On Wed, May 21, 2014 at 01:17:49PM +0200, Thierry Reding wrote: > On Wed, May 14, 2014 at 08:51:04PM +0200, Daniel Vetter wrote: > > From: Ville Syrjälä <ville.syrj...@linux.intel.com> > > > > Currently there's one per-device vblank disable timer, and it gets > > reset wheneven the vblank refcount for any crtc drops to zero. That > > "whenever" > > > means that one crtc could accidentally be keeping the vblank interrupts > > for other crtcs enabled even if there are no users for them. Make the > > disable timer per-crtc to avoid this issue. > > Very pedantically: s/crtc/CRTC/ and maybe even s/vblank/VBLANK/. Feel > free to ignore those, though. =) > > Also, and I may have asked before, why do we even need this timer? Why > not simply disable interrupts when the last vblank reference goes away?
Without intricate knowledge of where exactly the vblank interrupt fires wrt the hw frame counter the enabling/disabling of the vblank machinery as implemented in drm_irq.c is racy. Which means we shouldn't do it all the time. In i915 we are now solid enough with vblank handling in general and also well-covered in tests that we'll attempt to kill the disabling timer as the next step. Since keeping vblanks going when we don't need them if you have a hw vblank counter seriously hampers deep sleep states residency. But given how bug-riddled our vblank code was I want to move slowly. And we need to keep the hack for all those drivers which haven't properly been audited and tested (i.e. everyone else). -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
