drm/v3d: Define the fourcc modifier for the Broadcom UIF format.

This will be used by Mesa, and potentially other drivers in the
future, to describe tiled buffers.

Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20180621001703.13522-1-eric@anholt.net
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

include/uapi/drm/drm_fourcc.h

@@ -464,6 +464,27 @@ extern "C" {
 #define DRM_FORMAT_MOD_BROADCOM_SAND256 \
 	DRM_FORMAT_MOD_BROADCOM_SAND256_COL_HEIGHT(0)
 
+/* Broadcom UIF format
+ *
+ * This is the common format for the current Broadcom multimedia
+ * blocks, including V3D 3.x and newer, newer video codecs, and
+ * displays.
+ *
+ * The image consists of utiles (64b blocks), UIF blocks (2x2 utiles),
+ * and macroblocks (4x4 UIF blocks).  Those 4x4 UIF block groups are
+ * stored in columns, with padding between the columns to ensure that
+ * moving from one column to the next doesn't hit the same SDRAM page
+ * bank.
+ *
+ * To calculate the padding, it is assumed that each hardware block
+ * and the software driving it knows the platform's SDRAM page size,
+ * number of banks, and XOR address, and that it's identical between
+ * all blocks using the format.  This tiling modifier will use XOR as
+ * necessary to reduce the padding.  If a hardware block can't do XOR,
+ * the assumption is that a no-XOR tiling modifier will be created.
+ */
+#define DRM_FORMAT_MOD_BROADCOM_UIF fourcc_mod_code(BROADCOM, 6)
+
 #if defined(__cplusplus)
 }
 #endif