Adding upstream version 5.10.209.upstream/5.10.209upstream

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

1 files changed, 1230 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
new file mode 100644
index 000000000..d799ec14f
--- /dev/null
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -0,0 +1,1230 @@
+/*
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd
+ *
+ * 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, sub license,
+ * 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 (including the
+ * next paragraph) 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 NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS 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.
+ */
+
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+
+#include <drm/drm_atomic_state_helper.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_encoder.h>
+
+#include "drm_crtc_internal.h"
+
+/**
+ * DOC: overview
+ *
+ * &struct drm_bridge represents a device that hangs on to an encoder. These are
+ * handy when a regular &drm_encoder entity isn't enough to represent the entire
+ * encoder chain.
+ *
+ * A bridge is always attached to a single &drm_encoder at a time, but can be
+ * either connected to it directly, or through a chain of bridges::
+ *
+ *     [ CRTC ---> ] Encoder ---> Bridge A ---> Bridge B
+ *
+ * Here, the output of the encoder feeds to bridge A, and that furthers feeds to
+ * bridge B. Bridge chains can be arbitrarily long, and shall be fully linear:
+ * Chaining multiple bridges to the output of a bridge, or the same bridge to
+ * the output of different bridges, is not supported.
+ *
+ * Display drivers are responsible for linking encoders with the first bridge
+ * in the chains. This is done by acquiring the appropriate bridge with
+ * of_drm_find_bridge() or drm_of_find_panel_or_bridge(), or creating it for a
+ * panel with drm_panel_bridge_add_typed() (or the managed version
+ * devm_drm_panel_bridge_add_typed()). Once acquired, the bridge shall be
+ * attached to the encoder with a call to drm_bridge_attach().
+ *
+ * Bridges are responsible for linking themselves with the next bridge in the
+ * chain, if any. This is done the same way as for encoders, with the call to
+ * drm_bridge_attach() occurring in the &drm_bridge_funcs.attach operation.
+ *
+ * Once these links are created, the bridges can participate along with encoder
+ * functions to perform mode validation and fixup (through
+ * drm_bridge_chain_mode_valid() and drm_atomic_bridge_chain_check()), mode
+ * setting (through drm_bridge_chain_mode_set()), enable (through
+ * drm_atomic_bridge_chain_pre_enable() and drm_atomic_bridge_chain_enable())
+ * and disable (through drm_atomic_bridge_chain_disable() and
+ * drm_atomic_bridge_chain_post_disable()). Those functions call the
+ * corresponding operations provided in &drm_bridge_funcs in sequence for all
+ * bridges in the chain.
+ *
+ * For display drivers that use the atomic helpers
+ * drm_atomic_helper_check_modeset(),
+ * drm_atomic_helper_commit_modeset_enables() and
+ * drm_atomic_helper_commit_modeset_disables() (either directly in hand-rolled
+ * commit check and commit tail handlers, or through the higher-level
+ * drm_atomic_helper_check() and drm_atomic_helper_commit_tail() or
+ * drm_atomic_helper_commit_tail_rpm() helpers), this is done transparently and
+ * requires no intervention from the driver. For other drivers, the relevant
+ * DRM bridge chain functions shall be called manually.
+ *
+ * Bridges also participate in implementing the &drm_connector at the end of
+ * the bridge chain. Display drivers may use the drm_bridge_connector_init()
+ * helper to create the &drm_connector, or implement it manually on top of the
+ * connector-related operations exposed by the bridge (see the overview
+ * documentation of bridge operations for more details).
+ *
+ * &drm_bridge, like &drm_panel, aren't &drm_mode_object entities like planes,
+ * CRTCs, encoders or connectors and hence are not visible to userspace. They
+ * just provide additional hooks to get the desired output at the end of the
+ * encoder chain.
+ */
+
+static DEFINE_MUTEX(bridge_lock);
+static LIST_HEAD(bridge_list);
+
+/**
+ * drm_bridge_add - add the given bridge to the global bridge list
+ *
+ * @bridge: bridge control structure
+ */
+void drm_bridge_add(struct drm_bridge *bridge)
+{
+	mutex_init(&bridge->hpd_mutex);
+
+	mutex_lock(&bridge_lock);
+	list_add_tail(&bridge->list, &bridge_list);
+	mutex_unlock(&bridge_lock);
+}
+EXPORT_SYMBOL(drm_bridge_add);
+
+/**
+ * drm_bridge_remove - remove the given bridge from the global bridge list
+ *
+ * @bridge: bridge control structure
+ */
+void drm_bridge_remove(struct drm_bridge *bridge)
+{
+	mutex_lock(&bridge_lock);
+	list_del_init(&bridge->list);
+	mutex_unlock(&bridge_lock);
+
+	mutex_destroy(&bridge->hpd_mutex);
+}
+EXPORT_SYMBOL(drm_bridge_remove);
+
+static struct drm_private_state *
+drm_bridge_atomic_duplicate_priv_state(struct drm_private_obj *obj)
+{
+	struct drm_bridge *bridge = drm_priv_to_bridge(obj);
+	struct drm_bridge_state *state;
+
+	state = bridge->funcs->atomic_duplicate_state(bridge);
+	return state ? &state->base : NULL;
+}
+
+static void
+drm_bridge_atomic_destroy_priv_state(struct drm_private_obj *obj,
+				     struct drm_private_state *s)
+{
+	struct drm_bridge_state *state = drm_priv_to_bridge_state(s);
+	struct drm_bridge *bridge = drm_priv_to_bridge(obj);
+
+	bridge->funcs->atomic_destroy_state(bridge, state);
+}
+
+static const struct drm_private_state_funcs drm_bridge_priv_state_funcs = {
+	.atomic_duplicate_state = drm_bridge_atomic_duplicate_priv_state,
+	.atomic_destroy_state = drm_bridge_atomic_destroy_priv_state,
+};
+
+/**
+ * drm_bridge_attach - attach the bridge to an encoder's chain
+ *
+ * @encoder: DRM encoder
+ * @bridge: bridge to attach
+ * @previous: previous bridge in the chain (optional)
+ * @flags: DRM_BRIDGE_ATTACH_* flags
+ *
+ * Called by a kms driver to link the bridge to an encoder's chain. The previous
+ * argument specifies the previous bridge in the chain. If NULL, the bridge is
+ * linked directly at the encoder's output. Otherwise it is linked at the
+ * previous bridge's output.
+ *
+ * If non-NULL the previous bridge must be already attached by a call to this
+ * function.
+ *
+ * Note that bridges attached to encoders are auto-detached during encoder
+ * cleanup in drm_encoder_cleanup(), so drm_bridge_attach() should generally
+ * *not* be balanced with a drm_bridge_detach() in driver code.
+ *
+ * RETURNS:
+ * Zero on success, error code on failure
+ */
+int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
+		      struct drm_bridge *previous,
+		      enum drm_bridge_attach_flags flags)
+{
+	int ret;
+
+	if (!encoder || !bridge)
+		return -EINVAL;
+
+	if (previous && (!previous->dev || previous->encoder != encoder))
+		return -EINVAL;
+
+	if (bridge->dev)
+		return -EBUSY;
+
+	bridge->dev = encoder->dev;
+	bridge->encoder = encoder;
+
+	if (previous)
+		list_add(&bridge->chain_node, &previous->chain_node);
+	else
+		list_add(&bridge->chain_node, &encoder->bridge_chain);
+
+	if (bridge->funcs->attach) {
+		ret = bridge->funcs->attach(bridge, flags);
+		if (ret < 0)
+			goto err_reset_bridge;
+	}
+
+	if (bridge->funcs->atomic_reset) {
+		struct drm_bridge_state *state;
+
+		state = bridge->funcs->atomic_reset(bridge);
+		if (IS_ERR(state)) {
+			ret = PTR_ERR(state);
+			goto err_detach_bridge;
+		}
+
+		drm_atomic_private_obj_init(bridge->dev, &bridge->base,
+					    &state->base,
+					    &drm_bridge_priv_state_funcs);
+	}
+
+	return 0;
+
+err_detach_bridge:
+	if (bridge->funcs->detach)
+		bridge->funcs->detach(bridge);
+
+err_reset_bridge:
+	bridge->dev = NULL;
+	bridge->encoder = NULL;
+	list_del(&bridge->chain_node);
+	return ret;
+}
+EXPORT_SYMBOL(drm_bridge_attach);
+
+void drm_bridge_detach(struct drm_bridge *bridge)
+{
+	if (WARN_ON(!bridge))
+		return;
+
+	if (WARN_ON(!bridge->dev))
+		return;
+
+	if (bridge->funcs->atomic_reset)
+		drm_atomic_private_obj_fini(&bridge->base);
+
+	if (bridge->funcs->detach)
+		bridge->funcs->detach(bridge);
+
+	list_del(&bridge->chain_node);
+	bridge->dev = NULL;
+}
+
+/**
+ * DOC: bridge operations
+ *
+ * Bridge drivers expose operations through the &drm_bridge_funcs structure.
+ * The DRM internals (atomic and CRTC helpers) use the helpers defined in
+ * drm_bridge.c to call bridge operations. Those operations are divided in
+ * three big categories to support different parts of the bridge usage.
+ *
+ * - The encoder-related operations support control of the bridges in the
+ *   chain, and are roughly counterparts to the &drm_encoder_helper_funcs
+ *   operations. They are used by the legacy CRTC and the atomic modeset
+ *   helpers to perform mode validation, fixup and setting, and enable and
+ *   disable the bridge automatically.
+ *
+ *   The enable and disable operations are split in
+ *   &drm_bridge_funcs.pre_enable, &drm_bridge_funcs.enable,
+ *   &drm_bridge_funcs.disable and &drm_bridge_funcs.post_disable to provide
+ *   finer-grained control.
+ *
+ *   Bridge drivers may implement the legacy version of those operations, or
+ *   the atomic version (prefixed with atomic\_), in which case they shall also
+ *   implement the atomic state bookkeeping operations
+ *   (&drm_bridge_funcs.atomic_duplicate_state,
+ *   &drm_bridge_funcs.atomic_destroy_state and &drm_bridge_funcs.reset).
+ *   Mixing atomic and non-atomic versions of the operations is not supported.
+ *
+ * - The bus format negotiation operations
+ *   &drm_bridge_funcs.atomic_get_output_bus_fmts and
+ *   &drm_bridge_funcs.atomic_get_input_bus_fmts allow bridge drivers to
+ *   negotiate the formats transmitted between bridges in the chain when
+ *   multiple formats are supported. Negotiation for formats is performed
+ *   transparently for display drivers by the atomic modeset helpers. Only
+ *   atomic versions of those operations exist, bridge drivers that need to
+ *   implement them shall thus also implement the atomic version of the
+ *   encoder-related operations. This feature is not supported by the legacy
+ *   CRTC helpers.
+ *
+ * - The connector-related operations support implementing a &drm_connector
+ *   based on a chain of bridges. DRM bridges traditionally create a
+ *   &drm_connector for bridges meant to be used at the end of the chain. This
+ *   puts additional burden on bridge drivers, especially for bridges that may
+ *   be used in the middle of a chain or at the end of it. Furthermore, it
+ *   requires all operations of the &drm_connector to be handled by a single
+ *   bridge, which doesn't always match the hardware architecture.
+ *
+ *   To simplify bridge drivers and make the connector implementation more
+ *   flexible, a new model allows bridges to unconditionally skip creation of
+ *   &drm_connector and instead expose &drm_bridge_funcs operations to support
+ *   an externally-implemented &drm_connector. Those operations are
+ *   &drm_bridge_funcs.detect, &drm_bridge_funcs.get_modes,
+ *   &drm_bridge_funcs.get_edid, &drm_bridge_funcs.hpd_notify,
+ *   &drm_bridge_funcs.hpd_enable and &drm_bridge_funcs.hpd_disable. When
+ *   implemented, display drivers shall create a &drm_connector instance for
+ *   each chain of bridges, and implement those connector instances based on
+ *   the bridge connector operations.
+ *
+ *   Bridge drivers shall implement the connector-related operations for all
+ *   the features that the bridge hardware support. For instance, if a bridge
+ *   supports reading EDID, the &drm_bridge_funcs.get_edid shall be
+ *   implemented. This however doesn't mean that the DDC lines are wired to the
+ *   bridge on a particular platform, as they could also be connected to an I2C
+ *   controller of the SoC. Support for the connector-related operations on the
+ *   running platform is reported through the &drm_bridge.ops flags. Bridge
+ *   drivers shall detect which operations they can support on the platform
+ *   (usually this information is provided by ACPI or DT), and set the
+ *   &drm_bridge.ops flags for all supported operations. A flag shall only be
+ *   set if the corresponding &drm_bridge_funcs operation is implemented, but
+ *   an implemented operation doesn't necessarily imply that the corresponding
+ *   flag will be set. Display drivers shall use the &drm_bridge.ops flags to
+ *   decide which bridge to delegate a connector operation to. This mechanism
+ *   allows providing a single static const &drm_bridge_funcs instance in
+ *   bridge drivers, improving security by storing function pointers in
+ *   read-only memory.
+ *
+ *   In order to ease transition, bridge drivers may support both the old and
+ *   new models by making connector creation optional and implementing the
+ *   connected-related bridge operations. Connector creation is then controlled
+ *   by the flags argument to the drm_bridge_attach() function. Display drivers
+ *   that support the new model and create connectors themselves shall set the
+ *   %DRM_BRIDGE_ATTACH_NO_CONNECTOR flag, and bridge drivers shall then skip
+ *   connector creation. For intermediate bridges in the chain, the flag shall
+ *   be passed to the drm_bridge_attach() call for the downstream bridge.
+ *   Bridge drivers that implement the new model only shall return an error
+ *   from their &drm_bridge_funcs.attach handler when the
+ *   %DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is not set. New display drivers
+ *   should use the new model, and convert the bridge drivers they use if
+ *   needed, in order to gradually transition to the new model.
+ */
+
+/**
+ * drm_bridge_chain_mode_fixup - fixup proposed mode for all bridges in the
+ *				 encoder chain
+ * @bridge: bridge control structure
+ * @mode: desired mode to be set for the bridge
+ * @adjusted_mode: updated mode that works for this bridge
+ *
+ * Calls &drm_bridge_funcs.mode_fixup for all the bridges in the
+ * encoder chain, starting from the first bridge to the last.
+ *
+ * Note: the bridge passed should be the one closest to the encoder
+ *
+ * RETURNS:
+ * true on success, false on failure
+ */
+bool drm_bridge_chain_mode_fixup(struct drm_bridge *bridge,
+				 const struct drm_display_mode *mode,
+				 struct drm_display_mode *adjusted_mode)
+{
+	struct drm_encoder *encoder;
+
+	if (!bridge)
+		return true;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (!bridge->funcs->mode_fixup)
+			continue;
+
+		if (!bridge->funcs->mode_fixup(bridge, mode, adjusted_mode))
+			return false;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(drm_bridge_chain_mode_fixup);
+
+/**
+ * drm_bridge_chain_mode_valid - validate the mode against all bridges in the
+ *				 encoder chain.
+ * @bridge: bridge control structure
+ * @info: display info against which the mode shall be validated
+ * @mode: desired mode to be validated
+ *
+ * Calls &drm_bridge_funcs.mode_valid for all the bridges in the encoder
+ * chain, starting from the first bridge to the last. If at least one bridge
+ * does not accept the mode the function returns the error code.
+ *
+ * Note: the bridge passed should be the one closest to the encoder.
+ *
+ * RETURNS:
+ * MODE_OK on success, drm_mode_status Enum error code on failure
+ */
+enum drm_mode_status
+drm_bridge_chain_mode_valid(struct drm_bridge *bridge,
+			    const struct drm_display_info *info,
+			    const struct drm_display_mode *mode)
+{
+	struct drm_encoder *encoder;
+
+	if (!bridge)
+		return MODE_OK;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		enum drm_mode_status ret;
+
+		if (!bridge->funcs->mode_valid)
+			continue;
+
+		ret = bridge->funcs->mode_valid(bridge, info, mode);
+		if (ret != MODE_OK)
+			return ret;
+	}
+
+	return MODE_OK;
+}
+EXPORT_SYMBOL(drm_bridge_chain_mode_valid);
+
+/**
+ * drm_bridge_chain_disable - disables all bridges in the encoder chain
+ * @bridge: bridge control structure
+ *
+ * Calls &drm_bridge_funcs.disable op for all the bridges in the encoder
+ * chain, starting from the last bridge to the first. These are called before
+ * calling the encoder's prepare op.
+ *
+ * Note: the bridge passed should be the one closest to the encoder
+ */
+void drm_bridge_chain_disable(struct drm_bridge *bridge)
+{
+	struct drm_encoder *encoder;
+	struct drm_bridge *iter;
+
+	if (!bridge)
+		return;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+		if (iter->funcs->disable)
+			iter->funcs->disable(iter);
+
+		if (iter == bridge)
+			break;
+	}
+}
+EXPORT_SYMBOL(drm_bridge_chain_disable);
+
+/**
+ * drm_bridge_chain_post_disable - cleans up after disabling all bridges in the
+ *				   encoder chain
+ * @bridge: bridge control structure
+ *
+ * Calls &drm_bridge_funcs.post_disable op for all the bridges in the
+ * encoder chain, starting from the first bridge to the last. These are called
+ * after completing the encoder's prepare op.
+ *
+ * Note: the bridge passed should be the one closest to the encoder
+ */
+void drm_bridge_chain_post_disable(struct drm_bridge *bridge)
+{
+	struct drm_encoder *encoder;
+
+	if (!bridge)
+		return;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (bridge->funcs->post_disable)
+			bridge->funcs->post_disable(bridge);
+	}
+}
+EXPORT_SYMBOL(drm_bridge_chain_post_disable);
+
+/**
+ * drm_bridge_chain_mode_set - set proposed mode for all bridges in the
+ *			       encoder chain
+ * @bridge: bridge control structure
+ * @mode: desired mode to be set for the encoder chain
+ * @adjusted_mode: updated mode that works for this encoder chain
+ *
+ * Calls &drm_bridge_funcs.mode_set op for all the bridges in the
+ * encoder chain, starting from the first bridge to the last.
+ *
+ * Note: the bridge passed should be the one closest to the encoder
+ */
+void drm_bridge_chain_mode_set(struct drm_bridge *bridge,
+			       const struct drm_display_mode *mode,
+			       const struct drm_display_mode *adjusted_mode)
+{
+	struct drm_encoder *encoder;
+
+	if (!bridge)
+		return;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (bridge->funcs->mode_set)
+			bridge->funcs->mode_set(bridge, mode, adjusted_mode);
+	}
+}
+EXPORT_SYMBOL(drm_bridge_chain_mode_set);
+
+/**
+ * drm_bridge_chain_pre_enable - prepares for enabling all bridges in the
+ *				 encoder chain
+ * @bridge: bridge control structure
+ *
+ * Calls &drm_bridge_funcs.pre_enable op for all the bridges in the encoder
+ * chain, starting from the last bridge to the first. These are called
+ * before calling the encoder's commit op.
+ *
+ * Note: the bridge passed should be the one closest to the encoder
+ */
+void drm_bridge_chain_pre_enable(struct drm_bridge *bridge)
+{
+	struct drm_encoder *encoder;
+	struct drm_bridge *iter;
+
+	if (!bridge)
+		return;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+		if (iter->funcs->pre_enable)
+			iter->funcs->pre_enable(iter);
+
+		if (iter == bridge)
+			break;
+	}
+}
+EXPORT_SYMBOL(drm_bridge_chain_pre_enable);
+
+/**
+ * drm_bridge_chain_enable - enables all bridges in the encoder chain
+ * @bridge: bridge control structure
+ *
+ * Calls &drm_bridge_funcs.enable op for all the bridges in the encoder
+ * chain, starting from the first bridge to the last. These are called
+ * after completing the encoder's commit op.
+ *
+ * Note that the bridge passed should be the one closest to the encoder
+ */
+void drm_bridge_chain_enable(struct drm_bridge *bridge)
+{
+	struct drm_encoder *encoder;
+
+	if (!bridge)
+		return;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (bridge->funcs->enable)
+			bridge->funcs->enable(bridge);
+	}
+}
+EXPORT_SYMBOL(drm_bridge_chain_enable);
+
+/**
+ * drm_atomic_bridge_chain_disable - disables all bridges in the encoder chain
+ * @bridge: bridge control structure
+ * @old_state: old atomic state
+ *
+ * Calls &drm_bridge_funcs.atomic_disable (falls back on
+ * &drm_bridge_funcs.disable) op for all the bridges in the encoder chain,
+ * starting from the last bridge to the first. These are called before calling
+ * &drm_encoder_helper_funcs.atomic_disable
+ *
+ * Note: the bridge passed should be the one closest to the encoder
+ */
+void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge,
+				     struct drm_atomic_state *old_state)
+{
+	struct drm_encoder *encoder;
+	struct drm_bridge *iter;
+
+	if (!bridge)
+		return;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+		if (iter->funcs->atomic_disable) {
+			struct drm_bridge_state *old_bridge_state;
+
+			old_bridge_state =
+				drm_atomic_get_old_bridge_state(old_state,
+								iter);
+			if (WARN_ON(!old_bridge_state))
+				return;
+
+			iter->funcs->atomic_disable(iter, old_bridge_state);
+		} else if (iter->funcs->disable) {
+			iter->funcs->disable(iter);
+		}
+
+		if (iter == bridge)
+			break;
+	}
+}
+EXPORT_SYMBOL(drm_atomic_bridge_chain_disable);
+
+/**
+ * drm_atomic_bridge_chain_post_disable - cleans up after disabling all bridges
+ *					  in the encoder chain
+ * @bridge: bridge control structure
+ * @old_state: old atomic state
+ *
+ * Calls &drm_bridge_funcs.atomic_post_disable (falls back on
+ * &drm_bridge_funcs.post_disable) op for all the bridges in the encoder chain,
+ * starting from the first bridge to the last. These are called after completing
+ * &drm_encoder_helper_funcs.atomic_disable
+ *
+ * Note: the bridge passed should be the one closest to the encoder
+ */
+void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge,
+					  struct drm_atomic_state *old_state)
+{
+	struct drm_encoder *encoder;
+
+	if (!bridge)
+		return;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (bridge->funcs->atomic_post_disable) {
+			struct drm_bridge_state *old_bridge_state;
+
+			old_bridge_state =
+				drm_atomic_get_old_bridge_state(old_state,
+								bridge);
+			if (WARN_ON(!old_bridge_state))
+				return;
+
+			bridge->funcs->atomic_post_disable(bridge,
+							   old_bridge_state);
+		} else if (bridge->funcs->post_disable) {
+			bridge->funcs->post_disable(bridge);
+		}
+	}
+}
+EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);
+
+/**
+ * drm_atomic_bridge_chain_pre_enable - prepares for enabling all bridges in
+ *					the encoder chain
+ * @bridge: bridge control structure
+ * @old_state: old atomic state
+ *
+ * Calls &drm_bridge_funcs.atomic_pre_enable (falls back on
+ * &drm_bridge_funcs.pre_enable) op for all the bridges in the encoder chain,
+ * starting from the last bridge to the first. These are called before calling
+ * &drm_encoder_helper_funcs.atomic_enable
+ *
+ * Note: the bridge passed should be the one closest to the encoder
+ */
+void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge,
+					struct drm_atomic_state *old_state)
+{
+	struct drm_encoder *encoder;
+	struct drm_bridge *iter;
+
+	if (!bridge)
+		return;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+		if (iter->funcs->atomic_pre_enable) {
+			struct drm_bridge_state *old_bridge_state;
+
+			old_bridge_state =
+				drm_atomic_get_old_bridge_state(old_state,
+								iter);
+			if (WARN_ON(!old_bridge_state))
+				return;
+
+			iter->funcs->atomic_pre_enable(iter, old_bridge_state);
+		} else if (iter->funcs->pre_enable) {
+			iter->funcs->pre_enable(iter);
+		}
+
+		if (iter == bridge)
+			break;
+	}
+}
+EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable);
+
+/**
+ * drm_atomic_bridge_chain_enable - enables all bridges in the encoder chain
+ * @bridge: bridge control structure
+ * @old_state: old atomic state
+ *
+ * Calls &drm_bridge_funcs.atomic_enable (falls back on
+ * &drm_bridge_funcs.enable) op for all the bridges in the encoder chain,
+ * starting from the first bridge to the last. These are called after completing
+ * &drm_encoder_helper_funcs.atomic_enable
+ *
+ * Note: the bridge passed should be the one closest to the encoder
+ */
+void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
+				    struct drm_atomic_state *old_state)
+{
+	struct drm_encoder *encoder;
+
+	if (!bridge)
+		return;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
+		if (bridge->funcs->atomic_enable) {
+			struct drm_bridge_state *old_bridge_state;
+
+			old_bridge_state =
+				drm_atomic_get_old_bridge_state(old_state,
+								bridge);
+			if (WARN_ON(!old_bridge_state))
+				return;
+
+			bridge->funcs->atomic_enable(bridge, old_bridge_state);
+		} else if (bridge->funcs->enable) {
+			bridge->funcs->enable(bridge);
+		}
+	}
+}
+EXPORT_SYMBOL(drm_atomic_bridge_chain_enable);
+
+static int drm_atomic_bridge_check(struct drm_bridge *bridge,
+				   struct drm_crtc_state *crtc_state,
+				   struct drm_connector_state *conn_state)
+{
+	if (bridge->funcs->atomic_check) {
+		struct drm_bridge_state *bridge_state;
+		int ret;
+
+		bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
+							       bridge);
+		if (WARN_ON(!bridge_state))
+			return -EINVAL;
+
+		ret = bridge->funcs->atomic_check(bridge, bridge_state,
+						  crtc_state, conn_state);
+		if (ret)
+			return ret;
+	} else if (bridge->funcs->mode_fixup) {
+		if (!bridge->funcs->mode_fixup(bridge, &crtc_state->mode,
+					       &crtc_state->adjusted_mode))
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int select_bus_fmt_recursive(struct drm_bridge *first_bridge,
+				    struct drm_bridge *cur_bridge,
+				    struct drm_crtc_state *crtc_state,
+				    struct drm_connector_state *conn_state,
+				    u32 out_bus_fmt)
+{
+	unsigned int i, num_in_bus_fmts = 0;
+	struct drm_bridge_state *cur_state;
+	struct drm_bridge *prev_bridge;
+	u32 *in_bus_fmts;
+	int ret;
+
+	prev_bridge = drm_bridge_get_prev_bridge(cur_bridge);
+	cur_state = drm_atomic_get_new_bridge_state(crtc_state->state,
+						    cur_bridge);
+
+	/*
+	 * If bus format negotiation is not supported by this bridge, let's
+	 * pass MEDIA_BUS_FMT_FIXED to the previous bridge in the chain and
+	 * hope that it can handle this situation gracefully (by providing
+	 * appropriate default values).
+	 */
+	if (!cur_bridge->funcs->atomic_get_input_bus_fmts) {
+		if (cur_bridge != first_bridge) {
+			ret = select_bus_fmt_recursive(first_bridge,
+						       prev_bridge, crtc_state,
+						       conn_state,
+						       MEDIA_BUS_FMT_FIXED);
+			if (ret)
+				return ret;
+		}
+
+		/*
+		 * Driver does not implement the atomic state hooks, but that's
+		 * fine, as long as it does not access the bridge state.
+		 */
+		if (cur_state) {
+			cur_state->input_bus_cfg.format = MEDIA_BUS_FMT_FIXED;
+			cur_state->output_bus_cfg.format = out_bus_fmt;
+		}
+
+		return 0;
+	}
+
+	/*
+	 * If the driver implements ->atomic_get_input_bus_fmts() it
+	 * should also implement the atomic state hooks.
+	 */
+	if (WARN_ON(!cur_state))
+		return -EINVAL;
+
+	in_bus_fmts = cur_bridge->funcs->atomic_get_input_bus_fmts(cur_bridge,
+							cur_state,
+							crtc_state,
+							conn_state,
+							out_bus_fmt,
+							&num_in_bus_fmts);
+	if (!num_in_bus_fmts)
+		return -ENOTSUPP;
+	else if (!in_bus_fmts)
+		return -ENOMEM;
+
+	if (first_bridge == cur_bridge) {
+		cur_state->input_bus_cfg.format = in_bus_fmts[0];
+		cur_state->output_bus_cfg.format = out_bus_fmt;
+		kfree(in_bus_fmts);
+		return 0;
+	}
+
+	for (i = 0; i < num_in_bus_fmts; i++) {
+		ret = select_bus_fmt_recursive(first_bridge, prev_bridge,
+					       crtc_state, conn_state,
+					       in_bus_fmts[i]);
+		if (ret != -ENOTSUPP)
+			break;
+	}
+
+	if (!ret) {
+		cur_state->input_bus_cfg.format = in_bus_fmts[i];
+		cur_state->output_bus_cfg.format = out_bus_fmt;
+	}
+
+	kfree(in_bus_fmts);
+	return ret;
+}
+
+/*
+ * This function is called by &drm_atomic_bridge_chain_check() just before
+ * calling &drm_bridge_funcs.atomic_check() on all elements of the chain.
+ * It performs bus format negotiation between bridge elements. The negotiation
+ * happens in reverse order, starting from the last element in the chain up to
+ * @bridge.
+ *
+ * Negotiation starts by retrieving supported output bus formats on the last
+ * bridge element and testing them one by one. The test is recursive, meaning
+ * that for each tested output format, the whole chain will be walked backward,
+ * and each element will have to choose an input bus format that can be
+ * transcoded to the requested output format. When a bridge element does not
+ * support transcoding into a specific output format -ENOTSUPP is returned and
+ * the next bridge element will have to try a different format. If none of the
+ * combinations worked, -ENOTSUPP is returned and the atomic modeset will fail.
+ *
+ * This implementation is relying on
+ * &drm_bridge_funcs.atomic_get_output_bus_fmts() and
+ * &drm_bridge_funcs.atomic_get_input_bus_fmts() to gather supported
+ * input/output formats.
+ *
+ * When &drm_bridge_funcs.atomic_get_output_bus_fmts() is not implemented by
+ * the last element of the chain, &drm_atomic_bridge_chain_select_bus_fmts()
+ * tries a single format: &drm_connector.display_info.bus_formats[0] if
+ * available, MEDIA_BUS_FMT_FIXED otherwise.
+ *
+ * When &drm_bridge_funcs.atomic_get_input_bus_fmts() is not implemented,
+ * &drm_atomic_bridge_chain_select_bus_fmts() skips the negotiation on the
+ * bridge element that lacks this hook and asks the previous element in the
+ * chain to try MEDIA_BUS_FMT_FIXED. It's up to bridge drivers to decide what
+ * to do in that case (fail if they want to enforce bus format negotiation, or
+ * provide a reasonable default if they need to support pipelines where not
+ * all elements support bus format negotiation).
+ */
+static int
+drm_atomic_bridge_chain_select_bus_fmts(struct drm_bridge *bridge,
+					struct drm_crtc_state *crtc_state,
+					struct drm_connector_state *conn_state)
+{
+	struct drm_connector *conn = conn_state->connector;
+	struct drm_encoder *encoder = bridge->encoder;
+	struct drm_bridge_state *last_bridge_state;
+	unsigned int i, num_out_bus_fmts = 0;
+	struct drm_bridge *last_bridge;
+	u32 *out_bus_fmts;
+	int ret = 0;
+
+	last_bridge = list_last_entry(&encoder->bridge_chain,
+				      struct drm_bridge, chain_node);
+	last_bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
+							    last_bridge);
+
+	if (last_bridge->funcs->atomic_get_output_bus_fmts) {
+		const struct drm_bridge_funcs *funcs = last_bridge->funcs;
+
+		/*
+		 * If the driver implements ->atomic_get_output_bus_fmts() it
+		 * should also implement the atomic state hooks.
+		 */
+		if (WARN_ON(!last_bridge_state))
+			return -EINVAL;
+
+		out_bus_fmts = funcs->atomic_get_output_bus_fmts(last_bridge,
+							last_bridge_state,
+							crtc_state,
+							conn_state,
+							&num_out_bus_fmts);
+		if (!num_out_bus_fmts)
+			return -ENOTSUPP;
+		else if (!out_bus_fmts)
+			return -ENOMEM;
+	} else {
+		num_out_bus_fmts = 1;
+		out_bus_fmts = kmalloc(sizeof(*out_bus_fmts), GFP_KERNEL);
+		if (!out_bus_fmts)
+			return -ENOMEM;
+
+		if (conn->display_info.num_bus_formats &&
+		    conn->display_info.bus_formats)
+			out_bus_fmts[0] = conn->display_info.bus_formats[0];
+		else
+			out_bus_fmts[0] = MEDIA_BUS_FMT_FIXED;
+	}
+
+	for (i = 0; i < num_out_bus_fmts; i++) {
+		ret = select_bus_fmt_recursive(bridge, last_bridge, crtc_state,
+					       conn_state, out_bus_fmts[i]);
+		if (ret != -ENOTSUPP)
+			break;
+	}
+
+	kfree(out_bus_fmts);
+
+	return ret;
+}
+
+static void
+drm_atomic_bridge_propagate_bus_flags(struct drm_bridge *bridge,
+				      struct drm_connector *conn,
+				      struct drm_atomic_state *state)
+{
+	struct drm_bridge_state *bridge_state, *next_bridge_state;
+	struct drm_bridge *next_bridge;
+	u32 output_flags = 0;
+
+	bridge_state = drm_atomic_get_new_bridge_state(state, bridge);
+
+	/* No bridge state attached to this bridge => nothing to propagate. */
+	if (!bridge_state)
+		return;
+
+	next_bridge = drm_bridge_get_next_bridge(bridge);
+
+	/*
+	 * Let's try to apply the most common case here, that is, propagate
+	 * display_info flags for the last bridge, and propagate the input
+	 * flags of the next bridge element to the output end of the current
+	 * bridge when the bridge is not the last one.
+	 * There are exceptions to this rule, like when signal inversion is
+	 * happening at the board level, but that's something drivers can deal
+	 * with from their &drm_bridge_funcs.atomic_check() implementation by
+	 * simply overriding the flags value we've set here.
+	 */
+	if (!next_bridge) {
+		output_flags = conn->display_info.bus_flags;
+	} else {
+		next_bridge_state = drm_atomic_get_new_bridge_state(state,
+								next_bridge);
+		/*
+		 * No bridge state attached to the next bridge, just leave the
+		 * flags to 0.
+		 */
+		if (next_bridge_state)
+			output_flags = next_bridge_state->input_bus_cfg.flags;
+	}
+
+	bridge_state->output_bus_cfg.flags = output_flags;
+
+	/*
+	 * Propage the output flags to the input end of the bridge. Again, it's
+	 * not necessarily what all bridges want, but that's what most of them
+	 * do, and by doing that by default we avoid forcing drivers to
+	 * duplicate the "dummy propagation" logic.
+	 */
+	bridge_state->input_bus_cfg.flags = output_flags;
+}
+
+/**
+ * drm_atomic_bridge_chain_check() - Do an atomic check on the bridge chain
+ * @bridge: bridge control structure
+ * @crtc_state: new CRTC state
+ * @conn_state: new connector state
+ *
+ * First trigger a bus format negotiation before calling
+ * &drm_bridge_funcs.atomic_check() (falls back on
+ * &drm_bridge_funcs.mode_fixup()) op for all the bridges in the encoder chain,
+ * starting from the last bridge to the first. These are called before calling
+ * &drm_encoder_helper_funcs.atomic_check()
+ *
+ * RETURNS:
+ * 0 on success, a negative error code on failure
+ */
+int drm_atomic_bridge_chain_check(struct drm_bridge *bridge,
+				  struct drm_crtc_state *crtc_state,
+				  struct drm_connector_state *conn_state)
+{
+	struct drm_connector *conn = conn_state->connector;
+	struct drm_encoder *encoder;
+	struct drm_bridge *iter;
+	int ret;
+
+	if (!bridge)
+		return 0;
+
+	ret = drm_atomic_bridge_chain_select_bus_fmts(bridge, crtc_state,
+						      conn_state);
+	if (ret)
+		return ret;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+		int ret;
+
+		/*
+		 * Bus flags are propagated by default. If a bridge needs to
+		 * tweak the input bus flags for any reason, it should happen
+		 * in its &drm_bridge_funcs.atomic_check() implementation such
+		 * that preceding bridges in the chain can propagate the new
+		 * bus flags.
+		 */
+		drm_atomic_bridge_propagate_bus_flags(iter, conn,
+						      crtc_state->state);
+
+		ret = drm_atomic_bridge_check(iter, crtc_state, conn_state);
+		if (ret)
+			return ret;
+
+		if (iter == bridge)
+			break;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_atomic_bridge_chain_check);
+
+/**
+ * drm_bridge_detect - check if anything is attached to the bridge output
+ * @bridge: bridge control structure
+ *
+ * If the bridge supports output detection, as reported by the
+ * DRM_BRIDGE_OP_DETECT bridge ops flag, call &drm_bridge_funcs.detect for the
+ * bridge and return the connection status. Otherwise return
+ * connector_status_unknown.
+ *
+ * RETURNS:
+ * The detection status on success, or connector_status_unknown if the bridge
+ * doesn't support output detection.
+ */
+enum drm_connector_status drm_bridge_detect(struct drm_bridge *bridge)
+{
+	if (!(bridge->ops & DRM_BRIDGE_OP_DETECT))
+		return connector_status_unknown;
+
+	return bridge->funcs->detect(bridge);
+}
+EXPORT_SYMBOL_GPL(drm_bridge_detect);
+
+/**
+ * drm_bridge_get_modes - fill all modes currently valid for the sink into the
+ * @connector
+ * @bridge: bridge control structure
+ * @connector: the connector to fill with modes
+ *
+ * If the bridge supports output modes retrieval, as reported by the
+ * DRM_BRIDGE_OP_MODES bridge ops flag, call &drm_bridge_funcs.get_modes to
+ * fill the connector with all valid modes and return the number of modes
+ * added. Otherwise return 0.
+ *
+ * RETURNS:
+ * The number of modes added to the connector.
+ */
+int drm_bridge_get_modes(struct drm_bridge *bridge,
+			 struct drm_connector *connector)
+{
+	if (!(bridge->ops & DRM_BRIDGE_OP_MODES))
+		return 0;
+
+	return bridge->funcs->get_modes(bridge, connector);
+}
+EXPORT_SYMBOL_GPL(drm_bridge_get_modes);
+
+/**
+ * drm_bridge_get_edid - get the EDID data of the connected display
+ * @bridge: bridge control structure
+ * @connector: the connector to read EDID for
+ *
+ * If the bridge supports output EDID retrieval, as reported by the
+ * DRM_BRIDGE_OP_EDID bridge ops flag, call &drm_bridge_funcs.get_edid to
+ * get the EDID and return it. Otherwise return NULL.
+ *
+ * RETURNS:
+ * The retrieved EDID on success, or NULL otherwise.
+ */
+struct edid *drm_bridge_get_edid(struct drm_bridge *bridge,
+				 struct drm_connector *connector)
+{
+	if (!(bridge->ops & DRM_BRIDGE_OP_EDID))
+		return NULL;
+
+	return bridge->funcs->get_edid(bridge, connector);
+}
+EXPORT_SYMBOL_GPL(drm_bridge_get_edid);
+
+/**
+ * drm_bridge_hpd_enable - enable hot plug detection for the bridge
+ * @bridge: bridge control structure
+ * @cb: hot-plug detection callback
+ * @data: data to be passed to the hot-plug detection callback
+ *
+ * Call &drm_bridge_funcs.hpd_enable if implemented and register the given @cb
+ * and @data as hot plug notification callback. From now on the @cb will be
+ * called with @data when an output status change is detected by the bridge,
+ * until hot plug notification gets disabled with drm_bridge_hpd_disable().
+ *
+ * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
+ * bridge->ops. This function shall not be called when the flag is not set.
+ *
+ * Only one hot plug detection callback can be registered at a time, it is an
+ * error to call this function when hot plug detection is already enabled for
+ * the bridge.
+ */
+void drm_bridge_hpd_enable(struct drm_bridge *bridge,
+			   void (*cb)(void *data,
+				      enum drm_connector_status status),
+			   void *data)
+{
+	if (!(bridge->ops & DRM_BRIDGE_OP_HPD))
+		return;
+
+	mutex_lock(&bridge->hpd_mutex);
+
+	if (WARN(bridge->hpd_cb, "Hot plug detection already enabled\n"))
+		goto unlock;
+
+	bridge->hpd_cb = cb;
+	bridge->hpd_data = data;
+
+	if (bridge->funcs->hpd_enable)
+		bridge->funcs->hpd_enable(bridge);
+
+unlock:
+	mutex_unlock(&bridge->hpd_mutex);
+}
+EXPORT_SYMBOL_GPL(drm_bridge_hpd_enable);
+
+/**
+ * drm_bridge_hpd_disable - disable hot plug detection for the bridge
+ * @bridge: bridge control structure
+ *
+ * Call &drm_bridge_funcs.hpd_disable if implemented and unregister the hot
+ * plug detection callback previously registered with drm_bridge_hpd_enable().
+ * Once this function returns the callback will not be called by the bridge
+ * when an output status change occurs.
+ *
+ * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
+ * bridge->ops. This function shall not be called when the flag is not set.
+ */
+void drm_bridge_hpd_disable(struct drm_bridge *bridge)
+{
+	if (!(bridge->ops & DRM_BRIDGE_OP_HPD))
+		return;
+
+	mutex_lock(&bridge->hpd_mutex);
+	if (bridge->funcs->hpd_disable)
+		bridge->funcs->hpd_disable(bridge);
+
+	bridge->hpd_cb = NULL;
+	bridge->hpd_data = NULL;
+	mutex_unlock(&bridge->hpd_mutex);
+}
+EXPORT_SYMBOL_GPL(drm_bridge_hpd_disable);
+
+/**
+ * drm_bridge_hpd_notify - notify hot plug detection events
+ * @bridge: bridge control structure
+ * @status: output connection status
+ *
+ * Bridge drivers shall call this function to report hot plug events when they
+ * detect a change in the output status, when hot plug detection has been
+ * enabled by drm_bridge_hpd_enable().
+ *
+ * This function shall be called in a context that can sleep.
+ */
+void drm_bridge_hpd_notify(struct drm_bridge *bridge,
+			   enum drm_connector_status status)
+{
+	mutex_lock(&bridge->hpd_mutex);
+	if (bridge->hpd_cb)
+		bridge->hpd_cb(bridge->hpd_data, status);
+	mutex_unlock(&bridge->hpd_mutex);
+}
+EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify);
+
+#ifdef CONFIG_OF
+/**
+ * of_drm_find_bridge - find the bridge corresponding to the device node in
+ *			the global bridge list
+ *
+ * @np: device node
+ *
+ * RETURNS:
+ * drm_bridge control struct on success, NULL on failure
+ */
+struct drm_bridge *of_drm_find_bridge(struct device_node *np)
+{
+	struct drm_bridge *bridge;
+
+	mutex_lock(&bridge_lock);
+
+	list_for_each_entry(bridge, &bridge_list, list) {
+		if (bridge->of_node == np) {
+			mutex_unlock(&bridge_lock);
+			return bridge;
+		}
+	}
+
+	mutex_unlock(&bridge_lock);
+	return NULL;
+}
+EXPORT_SYMBOL(of_drm_find_bridge);
+#endif
+
+MODULE_AUTHOR("Ajay Kumar <ajaykumar.rs@samsung.com>");
+MODULE_DESCRIPTION("DRM bridge infrastructure");
+MODULE_LICENSE("GPL and additional rights");