drm/vc4: kms: Remove async modeset semaphore

Now that we have proper ordering guaranteed by the previous patch, the
semaphore is redundant and can be removed.

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20201204151138.1739736-7-maxime@cerno.tech

Author: mripard

drivers/gpu/drm/vc4/vc4_crtc.c

@@ -697,7 +697,6 @@ vc4_async_page_flip_complete(struct vc4_seqno_cb *cb)
 		container_of(cb, struct vc4_async_flip_state, cb);
 	struct drm_crtc *crtc = flip_state->crtc;
 	struct drm_device *dev = crtc->dev;
-	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct drm_plane *plane = crtc->primary;
 
 	vc4_plane_async_set_fb(plane, flip_state->fb);
@@ -729,8 +728,6 @@ vc4_async_page_flip_complete(struct vc4_seqno_cb *cb)
 	}
 
 	kfree(flip_state);
-
-	up(&vc4->async_modeset);
 }
 
 /* Implements async (non-vblank-synced) page flips.
@@ -745,7 +742,6 @@ static int vc4_async_page_flip(struct drm_crtc *crtc,
 			       uint32_t flags)
 {
 	struct drm_device *dev = crtc->dev;
-	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct drm_plane *plane = crtc->primary;
 	int ret = 0;
 	struct vc4_async_flip_state *flip_state;
@@ -774,15 +770,6 @@ static int vc4_async_page_flip(struct drm_crtc *crtc,
 	flip_state->crtc = crtc;
 	flip_state->event = event;
 
-	/* Make sure all other async modesetes have landed. */
-	ret = down_interruptible(&vc4->async_modeset);
-	if (ret) {
-		drm_framebuffer_put(fb);
-		vc4_bo_dec_usecnt(bo);
-		kfree(flip_state);
-		return ret;
-	}
-
 	/* Save the current FB before it's replaced by the new one in
 	 * drm_atomic_set_fb_for_plane(). We'll need the old FB in
 	 * vc4_async_page_flip_complete() to decrement the BO usecnt and keep

drivers/gpu/drm/vc4/vc4_drv.h

@@ -214,8 +214,6 @@ struct vc4_dev {
 		struct work_struct reset_work;
 	} hangcheck;
 
-	struct semaphore async_modeset;
-
 	struct drm_modeset_lock ctm_state_lock;
 	struct drm_private_obj ctm_manager;
 	struct drm_private_obj hvs_channels;

drivers/gpu/drm/vc4/vc4_kms.c

@@ -418,8 +418,6 @@ vc4_atomic_complete_commit(struct drm_atomic_state *state)
 		clk_set_min_rate(hvs->core_clk, 0);
 
 	drm_atomic_state_put(state);
-
-	up(&vc4->async_modeset);
 }
 
 static void commit_work(struct work_struct *work)
@@ -477,26 +475,17 @@ static int vc4_atomic_commit(struct drm_device *dev,
 			     struct drm_atomic_state *state,
 			     bool nonblock)
 {
-	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	int ret;
 
 	if (state->async_update) {
-		ret = down_interruptible(&vc4->async_modeset);
-		if (ret)
-			return ret;
-
 		ret = drm_atomic_helper_prepare_planes(dev, state);
-		if (ret) {
-			up(&vc4->async_modeset);
+		if (ret)
 			return ret;
-		}
 
 		drm_atomic_helper_async_commit(dev, state);
 
 		drm_atomic_helper_cleanup_planes(dev, state);
 
-		up(&vc4->async_modeset);
-
 		return 0;
 	}
 
@@ -512,21 +501,14 @@ static int vc4_atomic_commit(struct drm_device *dev,
 
 	INIT_WORK(&state->commit_work, commit_work);
 
-	ret = down_interruptible(&vc4->async_modeset);
-	if (ret)
-		return ret;
-
 	ret = drm_atomic_helper_prepare_planes(dev, state);
-	if (ret) {
-		up(&vc4->async_modeset);
+	if (ret)
 		return ret;
-	}
 
 	if (!nonblock) {
 		ret = drm_atomic_helper_wait_for_fences(dev, state, true);
 		if (ret) {
 			drm_atomic_helper_cleanup_planes(dev, state);
-			up(&vc4->async_modeset);
 			return ret;
 		}
 	}
@@ -1008,8 +990,6 @@ int vc4_kms_load(struct drm_device *dev)
 		vc4->load_tracker_enabled = true;
 	}
 
-	sema_init(&vc4->async_modeset, 1);
-
 	/* Set support for vblank irq fast disable, before drm_vblank_init() */
 	dev->vblank_disable_immediate = true;