diff options
| -rw-r--r-- | Documentation/DocBook/drm.tmpl | 5 | ||||
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gem_gtt.c | 60 |
2 files changed, 65 insertions, 0 deletions
diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl index 4fc5d730959b..f931b3decccd 100644 --- a/Documentation/DocBook/drm.tmpl +++ b/Documentation/DocBook/drm.tmpl @@ -4038,6 +4038,11 @@ int num_ioctls;</synopsis> !Pdrivers/gpu/drm/i915/intel_lrc.c Logical Rings, Logical Ring Contexts and Execlists !Idrivers/gpu/drm/i915/intel_lrc.c </sect2> + <sect2> + <title>Global GTT views</title> +!Pdrivers/gpu/drm/i915/i915_gem_gtt.c Global GTT views +!Idrivers/gpu/drm/i915/i915_gem_gtt.c + </sect2> </sect1> <sect1> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c index 9821a6095e53..cc3056f2c7f4 100644 --- a/drivers/gpu/drm/i915/i915_gem_gtt.c +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c @@ -30,6 +30,66 @@ #include "i915_trace.h" #include "intel_drv.h" +/** + * DOC: Global GTT views + * + * Background and previous state + * + * Historically objects could exists (be bound) in global GTT space only as + * singular instances with a view representing all of the object's backing pages + * in a linear fashion. This view will be called a normal view. + * + * To support multiple views of the same object, where the number of mapped + * pages is not equal to the backing store, or where the layout of the pages + * is not linear, concept of a GGTT view was added. + * + * One example of an alternative view is a stereo display driven by a single + * image. In this case we would have a framebuffer looking like this + * (2x2 pages): + * + * 12 + * 34 + * + * Above would represent a normal GGTT view as normally mapped for GPU or CPU + * rendering. In contrast, fed to the display engine would be an alternative + * view which could look something like this: + * + * 1212 + * 3434 + * + * In this example both the size and layout of pages in the alternative view is + * different from the normal view. + * + * Implementation and usage + * + * GGTT views are implemented using VMAs and are distinguished via enum + * i915_ggtt_view_type and struct i915_ggtt_view. + * + * A new flavour of core GEM functions which work with GGTT bound objects were + * added with the _view suffix. They take the struct i915_ggtt_view parameter + * encapsulating all metadata required to implement a view. + * + * As a helper for callers which are only interested in the normal view, + * globally const i915_ggtt_view_normal singleton instance exists. All old core + * GEM API functions, the ones not taking the view parameter, are operating on, + * or with the normal GGTT view. + * + * Code wanting to add or use a new GGTT view needs to: + * + * 1. Add a new enum with a suitable name. + * 2. Extend the metadata in the i915_ggtt_view structure if required. + * 3. Add support to i915_get_vma_pages(). + * + * New views are required to build a scatter-gather table from within the + * i915_get_vma_pages function. This table is stored in the vma.ggtt_view and + * exists for the lifetime of an VMA. + * + * Core API is designed to have copy semantics which means that passed in + * struct i915_ggtt_view does not need to be persistent (left around after + * calling the core API functions). + * + */ + const struct i915_ggtt_view i915_ggtt_view_normal; static void bdw_setup_private_ppat(struct drm_i915_private *dev_priv); |