On 29.05.2014 19:56, Daniel Vetter wrote: > On Thu, May 29, 2014 at 6:11 AM, Michel Dänzer <michel@xxxxxxxxxxx> wrote: >> >>> We could rename the off/on to pre/post_modeset if you like, but then >>> someone gets to audit all the other drivers. That someone isn't >>> going to be me. >> >> I appreciate your caution wrt other drivers, but I'm worried that having >> a second mechanism for keeping the DRM vblank counter consistent might >> cause subtle problems for drivers using the existing mechanism anyway. > > I think that risk is rather low. Only i915 has been stupid enough to > use both drm_vblank_off + pre/post_modeset in the normal crtc > enable/disable functions. Everyone else uses either or the other, > except for tegra which uses pre/post in the ->prepare/commit hooks and > off in the crtc->disable callback. So should still get consistent > results (since after ->disable vblank consistency stops mattering). > > The reason we do all this is that we want to kill the delayed vblank > put for i915, which is possible if you have a hw vblank counter. That should also be possible with pre/post_modeset. (Not sure eliminating it completely is a good idea for the reasons you mentioned before, but at least decreasing it significantly should be no problem. I think even dropping the default a lot for all drivers should be rather low risk) > There's apparently more stuff wrong here still, so while we wrestle > around probably best to leave other drivers out. I guess once this is > all done I have to roll it out across all drivers so that we have > consistent behaviour again ... Since AFAICT radeon isn't affected by the problem drm_vblank_off() was supposed to solve originally, I'd prefer if it didn't start using that and potentially suffer from all the trouble it seems to cause. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
