drm/fourcc: Introduce format modifier for DG2 clear color

DG2 clear color render compression uses Tile4 layout. Therefore, we need
to define a new format modifier for uAPI to support clear color rendering.

v2:
  Display version is fixed. [Imre]
  KDoc is enhanced for cc modifier. [Nanley & Lionel]
v3:
  Split out the modifier addition to a separate patch.
  Clarify the modifier layout description.

Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
cc: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Juha-Pekka Heikkilä <juha-pekka.heikkila@intel.com>
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Acked-by: Nanley Chery <nanley.g.chery@intel.com>
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220411143405.1073845-4-imre.deak@intel.com

include/uapi/drm/drm_fourcc.h

@@ -605,6 +605,20 @@ extern "C" {
  */
 #define I915_FORMAT_MOD_4_TILED_DG2_MC_CCS fourcc_mod_code(INTEL, 11)
 
+/*
+ * Intel Color Control Surface with Clear Color (CCS) for DG2 render compression.
+ *
+ * The main surface is Tile 4 and at plane index 0. The CCS data is stored
+ * outside of the GEM object in a reserved memory area dedicated for the
+ * storage of the CCS data for all RC/RC_CC/MC compressible GEM objects. The
+ * main surface pitch is required to be a multiple of four Tile 4 widths. The
+ * clear color is stored at plane index 1 and the pitch should be ignored. The
+ * format of the 256 bits of clear color data matches the one used for the
+ * I915_FORMAT_MOD_Y_TILED_GEN12_RC_CCS_CC modifier, see its description
+ * for details.
+ */
+#define I915_FORMAT_MOD_4_TILED_DG2_RC_CCS_CC fourcc_mod_code(INTEL, 12)
+
 /*
  * Tiled, NV12MT, grouped in 64 (pixels) x 32 (lines) -sized macroblocks
  *