On Fri, Dec 21, 2018 at 10:47:27AM +0100, Michel Dänzer wrote: > On 2018-12-20 6:16 p.m., Michel Dänzer wrote: > > On 2018-12-20 6:09 p.m., Daniel Vetter wrote: > >> On Thu, Dec 20, 2018 at 6:03 PM Alex Deucher <alexdeucher@xxxxxxxxx> wrote: > >>> On Thu, Dec 20, 2018 at 11:54 AM Daniel Vetter <daniel@xxxxxxxx> wrote: > >> > >>>> Not sure about the gamma thing since we had opposite bugs on i915 > >>>> about gamma not being vsynced and tearing terribly. Cursor is special > >>>> since it tends to be too small to notice tearing. > >>> > >>> Our cursor hw (and possibly gamma as well Nicholas? Harry?) is double > >>> buffered, so we can update it any time for the most part and the > >>> changes won't take affect until the next vupdate period. > >> > >> Hm, I guess we could make the gamma update optionally async, and let > >> drivers deal. The issue is that the current async helper stuff won't > >> cope with gamma updates (it's aimed at plane updates only, not at crtc > >> property updates). Or we get userspace to do proper atomic updates. Or > >> we do some faking in the kernel, e.g. waiting with the gamma update > >> until the next atomic update happens. But that kinda breaks > >> ->atomic_check. > > > > Would it be possible to merge gamma changes into a pending commit, if > > there is one, and create a new commit otherwise? > > > > Otherwise the atomic API just moves this same problem to be solved by > > userspace. > > Actually, I'm not sure this is even solvable in a Xorg driver. When it > gets called to update the gamma LUT: > > 1. If there's a pending atomic commit, it cannot amend that, can it? Yup, but on the kernel side we kinda have the same problem. > 2. It has no way of knowing when the next atomic commit would be > submitted e.g. for a page flip, so it kind of has to create its own > commit for the gamma update. Block handler is what I had in mind for the fallback commit, if no other commit happened meanwhile (which would need to include it). -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
