[PATCH v2 17/28] drm/atomic_sro: Provide helpers to implement hardware state readout

[Maxime Ripard <mripard@kernel.org>]

Drivers implementing SRO need to iterate over their KMS objects,
allocate a pristine state for each, call the readout hook, and store
the result in the SRO state container.

Provide helpers for each object type
(drm_atomic_helper_sro_readout_planes_state(),
drm_atomic_helper_sro_readout_crtcs_state(), etc.) and a top-level
drm_atomic_helper_sro_build_state() that calls them in sequence.

Also provide default implementations for the atomic_sro_compare_state
hooks: drm_atomic_helper_plane_compare_state(),
drm_atomic_helper_crtc_compare_state(),
drm_atomic_helper_connector_compare_state(), and
drm_atomic_helper_bridge_compare_state(). These compare the base
state fields and report mismatches through a drm_printer.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
 drivers/gpu/drm/Makefile                |   1 +
 drivers/gpu/drm/drm_atomic_sro_helper.c | 407 ++++++++++++++++++++++++++++++++
 include/drm/drm_atomic_sro_helper.h     |  28 +++
 3 files changed, 436 insertions(+)

diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 64705ac96bd1..082721f1453c 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -140,10 +140,11 @@ obj-$(CONFIG_DRM_TTM_HELPER) += drm_ttm_helper.o
 # Modesetting helpers
 #
 
 drm_kms_helper-y := \
 	drm_atomic_helper.o \
+	drm_atomic_sro_helper.o \
 	drm_atomic_state_helper.o \
 	drm_bridge_helper.o \
 	drm_crtc_helper.o \
 	drm_damage_helper.o \
 	drm_flip_work.o \
diff --git a/drivers/gpu/drm/drm_atomic_sro_helper.c b/drivers/gpu/drm/drm_atomic_sro_helper.c
new file mode 100644
index 000000000000..367d9bb7e442
--- /dev/null
+++ b/drivers/gpu/drm/drm_atomic_sro_helper.c
@@ -0,0 +1,407 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <drm/drm_atomic.h>
+#include <drm/drm_atomic_sro.h>
+#include <drm/drm_atomic_sro_helper.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_connector.h>
+#include <drm/drm_crtc.h>
+#include <drm/drm_encoder.h>
+#include <drm/drm_modeset_helper_vtables.h>
+#include <drm/drm_plane.h>
+#include <drm/drm_print.h>
+
+#include <linux/gfp.h>
+#include <linux/sched/mm.h>
+
+/**
+ * drm_atomic_helper_sro_readout_planes_state - read out all plane states from hardware
+ * @dev: DRM device
+ * @state: SRO state container to fill
+ *
+ * Iterates over all planes, allocates a state for each via
+ * atomic_create_state, and calls the plane's
+ * atomic_sro_readout_state hook to fill it from hardware.
+ *
+ * RETURNS:
+ *
+ * 0 on success, a negative error code otherwise.
+ */
+int
+drm_atomic_helper_sro_readout_planes_state(struct drm_device *dev,
+					   struct drm_atomic_sro_state *state)
+{
+	struct drm_plane *plane;
+
+	might_alloc(GFP_KERNEL);
+
+	drm_for_each_plane(plane, dev) {
+		const struct drm_plane_funcs *plane_funcs = plane->funcs;
+		struct drm_plane_state *plane_state;
+		int ret;
+
+		if (!plane_funcs->atomic_sro_readout_state) {
+			drm_warn(dev, "No plane readout implementation.");
+			continue;
+		}
+
+		drm_dbg_kms(dev, "Initializing Plane %s state.\n", plane->name);
+
+		plane_state = plane_funcs->atomic_create_state(plane);
+		if (drm_WARN_ON(dev, IS_ERR(plane_state)))
+			return 0;
+
+		ret = plane_funcs->atomic_sro_readout_state(plane, state,
+							    plane_state);
+		if (drm_WARN_ON(dev, ret)) {
+			plane_funcs->atomic_destroy_state(plane, plane_state);
+			return ret;
+		}
+
+		drm_atomic_sro_set_plane_state(state, plane, plane_state);
+	}
+
+	return 0;
+}
+
+/**
+ * drm_atomic_helper_sro_readout_crtcs_state - read out all CRTC states from hardware
+ * @dev: DRM device
+ * @state: SRO state container to fill
+ *
+ * Iterates over all CRTCs, allocates a state for each via
+ * atomic_create_state, and calls the CRTC's
+ * atomic_sro_readout_state hook to fill it from hardware.
+ *
+ * RETURNS:
+ *
+ * 0 on success, a negative error code otherwise.
+ */
+int
+drm_atomic_helper_sro_readout_crtcs_state(struct drm_device *dev,
+					  struct drm_atomic_sro_state *state)
+{
+	struct drm_crtc *crtc;
+
+	might_alloc(GFP_KERNEL);
+
+	drm_for_each_crtc(crtc, dev) {
+		const struct drm_crtc_funcs *crtc_funcs = crtc->funcs;
+		struct drm_crtc_state *crtc_state;
+		int ret;
+
+		if (!crtc_funcs->atomic_sro_readout_state) {
+			drm_warn(dev, "No CRTC readout implementation.");
+			continue;
+		}
+
+		drm_dbg_kms(dev, "Initializing CRTC %s state.\n", crtc->name);
+
+		crtc_state = crtc_funcs->atomic_create_state(crtc);
+		if (drm_WARN_ON(dev, IS_ERR(crtc_state)))
+			return PTR_ERR(crtc_state);
+
+		ret = crtc_funcs->atomic_sro_readout_state(crtc, state,
+							   crtc_state);
+		if (drm_WARN_ON(dev, ret)) {
+			crtc_funcs->atomic_destroy_state(crtc, crtc_state);
+			return ret;
+		}
+
+		drm_atomic_sro_set_crtc_state(state, crtc, crtc_state);
+	}
+
+	return 0;
+}
+
+/**
+ * drm_atomic_helper_sro_readout_connectors_state - read out all connector states from hardware
+ * @dev: DRM device
+ * @state: SRO state container to fill
+ *
+ * Iterates over all connectors, allocates a state for each via
+ * atomic_create_state, and calls the connector's
+ * atomic_sro_readout_state hook to fill it from hardware.
+ *
+ * RETURNS:
+ *
+ * 0 on success, a negative error code otherwise.
+ */
+int
+drm_atomic_helper_sro_readout_connectors_state(struct drm_device *dev,
+					       struct drm_atomic_sro_state *state)
+{
+	struct drm_connector_list_iter conn_iter;
+	struct drm_connector *connector;
+
+	might_alloc(GFP_KERNEL);
+
+	drm_connector_list_iter_begin(dev, &conn_iter);
+	drm_for_each_connector_iter(connector, &conn_iter) {
+		const struct drm_connector_funcs *conn_funcs = connector->funcs;
+		struct drm_connector_state *conn_state;
+		int ret;
+
+		if (!conn_funcs->atomic_sro_readout_state) {
+			drm_warn(dev, "No Connector readout implementation.");
+			continue;
+		}
+
+		drm_dbg_kms(dev, "Initializing Connector %s state.\n", connector->name);
+
+		conn_state = conn_funcs->atomic_create_state(connector);
+		if (drm_WARN_ON(dev, IS_ERR(conn_state)))
+			return PTR_ERR(conn_state);
+
+		ret = conn_funcs->atomic_sro_readout_state(connector, state,
+							   conn_state);
+		if (drm_WARN_ON(dev, ret)) {
+			conn_funcs->atomic_destroy_state(connector, conn_state);
+			return ret;
+		}
+
+		drm_atomic_sro_set_connector_state(state, connector, conn_state);
+	}
+	drm_connector_list_iter_end(&conn_iter);
+
+
+	return 0;
+}
+
+/**
+ * drm_atomic_helper_sro_readout_bridges_state - read out all bridge states from hardware
+ * @dev: DRM device
+ * @state: SRO state container to fill
+ *
+ * Iterates over all encoders and their bridge chains, allocates a state
+ * for each bridge via atomic_create_state, and calls the bridge's
+ * atomic_sro_readout_state hook to fill it from hardware.
+ *
+ * Bridges are handled separately from other private objects because
+ * bridge registration does not guarantee ordering. Traversing the
+ * encoder bridge chains ensures each bridge can query the state of
+ * preceding bridges in its chain.
+ *
+ * RETURNS:
+ *
+ * 0 on success, a negative error code otherwise.
+ */
+int
+drm_atomic_helper_sro_readout_bridges_state(struct drm_device *dev,
+					    struct drm_atomic_sro_state *state)
+{
+	struct drm_encoder *encoder;
+
+	might_alloc(GFP_KERNEL);
+
+	/*
+	 * It works a bit differently for bridges. Indeed they rely on a
+	 * drm_private_obj and drm_private_state, but bridge
+	 * registration doesn't guarantee ordering.
+	 *
+	 * In order for each bridge callback to be able to query the
+	 * previous bridge state, we thus need to read out the bridge
+	 * state by looking at each encoder and then traversing its
+	 * bridge list.
+	 *
+	 * And we'll then readout all the non-bridge drm_private_obj
+	 * later.
+	 */
+	drm_for_each_encoder(encoder, dev) {
+		struct drm_bridge *bridge;
+		int ret;
+
+		list_for_each_entry(bridge, &encoder->bridge_chain, chain_node) {
+			struct drm_private_obj *bridge_obj = &bridge->base;
+			const struct drm_private_state_funcs *bridge_obj_funcs =
+				bridge_obj->funcs;
+			struct drm_private_state *bridge_obj_state;
+
+			if (!bridge_obj_funcs->atomic_sro_readout_state) {
+				drm_warn(dev,
+					 "No bridge %s readout implementation.",
+					 bridge->name);
+				continue;
+			}
+
+			drm_dbg_kms(dev, "Initializing Bridge %s", bridge->name);
+
+			bridge_obj_state =
+				bridge_obj_funcs->atomic_create_state(
+					bridge_obj);
+			if (drm_WARN_ON(dev, IS_ERR(bridge_obj_state)))
+				return ret;
+
+			ret = bridge_obj_funcs->atomic_sro_readout_state(
+				bridge_obj, state, bridge_obj_state);
+			if (drm_WARN_ON(dev, ret)) {
+				bridge_obj_funcs->atomic_destroy_state(
+					bridge_obj, bridge_obj_state);
+				return ret;
+			}
+
+			drm_atomic_sro_set_private_obj_state(state, bridge_obj,
+							     bridge_obj_state);
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * drm_atomic_helper_sro_readout_private_objs_state - read out non-bridge private object states
+ * @dev: DRM device
+ * @state: SRO state container to fill
+ *
+ * Iterates over all private objects that are not bridges (bridges are
+ * handled by drm_atomic_helper_sro_readout_bridges_state()), allocates
+ * a state for each via atomic_create_state, and calls the object's
+ * atomic_sro_readout_state hook to fill it from hardware.
+ *
+ * RETURNS:
+ *
+ * 0 on success, a negative error code otherwise.
+ */
+int
+drm_atomic_helper_sro_readout_private_objs_state(struct drm_device *dev,
+						 struct drm_atomic_sro_state *state)
+{
+	struct drm_private_obj *privobj;
+
+	might_alloc(GFP_KERNEL);
+
+	drm_for_each_privobj(privobj, dev) {
+		const struct drm_private_state_funcs *priv_funcs =
+			privobj->funcs;
+		struct drm_private_state *priv_state;
+		int ret;
+
+		/*
+		 * We already accounted readout the bridge state earlier, we only
+		 * have to deal with !bridges drm_private_obj now.
+		 */
+		if (drm_private_obj_is_bridge(privobj))
+			continue;
+
+		if (!priv_funcs->atomic_sro_readout_state) {
+			drm_warn(dev,
+				 "No private object %s readout implementation.",
+				 privobj->name);
+			continue;
+		}
+
+		drm_dbg_kms(dev, "Initializing Private Object %s",
+			    privobj->name);
+
+		priv_state = priv_funcs->atomic_create_state(privobj);
+		if (drm_WARN_ON(dev, IS_ERR(priv_state)))
+			return PTR_ERR(priv_state);
+
+		ret = priv_funcs->atomic_sro_readout_state(privobj, state,
+							   priv_state);
+		if (drm_WARN_ON(dev, ret)) {
+			priv_funcs->atomic_destroy_state(privobj, priv_state);
+			return ret;
+		}
+
+		drm_atomic_sro_set_private_obj_state(state, privobj,
+						     priv_state);
+	}
+
+	return 0;
+}
+
+/**
+ * drm_atomic_helper_sro_build_state - build an SRO state from hardware
+ * @dev: DRM device to build the state for
+ *
+ * Allocates a &struct drm_atomic_sro_state and calls the readout hooks
+ * for CRTCs, planes, connectors, bridges, and private objects in
+ * sequence to fill it from the current hardware state.
+ *
+ * This is the default implementation for
+ * &drm_mode_config_helper_funcs.atomic_sro_build_state.
+ *
+ * RETURNS:
+ *
+ * A &struct drm_atomic_sro_state on success, an error pointer otherwise.
+ */
+struct drm_atomic_sro_state *
+drm_atomic_helper_sro_build_state(struct drm_device *dev)
+{
+	struct drm_atomic_sro_state *state;
+	struct drm_printer p = drm_dbg_printer(dev, DRM_UT_ATOMIC, NULL);
+	int ret;
+
+	drm_dbg_kms(dev, "Starting to build atomic state from hardware state.\n");
+
+	state = drm_atomic_sro_state_alloc(dev);
+	if (drm_WARN_ON(dev, !state))
+		return ERR_PTR(-ENOMEM);
+
+	ret = drm_atomic_helper_sro_readout_crtcs_state(dev, state);
+	if (ret)
+		goto err_state_free;
+
+	ret = drm_atomic_helper_sro_readout_planes_state(dev, state);
+	if (ret)
+		goto err_state_free;
+
+	ret = drm_atomic_helper_sro_readout_connectors_state(dev, state);
+	if (ret)
+		goto err_state_free;
+
+	ret = drm_atomic_helper_sro_readout_bridges_state(dev, state);
+	if (ret)
+		goto err_state_free;
+
+	ret = drm_atomic_helper_sro_readout_private_objs_state(dev, state);
+	if (ret)
+		goto err_state_free;
+
+	drm_atomic_sro_state_print(state, &p);
+
+	return state;
+
+err_state_free:
+	drm_atomic_sro_state_free(state);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(drm_atomic_helper_sro_build_state);
+
+/**
+ * drm_atomic_helper_sro_readout_state - default &drm_mode_config_funcs.atomic_sro_readout_state implementation
+ * @dev: DRM device to read out state for
+ *
+ * Checks if the device supports hardware state readout, builds the SRO
+ * state via &drm_mode_config_helper_funcs.atomic_sro_build_state,
+ * installs it as the current state of all DRM objects, and frees the
+ * SRO container.
+ *
+ * If the device does not support readout, this is a no-op.
+ *
+ * RETURNS:
+ *
+ * 0 on success, a negative error code otherwise.
+ */
+int drm_atomic_helper_sro_readout_state(struct drm_device *dev)
+{
+	const struct drm_mode_config_helper_funcs *funcs =
+		dev->mode_config.helper_private;
+	struct drm_atomic_sro_state *state;
+
+	if (!drm_atomic_sro_device_can_readout(dev)) {
+		drm_info(dev, "Device doesn't support hardware state readout.");
+		return 0;
+	}
+
+	state = funcs->atomic_sro_build_state(dev);
+	if (IS_ERR(state))
+		return PTR_ERR(state);
+
+	drm_atomic_sro_install_state(state);
+	drm_atomic_sro_state_free(state);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_atomic_helper_sro_readout_state);
diff --git a/include/drm/drm_atomic_sro_helper.h b/include/drm/drm_atomic_sro_helper.h
new file mode 100644
index 000000000000..a42ed8136a49
--- /dev/null
+++ b/include/drm/drm_atomic_sro_helper.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef DRM_ATOMIC_SRO_HELPER_H_
+#define DRM_ATOMIC_SRO_HELPER_H_
+
+struct drm_atomic_sro_state;
+struct drm_device;
+
+int
+drm_atomic_helper_sro_readout_planes_state(struct drm_device *dev,
+					   struct drm_atomic_sro_state *state);
+int
+drm_atomic_helper_sro_readout_crtcs_state(struct drm_device *dev,
+					  struct drm_atomic_sro_state *state);
+int
+drm_atomic_helper_sro_readout_connectors_state(struct drm_device *dev,
+					       struct drm_atomic_sro_state *state);
+int
+drm_atomic_helper_sro_readout_bridges_state(struct drm_device *dev,
+					    struct drm_atomic_sro_state *state);
+int
+drm_atomic_helper_sro_readout_private_objs_state(struct drm_device *dev,
+						 struct drm_atomic_sro_state *state);
+struct drm_atomic_sro_state *
+drm_atomic_helper_sro_build_state(struct drm_device *dev);
+int drm_atomic_helper_sro_readout_state(struct drm_device *dev);
+
+#endif /* DRM_ATOMIC_SRO_HELPER_H_ */

-- 
2.53.0