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charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: Linux phenom 5.10.32scarlett+ Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Sun, May 30, 2021 at 07:33:57AM -0700, Rob Clark wrote: > On Thu, May 20, 2021 at 9:29 AM Daniel Vetter wrote: > > > > On Wed, May 19, 2021 at 11:38:53AM -0700, Rob Clark wrote: > > > From: Rob Clark > > > > > > Signed-off-by: Rob Clark > > > --- > > > drivers/gpu/drm/drm_atomic_helper.c | 11 +++++++++++ > > > 1 file changed, 11 insertions(+) > > > > > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > > > index 560aaecba31b..fe10fc2e7f86 100644 > > > --- a/drivers/gpu/drm/drm_atomic_helper.c > > > +++ b/drivers/gpu/drm/drm_atomic_helper.c > > > @@ -1435,11 +1435,15 @@ int drm_atomic_helper_wait_for_fences(struct drm_device *dev, > > > int i, ret; > > > > > > for_each_new_plane_in_state(state, plane, new_plane_state, i) { > > > + u64 vblank_count; > > > + > > > if (!new_plane_state->fence) > > > continue; > > > > > > WARN_ON(!new_plane_state->fb); > > > > > > + vblank_count = drm_crtc_vblank_count(new_plane_state->crtc); > > > + > > > /* > > > * If waiting for fences pre-swap (ie: nonblock), userspace can > > > * still interrupt the operation. Instead of blocking until the > > > @@ -1449,6 +1453,13 @@ int drm_atomic_helper_wait_for_fences(struct drm_device *dev, > > > if (ret) > > > return ret; > > > > > > + /* > > > + * Check if we've missed a vblank while waiting, and if we have > > > + * signal the fence that it's signaler should be boosted > > > + */ > > > + if (vblank_count != drm_crtc_vblank_count(new_plane_state->crtc)) > > > + dma_fence_boost(new_plane_state->fence); > > > > I think we should do a lot better here: > > - maybe only bother doing this for single-crtc updates, and only if > > modeset isn't set. No one else cares about latency. > > > > - We should boost _right_ when we've missed the frame, so I think we > > should have a _timeout wait here that guesstimates when the vblank is > > over (might need to throw in a vblank wait if we missed) and then boost > > immediately. Not wait a bunch of frames (worst case) until we finally > > decide to boost. > > I was thinking about this a bit more.. How about rather than calling > some fence->op->boost() type thing when we are about to miss a vblank > (IMO that is also already too late), we do something more like > fence->ops->set_deadline() before we even wait? Hm yeah that sounds like a clean idea. Even more, why not add the deadline/waiter information to the callback we're adding? That way drivers can inspect it whenever they feel like and don't have to duplicate the tracking. And it's probably easier to tune/adjust to the myriads of use-cases (flip target miss, userspace wait, wakeup boost maybe too ...). I like this direction a lot more than what we discussed with post-miss hints thus far. > It's probably a bit impossible for a gpu driver to really predict how > long some rendering will take, but other cases like video decoder are > somewhat more predictable.. the fence provider could predict given the > remaining time until the deadline what clk rates are required to get > you there. Well if we do have a deadline the driver can note that in its scheduler and arm a driver to kick the clocks. Or maybe use past history to do this upfront. -Daniel > > BR, > -R > > > > > > Otherwise I really like this, I think it's about the only real reason i915 > > isn't using atomic helpers. > > > > Also adding Matt B for this topic. > > -Daniel > > > > > + > > > dma_fence_put(new_plane_state->fence); > > > new_plane_state->fence = NULL; > > > } > > > -- > > > 2.30.2 > > > > > > > -- > > Daniel Vetter > > Software Engineer, Intel Corporation > > http://blog.ffwll.ch -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch