On Wed, Apr 10, 2013 at 10:52:20AM +0200, Daniel Vetter wrote: > So the idea is now to enable fbc/psr when pageflipping and disable it > as soon as we detect a frontbuffer rendering event. Thanks to the > current gem api we can do this pretty cheaply: > - CPU writes to the frontbuffer call sw_finish_ioctl. I need to still > check whether that only applies to cpu maps or also gtt maps. > - GTT writes could easily be caught by unmapping userspace ptes (we > have the infrastructure for that already), but I hope we can avoid > that. > - Currently we have some fragile code in our execbuf handler to detect > render of the gpu. I think we can rip this all out and instead detect > frontbuffer gpu rendering in the busy ioctl - that has been > established as the canonical interface for userspace to ask the kernel > to flush the frontbuffer. Aside: This semantics was not designed, but > we've realized that this is what it is eventually ;-) To add my wishlist item: - a global property / param indicating the availabilty of FBC - a crtc property indicating the status of FBC That way X can avoid front buffer rendering when it would incur penalties and is likely to result in corruption (I'm sure the next generation of FBC will work, or maybe the next). -Chris -- Chris Wilson, Intel Open Source Technology Centre
