https://bugs.freedesktop.org/show_bug.cgi?id=38800
--- Comment #38 from Mario Kleiner mario.kleiner@tuebingen.mpg.de 2011-07-07 14:51:16 PDT --- (In reply to comment #37)
Maybe we should try and sort out why there is so much latency in the interrupt handler for Simon rather than rewriting the entire thing. Or we could just use the pflip interrupts where they are working and use the existing code on older asics.
Yes. I think that delay needs to be sorted out anyway - it would also kill dynamic clock switching which needs to happen within vblank afaik and any kind of realtime performance, e.g., with preempt_rt kernels, if not fixed. Then the immediate problem of Simon would go away. iirc correctly, the numbers should be closer to 10-30 usecs, instead of close to 400 usecs, tested on Core2Duo 2.2 Ghz rv530, and ancient Athlon 1.2 Ghz with r600.
But the proposed new design could make sense for a future pageflip ioctl v2 implementation to add robustness and some headroom for things like synchronized swaps across crtc's, swap groups, frame-sequential stereo, or lower latency flips. I will probably toy around with this in my spare time if we choose not to rewrite the entire thing now - which i would sort of prefer, given that the current implementation is tested to be pretty reliable on r500+ and i have actual users now starting to use/rely on the radeon timestamping being precise and reliable.