Instead of relying on color block names to get the transfer function
intention regarding encoding pixel's luminance, define supported
Electro-Optical Transfer Functions (EOTFs) and inverse EOTFs, that
includes pure gamma or standardized transfer functions.

v3:
- squash linear and unity TFs to identity (Pekka)
- define the right TFs for BT.709 (Pekka and Harry)
- add comment about AMD TF coefficients

Suggested-by: Harry Wentland <harry.wentl...@amd.com>
Reviewed-by: Harry Wentland <harry.wentl...@amd.com>
Signed-off-by: Melissa Wen <m...@igalia.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 27 +++++---
 .../amd/display/amdgpu_dm/amdgpu_dm_color.c   | 67 ++++++++++++++-----
 2 files changed, 71 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h 
b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
index ab89538d5663..98f7267d5ee7 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -716,16 +716,27 @@ static inline void amdgpu_dm_set_mst_status(uint8_t 
*status,
 
 extern const struct amdgpu_ip_block_version dm_ip_block;
 
+/* enum amdgpu_transfer_function: pre-defined transfer function supported by 
AMD.
+ *
+ * It includes standardized transfer functions and pure power functions. The
+ * transfer function coefficients are available at modules/color/color_gamma.c
+ */
 enum amdgpu_transfer_function {
        AMDGPU_TRANSFER_FUNCTION_DEFAULT,
-       AMDGPU_TRANSFER_FUNCTION_SRGB,
-       AMDGPU_TRANSFER_FUNCTION_BT709,
-       AMDGPU_TRANSFER_FUNCTION_PQ,
-       AMDGPU_TRANSFER_FUNCTION_LINEAR,
-       AMDGPU_TRANSFER_FUNCTION_UNITY,
-       AMDGPU_TRANSFER_FUNCTION_GAMMA22,
-       AMDGPU_TRANSFER_FUNCTION_GAMMA24,
-       AMDGPU_TRANSFER_FUNCTION_GAMMA26,
+       AMDGPU_TRANSFER_FUNCTION_SRGB_EOTF,
+       AMDGPU_TRANSFER_FUNCTION_BT709_INV_OETF,
+       AMDGPU_TRANSFER_FUNCTION_PQ_EOTF,
+       AMDGPU_TRANSFER_FUNCTION_IDENTITY,
+       AMDGPU_TRANSFER_FUNCTION_GAMMA22_EOTF,
+       AMDGPU_TRANSFER_FUNCTION_GAMMA24_EOTF,
+       AMDGPU_TRANSFER_FUNCTION_GAMMA26_EOTF,
+       AMDGPU_TRANSFER_FUNCTION_SRGB_INV_EOTF,
+       AMDGPU_TRANSFER_FUNCTION_BT709_OETF,
+       AMDGPU_TRANSFER_FUNCTION_PQ_INV_EOTF,
+       AMDGPU_TRANSFER_FUNCTION_GAMMA22_INV_EOTF,
+       AMDGPU_TRANSFER_FUNCTION_GAMMA24_INV_EOTF,
+       AMDGPU_TRANSFER_FUNCTION_GAMMA26_INV_EOTF,
+        AMDGPU_TRANSFER_FUNCTION_COUNT
 };
 
 struct dm_plane_state {
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c 
b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
index 8e02d2b1249d..a32abbd93a61 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
@@ -85,18 +85,57 @@ void amdgpu_dm_init_color_mod(void)
 }
 
 #ifdef AMD_PRIVATE_COLOR
-static const struct drm_prop_enum_list amdgpu_transfer_function_enum_list[] = {
-       { AMDGPU_TRANSFER_FUNCTION_DEFAULT, "Default" },
-       { AMDGPU_TRANSFER_FUNCTION_SRGB, "sRGB" },
-       { AMDGPU_TRANSFER_FUNCTION_BT709, "BT.709" },
-       { AMDGPU_TRANSFER_FUNCTION_PQ, "PQ (Perceptual Quantizer)" },
-       { AMDGPU_TRANSFER_FUNCTION_LINEAR, "Linear" },
-       { AMDGPU_TRANSFER_FUNCTION_UNITY, "Unity" },
-       { AMDGPU_TRANSFER_FUNCTION_GAMMA22, "Gamma 2.2" },
-       { AMDGPU_TRANSFER_FUNCTION_GAMMA24, "Gamma 2.4" },
-       { AMDGPU_TRANSFER_FUNCTION_GAMMA26, "Gamma 2.6" },
+static const char * const
+amdgpu_transfer_function_names[] = {
+       [AMDGPU_TRANSFER_FUNCTION_DEFAULT]              = "Default",
+       [AMDGPU_TRANSFER_FUNCTION_IDENTITY]             = "Identity",
+       [AMDGPU_TRANSFER_FUNCTION_SRGB_EOTF]            = "sRGB EOTF",
+       [AMDGPU_TRANSFER_FUNCTION_BT709_INV_OETF]       = "BT.709 inv_OETF",
+       [AMDGPU_TRANSFER_FUNCTION_PQ_EOTF]              = "PQ EOTF",
+       [AMDGPU_TRANSFER_FUNCTION_GAMMA22_EOTF]         = "Gamma 2.2 EOTF",
+       [AMDGPU_TRANSFER_FUNCTION_GAMMA24_EOTF]         = "Gamma 2.4 EOTF",
+       [AMDGPU_TRANSFER_FUNCTION_GAMMA26_EOTF]         = "Gamma 2.6 EOTF",
+       [AMDGPU_TRANSFER_FUNCTION_SRGB_INV_EOTF]        = "sRGB inv_EOTF",
+       [AMDGPU_TRANSFER_FUNCTION_BT709_OETF]           = "BT.709 OETF",
+       [AMDGPU_TRANSFER_FUNCTION_PQ_INV_EOTF]          = "PQ inv_EOTF",
+       [AMDGPU_TRANSFER_FUNCTION_GAMMA22_INV_EOTF]     = "Gamma 2.2 inv_EOTF",
+       [AMDGPU_TRANSFER_FUNCTION_GAMMA24_INV_EOTF]     = "Gamma 2.4 inv_EOTF",
+       [AMDGPU_TRANSFER_FUNCTION_GAMMA26_INV_EOTF]     = "Gamma 2.6 inv_EOTF",
 };
 
+static const u32 amdgpu_eotf =
+       BIT(AMDGPU_TRANSFER_FUNCTION_SRGB_EOTF) |
+       BIT(AMDGPU_TRANSFER_FUNCTION_BT709_INV_OETF) |
+       BIT(AMDGPU_TRANSFER_FUNCTION_PQ_EOTF) |
+       BIT(AMDGPU_TRANSFER_FUNCTION_GAMMA22_EOTF) |
+       BIT(AMDGPU_TRANSFER_FUNCTION_GAMMA24_EOTF) |
+       BIT(AMDGPU_TRANSFER_FUNCTION_GAMMA26_EOTF);
+
+static struct drm_property *
+amdgpu_create_tf_property(struct drm_device *dev,
+                         const char *name,
+                         u32 supported_tf)
+{
+       u32 transfer_functions = supported_tf |
+                                BIT(AMDGPU_TRANSFER_FUNCTION_DEFAULT) |
+                                BIT(AMDGPU_TRANSFER_FUNCTION_IDENTITY);
+       struct drm_prop_enum_list enum_list[AMDGPU_TRANSFER_FUNCTION_COUNT];
+       int i, len;
+
+       len = 0;
+       for (i = 0; i < AMDGPU_TRANSFER_FUNCTION_COUNT; i++) {
+               if ((transfer_functions & BIT(i)) == 0)
+                       continue;
+
+               enum_list[len].type = i;
+               enum_list[len].name = amdgpu_transfer_function_names[i];
+               len++;
+       }
+
+       return drm_property_create_enum(dev, DRM_MODE_PROP_ENUM,
+                                       name, enum_list, len);
+}
+
 int
 amdgpu_dm_create_color_properties(struct amdgpu_device *adev)
 {
@@ -117,11 +156,9 @@ amdgpu_dm_create_color_properties(struct amdgpu_device 
*adev)
                return -ENOMEM;
        adev->mode_info.plane_degamma_lut_size_property = prop;
 
-       prop = drm_property_create_enum(adev_to_drm(adev),
-                                       DRM_MODE_PROP_ENUM,
-                                       "AMD_PLANE_DEGAMMA_TF",
-                                       amdgpu_transfer_function_enum_list,
-                                       
ARRAY_SIZE(amdgpu_transfer_function_enum_list));
+       prop = amdgpu_create_tf_property(adev_to_drm(adev),
+                                        "AMD_PLANE_DEGAMMA_TF",
+                                        amdgpu_eotf);
        if (!prop)
                return -ENOMEM;
        adev->mode_info.plane_degamma_tf_property = prop;
-- 
2.40.1

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