https://bugs.freedesktop.org/show_bug.cgi?id=97075
--- Comment #3 from Christoph Haag haagch@frickel.club --- I put the issue in DRM/radeon instead of mesa/radeonsi because I thought it would be related to power management.
I tried echo high > /sys/class/drm/card1/device/power_dpm_force_performance_level and performance > /sys/class/drm/card1/device/power_dpm_state but it makes no difference, still just as slow.