drm/vc4: crtc: Move the BO Handling out of Common Page-Flip Handler

The function vc4_async_page_flip() handles asynchronous page-flips in
the vc4 driver.

However, it mixes some generic code with code that should only be run on
older generations that have the GPU handled by the vc4 driver.

Let's split the generic part out of vc4_async_page_flip() and into a
common function that we be reusable by an handler made for the BCM2711.
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220610115149.964394-12-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_crtc.c

@@ -835,40 +835,21 @@ static void vc4_async_page_flip_seqno_complete(struct vc4_seqno_cb *cb)
 		vc4_bo_dec_usecnt(bo);
 }
 
-/* Implements async (non-vblank-synced) page flips.
- *
- * The page flip ioctl needs to return immediately, so we grab the
- * modeset semaphore on the pipe, and queue the address update for
- * when V3D is done with the BO being flipped to.
- */
-static int vc4_async_page_flip(struct drm_crtc *crtc,
+static int
+vc4_async_page_flip_common(struct drm_crtc *crtc,
 			   struct drm_framebuffer *fb,
 			   struct drm_pending_vblank_event *event,
 			   uint32_t flags)
 {
 	struct drm_device *dev = crtc->dev;
 	struct drm_plane *plane = crtc->primary;
-	int ret = 0;
 	struct vc4_async_flip_state *flip_state;
 	struct drm_gem_cma_object *cma_bo = drm_fb_cma_get_gem_obj(fb, 0);
 	struct vc4_bo *bo = to_vc4_bo(&cma_bo->base);
 
-	/* Increment the BO usecnt here, so that we never end up with an
-	 * unbalanced number of vc4_bo_{dec,inc}_usecnt() calls when the
-	 * plane is later updated through the non-async path.
-	 * FIXME: we should move to generic async-page-flip when it's
-	 * available, so that we can get rid of this hand-made prepare_fb()
-	 * logic.
-	 */
-	ret = vc4_bo_inc_usecnt(bo);
-	if (ret)
-		return ret;
-
 	flip_state = kzalloc(sizeof(*flip_state), GFP_KERNEL);
-	if (!flip_state) {
-		vc4_bo_dec_usecnt(bo);
+	if (!flip_state)
 		return -ENOMEM;
-	}
 
 	drm_framebuffer_get(fb);
 	flip_state->fb = fb;
@@ -902,6 +883,48 @@ static int vc4_async_page_flip(struct drm_crtc *crtc,
 	return 0;
 }
 
+/* Implements async (non-vblank-synced) page flips.
+ *
+ * The page flip ioctl needs to return immediately, so we grab the
+ * modeset semaphore on the pipe, and queue the address update for
+ * when V3D is done with the BO being flipped to.
+ */
+static int vc4_async_page_flip(struct drm_crtc *crtc,
+			       struct drm_framebuffer *fb,
+			       struct drm_pending_vblank_event *event,
+			       uint32_t flags)
+{
+	struct drm_device *dev = crtc->dev;
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
+	struct drm_gem_cma_object *cma_bo = drm_fb_cma_get_gem_obj(fb, 0);
+	struct vc4_bo *bo = to_vc4_bo(&cma_bo->base);
+	int ret;
+
+	if (WARN_ON_ONCE(vc4->is_vc5))
+		return -ENODEV;
+
+	/*
+	 * Increment the BO usecnt here, so that we never end up with an
+	 * unbalanced number of vc4_bo_{dec,inc}_usecnt() calls when the
+	 * plane is later updated through the non-async path.
+	 *
+	 * FIXME: we should move to generic async-page-flip when
+	 * it's available, so that we can get rid of this
+	 * hand-made prepare_fb() logic.
+	 */
+	ret = vc4_bo_inc_usecnt(bo);
+	if (ret)
+		return ret;
+
+	ret = vc4_async_page_flip_common(crtc, fb, event, flags);
+	if (ret) {
+		vc4_bo_dec_usecnt(bo);
+		return ret;
+	}
+
+	return 0;
+}
+
 int vc4_page_flip(struct drm_crtc *crtc,
 		  struct drm_framebuffer *fb,
 		  struct drm_pending_vblank_event *event,