On 21/06/17 10:44 AM, Mario Kleiner wrote: > With instantaneous high precision vblank timestamping > that updates at leading edge of vblank, a cooked hw > vblank counter which increments at leading edge of > vblank, and reliable page flip execution and completion > at leading edge of vblank, we should meet the requirements > for fast/immediate vblank irq disable/enable. > > Testing on Linux-4.12-rc5 + drm-next on a Radeon HD 5770 > (DCE 4) with timing measurement equipment indicates this > works fine, so allow immediate vblank disable for power > saving. > > For debugging in case of unexpected trouble, booting > with kernel cmdline option drm.vblankoffdelay=0 > (or echo 0 > /sys/module/drm/parameters/vblankoffdelay) > would keep vblank irqs permanently on to approximate old > behavior. > > Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com> > Cc: Alex Deucher <alexander.deucher at amd.com> > Cc: Michel Dänzer <michel.daenzer at amd.com> My only doubt is whether this is also reliable on older (e.g. pre-R600) GPUs. For newer GPUs (tested on Kaveri): Reviewed-and-Tested-by: Michel Dänzer <michel.daenzer at amd.com> -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer
