When userspace queries the current vblank for the CRTC, we can reply with the cached value (using atomic reads to serialise with the vblank interrupt as necessary) without having to touch registers. In the instant disable case, this saves us from enabling/disabling the vblank around every query, greatly reducing the number of registers read and written.
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Imre Deak imre.deak@intel.com Cc: Daniel Vetter daniel.vetter@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Laurent Pinchart laurent.pinchart@ideasonboard.com Cc: Dave Airlie airlied@redhat.com --- drivers/gpu/drm/drm_irq.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index c8a34476570a..6c4570082b65 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -1585,7 +1585,18 @@ int drm_wait_vblank(struct drm_device *dev, void *data, if (crtc >= dev->num_crtcs) return -EINVAL;
- vblank = &dev->vblank[crtc]; + /* Fast-path the query for the current value (without an event) + * to avoid having to enable/disable the vblank interrupts. + */ + if ((vblwait->request.type & (_DRM_VBLANK_TYPES_MASK | _DRM_VBLANK_FLAGS_MASK)) == _DRM_VBLANK_RELATIVE && + vblwait->request.sequence == 0) { + struct timeval now; + + vblwait->reply.sequence = drm_vblank_count_and_time(dev, crtc, &now); + vblwait->reply.tval_sec = now.tv_sec; + vblwait->reply.tval_usec = now.tv_usec; + return 0; + }
ret = drm_vblank_get(dev, crtc); if (ret) { @@ -1619,6 +1630,8 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
DRM_DEBUG("waiting on vblank count %d, crtc %d\n", vblwait->request.sequence, crtc); + + vblank = &dev->vblank[crtc]; vblank->last_wait = vblwait->request.sequence; DRM_WAIT_ON(ret, vblank->queue, 3 * HZ, (((drm_vblank_count(dev, crtc) -