Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 686 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
new file mode 100644
index 000000000..bf31b9d92
--- /dev/null
+++ b/drivers/gpu/drm/drm_atomic_state_helper.c
@@ -0,0 +1,686 @@
+/*
+ * Copyright (C) 2018 Intel Corp.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors:
+ * Rob Clark <robdclark@gmail.com>
+ * Daniel Vetter <daniel.vetter@ffwll.ch>
+ */
+
+#include <drm/drm_atomic.h>
+#include <drm/drm_atomic_state_helper.h>
+#include <drm/drm_blend.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_connector.h>
+#include <drm/drm_crtc.h>
+#include <drm/drm_device.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_plane.h>
+#include <drm/drm_print.h>
+#include <drm/drm_vblank.h>
+#include <drm/drm_writeback.h>
+
+#include <linux/slab.h>
+#include <linux/dma-fence.h>
+
+/**
+ * DOC: atomic state reset and initialization
+ *
+ * Both the drm core and the atomic helpers assume that there is always the full
+ * and correct atomic software state for all connectors, CRTCs and planes
+ * available. Which is a bit a problem on driver load and also after system
+ * suspend. One way to solve this is to have a hardware state read-out
+ * infrastructure which reconstructs the full software state (e.g. the i915
+ * driver).
+ *
+ * The simpler solution is to just reset the software state to everything off,
+ * which is easiest to do by calling drm_mode_config_reset(). To facilitate this
+ * the atomic helpers provide default reset implementations for all hooks.
+ *
+ * On the upside the precise state tracking of atomic simplifies system suspend
+ * and resume a lot. For drivers using drm_mode_config_reset() a complete recipe
+ * is implemented in drm_atomic_helper_suspend() and drm_atomic_helper_resume().
+ * For other drivers the building blocks are split out, see the documentation
+ * for these functions.
+ */
+
+/**
+ * __drm_atomic_helper_crtc_state_reset - reset the CRTC state
+ * @crtc_state: atomic CRTC state, must not be NULL
+ * @crtc: CRTC object, must not be NULL
+ *
+ * Initializes the newly allocated @crtc_state with default
+ * values. This is useful for drivers that subclass the CRTC state.
+ */
+void
+__drm_atomic_helper_crtc_state_reset(struct drm_crtc_state *crtc_state,
+				     struct drm_crtc *crtc)
+{
+	crtc_state->crtc = crtc;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_crtc_state_reset);
+
+/**
+ * __drm_atomic_helper_crtc_reset - reset state on CRTC
+ * @crtc: drm CRTC
+ * @crtc_state: CRTC state to assign
+ *
+ * Initializes the newly allocated @crtc_state and assigns it to
+ * the &drm_crtc->state pointer of @crtc, usually required when
+ * initializing the drivers or when called from the &drm_crtc_funcs.reset
+ * hook.
+ *
+ * This is useful for drivers that subclass the CRTC state.
+ */
+void
+__drm_atomic_helper_crtc_reset(struct drm_crtc *crtc,
+			       struct drm_crtc_state *crtc_state)
+{
+	if (crtc_state)
+		__drm_atomic_helper_crtc_state_reset(crtc_state, crtc);
+
+	if (drm_dev_has_vblank(crtc->dev))
+		drm_crtc_vblank_reset(crtc);
+
+	crtc->state = crtc_state;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_crtc_reset);
+
+/**
+ * drm_atomic_helper_crtc_reset - default &drm_crtc_funcs.reset hook for CRTCs
+ * @crtc: drm CRTC
+ *
+ * Resets the atomic state for @crtc by freeing the state pointer (which might
+ * be NULL, e.g. at driver load time) and allocating a new empty state object.
+ */
+void drm_atomic_helper_crtc_reset(struct drm_crtc *crtc)
+{
+	struct drm_crtc_state *crtc_state =
+		kzalloc(sizeof(*crtc->state), GFP_KERNEL);
+
+	if (crtc->state)
+		crtc->funcs->atomic_destroy_state(crtc, crtc->state);
+
+	__drm_atomic_helper_crtc_reset(crtc, crtc_state);
+}
+EXPORT_SYMBOL(drm_atomic_helper_crtc_reset);
+
+/**
+ * __drm_atomic_helper_crtc_duplicate_state - copy atomic CRTC state
+ * @crtc: CRTC object
+ * @state: atomic CRTC state
+ *
+ * Copies atomic state from a CRTC's current state and resets inferred values.
+ * This is useful for drivers that subclass the CRTC state.
+ */
+void __drm_atomic_helper_crtc_duplicate_state(struct drm_crtc *crtc,
+					      struct drm_crtc_state *state)
+{
+	memcpy(state, crtc->state, sizeof(*state));
+
+	if (state->mode_blob)
+		drm_property_blob_get(state->mode_blob);
+	if (state->degamma_lut)
+		drm_property_blob_get(state->degamma_lut);
+	if (state->ctm)
+		drm_property_blob_get(state->ctm);
+	if (state->gamma_lut)
+		drm_property_blob_get(state->gamma_lut);
+	state->mode_changed = false;
+	state->active_changed = false;
+	state->planes_changed = false;
+	state->connectors_changed = false;
+	state->color_mgmt_changed = false;
+	state->zpos_changed = false;
+	state->commit = NULL;
+	state->event = NULL;
+	state->async_flip = false;
+
+	/* Self refresh should be canceled when a new update is available */
+	state->active = drm_atomic_crtc_effectively_active(state);
+	state->self_refresh_active = false;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_crtc_duplicate_state);
+
+/**
+ * drm_atomic_helper_crtc_duplicate_state - default state duplicate hook
+ * @crtc: drm CRTC
+ *
+ * Default CRTC state duplicate hook for drivers which don't have their own
+ * subclassed CRTC state structure.
+ */
+struct drm_crtc_state *
+drm_atomic_helper_crtc_duplicate_state(struct drm_crtc *crtc)
+{
+	struct drm_crtc_state *state;
+
+	if (WARN_ON(!crtc->state))
+		return NULL;
+
+	state = kmalloc(sizeof(*state), GFP_KERNEL);
+	if (state)
+		__drm_atomic_helper_crtc_duplicate_state(crtc, state);
+
+	return state;
+}
+EXPORT_SYMBOL(drm_atomic_helper_crtc_duplicate_state);
+
+/**
+ * __drm_atomic_helper_crtc_destroy_state - release CRTC state
+ * @state: CRTC state object to release
+ *
+ * Releases all resources stored in the CRTC state without actually freeing
+ * the memory of the CRTC state. This is useful for drivers that subclass the
+ * CRTC state.
+ */
+void __drm_atomic_helper_crtc_destroy_state(struct drm_crtc_state *state)
+{
+	if (state->commit) {
+		/*
+		 * In the event that a non-blocking commit returns
+		 * -ERESTARTSYS before the commit_tail work is queued, we will
+		 * have an extra reference to the commit object. Release it, if
+		 * the event has not been consumed by the worker.
+		 *
+		 * state->event may be freed, so we can't directly look at
+		 * state->event->base.completion.
+		 */
+		if (state->event && state->commit->abort_completion)
+			drm_crtc_commit_put(state->commit);
+
+		kfree(state->commit->event);
+		state->commit->event = NULL;
+
+		drm_crtc_commit_put(state->commit);
+	}
+
+	drm_property_blob_put(state->mode_blob);
+	drm_property_blob_put(state->degamma_lut);
+	drm_property_blob_put(state->ctm);
+	drm_property_blob_put(state->gamma_lut);
+}
+EXPORT_SYMBOL(__drm_atomic_helper_crtc_destroy_state);
+
+/**
+ * drm_atomic_helper_crtc_destroy_state - default state destroy hook
+ * @crtc: drm CRTC
+ * @state: CRTC state object to release
+ *
+ * Default CRTC state destroy hook for drivers which don't have their own
+ * subclassed CRTC state structure.
+ */
+void drm_atomic_helper_crtc_destroy_state(struct drm_crtc *crtc,
+					  struct drm_crtc_state *state)
+{
+	__drm_atomic_helper_crtc_destroy_state(state);
+	kfree(state);
+}
+EXPORT_SYMBOL(drm_atomic_helper_crtc_destroy_state);
+
+/**
+ * __drm_atomic_helper_plane_state_reset - resets plane state to default values
+ * @plane_state: atomic plane state, must not be NULL
+ * @plane: plane object, must not be NULL
+ *
+ * Initializes the newly allocated @plane_state with default
+ * values. This is useful for drivers that subclass the CRTC state.
+ */
+void __drm_atomic_helper_plane_state_reset(struct drm_plane_state *plane_state,
+					   struct drm_plane *plane)
+{
+	u64 val;
+
+	plane_state->plane = plane;
+	plane_state->rotation = DRM_MODE_ROTATE_0;
+
+	plane_state->alpha = DRM_BLEND_ALPHA_OPAQUE;
+	plane_state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
+
+	if (plane->color_encoding_property) {
+		if (!drm_object_property_get_default_value(&plane->base,
+							   plane->color_encoding_property,
+							   &val))
+			plane_state->color_encoding = val;
+	}
+
+	if (plane->color_range_property) {
+		if (!drm_object_property_get_default_value(&plane->base,
+							   plane->color_range_property,
+							   &val))
+			plane_state->color_range = val;
+	}
+
+	if (plane->zpos_property) {
+		if (!drm_object_property_get_default_value(&plane->base,
+							   plane->zpos_property,
+							   &val)) {
+			plane_state->zpos = val;
+			plane_state->normalized_zpos = val;
+		}
+	}
+}
+EXPORT_SYMBOL(__drm_atomic_helper_plane_state_reset);
+
+/**
+ * __drm_atomic_helper_plane_reset - reset state on plane
+ * @plane: drm plane
+ * @plane_state: plane state to assign
+ *
+ * Initializes the newly allocated @plane_state and assigns it to
+ * the &drm_crtc->state pointer of @plane, usually required when
+ * initializing the drivers or when called from the &drm_plane_funcs.reset
+ * hook.
+ *
+ * This is useful for drivers that subclass the plane state.
+ */
+void __drm_atomic_helper_plane_reset(struct drm_plane *plane,
+				     struct drm_plane_state *plane_state)
+{
+	if (plane_state)
+		__drm_atomic_helper_plane_state_reset(plane_state, plane);
+
+	plane->state = plane_state;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_plane_reset);
+
+/**
+ * drm_atomic_helper_plane_reset - default &drm_plane_funcs.reset hook for planes
+ * @plane: drm plane
+ *
+ * Resets the atomic state for @plane by freeing the state pointer (which might
+ * be NULL, e.g. at driver load time) and allocating a new empty state object.
+ */
+void drm_atomic_helper_plane_reset(struct drm_plane *plane)
+{
+	if (plane->state)
+		__drm_atomic_helper_plane_destroy_state(plane->state);
+
+	kfree(plane->state);
+	plane->state = kzalloc(sizeof(*plane->state), GFP_KERNEL);
+	if (plane->state)
+		__drm_atomic_helper_plane_reset(plane, plane->state);
+}
+EXPORT_SYMBOL(drm_atomic_helper_plane_reset);
+
+/**
+ * __drm_atomic_helper_plane_duplicate_state - copy atomic plane state
+ * @plane: plane object
+ * @state: atomic plane state
+ *
+ * Copies atomic state from a plane's current state. This is useful for
+ * drivers that subclass the plane state.
+ */
+void __drm_atomic_helper_plane_duplicate_state(struct drm_plane *plane,
+					       struct drm_plane_state *state)
+{
+	memcpy(state, plane->state, sizeof(*state));
+
+	if (state->fb)
+		drm_framebuffer_get(state->fb);
+
+	state->fence = NULL;
+	state->commit = NULL;
+	state->fb_damage_clips = NULL;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_plane_duplicate_state);
+
+/**
+ * drm_atomic_helper_plane_duplicate_state - default state duplicate hook
+ * @plane: drm plane
+ *
+ * Default plane state duplicate hook for drivers which don't have their own
+ * subclassed plane state structure.
+ */
+struct drm_plane_state *
+drm_atomic_helper_plane_duplicate_state(struct drm_plane *plane)
+{
+	struct drm_plane_state *state;
+
+	if (WARN_ON(!plane->state))
+		return NULL;
+
+	state = kmalloc(sizeof(*state), GFP_KERNEL);
+	if (state)
+		__drm_atomic_helper_plane_duplicate_state(plane, state);
+
+	return state;
+}
+EXPORT_SYMBOL(drm_atomic_helper_plane_duplicate_state);
+
+/**
+ * __drm_atomic_helper_plane_destroy_state - release plane state
+ * @state: plane state object to release
+ *
+ * Releases all resources stored in the plane state without actually freeing
+ * the memory of the plane state. This is useful for drivers that subclass the
+ * plane state.
+ */
+void __drm_atomic_helper_plane_destroy_state(struct drm_plane_state *state)
+{
+	if (state->fb)
+		drm_framebuffer_put(state->fb);
+
+	if (state->fence)
+		dma_fence_put(state->fence);
+
+	if (state->commit)
+		drm_crtc_commit_put(state->commit);
+
+	drm_property_blob_put(state->fb_damage_clips);
+}
+EXPORT_SYMBOL(__drm_atomic_helper_plane_destroy_state);
+
+/**
+ * drm_atomic_helper_plane_destroy_state - default state destroy hook
+ * @plane: drm plane
+ * @state: plane state object to release
+ *
+ * Default plane state destroy hook for drivers which don't have their own
+ * subclassed plane state structure.
+ */
+void drm_atomic_helper_plane_destroy_state(struct drm_plane *plane,
+					   struct drm_plane_state *state)
+{
+	__drm_atomic_helper_plane_destroy_state(state);
+	kfree(state);
+}
+EXPORT_SYMBOL(drm_atomic_helper_plane_destroy_state);
+
+/**
+ * __drm_atomic_helper_connector_state_reset - reset the connector state
+ * @conn_state: atomic connector state, must not be NULL
+ * @connector: connectotr object, must not be NULL
+ *
+ * Initializes the newly allocated @conn_state with default
+ * values. This is useful for drivers that subclass the connector state.
+ */
+void
+__drm_atomic_helper_connector_state_reset(struct drm_connector_state *conn_state,
+					  struct drm_connector *connector)
+{
+	conn_state->connector = connector;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_connector_state_reset);
+
+/**
+ * __drm_atomic_helper_connector_reset - reset state on connector
+ * @connector: drm connector
+ * @conn_state: connector state to assign
+ *
+ * Initializes the newly allocated @conn_state and assigns it to
+ * the &drm_connector->state pointer of @connector, usually required when
+ * initializing the drivers or when called from the &drm_connector_funcs.reset
+ * hook.
+ *
+ * This is useful for drivers that subclass the connector state.
+ */
+void
+__drm_atomic_helper_connector_reset(struct drm_connector *connector,
+				    struct drm_connector_state *conn_state)
+{
+	if (conn_state)
+		__drm_atomic_helper_connector_state_reset(conn_state, connector);
+
+	connector->state = conn_state;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_connector_reset);
+
+/**
+ * drm_atomic_helper_connector_reset - default &drm_connector_funcs.reset hook for connectors
+ * @connector: drm connector
+ *
+ * Resets the atomic state for @connector by freeing the state pointer (which
+ * might be NULL, e.g. at driver load time) and allocating a new empty state
+ * object.
+ */
+void drm_atomic_helper_connector_reset(struct drm_connector *connector)
+{
+	struct drm_connector_state *conn_state =
+		kzalloc(sizeof(*conn_state), GFP_KERNEL);
+
+	if (connector->state)
+		__drm_atomic_helper_connector_destroy_state(connector->state);
+
+	kfree(connector->state);
+	__drm_atomic_helper_connector_reset(connector, conn_state);
+}
+EXPORT_SYMBOL(drm_atomic_helper_connector_reset);
+
+/**
+ * drm_atomic_helper_connector_tv_reset - Resets TV connector properties
+ * @connector: DRM connector
+ *
+ * Resets the TV-related properties attached to a connector.
+ */
+void drm_atomic_helper_connector_tv_reset(struct drm_connector *connector)
+{
+	struct drm_cmdline_mode *cmdline = &connector->cmdline_mode;
+	struct drm_connector_state *state = connector->state;
+
+	state->tv.margins.left = cmdline->tv_margins.left;
+	state->tv.margins.right = cmdline->tv_margins.right;
+	state->tv.margins.top = cmdline->tv_margins.top;
+	state->tv.margins.bottom = cmdline->tv_margins.bottom;
+}
+EXPORT_SYMBOL(drm_atomic_helper_connector_tv_reset);
+
+/**
+ * __drm_atomic_helper_connector_duplicate_state - copy atomic connector state
+ * @connector: connector object
+ * @state: atomic connector state
+ *
+ * Copies atomic state from a connector's current state. This is useful for
+ * drivers that subclass the connector state.
+ */
+void
+__drm_atomic_helper_connector_duplicate_state(struct drm_connector *connector,
+					    struct drm_connector_state *state)
+{
+	memcpy(state, connector->state, sizeof(*state));
+	if (state->crtc)
+		drm_connector_get(connector);
+	state->commit = NULL;
+
+	if (state->hdr_output_metadata)
+		drm_property_blob_get(state->hdr_output_metadata);
+
+	/* Don't copy over a writeback job, they are used only once */
+	state->writeback_job = NULL;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_connector_duplicate_state);
+
+/**
+ * drm_atomic_helper_connector_duplicate_state - default state duplicate hook
+ * @connector: drm connector
+ *
+ * Default connector state duplicate hook for drivers which don't have their own
+ * subclassed connector state structure.
+ */
+struct drm_connector_state *
+drm_atomic_helper_connector_duplicate_state(struct drm_connector *connector)
+{
+	struct drm_connector_state *state;
+
+	if (WARN_ON(!connector->state))
+		return NULL;
+
+	state = kmalloc(sizeof(*state), GFP_KERNEL);
+	if (state)
+		__drm_atomic_helper_connector_duplicate_state(connector, state);
+
+	return state;
+}
+EXPORT_SYMBOL(drm_atomic_helper_connector_duplicate_state);
+
+/**
+ * __drm_atomic_helper_connector_destroy_state - release connector state
+ * @state: connector state object to release
+ *
+ * Releases all resources stored in the connector state without actually
+ * freeing the memory of the connector state. This is useful for drivers that
+ * subclass the connector state.
+ */
+void
+__drm_atomic_helper_connector_destroy_state(struct drm_connector_state *state)
+{
+	if (state->crtc)
+		drm_connector_put(state->connector);
+
+	if (state->commit)
+		drm_crtc_commit_put(state->commit);
+
+	if (state->writeback_job)
+		drm_writeback_cleanup_job(state->writeback_job);
+
+	drm_property_blob_put(state->hdr_output_metadata);
+}
+EXPORT_SYMBOL(__drm_atomic_helper_connector_destroy_state);
+
+/**
+ * drm_atomic_helper_connector_destroy_state - default state destroy hook
+ * @connector: drm connector
+ * @state: connector state object to release
+ *
+ * Default connector state destroy hook for drivers which don't have their own
+ * subclassed connector state structure.
+ */
+void drm_atomic_helper_connector_destroy_state(struct drm_connector *connector,
+					  struct drm_connector_state *state)
+{
+	__drm_atomic_helper_connector_destroy_state(state);
+	kfree(state);
+}
+EXPORT_SYMBOL(drm_atomic_helper_connector_destroy_state);
+
+/**
+ * __drm_atomic_helper_private_obj_duplicate_state - copy atomic private state
+ * @obj: CRTC object
+ * @state: new private object state
+ *
+ * Copies atomic state from a private objects's current state and resets inferred values.
+ * This is useful for drivers that subclass the private state.
+ */
+void __drm_atomic_helper_private_obj_duplicate_state(struct drm_private_obj *obj,
+						     struct drm_private_state *state)
+{
+	memcpy(state, obj->state, sizeof(*state));
+}
+EXPORT_SYMBOL(__drm_atomic_helper_private_obj_duplicate_state);
+
+/**
+ * __drm_atomic_helper_bridge_duplicate_state() - Copy atomic bridge state
+ * @bridge: bridge object
+ * @state: atomic bridge state
+ *
+ * Copies atomic state from a bridge's current state and resets inferred values.
+ * This is useful for drivers that subclass the bridge state.
+ */
+void __drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge,
+						struct drm_bridge_state *state)
+{
+	__drm_atomic_helper_private_obj_duplicate_state(&bridge->base,
+							&state->base);
+	state->bridge = bridge;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_bridge_duplicate_state);
+
+/**
+ * drm_atomic_helper_bridge_duplicate_state() - Duplicate a bridge state object
+ * @bridge: bridge object
+ *
+ * Allocates a new bridge state and initializes it with the current bridge
+ * state values. This helper is meant to be used as a bridge
+ * &drm_bridge_funcs.atomic_duplicate_state hook for bridges that don't
+ * subclass the bridge state.
+ */
+struct drm_bridge_state *
+drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge)
+{
+	struct drm_bridge_state *new;
+
+	if (WARN_ON(!bridge->base.state))
+		return NULL;
+
+	new = kzalloc(sizeof(*new), GFP_KERNEL);
+	if (new)
+		__drm_atomic_helper_bridge_duplicate_state(bridge, new);
+
+	return new;
+}
+EXPORT_SYMBOL(drm_atomic_helper_bridge_duplicate_state);
+
+/**
+ * drm_atomic_helper_bridge_destroy_state() - Destroy a bridge state object
+ * @bridge: the bridge this state refers to
+ * @state: bridge state to destroy
+ *
+ * Destroys a bridge state previously created by
+ * &drm_atomic_helper_bridge_reset() or
+ * &drm_atomic_helper_bridge_duplicate_state(). This helper is meant to be
+ * used as a bridge &drm_bridge_funcs.atomic_destroy_state hook for bridges
+ * that don't subclass the bridge state.
+ */
+void drm_atomic_helper_bridge_destroy_state(struct drm_bridge *bridge,
+					    struct drm_bridge_state *state)
+{
+	kfree(state);
+}
+EXPORT_SYMBOL(drm_atomic_helper_bridge_destroy_state);
+
+/**
+ * __drm_atomic_helper_bridge_reset() - Initialize a bridge state to its
+ *					default
+ * @bridge: the bridge this state refers to
+ * @state: bridge state to initialize
+ *
+ * Initializes the bridge state to default values. This is meant to be called
+ * by the bridge &drm_bridge_funcs.atomic_reset hook for bridges that subclass
+ * the bridge state.
+ */
+void __drm_atomic_helper_bridge_reset(struct drm_bridge *bridge,
+				      struct drm_bridge_state *state)
+{
+	memset(state, 0, sizeof(*state));
+	state->bridge = bridge;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_bridge_reset);
+
+/**
+ * drm_atomic_helper_bridge_reset() - Allocate and initialize a bridge state
+ *				      to its default
+ * @bridge: the bridge this state refers to
+ *
+ * Allocates the bridge state and initializes it to default values. This helper
+ * is meant to be used as a bridge &drm_bridge_funcs.atomic_reset hook for
+ * bridges that don't subclass the bridge state.
+ */
+struct drm_bridge_state *
+drm_atomic_helper_bridge_reset(struct drm_bridge *bridge)
+{
+	struct drm_bridge_state *bridge_state;
+
+	bridge_state = kzalloc(sizeof(*bridge_state), GFP_KERNEL);
+	if (!bridge_state)
+		return ERR_PTR(-ENOMEM);
+
+	__drm_atomic_helper_bridge_reset(bridge, bridge_state);
+	return bridge_state;
+}
+EXPORT_SYMBOL(drm_atomic_helper_bridge_reset);