https://bugzilla.kernel.org/show_bug.cgi?id=60523
--- Comment #31 from Alex Deucher alexdeucher@gmail.com --- (In reply to Christian Birchinger from comment #30)
Maybe the same reason why Tobias is stuck at level 2.
Right you both seem to be afflicted but the same issue.
Since i'm no longer able to use tools like xvidtune and the online modeline calculator tells me 1600x1200 85hz requires >300Mhz pixel clock, so i'm probably stuck at trying out lots of predefined modes that got pasted online.
You can use gtf or cvt to generate modelines and add them manually with xrandr.
How would i calculate the vblank period from modelines? It would really help if i at least knew a mode is within the specs before trying it out.
See r600_dpm_get_vblank_time() in r600_dpm.c for the formula:
line_time_us = (mode.crtc_htotal * 1000) / mode.clock; vblank_lines = mode.crtc_vblank_end - mode.crtc_vdisplay; vblank_time_us = vblank_lines * line_time_us;