drm: Add reference counting to drm_atomic_state

drm_atomic_state has a complicated single owner model that tracks the
single reference from allocation through to destruction on another
thread - or perhaps on a local error path. We can simplify this tracking
by using reference counting (at a cost of a few more atomics). This is
even more beneficial when the lifetime of the state becomes more
convoluted than being passed to a single worker thread for the commit.

v2: Double check !intel atomic_commit functions for missing gets
v3: Update kerneldocs
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161014121833.439-27-chris@chris-wilson.co.uk

drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c

@@ -464,7 +464,7 @@ atmel_hlcdc_dc_atomic_complete(struct atmel_hlcdc_dc_commit *commit)
 
 	drm_atomic_helper_cleanup_planes(dev, old_state);
 
-	drm_atomic_state_free(old_state);
+	drm_atomic_state_put(old_state);
 
 	/* Complete the commit, wake up any waiter. */
 	spin_lock(&dc->commit.wait.lock);
@@ -521,6 +521,7 @@ static int atmel_hlcdc_dc_atomic_commit(struct drm_device *dev,
 	/* Swap the state, this is the point of no return. */
 	drm_atomic_helper_swap_state(state, true);
 
+	drm_atomic_state_get(state);
 	if (async)
 		queue_work(dc->wq, &commit->work);
 	else

drivers/gpu/drm/drm_atomic.c

@@ -74,6 +74,8 @@ EXPORT_SYMBOL(drm_atomic_state_default_release);
 int
 drm_atomic_state_init(struct drm_device *dev, struct drm_atomic_state *state)
 {
+	kref_init(&state->ref);
+
 	/* TODO legacy paths should maybe do a better job about
 	 * setting this appropriately?
 	 */
@@ -215,22 +217,16 @@ void drm_atomic_state_clear(struct drm_atomic_state *state)
 EXPORT_SYMBOL(drm_atomic_state_clear);
 
 /**
- * drm_atomic_state_free - free all memory for an atomic state
- * @state: atomic state to deallocate
+ * __drm_atomic_state_free - free all memory for an atomic state
+ * @ref: This atomic state to deallocate
  *
  * This frees all memory associated with an atomic state, including all the
  * per-object state for planes, crtcs and connectors.
  */
-void drm_atomic_state_free(struct drm_atomic_state *state)
+void __drm_atomic_state_free(struct kref *ref)
 {
-	struct drm_device *dev;
-	struct drm_mode_config *config;
-
-	if (!state)
-		return;
-
-	dev = state->dev;
-	config = &dev->mode_config;
+	struct drm_atomic_state *state = container_of(ref, typeof(*state), ref);
+	struct drm_mode_config *config = &state->dev->mode_config;
 
 	drm_atomic_state_clear(state);
 
@@ -243,7 +239,7 @@ void drm_atomic_state_free(struct drm_atomic_state *state)
 		kfree(state);
 	}
 }
-EXPORT_SYMBOL(drm_atomic_state_free);
+EXPORT_SYMBOL(__drm_atomic_state_free);
 
 /**
  * drm_atomic_get_crtc_state - get crtc state
@@ -1742,7 +1738,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 	if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) {
 		/*
 		 * Unlike commit, check_only does not clean up state.
-		 * Below we call drm_atomic_state_free for it.
+		 * Below we call drm_atomic_state_put for it.
 		 */
 		ret = drm_atomic_check_only(state);
 	} else if (arg->flags & DRM_MODE_ATOMIC_NONBLOCK) {
@@ -1775,8 +1771,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 		goto retry;
 	}
 
-	if (ret || arg->flags & DRM_MODE_ATOMIC_TEST_ONLY)
-		drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 
 	drm_modeset_drop_locks(&ctx);
 	drm_modeset_acquire_fini(&ctx);

drivers/gpu/drm/drm_atomic_helper.c

@@ -1208,7 +1208,7 @@ static void commit_tail(struct drm_atomic_state *state)
 
 	drm_atomic_helper_commit_cleanup_done(state);
 
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 }
 
 static void commit_work(struct work_struct *work)
@@ -1290,6 +1290,7 @@ int drm_atomic_helper_commit(struct drm_device *dev,
 	 * make sure work items don't artifically stall on each another.
 	 */
 
+	drm_atomic_state_get(state);
 	if (nonblock)
 		queue_work(system_unbound_wq, &state->commit_work);
 	else
@@ -1591,7 +1592,7 @@ EXPORT_SYMBOL(drm_atomic_helper_commit_hw_done);
  *
  * This signals completion of the atomic update @state, including any cleanup
  * work. If used, it must be called right before calling
- * drm_atomic_state_free().
+ * drm_atomic_state_put().
  *
  * This is part of the atomic helper support for nonblocking commits, see
  * drm_atomic_helper_setup_commit() for an overview.
@@ -2114,18 +2115,13 @@ int drm_atomic_helper_update_plane(struct drm_plane *plane,
 		state->legacy_cursor_update = true;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2187,18 +2183,13 @@ int drm_atomic_helper_disable_plane(struct drm_plane *plane)
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2327,18 +2318,13 @@ int drm_atomic_helper_set_config(struct drm_mode_set *set)
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2480,11 +2466,8 @@ int drm_atomic_helper_disable_all(struct drm_device *dev,
 	}
 
 	err = drm_atomic_commit(state);
-
 free:
-	if (err < 0)
-		drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return err;
 }
 EXPORT_SYMBOL(drm_atomic_helper_disable_all);
@@ -2535,7 +2518,7 @@ struct drm_atomic_state *drm_atomic_helper_suspend(struct drm_device *dev)
 
 	err = drm_atomic_helper_disable_all(dev, &ctx);
 	if (err < 0) {
-		drm_atomic_state_free(state);
+		drm_atomic_state_put(state);
 		state = ERR_PTR(err);
 		goto unlock;
 	}
@@ -2624,18 +2607,13 @@ drm_atomic_helper_crtc_set_property(struct drm_crtc *crtc,
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2684,18 +2662,13 @@ drm_atomic_helper_plane_set_property(struct drm_plane *plane,
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2744,18 +2717,13 @@ drm_atomic_helper_connector_set_property(struct drm_connector *connector,
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2828,18 +2796,13 @@ int drm_atomic_helper_page_flip(struct drm_crtc *crtc,
 	}
 
 	ret = drm_atomic_nonblocking_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -2915,19 +2878,14 @@ int drm_atomic_helper_connector_dpms(struct drm_connector *connector,
 	crtc_state->active = active;
 
 	ret = drm_atomic_commit(state);
-	if (ret != 0)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
 	connector->dpms = old_mode;
-	drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);
@@ -3334,7 +3292,7 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,
 
 free:
 	if (err < 0) {
-		drm_atomic_state_free(state);
+		drm_atomic_state_put(state);
 		state = ERR_PTR(err);
 	}
 
@@ -3449,22 +3407,14 @@ int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc,
 		goto fail;
 
 	ret = drm_atomic_commit(state);
-	if (ret)
-		goto fail;
-
-	/* Driver takes ownership of state on successful commit. */
-
-	drm_property_unreference_blob(blob);
-
-	return 0;
 fail:
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 	drm_property_unreference_blob(blob);
-
 	return ret;
+
 backoff:
 	drm_atomic_state_clear(state);
 	drm_atomic_legacy_backoff(state);

drivers/gpu/drm/drm_fb_helper.c

@@ -367,9 +367,7 @@ static int restore_fbdev_mode_atomic(struct drm_fb_helper *fb_helper)
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	if (ret != 0)
-		drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
 
 backoff:
@@ -1361,16 +1359,13 @@ static int pan_display_atomic(struct fb_var_screeninfo *var,
 	info->var.xoffset = var->xoffset;
 	info->var.yoffset = var->yoffset;
 
-
 fail:
 	drm_atomic_clean_old_fb(dev, plane_mask, ret);
 
 	if (ret == -EDEADLK)
 		goto backoff;
 
-	if (ret != 0)
-		drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 	return ret;
 
 backoff:

drivers/gpu/drm/exynos/exynos_drm_drv.c

@@ -69,7 +69,7 @@ static void exynos_atomic_commit_complete(struct exynos_atomic_commit *commit)
 
 	drm_atomic_helper_cleanup_planes(dev, state);
 
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 
 	spin_lock(&priv->lock);
 	priv->pending &= ~commit->crtcs;
@@ -254,6 +254,7 @@ int exynos_atomic_commit(struct drm_device *dev, struct drm_atomic_state *state,
 
 	drm_atomic_helper_swap_state(state, true);
 
+	drm_atomic_state_get(state);
 	if (nonblock)
 		schedule_work(&commit->work);
 	else

drivers/gpu/drm/i915/i915_debugfs.c

@@ -3941,10 +3941,9 @@ static void hsw_trans_edp_pipe_A_crc_wa(struct drm_i915_private *dev_priv,
 
 	ret = drm_atomic_commit(state);
 out:
-	drm_modeset_unlock_all(dev);
 	WARN(ret, "Toggling workaround to %i returns %i\n", enable, ret);
-	if (ret)
-		drm_atomic_state_free(state);
+	drm_modeset_unlock_all(dev);
+	drm_atomic_state_put(state);
 }
 
 static int ivb_pipe_crc_ctl_reg(struct drm_i915_private *dev_priv,

drivers/gpu/drm/i915/intel_display.c

@@ -3582,7 +3582,7 @@ void intel_prepare_reset(struct drm_i915_private *dev_priv)
 	return;
 
 err:
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 }
 
 void intel_finish_reset(struct drm_i915_private *dev_priv)
@@ -3643,6 +3643,8 @@ void intel_finish_reset(struct drm_i915_private *dev_priv)
 		intel_hpd_init(dev_priv);
 	}
 
+	if (state)
+		drm_atomic_state_put(state);
 	drm_modeset_drop_locks(ctx);
 	drm_modeset_acquire_fini(ctx);
 	mutex_unlock(&dev->mode_config.mutex);
@@ -6882,7 +6884,7 @@ static void intel_crtc_disable_noatomic(struct drm_crtc *crtc)
 
 	dev_priv->display.crtc_disable(crtc_state, state);
 
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 
 	DRM_DEBUG_KMS("[CRTC:%d:%s] hw state adjusted, was enabled, now disabled\n",
 		      crtc->base.id, crtc->name);
@@ -11249,8 +11251,8 @@ bool intel_get_load_detect_pipe(struct drm_connector *connector,
 	return true;
 
 fail:
-	drm_atomic_state_free(state);
-	drm_atomic_state_free(restore_state);
+	drm_atomic_state_put(state);
+	drm_atomic_state_put(restore_state);
 	restore_state = state = NULL;
 
 	if (ret == -EDEADLK) {
@@ -11279,10 +11281,9 @@ void intel_release_load_detect_pipe(struct drm_connector *connector,
 		return;
 
 	ret = drm_atomic_commit(state);
-	if (ret) {
+	if (ret)
 		DRM_DEBUG_KMS("Couldn't release load detect pipe: %i\n", ret);
-		drm_atomic_state_free(state);
-	}
+	drm_atomic_state_put(state);
 }
 
 static int i9xx_pll_refclk(struct drm_device *dev,
@@ -12350,8 +12351,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 			goto retry;
 		}
 
-		if (ret)
-			drm_atomic_state_free(state);
+		drm_atomic_state_put(state);
 
 		if (ret == 0 && event) {
 			spin_lock_irq(&dev->event_lock);
@@ -14437,7 +14437,7 @@ static void intel_atomic_commit_tail(struct drm_atomic_state *state)
 
 	drm_atomic_helper_commit_cleanup_done(state);
 
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 
 	/* As one of the primary mmio accessors, KMS has a high likelihood
 	 * of triggering bugs in unclaimed access. After we finish
@@ -14520,6 +14520,7 @@ static int intel_atomic_commit(struct drm_device *dev,
 	intel_shared_dpll_commit(state);
 	intel_atomic_track_fbs(state);
 
+	drm_atomic_state_get(state);
 	if (nonblock)
 		queue_work(system_unbound_wq, &state->commit_work);
 	else
@@ -14561,9 +14562,8 @@ void intel_crtc_restore_mode(struct drm_crtc *crtc)
 		goto retry;
 	}
 
-	if (ret)
 out:
-		drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 }
 
 /*
@@ -16305,8 +16305,8 @@ static void sanitize_watermarks(struct drm_device *dev)
 		dev_priv->display.optimize_watermarks(cs);
 	}
 
-	drm_atomic_state_free(state);
 fail:
+	drm_atomic_state_put(state);
 	drm_modeset_drop_locks(&ctx);
 	drm_modeset_acquire_fini(&ctx);
 }
@@ -16943,10 +16943,9 @@ void intel_display_resume(struct drm_device *dev)
 	drm_modeset_acquire_fini(&ctx);
 	mutex_unlock(&dev->mode_config.mutex);
 
-	if (ret) {
+	if (ret)
 		DRM_ERROR("Restoring old state failed with %i\n", ret);
-		drm_atomic_state_free(state);
-	}
+	drm_atomic_state_put(state);
 }
 
 void intel_modeset_gem_init(struct drm_device *dev)

drivers/gpu/drm/i915/intel_sprite.c

@@ -987,9 +987,7 @@ int intel_sprite_set_colorkey(struct drm_device *dev, void *data,
 		drm_modeset_backoff(&ctx);
 	}
 
-	if (ret)
-		drm_atomic_state_free(state);
-
+	drm_atomic_state_put(state);
 out:
 	drm_modeset_drop_locks(&ctx);
 	drm_modeset_acquire_fini(&ctx);

drivers/gpu/drm/mediatek/mtk_drm_drv.c

@@ -83,7 +83,7 @@ static void mtk_atomic_complete(struct mtk_drm_private *private,
 	drm_atomic_helper_wait_for_vblanks(drm, state);
 
 	drm_atomic_helper_cleanup_planes(drm, state);
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 }
 
 static void mtk_atomic_work(struct work_struct *work)
@@ -110,6 +110,7 @@ static int mtk_atomic_commit(struct drm_device *drm,
 
 	drm_atomic_helper_swap_state(state, true);
 
+	drm_atomic_state_get(state);
 	if (async)
 		mtk_atomic_schedule(private, state);
 	else

drivers/gpu/drm/msm/msm_atomic.c

@@ -141,7 +141,7 @@ static void complete_commit(struct msm_commit *c, bool async)
 
 	kms->funcs->complete_commit(kms, state);
 
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 
 	commit_destroy(c);
 }
@@ -256,6 +256,7 @@ int msm_atomic_commit(struct drm_device *dev,
 	 * current layout.
 	 */
 
+	drm_atomic_state_get(state);
 	if (nonblock) {
 		queue_work(priv->atomic_wq, &c->work);
 		return 0;

drivers/gpu/drm/omapdrm/omap_drv.c

@@ -105,7 +105,7 @@ static void omap_atomic_complete(struct omap_atomic_state_commit *commit)
 
 	dispc_runtime_put();
 
-	drm_atomic_state_free(old_state);
+	drm_atomic_state_put(old_state);
 
 	/* Complete the commit, wake up any waiter. */
 	spin_lock(&priv->commit.lock);
@@ -176,6 +176,7 @@ static int omap_atomic_commit(struct drm_device *dev,
 	/* Swap the state, this is the point of no return. */
 	drm_atomic_helper_swap_state(state, true);
 
+	drm_atomic_state_get(state);
 	if (nonblock)
 		schedule_work(&commit->work);
 	else

drivers/gpu/drm/rcar-du/rcar_du_kms.c

@@ -264,7 +264,7 @@ static void rcar_du_atomic_complete(struct rcar_du_commit *commit)
 
 	drm_atomic_helper_cleanup_planes(dev, old_state);
 
-	drm_atomic_state_free(old_state);
+	drm_atomic_state_put(old_state);
 
 	/* Complete the commit, wake up any waiter. */
 	spin_lock(&rcdu->commit.wait.lock);
@@ -330,6 +330,7 @@ static int rcar_du_atomic_commit(struct drm_device *dev,
 	/* Swap the state, this is the point of no return. */
 	drm_atomic_helper_swap_state(state, true);
 
+	drm_atomic_state_get(state);
 	if (nonblock)
 		schedule_work(&commit->work);
 	else

drivers/gpu/drm/sti/sti_drv.c

@@ -184,7 +184,7 @@ static void sti_atomic_complete(struct sti_private *private,
 	drm_atomic_helper_wait_for_vblanks(drm, state);
 
 	drm_atomic_helper_cleanup_planes(drm, state);
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 }
 
 static void sti_atomic_work(struct work_struct *work)
@@ -217,6 +217,7 @@ static int sti_atomic_commit(struct drm_device *drm,
 
 	drm_atomic_helper_swap_state(state, true);
 
+	drm_atomic_state_get(state);
 	if (nonblock)
 		sti_atomic_schedule(private, state);
 	else

drivers/gpu/drm/tegra/drm.c

@@ -63,7 +63,7 @@ static void tegra_atomic_complete(struct tegra_drm *tegra,
 	drm_atomic_helper_wait_for_vblanks(drm, state);
 
 	drm_atomic_helper_cleanup_planes(drm, state);
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 }
 
 static void tegra_atomic_work(struct work_struct *work)
@@ -96,6 +96,7 @@ static int tegra_atomic_commit(struct drm_device *drm,
 
 	drm_atomic_helper_swap_state(state, true);
 
+	drm_atomic_state_get(state);
 	if (nonblock)
 		tegra_atomic_schedule(tegra, state);
 	else

drivers/gpu/drm/tilcdc/tilcdc_drv.c

@@ -143,8 +143,6 @@ static int tilcdc_commit(struct drm_device *dev,
 
 	drm_atomic_helper_cleanup_planes(dev, state);
 
-	drm_atomic_state_free(state);
-
 	return 0;
 }
 

drivers/gpu/drm/vc4/vc4_kms.c

@@ -61,7 +61,7 @@ vc4_atomic_complete_commit(struct vc4_commit *c)
 
 	drm_atomic_helper_cleanup_planes(dev, state);
 
-	drm_atomic_state_free(state);
+	drm_atomic_state_put(state);
 
 	up(&vc4->async_modeset);
 
@@ -173,6 +173,7 @@ static int vc4_atomic_commit(struct drm_device *dev,
 	 * current layout.
 	 */
 
+	drm_atomic_state_get(state);
 	if (nonblock) {
 		vc4_queue_seqno_cb(dev, &c->cb, wait_seqno,
 				   vc4_atomic_complete_commit_seqno_cb);

include/drm/drm_atomic.h

@@ -153,6 +153,7 @@ struct __drm_connnectors_state {
 
 /**
  * struct drm_atomic_state - the global state object for atomic updates
+ * @ref: count of all references to this state (will not be freed until zero)
  * @dev: parent DRM device
  * @allow_modeset: allow full modeset
  * @legacy_cursor_update: hint to enforce legacy cursor IOCTL semantics
@@ -164,6 +165,8 @@ struct __drm_connnectors_state {
  * @acquire_ctx: acquire context for this atomic modeset state update
  */
 struct drm_atomic_state {
+	struct kref ref;
+
 	struct drm_device *dev;
 	bool allow_modeset : 1;
 	bool legacy_cursor_update : 1;
@@ -193,7 +196,33 @@ static inline void drm_crtc_commit_get(struct drm_crtc_commit *commit)
 struct drm_atomic_state * __must_check
 drm_atomic_state_alloc(struct drm_device *dev);
 void drm_atomic_state_clear(struct drm_atomic_state *state);
-void drm_atomic_state_free(struct drm_atomic_state *state);
+
+/**
+ * drm_atomic_state_get - acquire a reference to the atomic state
+ * @state: The atomic state
+ *
+ * Returns a new reference to the @state
+ */
+static inline struct drm_atomic_state *
+drm_atomic_state_get(struct drm_atomic_state *state)
+{
+	kref_get(&state->ref);
+	return state;
+}
+
+void __drm_atomic_state_free(struct kref *ref);
+
+/**
+ * drm_atomic_state_put - release a reference to the atomic state
+ * @state: The atomic state
+ *
+ * This releases a reference to @state which is freed after removing the
+ * final reference. No locking required and callable from any context.
+ */
+static inline void drm_atomic_state_put(struct drm_atomic_state *state)
+{
+	kref_put(&state->ref, __drm_atomic_state_free);
+}
 
 int  __must_check
 drm_atomic_state_init(struct drm_device *dev, struct drm_atomic_state *state);

include/drm/drm_plane.h

@@ -88,7 +88,6 @@ struct drm_plane_state {
 	struct drm_atomic_state *state;
 };
 
-
 /**
  * struct drm_plane_funcs - driver plane control functions
  */