https://bugs.freedesktop.org/show_bug.cgi?id=39202 --- Comment #31 from Ilija Hadzic <ihadzic@xxxxxxxxxxxxxxxxxxxxxx> 2011-08-18 06:20:18 PDT --- (In reply to comment #28) > > the max fps is 60!!! > but if I enable vsync in kde desktop effects settings or doing "vblank_mode=1 > kwin --replace" the fps goes to 100!!! > In these conditions vblank_mode=0 glxgears and vblank_mode=1 glxgears have the > same output (2000 FPS). > This has no sense. I am assuming that your DDX (xf86-video-ati library) is 6.14.2 (latest). If you use that DDX and a kernel prior to crtc>1 commit, then the behavior of glxgears is an expected one. Prior to the offending commit, vblank synchronization for crtcs that are higher than 1 didn't work. System was synchronizing on wrong crtc numbers and the appearance of working was mostly an accident than design. The fix included both the kernel and user space patches and a check was added to DDX against the kernel capabilities. So what happens in your case, is that when you boot up the old kernel and probably keep the new DDX, the DDX decides that it's missing a kernel capability and decides not to syncronize to vblank no matter what you set vblank_mode for. That's why you see 2000+ fps in both cases. When it comes to KDE, I am not familiar enough to comment, but I speculate that KDE actually bypasses the DDX and calls vblank synchronization ioctl directly through libdrm. KDE would in that case be responsible for specifying the correct CRTC and the CRTC number depends on which connector you are. I see you are using an Evergreen GPU that has 6 crtcs so you could be sitting on a crtc whose number is greater than 1. If that's so, and assuming that KDE indeed specifies correct crtc, it could very well be that your lower FPS with the newer kernel is correct because that's what CRTC ticks at. With older kernel you may be synchronizing to an incorrect CRTC that just so happens to tick at 100fps, but that's an accident. Try changing the connector you use on your evergreen part, use the kernel *with* the offending patch and *with* synchronization turned on and see if the FPS changes with the connector. If you find one that gives you 100fps, then that's probably the one on which the old broken kernel picked up the synchronization from. BTW, on the part you are using, I have noticed that if you connect all three connectors, HDMI will be CRTC 0, VGA will be CRTC 1 and DVI will be CRTC 2. In that case, an old kernel will be broken on DVI (which is the one that people are most likely to look at) -- Configure bugmail: https://bugs.freedesktop.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are the assignee for the bug. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
