i965/msaa: Allocate MCS buffer when CMS MSAA is in use.

To implement Gen7's CMS MSAA layout, we need an extra buffer, the MCS
(Multisample Control Surface) buffer.  This patch introduces code for
allocating and deallocating the buffer, and storing a pointer to it in
the intel_mipmap_tree struct.

No functional change, since the CMS layout is not enabled yet.

Reviewed-by: Chad Versace <[email protected]>

3 files changed, 69 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/intel/intel_fbo.c b/src/mesa/drivers/dri/intel/intel_fbo.c
index a801bb74c7e..b86df6ccba2 100644
--- a/src/mesa/drivers/dri/intel/intel_fbo.c
+++ b/src/mesa/drivers/dri/intel/intel_fbo.c
@@ -282,6 +282,14 @@ intel_alloc_renderbuffer_storage(struct gl_context * ctx, struct gl_renderbuffer
       }
    }
 
+   if (irb->mt->msaa_layout == INTEL_MSAA_LAYOUT_CMS) {
+      bool ok = intel_miptree_alloc_mcs(intel, irb->mt, rb->NumSamples);
+      if (!ok) {
+         intel_miptree_release(&irb->mt);
+         return false;
+      }
+   }
+
    return true;
 }
 
diff --git a/src/mesa/drivers/dri/intel/intel_mipmap_tree.c b/src/mesa/drivers/dri/intel/intel_mipmap_tree.c
index 7c95b7924ca..358431b2081 100644
--- a/src/mesa/drivers/dri/intel/intel_mipmap_tree.c
+++ b/src/mesa/drivers/dri/intel/intel_mipmap_tree.c
@@ -407,6 +407,7 @@ intel_miptree_release(struct intel_mipmap_tree **mt)
       intel_region_release(&((*mt)->region));
       intel_miptree_release(&(*mt)->stencil_mt);
       intel_miptree_release(&(*mt)->hiz_mt);
+      intel_miptree_release(&(*mt)->mcs_mt);
       intel_resolve_map_clear(&(*mt)->hiz_map);
 
       for (i = 0; i < MAX_TEXTURE_LEVELS; i++) {
@@ -638,6 +639,52 @@ intel_miptree_copy_teximage(struct intel_context *intel,
 }
 
 bool
+intel_miptree_alloc_mcs(struct intel_context *intel,
+                        struct intel_mipmap_tree *mt,
+                        GLuint num_samples)
+{
+   assert(mt->mcs_mt == NULL);
+   assert(intel->gen >= 7); /* MCS only used on Gen7+ */
+   assert(num_samples == 4); /* TODO: support 8x MSAA */
+
+   /* From the Ivy Bridge PRM, Vol4 Part1 p76, "MCS Base Address":
+    *
+    *     "The MCS surface must be stored as Tile Y."
+    *
+    * We set msaa_format to INTEL_MSAA_LAYOUT_CMS to force
+    * intel_miptree_create() to use Y tiling.  msaa_format is otherwise
+    * ignored for the MCS miptree.
+    */
+   mt->mcs_mt = intel_miptree_create(intel,
+                                     mt->target,
+                                     MESA_FORMAT_A8,
+                                     mt->first_level,
+                                     mt->last_level,
+                                     mt->width0,
+                                     mt->height0,
+                                     mt->depth0,
+                                     true,
+                                     0 /* num_samples */,
+                                     INTEL_MSAA_LAYOUT_CMS);
+
+   /* From the Ivy Bridge PRM, Vol 2 Part 1 p326:
+    *
+    *     When MCS buffer is enabled and bound to MSRT, it is required that it
+    *     is cleared prior to any rendering.
+    *
+    * Since we don't use the MCS buffer for any purpose other than rendering,
+    * it makes sense to just clear it immediately upon allocation.
+    *
+    * Note: the clear value for MCS buffers is all 1's, so we memset to 0xff.
+    */
+   void *data = intel_region_map(intel, mt->mcs_mt->region, 0);
+   memset(data, 0xff, mt->mcs_mt->region->bo->size);
+   intel_region_unmap(intel, mt->mcs_mt->region);
+
+   return mt->mcs_mt;
+}
+
+bool
 intel_miptree_alloc_hiz(struct intel_context *intel,
 			struct intel_mipmap_tree *mt,
                         GLuint num_samples)
diff --git a/src/mesa/drivers/dri/intel/intel_mipmap_tree.h b/src/mesa/drivers/dri/intel/intel_mipmap_tree.h
index 38412cd1b7f..74fcc796cf5 100644
--- a/src/mesa/drivers/dri/intel/intel_mipmap_tree.h
+++ b/src/mesa/drivers/dri/intel/intel_mipmap_tree.h
@@ -276,6 +276,15 @@ struct intel_mipmap_tree
     */
    struct intel_mipmap_tree *stencil_mt;
 
+   /**
+    * \brief MCS miptree for multisampled textures.
+    *
+    * This miptree contains the "multisample control surface", which stores
+    * the necessary information to implement compressed MSAA on Gen7+
+    * (INTEL_MSAA_FORMAT_CMS).
+    */
+   struct intel_mipmap_tree *mcs_mt;
+
    /* These are also refcounted:
     */
    GLuint refcount;
@@ -388,6 +397,11 @@ intel_miptree_s8z24_gather(struct intel_context *intel,
                            uint32_t level,
                            uint32_t layer);
 
+bool
+intel_miptree_alloc_mcs(struct intel_context *intel,
+                        struct intel_mipmap_tree *mt,
+                        GLuint num_samples);
+
 /**
  * \name Miptree HiZ functions
  * \{