From: Bhawanpreet Lakha <bhawanpreet.la...@amd.com>

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 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_TF_UNDEFINED
                the legacy case where the TF in/out of blending space is
                undefined
        DRM_TF_SRGB
                roughly 2.4 gamma with initial linear section
        DRM_TF_BT709
                Similar to Gamma 2.2-2.8
        DRM_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().

v2:
 - drop "color" from transfer function name (Harry)
 - add DRM_TF_UNDEFINED enum as legacy default (Harry)

Signed-off-by: Bhawanpreet Lakha <bhawanpreet.la...@amd.com>
Signed-off-by: Harry Wentland <harry.wentl...@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  4 +-
 .../gpu/drm/arm/display/komeda/komeda_plane.c |  4 +-
 drivers/gpu/drm/arm/malidp_planes.c           |  4 +-
 drivers/gpu/drm/armada/armada_overlay.c       |  4 +-
 drivers/gpu/drm/drm_atomic_uapi.c             |  4 ++
 drivers/gpu/drm/drm_color_mgmt.c              | 64 +++++++++++++++++--
 drivers/gpu/drm/i915/display/intel_sprite.c   |  4 +-
 .../drm/i915/display/skl_universal_plane.c    |  4 +-
 drivers/gpu/drm/nouveau/dispnv04/overlay.c    |  4 +-
 drivers/gpu/drm/omapdrm/omap_plane.c          |  4 +-
 drivers/gpu/drm/sun4i/sun8i_vi_layer.c        |  4 +-
 drivers/gpu/drm/tidss/tidss_plane.c           |  6 +-
 include/drm/drm_color_mgmt.h                  | 18 +++++-
 include/drm/drm_plane.h                       | 16 +++++
 14 files changed, 128 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 
b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index b5b5ccf0ed71..63ddae9c5abe 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -7276,7 +7276,9 @@ 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_TF_SRGB),
+                       DRM_COLOR_YCBCR_BT709, DRM_COLOR_YCBCR_LIMITED_RANGE,
+                       DRM_TF_SRGB);
        }
 
        supported_rotations =
diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_plane.c 
b/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
index d63d83800a8a..811f79ab6d32 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_plane.c
+++ b/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_TF_UNDEFINED),
                        DRM_COLOR_YCBCR_BT601,
-                       DRM_COLOR_YCBCR_LIMITED_RANGE);
+                       DRM_COLOR_YCBCR_LIMITED_RANGE,
+                       DRM_TF_UNDEFINED);
        if (err)
                goto cleanup;
 
diff --git a/drivers/gpu/drm/arm/malidp_planes.c 
b/drivers/gpu/drm/arm/malidp_planes.c
index 8c2ab3d653b7..98d308262880 100644
--- a/drivers/gpu/drm/arm/malidp_planes.c
+++ b/drivers/gpu/drm/arm/malidp_planes.c
@@ -1030,7 +1030,9 @@ 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_TF_UNDEFINED),
+                                       enc, range,
+                                       DRM_TF_UNDEFINED);
                        if (!ret)
                                /* program the HW registers */
                                malidp_de_set_color_encoding(plane, enc, range);
diff --git a/drivers/gpu/drm/armada/armada_overlay.c 
b/drivers/gpu/drm/armada/armada_overlay.c
index d3e3e5fdc390..f7792444cb73 100644
--- a/drivers/gpu/drm/armada/armada_overlay.c
+++ b/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_TF_UNDEFINED),
                                                DEFAULT_ENCODING,
-                                               DRM_COLOR_YCBCR_LIMITED_RANGE);
+                                               DRM_COLOR_YCBCR_LIMITED_RANGE,
+                                               DRM_TF_UNDEFINED);
 
        return ret;
 }
diff --git a/drivers/gpu/drm/drm_atomic_uapi.c 
b/drivers/gpu/drm/drm_atomic_uapi.c
index 7e48d40600ff..9582515dd12e 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -596,6 +596,8 @@ 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->transfer_function_property) {
+               state->transfer_function = val;
        } else if (property == config->prop_fb_damage_clips) {
                ret = drm_atomic_replace_property_blob_from_id(dev,
                                        &state->fb_damage_clips,
@@ -662,6 +664,8 @@ 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->transfer_function_property) {
+               *val = state->transfer_function;
        } else if (property == config->prop_fb_damage_clips) {
                *val = (state->fb_damage_clips) ?
                        state->fb_damage_clips->base.id : 0;
diff --git a/drivers/gpu/drm/drm_color_mgmt.c b/drivers/gpu/drm/drm_color_mgmt.c
index bb14f488c8f6..daf62fb090a6 100644
--- a/drivers/gpu/drm/drm_color_mgmt.c
+++ b/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.
  */
 
 /**
@@ -476,6 +481,11 @@ static const char * const color_range_name[] = {
        [DRM_COLOR_YCBCR_LIMITED_RANGE] = "YCbCr limited range",
 };
 
+static const char * const tf_name[] = {
+       [DRM_TF_UNDEFINED] = "undefined",
+       [DRM_TF_SRGB] = "sRGB",
+       [DRM_TF_PQ2084] = "PQ2084",
+};
 /**
  * drm_get_color_encoding_name - return a string for color encoding
  * @encoding: color encoding to compute name of
@@ -506,30 +516,49 @@ const char *drm_get_color_range_name(enum drm_color_range 
range)
        return color_range_name[range];
 }
 
+/**
+ * drm_get_transfer_function - return a string for 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_transfer_function_name(enum drm_transfer_function tf)
+{
+       if (WARN_ON(tf >= ARRAY_SIZE(tf_name)))
+               return "unknown";
+
+       return 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: bitfield indicating supported 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 
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_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_TF_MAX))];
        int i, len;
 
        if (WARN_ON(supported_encodings == 0 ||
@@ -542,6 +571,11 @@ 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_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)
@@ -580,6 +614,26 @@ 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_TF_MAX; i++) {
+               if ((supported_tfs & BIT(i)) == 0)
+                       continue;
+
+               enum_list[len].type = i;
+               enum_list[len].name = tf_name[i];
+               len++;
+       }
+
+       prop = drm_property_create_enum(dev, 0, "TRANSFER_FUNCTION",
+                                       enum_list, len);
+       if (!prop)
+               return -ENOMEM;
+       plane->transfer_function_property = prop;
+       drm_object_attach_property(&plane->base, prop, default_tf);
+       if (plane->state)
+               plane->state->transfer_function = default_tf;
+
        return 0;
 }
 EXPORT_SYMBOL(drm_plane_create_color_properties);
diff --git a/drivers/gpu/drm/i915/display/intel_sprite.c 
b/drivers/gpu/drm/i915/display/intel_sprite.c
index 4ae9a7455b23..b3f7aca3795b 100644
--- a/drivers/gpu/drm/i915/display/intel_sprite.c
+++ b/drivers/gpu/drm/i915/display/intel_sprite.c
@@ -1850,8 +1850,10 @@ 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_TF_UNDEFINED),
                                          DRM_COLOR_YCBCR_BT709,
-                                         DRM_COLOR_YCBCR_LIMITED_RANGE);
+                                         DRM_COLOR_YCBCR_LIMITED_RANGE,
+                                         DRM_TF_UNDEFINED);
 
        zpos = sprite + 1;
        drm_plane_create_zpos_immutable_property(&plane->base, zpos);
diff --git a/drivers/gpu/drm/i915/display/skl_universal_plane.c 
b/drivers/gpu/drm/i915/display/skl_universal_plane.c
index 92a4fd508e92..df596431151d 100644
--- a/drivers/gpu/drm/i915/display/skl_universal_plane.c
+++ b/drivers/gpu/drm/i915/display/skl_universal_plane.c
@@ -2160,8 +2160,10 @@ 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_TF_UNDEFINED),
                                          DRM_COLOR_YCBCR_BT709,
-                                         DRM_COLOR_YCBCR_LIMITED_RANGE);
+                                         DRM_COLOR_YCBCR_LIMITED_RANGE,
+                                         DRM_TF_UNDEFINED);
 
        drm_plane_create_alpha_property(&plane->base);
        drm_plane_create_blend_mode_property(&plane->base,
diff --git a/drivers/gpu/drm/nouveau/dispnv04/overlay.c 
b/drivers/gpu/drm/nouveau/dispnv04/overlay.c
index 37e63e98cd08..64e1793212b4 100644
--- a/drivers/gpu/drm/nouveau/dispnv04/overlay.c
+++ b/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_TF_UNDEFINED),
                                          DRM_COLOR_YCBCR_BT601,
-                                         DRM_COLOR_YCBCR_LIMITED_RANGE);
+                                         DRM_COLOR_YCBCR_LIMITED_RANGE,
+                                         DRM_TF_UNDEFINED);
 
        plane->set_params = nv10_set_params;
        nv10_set_params(plane);
diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c 
b/drivers/gpu/drm/omapdrm/omap_plane.c
index 801da917507d..ca7559824dcd 100644
--- a/drivers/gpu/drm/omapdrm/omap_plane.c
+++ b/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_TF_UNDEFINED),
                                                  DRM_COLOR_YCBCR_BT601,
-                                                 DRM_COLOR_YCBCR_FULL_RANGE);
+                                                 DRM_COLOR_YCBCR_FULL_RANGE,
+                                                 DRM_TF_UNDEFINED);
 
        return plane;
 
diff --git a/drivers/gpu/drm/sun4i/sun8i_vi_layer.c 
b/drivers/gpu/drm/sun4i/sun8i_vi_layer.c
index 1c86c2dd0bbf..eda8f51bafd7 100644
--- a/drivers/gpu/drm/sun4i/sun8i_vi_layer.c
+++ b/drivers/gpu/drm/sun4i/sun8i_vi_layer.c
@@ -600,8 +600,10 @@ 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_TF_UNDEFINED),
                                                DRM_COLOR_YCBCR_BT709,
-                                               DRM_COLOR_YCBCR_LIMITED_RANGE);
+                                               DRM_COLOR_YCBCR_LIMITED_RANGE,
+                                               DRM_TF_UNDEFINED);
        if (ret) {
                dev_err(drm->dev, "Couldn't add encoding and range 
properties!\n");
                return ERR_PTR(ret);
diff --git a/drivers/gpu/drm/tidss/tidss_plane.c 
b/drivers/gpu/drm/tidss/tidss_plane.c
index 1acd15aa4193..a1336ecd5fd5 100644
--- a/drivers/gpu/drm/tidss/tidss_plane.c
+++ b/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 transfer_functions = BIT(DRM_TF_UNDEFINED;
        u32 default_encoding = DRM_COLOR_YCBCR_BT601;
        u32 default_range = DRM_COLOR_YCBCR_FULL_RANGE;
+       u32 default_tf = DRM_TF_UNDEFINED;;
        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,
+                                               transfer_functions,
                                                default_encoding,
-                                               default_range);
+                                               default_range,
+                                               default_tf);
        if (ret)
                goto err;
 
diff --git a/include/drm/drm_color_mgmt.h b/include/drm/drm_color_mgmt.h
index 81c298488b0c..370bbc55b744 100644
--- a/include/drm/drm_color_mgmt.h
+++ b/include/drm/drm_color_mgmt.h
@@ -87,11 +87,27 @@ enum drm_color_range {
        DRM_COLOR_RANGE_MAX,
 };
 
+/**
+ * enum drm_transfer_function - common transfer function used for sdr/hdr 
formats
+ *
+ * DRM_TF_UNDEFINED - The legacy case where a TF in and out of the blending
+ *                    space is undefined
+ * DRM_TF_SRGB - Based on gamma curve and is used for printer/monitors/web
+ * DRM_TF_PQ2084 - Used for HDR and allows for up to 10,000 nit support.
+*/
+enum drm_transfer_function {
+       DRM_TF_UNDEFINED,
+       DRM_TF_SRGB,
+       DRM_TF_PQ2084,
+       DRM_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_transfer_function default_tf);
 
 /**
  * enum drm_color_lut_tests - hw-specific LUT tests to perform
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index 1294610e84f4..cff56994513f 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -179,6 +179,14 @@ struct drm_plane_state {
         */
        enum drm_color_range color_range;
 
+       /**
+        * @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_transfer_function transfer_function;
        /**
         * @fb_damage_clips:
         *
@@ -741,6 +749,14 @@ struct drm_plane {
         * See drm_plane_create_color_properties().
         */
        struct drm_property *color_range_property;
+       /**
+        * @transfer_function_property:
+        *
+        * Optional "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 *transfer_function_property;
 
        /**
         * @scaling_filter_property: property to apply a particular filter while
-- 
2.32.0

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