panfrost: Cleanup PAN_ALLOCATE_*

While we're at it, prompted by a semantics issue around INVISIBLE, also
add a separate DELAY_MMAP flag.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>

src/gallium/drivers/panfrost/pan_screen.h

@@ -43,10 +43,24 @@ struct panfrost_resource;
 struct panfrost_screen;
 
 /* Flags for allocated memory */
-#define PAN_ALLOCATE_EXECUTE (1 << 0)
-#define PAN_ALLOCATE_GROWABLE (1 << 1)
-#define PAN_ALLOCATE_INVISIBLE (1 << 2)
-#define PAN_ALLOCATE_COHERENT_LOCAL (1 << 3)
+
+/* This memory region is executable */
+#define PAN_ALLOCATE_EXECUTE            (1 << 0)
+
+/* This memory region should be lazily allocated and grow-on-page-fault. Must
+ * be used in conjunction with INVISIBLE */
+#define PAN_ALLOCATE_GROWABLE           (1 << 1)
+
+/* This memory region should not be mapped to the CPU */
+#define PAN_ALLOCATE_INVISIBLE          (1 << 2)
+
+/* This memory region will be used for varyings and needs to have the cache
+ * bits twiddled accordingly */
+#define PAN_ALLOCATE_COHERENT_LOCAL     (1 << 3)
+
+/* This region may not be used immediately and will not mmap on allocate
+ * (semantically distinct from INVISIBLE, which cannot never be mmaped) */
+#define PAN_ALLOCATE_DELAY_MMAP         (1 << 4)
 
 /* Transient slab size. This is a balance between fragmentation against cache
  * locality and ease of bookkeeping */