Describe some expected behavior of the AMD DM color mgmt programming.
Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
Signed-off-by: Melissa Wen <mwen@xxxxxxxxxx>
---
.../drm/amd/display/amdgpu_dm/amdgpu_dm_color.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 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 2ecfa0e886e8..2b2826a1d855 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
@@ -660,13 +660,25 @@ int amdgpu_dm_update_crtc_color_mgmt(struct dm_crtc_state *crtc)
crtc->cm_is_degamma_srgb = true;
stream->out_transfer_func->type = TF_TYPE_DISTRIBUTED_POINTS;
stream->out_transfer_func->tf = TRANSFER_FUNCTION_SRGB;
-
+ /*
+ * Note: although we pass has_rom as parameter here, we never
+ * actually use ROM because the color module only takes the ROM
+ * path if transfer_func->type == PREDEFINED.
+ *
+ * See more in mod_color_calculate_regamma_params()
+ */
r = __set_legacy_tf(stream->out_transfer_func, regamma_lut,
regamma_size, has_rom);
if (r)
return r;
} else if (has_regamma) {
- /* If atomic regamma, CRTC RGM goes into RGM LUT. */
+ /*
+ * CRTC RGM goes into RGM LUT.
+ *
+ * Note: there is no implicit sRGB regamma here. We are using
+ * degamma calculation from color module to calculate the curve
+ * from a linear base.
+ */
stream->out_transfer_func->type = TF_TYPE_DISTRIBUTED_POINTS;
stream->out_transfer_func->tf = TRANSFER_FUNCTION_LINEAR;
--
2.40.1
