[RFC v5 2/8] drm: Add Plane Degamma properties

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Add Plane Degamma as a blob property and plane degamma size as
a range property.

v2: Rebase

v3: Fixed Sean, Paul's review comments. Moved the property from
mode_config to drm_plane. Created a helper function to instantiate
these properties and removed from drm_mode_create_standard_properties
Added property documentation as suggested by Daniel, Vetter.

v4: Rebase

v5: Added "Display Color Hardware Pipeline" flow to kernel
documentation as suggested by "Ville Syrjala" and "Brian Starkey".
Moved the property creation to drm_color_mgmt.c file to consolidate
all color operations at one place.

Signed-off-by: Uma Shankar <uma.shankar@xxxxxxxxx>
Reviewed-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@xxxxxxx>
---
 Documentation/gpu/drm-kms.rst       | 90 +++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_atomic.c        | 13 ++++++
 drivers/gpu/drm/drm_atomic_helper.c |  6 +++
 drivers/gpu/drm/drm_color_mgmt.c    | 44 ++++++++++++++++--
 include/drm/drm_plane.h             | 24 ++++++++++
 5 files changed, 174 insertions(+), 3 deletions(-)

diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst
index f8f5bf1..253d546 100644
--- a/Documentation/gpu/drm-kms.rst
+++ b/Documentation/gpu/drm-kms.rst
@@ -551,12 +551,102 @@ Plane Composition Properties
 Color Management Properties
 ---------------------------
 
+Below is how a typical hardware pipeline for color
+will look like:
+
+.. kernel-render:: DOT
+   :alt: Display Color Pipeline
+   :caption: Display Color Pipeline Overview
+
+   digraph "KMS" {
+      node [shape=box]
+
+      subgraph cluster_static {
+          style=dashed
+          label="Display Color Hardware Blocks"
+
+          node [bgcolor=grey style=filled]
+          "Plane Degamma A" -> "Plane CSC/CTM A"
+          "Plane CSC/CTM A" -> "Plane Gamma A"
+          "Pipe Blender" [color=lightblue,style=filled, width=5.25, height=0.75];
+          "Plane Gamma A" -> "Pipe Blender"
+	  "Pipe Blender" -> "Pipe DeGamma"
+          "Pipe DeGamma" -> "Pipe CSC/CTM"
+          "Pipe CSC/CTM" -> "Pipe Gamma"
+          "Pipe Gamma" -> "Pipe Output"
+      }
+
+      subgraph cluster_static {
+          style=dashed
+
+          node [shape=box]
+          "Plane Degamma B" -> "Plane CSC/CTM B"
+          "Plane CSC/CTM B" -> "Plane Gamma B"
+          "Plane Gamma B" -> "Pipe Blender"
+      }
+
+      subgraph cluster_static {
+          style=dashed
+
+          node [shape=box]
+          "Plane Degamma C" -> "Plane CSC/CTM C"
+          "Plane CSC/CTM C" -> "Plane Gamma C"
+          "Plane Gamma C" -> "Pipe Blender"
+      }
+
+      subgraph cluster_fb {
+          style=dashed
+          label="RAM"
+
+          node [shape=box width=1.7 height=0.2]
+
+          "FB 1" -> "Plane Degamma A"
+          "FB 2" -> "Plane Degamma B"
+          "FB 3" -> "Plane Degamma C"
+      }
+   }
+
+In real world usecases,
+
+1. Plane Degamma can be used to linearize a non linear gamma
+encoded framebuffer. This is needed to do any linear math like
+color space conversion. For ex, linearize frames encoded in SRGB
+or by HDR curve.
+
+2. Later Plane CTM block can convert the content to some different
+colorspace. For ex, SRGB to BT2020 etc.
+
+3. Plane Gamma block can be used later to re-apply the non-linear
+curve. This can also be used to apply Tone Mapping for HDR usecases.
+
+All the layers or framebuffers need to be converted to same color
+space and format before blending. The plane color hardware blocks
+can help with this. Once the Data is blended, similar color processing
+can be done on blended output using pipe color hardware blocks.
+
+DRM Properties have been created to define and expose all these
+hardware blocks to userspace. A userspace application (compositor
+or any color app) can use these interfaces and define policies to
+efficiently use the display hardware for such color operations.
+
+Pipe Color Management Properties
+---------------------------------
+
 .. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
    :doc: overview
 
 .. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
    :export:
 
+Plane Color Management Properties
+---------------------------------
+
+.. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
+   :doc: Plane Color Properties
+
+.. kernel-doc:: drivers/gpu/drm/drm_color_mgmt.c
+   :doc: export
+
 Tile Group Property
 -------------------
 
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index d0478ab..e716614 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -857,6 +857,8 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
 {
 	struct drm_device *dev = plane->dev;
 	struct drm_mode_config *config = &dev->mode_config;
+	bool replaced = false;
+	int ret;
 
 	if (property == config->prop_fb_id) {
 		struct drm_framebuffer *fb = drm_framebuffer_lookup(dev, NULL, val);
@@ -910,6 +912,13 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
 		state->color_encoding = val;
 	} else if (property == plane->color_range_property) {
 		state->color_range = val;
+	} else if (property == plane->degamma_lut_property) {
+		ret = drm_atomic_replace_property_blob_from_id(dev,
+					&state->degamma_lut,
+					val, -1, sizeof(struct drm_color_lut),
+					&replaced);
+		state->color_mgmt_changed |= replaced;
+		return ret;
 	} else if (plane->funcs->atomic_set_property) {
 		return plane->funcs->atomic_set_property(plane, state,
 				property, val);
@@ -980,6 +989,9 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
 		*val = state->color_encoding;
 	} else if (property == plane->color_range_property) {
 		*val = state->color_range;
+	} else if (property == plane->degamma_lut_property) {
+		*val = (state->degamma_lut) ?
+			state->degamma_lut->base.id : 0;
 	} else if (plane->funcs->atomic_get_property) {
 		return plane->funcs->atomic_get_property(plane, state, property, val);
 	} else {
@@ -1120,6 +1132,7 @@ static void drm_atomic_plane_print_state(struct drm_printer *p,
 		   drm_get_color_encoding_name(state->color_encoding));
 	drm_printf(p, "\tcolor-range=%s\n",
 		   drm_get_color_range_name(state->color_range));
+	drm_printf(p, "\tcolor_mgmt_changed=%d\n", state->color_mgmt_changed);
 
 	if (plane->funcs->atomic_print_state)
 		plane->funcs->atomic_print_state(p, state);
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 2c23a48..203137e 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -3614,6 +3614,10 @@ void __drm_atomic_helper_plane_duplicate_state(struct drm_plane *plane,
 
 	state->fence = NULL;
 	state->commit = NULL;
+
+	if (state->degamma_lut)
+		drm_property_blob_get(state->degamma_lut);
+	state->color_mgmt_changed = false;
 }
 EXPORT_SYMBOL(__drm_atomic_helper_plane_duplicate_state);
 
@@ -3658,6 +3662,8 @@ void __drm_atomic_helper_plane_destroy_state(struct drm_plane_state *state)
 
 	if (state->commit)
 		drm_crtc_commit_put(state->commit);
+
+	drm_property_blob_put(state->degamma_lut);
 }
 EXPORT_SYMBOL(__drm_atomic_helper_plane_destroy_state);
 
diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c
index 1bdcc1a..d8a9e8b 100644
--- a/drivers/gpu/drm/drm_color_mgmt.c
+++ b/drivers/gpu/drm/drm_color_mgmt.c
@@ -29,11 +29,11 @@
 /**
  * DOC: overview
  *
- * Color management or color space adjustments is supported through a set of 5
- * properties on the &drm_crtc object. They are set up by calling
+ * Pipe Color management or color space adjustments is supported through a
+ * set of 5 properties on the &drm_crtc object. They are set up by calling
  * drm_crtc_enable_color_mgmt().
  *
- * "DEGAMMA_LUT”:
+ * "DEGAMMA_LUT
  *	Blob property to set the degamma lookup table (LUT) mapping pixel data
  *	from the framebuffer before it is given to the transformation matrix.
  *	The data is interpreted as an array of &struct drm_color_lut elements.
@@ -491,3 +491,41 @@ int drm_plane_create_color_properties(struct drm_plane *plane,
 	return 0;
 }
 EXPORT_SYMBOL(drm_plane_create_color_properties);
+
+/**
+ * DOC: Plane Color Properties
+ *
+ * Plane Color management or color space adjustments is supported
+ * through a set of 5 properties on the &drm_plane object.
+ *
+ * degamma_lut_property:
+ *     Blob property which allows a userspace to provide LUT values
+ *     to apply degamma curve using the h/w plane degamma processing
+ *     engine, thereby making the content as linear for further color
+ *     processing.
+ *
+ * degamma_lut_size_property:
+ *     Range Property to indicate size of the plane degamma LUT.
+ */
+int drm_plane_color_create_prop(struct drm_device *dev,
+				struct drm_plane *plane)
+{
+	struct drm_property *prop;
+
+	prop = drm_property_create(dev,
+			DRM_MODE_PROP_BLOB,
+			"PLANE_DEGAMMA_LUT", 0);
+	if (!prop)
+		return -ENOMEM;
+	plane->degamma_lut_property = prop;
+
+	prop = drm_property_create_range(dev,
+			DRM_MODE_PROP_IMMUTABLE,
+			"PLANE_DEGAMMA_LUT_SIZE", 0, UINT_MAX);
+	if (!prop)
+		return -ENOMEM;
+	plane->degamma_lut_size_property = prop;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_plane_color_create_prop);
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index 16f5b666..7f0d961 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -182,6 +182,14 @@ struct drm_plane_state {
 	 */
 	bool visible;
 
+	/* @degamma_lut:
+	 *
+	 * Lookup table for converting framebuffer pixel data before apply the
+	 * color conversion matrix @ctm. See drm_plane_enable_color_mgmt(). The
+	 * blob (if not NULL) is an array of &struct drm_color_lut_ext.
+	 */
+	struct drm_property_blob *degamma_lut;
+
 	/**
 	 * @commit: Tracks the pending commit to prevent use-after-free conditions,
 	 * and for async plane updates.
@@ -192,6 +200,8 @@ struct drm_plane_state {
 
 	/** @state: backpointer to global drm_atomic_state */
 	struct drm_atomic_state *state;
+
+	u8 color_mgmt_changed : 1;
 };
 
 static inline struct drm_rect
@@ -692,6 +702,18 @@ struct drm_plane {
 	 * See drm_plane_create_color_properties().
 	 */
 	struct drm_property *color_range_property;
+
+	/**
+	 * @degamma_lut_property: Optional Plane property to set the LUT
+	 * used to convert the framebuffer's colors to linear gamma.
+	 */
+	struct drm_property *degamma_lut_property;
+
+	/**
+	 * @degamma_lut_size_property: Optional Plane property for the
+	 * size of the degamma LUT as supported by the driver (read-only).
+	 */
+	struct drm_property *degamma_lut_size_property;
 };
 
 #define obj_to_plane(x) container_of(x, struct drm_plane, base)
@@ -741,6 +763,8 @@ static inline u32 drm_plane_mask(const struct drm_plane *plane)
 int drm_mode_plane_set_obj_prop(struct drm_plane *plane,
 				       struct drm_property *property,
 				       uint64_t value);
+int drm_plane_color_create_prop(struct drm_device *dev,
+				struct drm_plane *plane);
 
 /**
  * drm_plane_find - find a &drm_plane
-- 
1.9.1

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