[PATCH 2/2] drm/amd/display: Remove wait for hw/flip done in atomic check

[Nicholas Kazlauskas]

[Why]
Atomic check can't truly be non-blocking if amdgpu_dm is waiting for
hw_done and flip_done in atomic check. This introduces waits when
any previous non-blocking commits queued work on a worker thread and
a new atomic commit attempts to do another full update/modeset.

[How]
Drop the waits and move the global lock acqusition into atomic check.

This is fine to do since commit tail waits for these dependencies
before calling amdgpu_dm_atomic_commit_tail.

This is only safe as long as DC never queries anything from within
current_state when doing validation in atomic_check. This is the
case as of writing, but any future uses of dc->current_state from
within atomic_check should be considered incorrect.

Cc: Harry Wentland <harry.wentland at amd.com>
Cc: Leo Li <sunpeng.li at amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 58 ++-----------------
 1 file changed, 6 insertions(+), 52 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 3ae438d9849f..fe21bb86b66a 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -5078,57 +5078,6 @@ void dm_restore_drm_connector_state(struct drm_device *dev,
 		dm_force_atomic_commit(&aconnector->base);
 }
 
-/*
- * Grabs all modesetting locks to serialize against any blocking commits,
- * Waits for completion of all non blocking commits.
- */
-static int do_aquire_global_lock(struct drm_device *dev,
-				 struct drm_atomic_state *state)
-{
-	struct drm_crtc *crtc;
-	struct drm_crtc_commit *commit;
-	long ret;
-
-	/*
-	 * Adding all modeset locks to aquire_ctx will
-	 * ensure that when the framework release it the
-	 * extra locks we are locking here will get released to
-	 */
-	ret = drm_modeset_lock_all_ctx(dev, state->acquire_ctx);
-	if (ret)
-		return ret;
-
-	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
-		spin_lock(&crtc->commit_lock);
-		commit = list_first_entry_or_null(&crtc->commit_list,
-				struct drm_crtc_commit, commit_entry);
-		if (commit)
-			drm_crtc_commit_get(commit);
-		spin_unlock(&crtc->commit_lock);
-
-		if (!commit)
-			continue;
-
-		/*
-		 * Make sure all pending HW programming completed and
-		 * page flips done
-		 */
-		ret = wait_for_completion_interruptible_timeout(&commit->hw_done, 10*HZ);
-
-		if (ret > 0)
-			ret = wait_for_completion_interruptible_timeout(
-					&commit->flip_done, 10*HZ);
-
-		if (ret == 0)
-			DRM_ERROR("[CRTC:%d:%s] hw_done or flip_done "
-				  "timed out\n", crtc->base.id, crtc->name);
-
-		drm_crtc_commit_put(commit);
-	}
-
-	return ret < 0 ? ret : 0;
-}
-
 void set_freesync_on_stream(struct amdgpu_display_manager *dm,
 			    struct dm_crtc_state *new_crtc_state,
 			    struct dm_connector_state *new_con_state,
@@ -5793,7 +5742,12 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
 		if (ret)
 			goto fail;
 
-		ret = do_aquire_global_lock(dev, state);
+		/*
+		 * This should be replaced with finer locking on the
+		 * on the appropriate resources when possible.
+		 * For now it's safer to grab everything.
+		 */
+		ret = drm_modeset_lock_all_ctx(dev, state->acquire_ctx);
 		if (ret)
 			goto fail;
 
-- 
2.17.1