[RFC PATCH 37/40] drm/amd/display: handle empty LUTs in __set_input_tf

[Melissa Wen]

From: Joshua Ashton <jos...@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 <jos...@froggi.es>
---
 .../amd/display/amdgpu_dm/amdgpu_dm_color.c   | 21 ++++++++++++-------
 1 file changed, 13 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 e17141fc8d12..baa7fea9ebae 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
@@ -349,21 +349,26 @@ 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;
 }
 
+
 #ifdef CONFIG_STEAM_DECK
 static enum dc_transfer_func_predefined drm_tf_to_dc_tf(enum 
drm_transfer_function drm_tf)
 {
-- 
2.39.2