- * bits0-15 are for generic caching control (i.e. the above defined
- * values). bits16-31 are reserved for platform-specific variations
- * (e.g. l3$ caching on gen7). */
+ * The supported @caching values:
+ *
+ * I915_CACHING_NONE:
+ *
+ * GPU access is not coherent with CPU caches. Default for machines
+ * without an LLC. This means manual flushing might be needed, if we
+ * want GPU access to be coherent.
+ *
+ * I915_CACHING_CACHED:
+ *
+ * GPU access is coherent with CPU caches and furthermore the data is
+ * cached in last-level caches shared between CPU cores and the GPU GT.
+ *
+ * I915_CACHING_DISPLAY:
+ *
+ * Special GPU caching mode which is coherent with the scanout engines.
+ * Transparently falls back to I915_CACHING_NONE on platforms where no
+ * special cache mode (like write-through or gfdt flushing) is
+ * available. The kernel automatically sets this mode when using a
+ * buffer as a scanout target. Userspace can manually set this mode to
+ * avoid a costly stall and clflush in the hotpath of drawing the first
+ * frame.
+ */
+#define I915_CACHING_NONE 0
+#define I915_CACHING_CACHED 1
+#define I915_CACHING_DISPLAY 2