Merge tag 'drm-intel-next-2016-01-24' of git://anongit.freedesktop.org/drm-intel into drm-next

- support for v3 vbt dsi blocks (Jani)
- improve mmio debug checks (Mika Kuoppala)
- reorg the ddi port translation table entries and related code (Ville)
- reorg gen8 interrupt handling for future platforms (Tvrtko)
- refactor tile width/height computations for framebuffers (Ville)
- kerneldoc integration for intel_pm.c (Jani)
- move default context from engines to device-global dev_priv (Dave Gordon)
- make seqno/irq ordering coherent with execlist (Chris)
- decouple internal engine number from UABI (Chris&Tvrtko)
- tons of small fixes all over, as usual

* tag 'drm-intel-next-2016-01-24' of git://anongit.freedesktop.org/drm-intel: (148 commits)
  drm/i915: Update DRIVER_DATE to 20160124
  drm/i915: Seal busy-ioctl uABI and prevent leaking of internal ids
  drm/i915: Decouple execbuf uAPI from internal implementation
  drm/i915: Use ordered seqno write interrupt generation on gen8+ execlists
  drm/i915: Limit the auto arming of mmio debugs on vlv/chv
  drm/i915: Tune down "GT register while GT waking disabled" message
  drm/i915: tidy up a few leftovers
  drm/i915: abolish separate per-ring default_context pointers
  drm/i915: simplify allocation of driver-internal requests
  drm/i915: Fix NULL plane->fb oops on SKL
  drm/i915: Do not put big intel_crtc_state on the stack
  Revert "drm/i915: Add two-stage ILK-style watermark programming (v10)"
  drm/i915: add DOC: headline to RC6 kernel-doc
  drm/i915: turn some bogus kernel-doc comments to normal comments
  drm/i915/sdvo: revert bogus kernel-doc comments to normal comments
  drm/i915/gen9: Correct max save/restore register count during gpu reset with GuC
  drm/i915: Demote user facing DMC firmware load failure message
  drm/i915: use hlist_for_each_entry
  drm/i915: skl_update_scaler() wants a rotation bitmask instead of bit number
  drm/i915: Don't reject primary plane windowing with color keying enabled on SKL+
  ...

include/uapi/drm/i915_drm.h

@@ -812,10 +812,35 @@ struct drm_i915_gem_busy {
 	/** Handle of the buffer to check for busy */
 	__u32 handle;
 
-	/** Return busy status (1 if busy, 0 if idle).
-	 * The high word is used to indicate on which rings the object
-	 * currently resides:
-	 *  16:31 - busy (r or r/w) rings (16 render, 17 bsd, 18 blt, etc)
+	/** Return busy status
+	 *
+	 * A return of 0 implies that the object is idle (after
+	 * having flushed any pending activity), and a non-zero return that
+	 * the object is still in-flight on the GPU. (The GPU has not yet
+	 * signaled completion for all pending requests that reference the
+	 * object.)
+	 *
+	 * The returned dword is split into two fields to indicate both
+	 * the engines on which the object is being read, and the
+	 * engine on which it is currently being written (if any).
+	 *
+	 * The low word (bits 0:15) indicate if the object is being written
+	 * to by any engine (there can only be one, as the GEM implicit
+	 * synchronisation rules force writes to be serialised). Only the
+	 * engine for the last write is reported.
+	 *
+	 * The high word (bits 16:31) are a bitmask of which engines are
+	 * currently reading from the object. Multiple engines may be
+	 * reading from the object simultaneously.
+	 *
+	 * The value of each engine is the same as specified in the
+	 * EXECBUFFER2 ioctl, i.e. I915_EXEC_RENDER, I915_EXEC_BSD etc.
+	 * Note I915_EXEC_DEFAULT is a symbolic value and is mapped to
+	 * the I915_EXEC_RENDER engine for execution, and so it is never
+	 * reported as active itself. Some hardware may have parallel
+	 * execution engines, e.g. multiple media engines, which are
+	 * mapped to the same identifier in the EXECBUFFER2 ioctl and
+	 * so are not separately reported for busyness.
 	 */
 	__u32 busy;
 };