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.
Please attach your dmesg output and xorg log (if using X).
Created attachment 143126 [details] dmesg log
Created attachment 143127 [details] xorg log
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
(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.
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.
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