[PATCH 34/36] drm/amd/display: handle empty LUTs in __set_input_tf

[Melissa Wen <mwen@igalia.com>]

From: Joshua Ashton <joshua@froggi.es>

Unlike degamma, blend gamma doesn't support hardcoded curve
(predefined/ROM), but we can use AMD color module to fill blend gamma
parameters when we have non-linear plane gamma TF without plane gamma
LUT. The regular degamma path doesn't hit this.

Signed-off-by: Joshua Ashton <joshua@froggi.es>
Signed-off-by: Melissa Wen <mwen@igalia.com>
---
 .../amd/display/amdgpu_dm/amdgpu_dm_color.c   | 20 +++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

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 b075c9f6e717..a441c02380f2 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
@@ -351,17 +351,21 @@ static int __set_input_tf(struct dc_transfer_func *func,
 	struct dc_gamma *gamma = NULL;
 	bool res;
 
-	gamma = dc_create_gamma();
-	if (!gamma)
-		return -ENOMEM;
+	if (lut_size) {
+		gamma = dc_create_gamma();
+		if (!gamma)
+			return -ENOMEM;
 
-	gamma->type = GAMMA_CUSTOM;
-	gamma->num_entries = lut_size;
+		gamma->type = GAMMA_CUSTOM;
+		gamma->num_entries = lut_size;
 
-	__drm_lut_to_dc_gamma(lut, gamma, false);
+		__drm_lut_to_dc_gamma(lut, gamma, false);
+	}
 
-	res = mod_color_calculate_degamma_params(NULL, func, gamma, true);
-	dc_gamma_release(&gamma);
+	res = mod_color_calculate_degamma_params(NULL, func, gamma, gamma != NULL);
+
+	if (gamma)
+		dc_gamma_release(&gamma);
 
 	return res ? 0 : -ENOMEM;
 }
-- 
2.39.2