Documentation/gpu: Add asynchronous flip documentation for i915

.. kernel-doc:: drivers/gpu/drm/i915/display/intel_atomic_plane.c

   :internal:

Asynchronous Page Flip

----------------------

.. kernel-doc:: drivers/gpu/drm/i915/display/intel_display.c

   :doc: asynchronous flip implementation

Output Probing

--------------

	return false;

}

/**

 * DOC: asynchronous flip implementation

 *

 * Asynchronous page flip is the implementation for the DRM_MODE_PAGE_FLIP_ASYNC

 * flag. Currently async flip is only supported via the drmModePageFlip IOCTL.

 * Correspondingly, support is currently added for primary plane only.

 *

 * Async flip can only change the plane surface address, so anything else

 * changing is rejected from the intel_atomic_check_async() function.

 * Once this check is cleared, flip done interrupt is enabled using

 * the skl_enable_flip_done() function.

 *

 * As soon as the surface address register is written, flip done interrupt is

 * generated and the requested events are sent to the usersapce in the interrupt

 * handler itself. The timestamp and sequence sent during the flip done event

 * correspond to the last vblank and have no relation to the actual time when

 * the flip done event was sent.

 */

static int intel_atomic_check_async(struct intel_atomic_state *state)

{

	struct drm_i915_private *i915 = to_i915(state->base.dev);