Hi pekka I debug the presentation time recently. I have checked each user call drmAtomicCommit get the corresponding pageflip event. But some presentation results (c2p) are a little weird. They are 1~5ms or -1 ~ -5 ms. some results are normal(8 ~ 20 ms). I used to explain the weird result is because pageflip return last frame's timestamp, but I can't explain the normal results.
I suspect whether the kernel and user have the same time start point. It's just a guess, I have no evidence. Do you have some tips about the c2p results? Thank you. Best Regards Nancy 2018-05-12 23:17 GMT+08:00 Pekka Paalanen <ppaala...@gmail.com>: > On Thu, 10 May 2018 12:53:49 +0800 > zou lan <nancy.lan....@gmail.com> wrote: > > > Hi pekka > > > > I test presentation on my side. The presentation results is not accurate > > because our pageflip event send last frame's timestamp every time. So > > weston_output_finish_frame send last frame's present tine > > to current frame's feedback. For this situation, I just delay one frame > to > > send present event. Does this get the right c2p time? Thank you. > > Hi Nancy, > > I think your driver needs to get fixed, so that it provides the > correct timestamp instead of an outdated one. If this is a kernel > DRM driver, then the behaviour you describe is clearly a bug. The > timestamp of the pageflip event signifies the time the new frame > starts transmitting out of the connector. I believe there should be > DRM driver API documentation stating that. > > This is also what weston_output_finish_frame() expects. Anything > else will cause the frame scheduling to misbehave. > > It may be possible to work around the bug as you suggest, but that > will make the compositor incorrect on any other driver, and it may > cause other subtle breakage (the timestamp may be correct, but the > time the event gets sent is now wrong and might even be delayed > indefinitely if nothing causes a repaint). > > > Thanks, > pq >
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