Bug 109359

Summary: Flickering and artifacts on dual 4K displays from RX 570
Product: DRI Reporter: Timur Kristóf <venemo>
Component: DRM/AMDgpuAssignee: Default DRI bug account <dri-devel>
Status: RESOLVED MOVED QA Contact:
Severity: normal    
Priority: medium CC: at46n, harry.wentland, sunpeng.li
Version: unspecified   
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
dmesg log
none
xorg log none

Description Timur Kristóf 2019-01-14 21:21:45 UTC 
There are two Dell U2718Q 4K monitors connected to a Sapphire Pulse RX 570 ITX card, one using the DisplayPort output and the other using the HDMI output.

There is a visible flickering artifact on both displays. There is no problem when only a single display is connected.

Searching online yields a couple of results that suggest a workaround: manually increasing the shader and/or memory clock of the GPU. On the RX 570 the following commands can get rid of the problem:

echo "manual" > /sys/class/drm/card0/device/power_dpm_force_performance_level
echo "2" > /sys/class/drm/card0/device/pp_dpm_mclk
echo "5 6 7" > /sys/class/drm/card0/device/pp_dpm_sclk

However, I believe the amdgpu driver should be able to figure out the correct necessary clock settings on its own. The problem exists in Linux 4.19 and 5.0-rc1 as well.
Comment 1 Alex Deucher 2019-01-14 21:38:02 UTC 
Please attach your dmesg output and xorg log (if using X).
Comment 2 Timur Kristóf 2019-01-15 14:26:50 UTC 
Created attachment 143126 [details]
dmesg log
Comment 3 Timur Kristóf 2019-01-15 14:28:12 UTC 
Created attachment 143127 [details]
xorg log
Comment 4 keziolio123 2019-01-22 21:31:06 UTC 
I have the same issue with an RX480 if i set amdgpu.ppfeaturemask=0xffffffff (for overclocking), without any command line changes there is no flickering
Comment 5 Timur Kristóf 2019-01-22 23:04:00 UTC 
(In reply to keziolio123 from comment #4)
> I have the same issue with an RX480 if i set amdgpu.ppfeaturemask=0xffffffff
> (for overclocking), without any command line changes there is no flickering

That's because when you overclock, your clock speed gets high enough so that flickering doesn't happen.
Comment 6 Timur Kristóf 2019-06-26 13:52:17 UTC 
I forgot about this bug. Looks like I misunderstood keziolio's last comment. Yes, I can confirm that the problem is not present when amdgpu.ppfeaturemask is not set on the kernel command line.
Comment 7 Martin Peres 2019-11-19 09:10:45 UTC 
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