Comment # 32
on bug 102646
from Peter
(In reply to L.Y. Sim from comment #30) > I have this issue on a 3840x1600 Acer XR382CQK with an RX560 with Kernel > 4.18.5-1 on Manjaro. > > When I set the refresh rate to 75Hz, severe artifacts and flickering appear. > > Both > > echo high > /sys/class/drm/card0/device/power_dpm_force_performance_level > and > > echo low > /sys/class/drm/card0/device/power_dpm_force_performance_level > > stop the flickering and artifacting, and I can see via > > cat /sys/class/drm/card0/device/pp_dpm_mclk > > that the memory clocks are set to 1750Mhz and 300Mhz respectively. > > However, if /sys/class/drm/card0/device/power_dpm_force_performance_level is > set to auto, I can see (via watching /sys/class/drm/card0/device/pp_dpm_mclk > with time intervals around 0.1s), that the memory clock oscillates rapidly > between 300Mhz, 625Mhz and 1750Mhz. > > So it seems to me that the rapid change in memory frequency is what's > causing the flickering. I think the "rapid change in memory frequency" really is the problem: When I echo manual > /sys/class/drm/card0/device/power_dpm_force_performance_level and then echo "0" > /sys/class/drm/card0/device/pp_dpm_mclk or echo "1" > /sys/class/drm/card0/device/pp_dpm_mclk or echo "2" > /sys/class/drm/card0/device/pp_dpm_mclk there is no more flickering. (This limits the memory clock to 300Mhz, 1000 or 2000Mhz on my RX580 card. Using Arch Linux kernel 4.18.16 by the way.) Whereas or echo "0 1 2" > /sys/class/drm/card0/device/pp_dpm_mclk or any combination of 2 memory clock frequencies brings flickering back.
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