drm/color: Add Color transfer functions for HDR/SDR

Due to the way displays and human vision work it is most effective to
encode luminance information in a non-linear space.

For SDR this non-linear mapping is assumed to roughly use a gamma 2.2 curve.
This was due to the way CRTs worked and was fine for SDR content with a
low luminance range.

The large luminance range (0-10,000 nits) for HDR exposes some
short-comings of a simple gamma curve that have been addressed
through various Electro-Optical Transfer Functions (EOTFs).

Rather than assuming how framebuffer content is encoded we want to
make sure userspace presenting HDR content is explicit about the
EOTF of the content, so a driver can decide whether the content
can be supported or not.

This Patch adds common color transfer functions for SDR/HDR. These can
be used to communicate with the driver regarding the transformation to
use for a given plane.

enums added:
	DRM_COLOR_TF_SRGB
		roughly 2.4 gamma with initial linear section
	DRM_COLOR_TF_BT709
		Similar to Gamma 2.2-2.8
	DRM_COLOR_TF_PQ2084
		most common tf used for HDR video (HDR10/Dolby). Can support up
		to 10,000 nits

The usage is similar to color_encoding and color_range where the driver
can specify the default and supported tfs and pass it into
drm_plane_create_color_properties().

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -7039,7 +7039,9 @@ static int amdgpu_dm_plane_init(struct amdgpu_display_manager *dm,
 			BIT(DRM_COLOR_YCBCR_BT2020),
 			BIT(DRM_COLOR_YCBCR_LIMITED_RANGE) |
 			BIT(DRM_COLOR_YCBCR_FULL_RANGE),
-			DRM_COLOR_YCBCR_BT709, DRM_COLOR_YCBCR_LIMITED_RANGE);
+			BIT(DRM_COLOR_TF_SRGB),
+			DRM_COLOR_YCBCR_BT709, DRM_COLOR_YCBCR_LIMITED_RANGE,
+			DRM_COLOR_TF_SRGB);
 	}
 
 	supported_rotations =

drivers/gpu/drm/arm/display/komeda/komeda_plane.c

@@ -302,8 +302,10 @@ static int komeda_plane_add(struct komeda_kms_dev *kms,
 			BIT(DRM_COLOR_YCBCR_BT2020),
 			BIT(DRM_COLOR_YCBCR_LIMITED_RANGE) |
 			BIT(DRM_COLOR_YCBCR_FULL_RANGE),
+			BIT(DRM_COLOR_TF_SRGB),
 			DRM_COLOR_YCBCR_BT601,
-			DRM_COLOR_YCBCR_LIMITED_RANGE);
+			DRM_COLOR_YCBCR_LIMITED_RANGE,
+			DRM_COLOR_TF_SRGB);
 	if (err)
 		goto cleanup;
 

drivers/gpu/drm/arm/malidp_planes.c

@@ -1025,7 +1025,9 @@ int malidp_de_planes_init(struct drm_device *drm)
 					BIT(DRM_COLOR_YCBCR_BT2020),
 					BIT(DRM_COLOR_YCBCR_LIMITED_RANGE) | \
 					BIT(DRM_COLOR_YCBCR_FULL_RANGE),
-					enc, range);
+					BIT(DRM_COLOR_SRGB),
+					enc, range,
+					DRM_COLOR_SRGB);
 			if (!ret)
 				/* program the HW registers */
 				malidp_de_set_color_encoding(plane, enc, range);

drivers/gpu/drm/armada/armada_overlay.c

@@ -596,8 +596,10 @@ int armada_overlay_plane_create(struct drm_device *dev, unsigned long crtcs)
 						BIT(DRM_COLOR_YCBCR_BT601) |
 						BIT(DRM_COLOR_YCBCR_BT709),
 						BIT(DRM_COLOR_YCBCR_LIMITED_RANGE),
+						BIT(DRM_COLOR_TF_SRGB),
 						DEFAULT_ENCODING,
-						DRM_COLOR_YCBCR_LIMITED_RANGE);
+						DRM_COLOR_YCBCR_LIMITED_RANGE,
+						DRM_COLOR_TF_SRGB);
 
 	return ret;
 }

drivers/gpu/drm/drm_atomic_uapi.c

@@ -595,6 +595,8 @@ 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->color_tf_property) {
+		state->color_tf = val;
 	} else if (property == config->prop_fb_damage_clips) {
 		ret = drm_atomic_replace_property_blob_from_id(dev,
 					&state->fb_damage_clips,
@@ -661,6 +663,8 @@ drm_atomic_plane_get_property(struct drm_plane *plane,
 		*val = state->color_encoding;
 	} else if (property == plane->color_range_property) {
 		*val = state->color_range;
+	} else if (property == plane->color_tf_property) {
+		*val = state->color_tf;
 	} else if (property == config->prop_fb_damage_clips) {
 		*val = (state->fb_damage_clips) ?
 			state->fb_damage_clips->base.id : 0;

drivers/gpu/drm/drm_color_mgmt.c

@@ -106,6 +106,11 @@
  * 	Optional plane enum property to support different non RGB
  * 	color parameter ranges. The driver can provide a subset of
  * 	standard enum values supported by the DRM plane.
+ *
+ * "COLOR_TRANFER_FUNCTION":
+ * 	Optional plane enum property to support different
+ * 	color luminance mappings. The driver can provide a subset of
+ * 	standard enum values supported by the DRM plane.
  */
 
 /**
@@ -480,6 +485,10 @@ static const char * const color_range_name[] = {
 	[DRM_COLOR_YCBCR_LIMITED_RANGE] = "YCbCr limited range",
 };
 
+static const char * const color_tf_name[] = {
+	[DRM_COLOR_TF_SRGB] = "sRGB",
+	[DRM_COLOR_TF_PQ2084] = "PQ2084",
+};
 /**
  * drm_get_color_encoding_name - return a string for color encoding
  * @encoding: color encoding to compute name of
@@ -510,30 +519,49 @@ const char *drm_get_color_range_name(enum drm_color_range range)
 	return color_range_name[range];
 }
 
+/**
+ * drm_get_color_transfer_function - return a string for color transfer function
+ * @tf: transfer function to compute name of
+ *
+ * In contrast to the other drm_get_*_name functions this one here returns a
+ * const pointer and hence is threadsafe.
+ */
+const char *drm_get_color_transfer_function_name(enum drm_color_transfer_function tf)
+{
+	if (WARN_ON(tf >= ARRAY_SIZE(color_tf_name)))
+		return "unknown";
+
+	return color_tf_name[tf];
+}
 /**
  * drm_plane_create_color_properties - color encoding related plane properties
  * @plane: plane object
  * @supported_encodings: bitfield indicating supported color encodings
  * @supported_ranges: bitfileld indicating supported color ranges
+ * @supported_tfs: bitfileld indicating supported color transfer functions
  * @default_encoding: default color encoding
  * @default_range: default color range
+ * @default_tf: default color transfer function
  *
- * Create and attach plane specific COLOR_ENCODING and COLOR_RANGE
- * properties to @plane. The supported encodings and ranges should
- * be provided in supported_encodings and supported_ranges bitmasks.
+ * Create and attach plane specific COLOR_ENCODING, COLOR_RANGE and COLOR_TRANSFER_FUNCTION
+ * properties to @plane. The supported encodings, ranges  and tfs should
+ * be provided in supported_encodings, supported_ranges and supported_tfs bitmasks.
  * Each bit set in the bitmask indicates that its number as enum
  * value is supported.
  */
 int drm_plane_create_color_properties(struct drm_plane *plane,
 				      u32 supported_encodings,
 				      u32 supported_ranges,
+				      u32 supported_tfs,
 				      enum drm_color_encoding default_encoding,
-				      enum drm_color_range default_range)
+				      enum drm_color_range default_range,
+				      enum drm_color_transfer_function default_tf)
 {
 	struct drm_device *dev = plane->dev;
 	struct drm_property *prop;
 	struct drm_prop_enum_list enum_list[max_t(int, DRM_COLOR_ENCODING_MAX,
-						       DRM_COLOR_RANGE_MAX)];
+						       max_t(int, DRM_COLOR_RANGE_MAX,
+							     DRM_COLOR_TF_MAX))];
 	int i, len;
 
 	if (WARN_ON(supported_encodings == 0 ||
@@ -546,6 +574,11 @@ int drm_plane_create_color_properties(struct drm_plane *plane,
 		    (supported_ranges & BIT(default_range)) == 0))
 		return -EINVAL;
 
+	if (WARN_ON(supported_tfs == 0 ||
+		    (supported_tfs & -BIT(DRM_COLOR_TF_MAX)) != 0 ||
+		    (supported_tfs & BIT(default_tf)) == 0))
+		return -EINVAL;
+
 	len = 0;
 	for (i = 0; i < DRM_COLOR_ENCODING_MAX; i++) {
 		if ((supported_encodings & BIT(i)) == 0)
@@ -584,6 +617,26 @@ int drm_plane_create_color_properties(struct drm_plane *plane,
 	if (plane->state)
 		plane->state->color_range = default_range;
 
+
+	len = 0;
+	for (i = 0; i < DRM_COLOR_TF_MAX; i++) {
+		if ((supported_tfs & BIT(i)) == 0)
+			continue;
+
+		enum_list[len].type = i;
+		enum_list[len].name = color_tf_name[i];
+		len++;
+	}
+
+	prop = drm_property_create_enum(dev, 0, "COLOR_TRANSFER_FUNCTION",
+					enum_list, len);
+	if (!prop)
+		return -ENOMEM;
+	plane->color_tf_property = prop;
+	drm_object_attach_property(&plane->base, prop, default_tf);
+	if (plane->state)
+		plane->state->color_tf = default_tf;
+
 	return 0;
 }
 EXPORT_SYMBOL(drm_plane_create_color_properties);

drivers/gpu/drm/i915/display/intel_sprite.c

@@ -1849,8 +1849,10 @@ intel_sprite_plane_create(struct drm_i915_private *dev_priv,
 					  BIT(DRM_COLOR_YCBCR_BT709),
 					  BIT(DRM_COLOR_YCBCR_LIMITED_RANGE) |
 					  BIT(DRM_COLOR_YCBCR_FULL_RANGE),
+					  BIT(DRM_COLOR_TF_SRGB),
 					  DRM_COLOR_YCBCR_BT709,
-					  DRM_COLOR_YCBCR_LIMITED_RANGE);
+					  DRM_COLOR_YCBCR_LIMITED_RANGE,
+					  DRM_COLOR_TF_SRGB);
 
 	zpos = sprite + 1;
 	drm_plane_create_zpos_immutable_property(&plane->base, zpos);

drivers/gpu/drm/i915/display/skl_universal_plane.c

@@ -2044,8 +2044,10 @@ skl_universal_plane_create(struct drm_i915_private *dev_priv,
 					  supported_csc,
 					  BIT(DRM_COLOR_YCBCR_LIMITED_RANGE) |
 					  BIT(DRM_COLOR_YCBCR_FULL_RANGE),
+					  BIT(DRM_COLOR_TF_SRGB),
 					  DRM_COLOR_YCBCR_BT709,
-					  DRM_COLOR_YCBCR_LIMITED_RANGE);
+					  DRM_COLOR_YCBCR_LIMITED_RANGE,
+					  DRM_COLOR_TF_SRGB);
 
 	drm_plane_create_alpha_property(&plane->base);
 	drm_plane_create_blend_mode_property(&plane->base,

drivers/gpu/drm/nouveau/dispnv04/overlay.c

@@ -345,8 +345,10 @@ nv10_overlay_init(struct drm_device *device)
 					  BIT(DRM_COLOR_YCBCR_BT601) |
 					  BIT(DRM_COLOR_YCBCR_BT709),
 					  BIT(DRM_COLOR_YCBCR_LIMITED_RANGE),
+					  BIT(DRM_COLOR_TF_SRGB),
 					  DRM_COLOR_YCBCR_BT601,
-					  DRM_COLOR_YCBCR_LIMITED_RANGE);
+					  DRM_COLOR_YCBCR_LIMITED_RANGE,
+					  DRM_COLOR_TF_SRGB);
 
 	plane->set_params = nv10_set_params;
 	nv10_set_params(plane);

drivers/gpu/drm/omapdrm/omap_plane.c

@@ -325,8 +325,10 @@ struct drm_plane *omap_plane_init(struct drm_device *dev,
 						  BIT(DRM_COLOR_YCBCR_BT709),
 						  BIT(DRM_COLOR_YCBCR_FULL_RANGE) |
 						  BIT(DRM_COLOR_YCBCR_LIMITED_RANGE),
+						  BIT(DRM_COLOR_TF_SRGB),
 						  DRM_COLOR_YCBCR_BT601,
-						  DRM_COLOR_YCBCR_FULL_RANGE);
+						  DRM_COLOR_YCBCR_FULL_RANGE,
+						  DRM_COLOR_TF_SRGB);
 
 	return plane;
 

drivers/gpu/drm/sun4i/sun8i_vi_layer.c

@@ -594,8 +594,10 @@ struct sun8i_vi_layer *sun8i_vi_layer_init_one(struct drm_device *drm,
 	ret = drm_plane_create_color_properties(&layer->plane,
 						supported_encodings,
 						supported_ranges,
+						BIT(DRM_COLOR_TF_SRGB),
 						DRM_COLOR_YCBCR_BT709,
-						DRM_COLOR_YCBCR_LIMITED_RANGE);
+						DRM_COLOR_YCBCR_LIMITED_RANGE,
+						DRM_COLOR_TF_SRGB);
 	if (ret) {
 		dev_err(drm->dev, "Couldn't add encoding and range properties!\n");
 		return ERR_PTR(ret);

drivers/gpu/drm/tidss/tidss_plane.c

@@ -186,8 +186,10 @@ struct tidss_plane *tidss_plane_create(struct tidss_device *tidss,
 			       BIT(DRM_COLOR_YCBCR_BT709));
 	u32 color_ranges = (BIT(DRM_COLOR_YCBCR_FULL_RANGE) |
 			    BIT(DRM_COLOR_YCBCR_LIMITED_RANGE));
+	u32 color_tfs = BIT(DRM_COLOR_TF_SRGB;
 	u32 default_encoding = DRM_COLOR_YCBCR_BT601;
 	u32 default_range = DRM_COLOR_YCBCR_FULL_RANGE;
+	u32 default_tf = DRM_COLOR_TF_SRGB;;
 	u32 blend_modes = (BIT(DRM_MODE_BLEND_PREMULTI) |
 			   BIT(DRM_MODE_BLEND_COVERAGE));
 	int ret;
@@ -217,8 +219,10 @@ struct tidss_plane *tidss_plane_create(struct tidss_device *tidss,
 	ret = drm_plane_create_color_properties(&tplane->plane,
 						color_encodings,
 						color_ranges,
+						color_tfs,
 						default_encoding,
-						default_range);
+						default_range,
+						default_tf);
 	if (ret)
 		goto err;
 

include/drm/drm_color_mgmt.h

@@ -91,11 +91,24 @@ enum drm_color_range {
 	DRM_COLOR_RANGE_MAX,
 };
 
+/**
+ * enum drm_color_transfer_function - common transfer function used for sdr/hdr formats
+ *
+ * DRM_COLOR_TF_SRGB - Based on gamma curve and is used for printer/monitors/web
+ * DRM_COLOR_TF_PQ2084 - Used for HDR and allows for up to 10,000 nit support.
+*/
+enum drm_color_transfer_function {
+	DRM_COLOR_TF_SRGB,
+	DRM_COLOR_TF_PQ2084,
+	DRM_COLOR_TF_MAX,
+};
 int drm_plane_create_color_properties(struct drm_plane *plane,
 				      u32 supported_encodings,
 				      u32 supported_ranges,
+				      u32 supported_tf,
 				      enum drm_color_encoding default_encoding,
-				      enum drm_color_range default_range);
+				      enum drm_color_range default_range,
+				      enum drm_color_transfer_function default_tf);
 
 /**
  * enum drm_color_lut_tests - hw-specific LUT tests to perform

include/drm/drm_plane.h

@@ -179,6 +179,14 @@ struct drm_plane_state {
 	 */
 	enum drm_color_range color_range;
 
+	/**
+	 * @color_transfer_function:
+	 *
+	 * Transfer function for HDR color/luminance mapping. This will allow the
+	 * driver to know what transfer function should be used to for the current
+	 * format for a proper HDR color/luminance output.
+	 */
+	enum drm_color_transfer_function color_tf;
 	/**
 	 * @fb_damage_clips:
 	 *
@@ -741,6 +749,14 @@ struct drm_plane {
 	 * See drm_plane_create_color_properties().
 	 */
 	struct drm_property *color_range_property;
+	/**
+	 * @color_tf_property:
+	 *
+	 * Optional "COLOR_TRANSFER_FUNCTION" enum property for specifying
+	 * color transfer function for non RGB formats, mostly used for HDR.
+	 * See drm_plane_create_color_properties().
+	 */
+	struct drm_property *color_tf_property;
 
 	/**
 	 * @scaling_filter_property: property to apply a particular filter while