On Wed, Mar 30, 2016 at 03:41:26PM +0200, Maarten Lankhorst wrote: > Op 30-03-16 om 15:13 schreef Ville Syrjälä: > > On Tue, Mar 29, 2016 at 03:38:55PM +0200, Maarten Lankhorst wrote: > >> This function is useful for gen2 intel devices which have no frame > >> counter, but need a way to determine the current vblank count without > >> racing with the vblank interrupt handler. > >> > >> intel_pipe_update_start checks if no vblank interrupt will occur > >> during vblank evasion, but cannot check whether the vblank handler has > >> run to completion. This function uses the timestamps to determine > >> when the last vblank has happened, and interpolates from there. > > Didn't really read it in detail, but on a glance it seems too > > complicated to me. All we should really need is something like this: > > > > drm_vblank_get(); > > drm_update_vblank_count(); > > accurate = drm_vblank_count(); > > > Updating from non vblank irq context might cause the vblank clock to drift, or at least contend the vblank lock. I don't see a problem. The scanout position is anyway used to fix up the timestamp. > > This is why I call drm_vblank_count_and_time, and then interpolate as if update_vblank_count was called on the result. > > ~Maarten -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
