On 18/08/16 08:51 AM, Mario Kleiner wrote: > > That's what the ati-ddx/amdgpu-ddx does at the moment, as it detects the > mismatch in tiling flags and uses the DRI3/Present copy path instead of > the pageflip path. The problem is that the servers Present > implementation doesn't request a vsync'ed start of the copy operation [...] It waits for vblank before starting the copy. > There is this other approach from NVidia's Alex Goins for their > proprietary driver, whose patches landed in the X-Server 1.19 master > branch a couple of weeks ago. I haven't read his patches in detail yet, > and i so far couldn't successfully test them with the reference > implementation in modesetting ddx 1.19. Afaik there the display gpu > exports a pair of scanout friendly, page flipping compatible dmabufs (i > assume linear, contiguous, accessible by the display engines), FWIW, that wouldn't be possible with our "older" GPUs which can't scan out from GTT: A BO can be either shared with another GPU or scanout friendly, not both at the same time. > and the offload gpu imports those and renders into them. That saves > one extra copy, so should be somewhat more efficient. Using two shared buffers actually isn't as efficient as possible wrt inter-GPU bandwidth. > Setting it up seems to be more involved and less flexible though. So far > i couldn't make it work here for testing. Maybe bugs, maybe mistakes on > my side, maybe i just have the wrong hardware for it. Yeah, my impression has been it's a rather complicated solution geared towards the Intel iGPU + proprietary nVidia use case. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
