signal, resuming from standby brings it back.

Things I have tried so far:
1. Disabling DPM with "echo high > /sys/class/drm/card0/device/power_profile"
-> Same results

2. Using Linux 4.15-RC3 with enabled DC (amdgpu.dc=1)
-> Refresh rates higher than 60 Hz are not supported
-> Is this known or should I file a separate bug report?

Hardware:
PowerColor RX 560 (POLARIS 11)
LG Electronics 24GM77-B, connected via DVI cable

Software:
Linux 4.14.5 x86_64
Mesa 17.2.6
Xorg 1.19.5
xf86-video-amdgpu 1.4.0
Comment 1 Thomas Lange 2017-12-13 19:27:09 UTC 
Created attachment 136149 [details]
Output of xrandr

If you need more information, let me know.
Comment 2 Thomas Lange 2017-12-13 19:30:48 UTC 
Created attachment 136150 [details]
Xorg log
Comment 3 Harry Wentland 2017-12-21 00:37:38 UTC 
I'm working on fixing DVI on DC with timings requiring dual link, like I assume your 120+ Hz timings require. That work is tracked under https://bugs.freedesktop.org/show_bug.cgi?id=103953.
Comment 4 Thomas Lange 2018-07-19 20:57:11 UTC 
With kernel 4.17.7 I am no longer able to reproduce this. Hence marking as RESOLVED.

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