drm/amd/display: Disable CRTC degamma LUT for DCN401

commit 97a0f2b upstream.

In DCN401 pre-blending degamma LUT isn't affecting cursor as in previous
DCN version. As this is not the behavior close to what is expected for
CRTC degamma LUT, disable CRTC degamma LUT property in this HW.

Link: https://gitlab.freedesktop.org/drm/amd/-/issues/4176

Author: melissawen

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c

@@ -731,7 +731,16 @@ int amdgpu_dm_crtc_init(struct amdgpu_display_manager *dm,
 	 * support programmable degamma anywhere.
 	 */
 	is_dcn = dm->adev->dm.dc->caps.color.dpp.dcn_arch;
-	drm_crtc_enable_color_mgmt(&acrtc->base, is_dcn ? MAX_COLOR_LUT_ENTRIES : 0,
+	/* Dont't enable DRM CRTC degamma property for DCN401 since the
+	 * pre-blending degamma LUT doesn't apply to cursor, and therefore
+	 * can't work similar to a post-blending degamma LUT as in other hw
+	 * versions.
+	 * TODO: revisit it once KMS plane color API is merged.
+	 */
+	drm_crtc_enable_color_mgmt(&acrtc->base,
+				   (is_dcn &&
+				    dm->adev->dm.dc->ctx->dce_version != DCN_VERSION_4_01) ?
+				     MAX_COLOR_LUT_ENTRIES : 0,
 				   true, MAX_COLOR_LUT_ENTRIES);
 
 	drm_mode_crtc_set_gamma_size(&acrtc->base, MAX_COLOR_LEGACY_LUT_ENTRIES);