drm/i915: Use the same vblank worker for atomic unpin

In case of legacy cursor update, the cursor VMA needs to be unpinned
only after vblank. This exceeds the lifetime of the whole atomic commit.

Any trick I attempted to keep the atomic commit alive didn't work, as
drm_atomic_helper_setup_commit() force throttles on any old commit that
wasn't cleaned up.

The only option remaining is to remove the plane from the atomic commit,
and use the same path as the legacy cursor update to clean the state
after vblank.

Changes since previous version:
- Call the memset for plane state immediately when scheduling vblank,
  this prevents a use-after-free in cursor cleanup.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240522053341.137592-4-maarten.lankhorst@linux.intel.com

drivers/gpu/drm/i915/display/intel_atomic_plane.c

@@ -43,6 +43,7 @@
 #include "i9xx_plane_regs.h"
 #include "intel_atomic_plane.h"
 #include "intel_cdclk.h"
+#include "intel_cursor.h"
 #include "intel_display_rps.h"
 #include "intel_display_trace.h"
 #include "intel_display_types.h"
@@ -1201,7 +1202,6 @@ intel_cleanup_plane_fb(struct drm_plane *plane,
 
 	intel_display_rps_mark_interactive(dev_priv, state, false);
 
-	/* Should only be called after a successful intel_prepare_plane_fb()! */
 	intel_plane_unpin_fb(old_plane_state);
 }
 
@@ -1214,3 +1214,14 @@ void intel_plane_helper_add(struct intel_plane *plane)
 {
 	drm_plane_helper_add(&plane->base, &intel_plane_helper_funcs);
 }
+
+void intel_plane_init_cursor_vblank_work(struct intel_plane_state *old_plane_state,
+					 struct intel_plane_state *new_plane_state)
+{
+	if (!old_plane_state->ggtt_vma ||
+	    old_plane_state->ggtt_vma == new_plane_state->ggtt_vma)
+		return;
+
+	drm_vblank_work_init(&old_plane_state->unpin_work, old_plane_state->uapi.crtc,
+			     intel_cursor_unpin_work);
+}

drivers/gpu/drm/i915/display/intel_atomic_plane.h

@@ -71,5 +71,7 @@ void intel_plane_set_invisible(struct intel_crtc_state *crtc_state,
 			       struct intel_plane_state *plane_state);
 void intel_plane_helper_add(struct intel_plane *plane);
 bool intel_plane_needs_physical(struct intel_plane *plane);
+void intel_plane_init_cursor_vblank_work(struct intel_plane_state *old_plane_state,
+					 struct intel_plane_state *new_plane_state);
 
 #endif /* __INTEL_ATOMIC_PLANE_H__ */

drivers/gpu/drm/i915/display/intel_crtc.c

@@ -496,6 +496,19 @@ void intel_pipe_update_start(struct intel_atomic_state *state,
 	if (intel_crtc_needs_vblank_work(new_crtc_state))
 		intel_crtc_vblank_work_init(new_crtc_state);
 
+	if (state->base.legacy_cursor_update) {
+		struct intel_plane *plane;
+		struct intel_plane_state *old_plane_state, *new_plane_state;
+		int i;
+
+		for_each_oldnew_intel_plane_in_state(state, plane, old_plane_state,
+						     new_plane_state, i) {
+			if (old_plane_state->uapi.crtc == &crtc->base)
+				intel_plane_init_cursor_vblank_work(old_plane_state,
+								    new_plane_state);
+		}
+	}
+
 	intel_vblank_evade_init(old_crtc_state, new_crtc_state, &evade);
 
 	if (drm_WARN_ON(&dev_priv->drm, drm_crtc_vblank_get(&crtc->base)))
@@ -621,6 +634,24 @@ void intel_pipe_update_end(struct intel_atomic_state *state,
 		intel_crtc_arm_vblank_event(new_crtc_state);
 	}
 
+	if (state->base.legacy_cursor_update) {
+		struct intel_plane *plane;
+		struct intel_plane_state *old_plane_state;
+		int i;
+
+		for_each_old_intel_plane_in_state(state, plane, old_plane_state, i) {
+			if (old_plane_state->uapi.crtc == &crtc->base &&
+			    old_plane_state->unpin_work.vblank) {
+				drm_vblank_work_schedule(&old_plane_state->unpin_work,
+							 drm_crtc_accurate_vblank_count(&crtc->base) + 1,
+							 false);
+
+				/* Remove plane from atomic state, cleanup/free is done from vblank worker. */
+				memset(&state->base.planes[i], 0, sizeof(state->base.planes[i]));
+			}
+		}
+	}
+
 	/*
 	 * Send VRR Push to terminate Vblank. If we are already in vblank
 	 * this has to be done _after_ sampling the frame counter, as

drivers/gpu/drm/i915/display/intel_cursor.c

@@ -761,7 +761,7 @@ static bool intel_cursor_format_mod_supported(struct drm_plane *_plane,
 	return format == DRM_FORMAT_ARGB8888;
 }
 
-static void intel_cursor_unpin_work(struct kthread_work *base)
+void intel_cursor_unpin_work(struct kthread_work *base)
 {
 	struct drm_vblank_work *work = to_drm_vblank_work(base);
 	struct intel_plane_state *plane_state =

drivers/gpu/drm/i915/display/intel_cursor.h

@@ -9,9 +9,12 @@
 enum pipe;
 struct drm_i915_private;
 struct intel_plane;
+struct kthread_work;
 
 struct intel_plane *
 intel_cursor_plane_create(struct drm_i915_private *dev_priv,
 			  enum pipe pipe);
 
+void intel_cursor_unpin_work(struct kthread_work *base);
+
 #endif