drm/amd/display: Split enabling CRTC interrupts into two passes

[Why]
When disabling all the pipes for a CRTC the page-flip interrupt also
gets disabled on Raven. We can't re-enable the page-flip interrupt
unless we give DC at least one active DC plane.

We currently enable interrupts after the call to dc_commit_state since
there's currently no valid sequence that should disable all the planes
or re-enable planes for a CRTC without first going through
dc_commit_state.

If we were to allow for a CRTC to be enabled with no primary plane this
would not be the case - the call to dc_commit_updates_for_stream would
enable the planes when going from zero to at least one active plane,
but manage_dm_interrupts would have been called too early.

This results in a page-flip timeout on any subsequent commits since we
think the page-flip are now enabled when they're actually disabled.

We need to enable interrupts after the call to
dc_commit_updates_for_stream.

[How]
Split enabling interrupts into two passes. One pass before
dc_commit_updates_for_stream and one after it.

Shifting all the interrupts to be strictly below the call doesn't
currently work even though it should in theory. We end up queuing
off the vblank event to be handle by the flip handler before it's
actually enabled in some cases, particularly:

old_crtc_state->active = false -> new_crtc_state->active = true

The framebuffer states haven't changed and we can technically still
do a "pageflip" in this case and send back the event.
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: David Francis <David.Francis@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -5429,6 +5429,63 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
 	kfree(bundle);
 }
 
+/*
+ * Enable interrupts on CRTCs that are newly active, undergone
+ * a modeset, or have active planes again.
+ *
+ * Done in two passes, based on the for_modeset flag:
+ * Pass 1: For CRTCs going through modeset
+ * Pass 2: For CRTCs going from 0 to n active planes
+ *
+ * Interrupts can only be enabled after the planes are programmed,
+ * so this requires a two-pass approach since we don't want to
+ * just defer the interrupts until after commit planes every time.
+ */
+static void amdgpu_dm_enable_crtc_interrupts(struct drm_device *dev,
+					     struct drm_atomic_state *state,
+					     bool for_modeset)
+{
+	struct amdgpu_device *adev = dev->dev_private;
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *old_crtc_state, *new_crtc_state;
+	int i;
+
+	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state,
+				      new_crtc_state, i) {
+		struct amdgpu_crtc *acrtc = to_amdgpu_crtc(crtc);
+		struct dm_crtc_state *dm_new_crtc_state =
+			to_dm_crtc_state(new_crtc_state);
+		struct dm_crtc_state *dm_old_crtc_state =
+			to_dm_crtc_state(old_crtc_state);
+		bool modeset = drm_atomic_crtc_needs_modeset(new_crtc_state);
+		bool run_pass;
+
+		run_pass = (for_modeset && modeset) ||
+			   (!for_modeset && !modeset &&
+			    !dm_old_crtc_state->interrupts_enabled);
+
+		if (!run_pass)
+			continue;
+
+		/* Handle vrr on->off / off->on transitions */
+		amdgpu_dm_handle_vrr_transition(dm_old_crtc_state,
+						dm_new_crtc_state);
+
+		if (!dm_new_crtc_state->interrupts_enabled)
+			continue;
+
+		manage_dm_interrupts(adev, acrtc, true);
+
+#ifdef CONFIG_DEBUG_FS
+		/* The stream has changed so CRC capture needs to re-enabled. */
+		if (dm_new_crtc_state->crc_enabled) {
+			dm_new_crtc_state->crc_enabled = false;
+			amdgpu_dm_crtc_set_crc_source(crtc, "auto");
+		}
+#endif
+	}
+}
+
 /*
  * amdgpu_dm_crtc_copy_transient_flags - copy mirrored flags from DRM to DC
  * @crtc_state: the DRM CRTC state
@@ -5709,42 +5766,14 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 		pre_update_freesync_state_on_stream(dm, dm_new_crtc_state);
 	}
 
-	/*
-	 * Enable interrupts on CRTCs that are newly active, undergone
-	 * a modeset, or have active planes again.
-	 */
+	/* Count number of newly disabled CRTCs for dropping PM refs later. */
 	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state,
-			new_crtc_state, i) {
-		struct amdgpu_crtc *acrtc = to_amdgpu_crtc(crtc);
-		bool enable;
-
+				      new_crtc_state, i)
 		if (old_crtc_state->active && !new_crtc_state->active)
 			crtc_disable_count++;
 
-		dm_new_crtc_state = to_dm_crtc_state(new_crtc_state);
-		dm_old_crtc_state = to_dm_crtc_state(old_crtc_state);
-
-		/* Handle vrr on->off / off->on transitions */
-		amdgpu_dm_handle_vrr_transition(dm_old_crtc_state,
-						dm_new_crtc_state);
-
-		enable = dm_new_crtc_state->interrupts_enabled &&
-			 (!dm_old_crtc_state->interrupts_enabled ||
-			  drm_atomic_crtc_needs_modeset(new_crtc_state));
-
-		if (!enable)
-			continue;
-
-		manage_dm_interrupts(adev, acrtc, true);
-
-#ifdef CONFIG_DEBUG_FS
-		/* The stream has changed so CRC capture needs to re-enabled. */
-		if (dm_new_crtc_state->crc_enabled) {
-			dm_new_crtc_state->crc_enabled = false;
-			amdgpu_dm_crtc_set_crc_source(crtc, "auto");
-		}
-#endif
-	}
+	/* Enable interrupts for CRTCs going through a modeset. */
+	amdgpu_dm_enable_crtc_interrupts(dev, state, true);
 
 	for_each_new_crtc_in_state(state, crtc, new_crtc_state, j)
 		if (new_crtc_state->pageflip_flags & DRM_MODE_PAGE_FLIP_ASYNC)
@@ -5759,6 +5788,8 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 						dm, crtc, wait_for_vblank);
 	}
 
+	/* Enable interrupts for CRTCs going from 0 to n active planes. */
+	amdgpu_dm_enable_crtc_interrupts(dev, state, false);
 
 	/*
 	 * send vblank event on all events not handled in flip and