i965: Move singlesample_mt to the renderbuffer.

Since only window system renderbuffers can have a singlesample_mt, this
lets us drop a bunch of sanity checking to make sure that we're just a
renderbuffer-like thing.

v2: Fix a badly-written comment (thanks Kenneth!), drop the now trivial
    helper function for set_needs_downsample.

Reviewed-by: Kenneth Graunke <[email protected]>

8 files changed, 168 insertions, 276 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
index 0aeb651cefd..39a15edfd8f 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp
@@ -193,7 +193,7 @@ do_blorp_blit(struct brw_context *brw, GLbitfield buffer_bit,
                            dstX0, dstY0, dstX1, dstY1,
                            filter, mirror_x, mirror_y);
 
-   intel_renderbuffer_set_needs_downsample(dst_irb);
+   dst_irb->need_downsample = true;
 }
 
 static bool
diff --git a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
index 94672e00e35..9159df5978c 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
@@ -592,7 +592,7 @@ brw_blorp_clear_color(struct brw_context *brw, struct gl_framebuffer *fb,
             return false;
       }
 
-      intel_renderbuffer_set_needs_downsample(irb);
+      irb->need_downsample = true;
    }
 
    return true;
diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
index ba2f971bcc1..1071f9f805c 100644
--- a/src/mesa/drivers/dri/i965/brw_context.c
+++ b/src/mesa/drivers/dri/i965/brw_context.c
@@ -997,7 +997,7 @@ intel_resolve_for_dri2_flush(struct brw_context *brw,
       if (rb->mt->num_samples <= 1)
          intel_miptree_resolve_color(brw, rb->mt);
       else
-         intel_miptree_downsample(brw, rb->mt);
+         intel_renderbuffer_downsample(brw, rb);
    }
 }
 
@@ -1270,10 +1270,9 @@ intel_process_dri2_buffer(struct brw_context *brw,
            rb->mt->region->name == buffer->name)
           return;
    } else {
-       if (rb->mt &&
-           rb->mt->singlesample_mt &&
-           rb->mt->singlesample_mt->region &&
-           rb->mt->singlesample_mt->region->name == buffer->name)
+       if (rb->singlesample_mt &&
+           rb->singlesample_mt->region &&
+           rb->singlesample_mt->region->name == buffer->name)
           return;
    }
 
@@ -1308,7 +1307,7 @@ intel_process_dri2_buffer(struct brw_context *brw,
        (buffer->attachment == __DRI_BUFFER_FRONT_LEFT ||
         buffer->attachment == __DRI_BUFFER_FAKE_FRONT_LEFT) &&
        rb->Base.Base.NumSamples > 1) {
-      intel_miptree_upsample(brw, rb->mt);
+      intel_renderbuffer_upsample(brw, rb);
    }
 
    assert(rb->mt);
@@ -1355,10 +1354,9 @@ intel_update_image_buffer(struct brw_context *intel,
            rb->mt->region->bo == region->bo)
           return;
    } else {
-       if (rb->mt &&
-           rb->mt->singlesample_mt &&
-           rb->mt->singlesample_mt->region &&
-           rb->mt->singlesample_mt->region->bo == region->bo)
+       if (rb->singlesample_mt &&
+           rb->singlesample_mt->region &&
+           rb->singlesample_mt->region->bo == region->bo)
           return;
    }
 
@@ -1367,7 +1365,7 @@ intel_update_image_buffer(struct brw_context *intel,
    if (intel->is_front_buffer_rendering &&
        buffer_type == __DRI_IMAGE_BUFFER_FRONT &&
        rb->Base.Base.NumSamples > 1) {
-      intel_miptree_upsample(intel, rb->mt);
+      intel_renderbuffer_upsample(intel, rb);
    }
 }
 
diff --git a/src/mesa/drivers/dri/i965/brw_draw.c b/src/mesa/drivers/dri/i965/brw_draw.c
index 484c4c181b1..540834c2422 100644
--- a/src/mesa/drivers/dri/i965/brw_draw.c
+++ b/src/mesa/drivers/dri/i965/brw_draw.c
@@ -351,9 +351,9 @@ static void brw_postdraw_set_buffers_need_resolve(struct brw_context *brw)
       front_irb = intel_get_renderbuffer(fb, BUFFER_FRONT_LEFT);
 
    if (front_irb)
-      intel_renderbuffer_set_needs_downsample(front_irb);
+      front_irb->need_downsample = true;
    if (back_irb)
-      intel_renderbuffer_set_needs_downsample(back_irb);
+      back_irb->need_downsample = true;
    if (depth_irb && ctx->Depth.Mask)
       intel_renderbuffer_att_set_needs_depth_resolve(depth_att);
 }
diff --git a/src/mesa/drivers/dri/i965/intel_fbo.c b/src/mesa/drivers/dri/i965/intel_fbo.c
index cd148f0f488..d11cdb6605c 100644
--- a/src/mesa/drivers/dri/i965/intel_fbo.c
+++ b/src/mesa/drivers/dri/i965/intel_fbo.c
@@ -74,11 +74,41 @@ intel_delete_renderbuffer(struct gl_context *ctx, struct gl_renderbuffer *rb)
    ASSERT(irb);
 
    intel_miptree_release(&irb->mt);
+   intel_miptree_release(&irb->singlesample_mt);
 
    _mesa_delete_renderbuffer(ctx, rb);
 }
 
 /**
+ * \brief Downsample a winsys renderbuffer from mt to singlesample_mt.
+ *
+ * If the miptree needs no downsample, then skip.
+ */
+void
+intel_renderbuffer_downsample(struct brw_context *brw,
+                              struct intel_renderbuffer *irb)
+{
+   if (!irb->need_downsample)
+      return;
+   intel_miptree_updownsample(brw, irb->mt, irb->singlesample_mt);
+   irb->need_downsample = false;
+}
+
+/**
+ * \brief Upsample a winsys renderbuffer from singlesample_mt to mt.
+ *
+ * The upsample is done unconditionally.
+ */
+void
+intel_renderbuffer_upsample(struct brw_context *brw,
+                            struct intel_renderbuffer *irb)
+{
+   assert(!irb->need_downsample);
+
+   intel_miptree_updownsample(brw, irb->singlesample_mt, irb->mt);
+}
+
+/**
  * \see dd_function_table::MapRenderbuffer
  */
 static void
@@ -92,6 +122,7 @@ intel_map_renderbuffer(struct gl_context *ctx,
    struct brw_context *brw = brw_context(ctx);
    struct swrast_renderbuffer *srb = (struct swrast_renderbuffer *)rb;
    struct intel_renderbuffer *irb = intel_renderbuffer(rb);
+   struct intel_mipmap_tree *mt;
    void *map;
    int stride;
 
@@ -106,6 +137,39 @@ intel_map_renderbuffer(struct gl_context *ctx,
 
    intel_prepare_render(brw);
 
+   /* The MapRenderbuffer API should always return a single-sampled mapping.
+    * The case we are asked to map multisampled RBs is in glReadPixels() (or
+    * swrast paths like glCopyTexImage()) from a window-system MSAA buffer,
+    * and GL expects an automatic resolve to happen.
+    *
+    * If it's a color miptree, there is a ->singlesample_mt which wraps the
+    * actual window system renderbuffer (which we may resolve to at any time),
+    * while the miptree itself is our driver-private allocation.  If it's a
+    * depth or stencil miptree, we have a private MSAA buffer and no shared
+    * singlesample buffer, and since we don't expect anybody to ever actually
+    * resolve it, we just make a temporary singlesample buffer now when we
+    * have to.
+    */
+   if (rb->NumSamples > 1) {
+      if (!irb->singlesample_mt) {
+         irb->singlesample_mt =
+            intel_miptree_create_for_renderbuffer(brw, irb->mt->format,
+                                                  rb->Width, rb->Height,
+                                                  0 /*num_samples*/);
+         if (!irb->singlesample_mt)
+            goto fail;
+         irb->singlesample_mt_is_tmp = true;
+         irb->need_downsample = true;
+      }
+
+      intel_renderbuffer_downsample(brw, irb);
+      mt = irb->singlesample_mt;
+
+      irb->need_map_upsample = mode & GL_MAP_WRITE_BIT;
+   } else {
+      mt = irb->mt;
+   }
+
    /* For a window-system renderbuffer, we need to flip the mapping we receive
     * upside-down.  So we need to ask for a rectangle on flipped vertically, and
     * we then return a pointer to the bottom of it with a negative stride.
@@ -114,7 +178,7 @@ intel_map_renderbuffer(struct gl_context *ctx,
       y = rb->Height - y - h;
    }
 
-   intel_miptree_map(brw, irb->mt, irb->mt_level, irb->mt_layer,
+   intel_miptree_map(brw, mt, irb->mt_level, irb->mt_layer,
 		     x, y, w, h, mode, &map, &stride);
 
    if (rb->Name == 0) {
@@ -128,6 +192,11 @@ intel_map_renderbuffer(struct gl_context *ctx,
 
    *out_map = map;
    *out_stride = stride;
+   return;
+
+fail:
+   *out_map = NULL;
+   *out_stride = 0;
 }
 
 /**
@@ -140,6 +209,7 @@ intel_unmap_renderbuffer(struct gl_context *ctx,
    struct brw_context *brw = brw_context(ctx);
    struct swrast_renderbuffer *srb = (struct swrast_renderbuffer *)rb;
    struct intel_renderbuffer *irb = intel_renderbuffer(rb);
+   struct intel_mipmap_tree *mt;
 
    DBG("%s: rb %d (%s)\n", __FUNCTION__,
        rb->Name, _mesa_get_format_name(rb->Format));
@@ -150,7 +220,21 @@ intel_unmap_renderbuffer(struct gl_context *ctx,
       return;
    }
 
-   intel_miptree_unmap(brw, irb->mt, irb->mt_level, irb->mt_layer);
+   if (rb->NumSamples > 1) {
+      mt = irb->singlesample_mt;
+   } else {
+      mt = irb->mt;
+   }
+
+   intel_miptree_unmap(brw, mt, irb->mt_level, irb->mt_layer);
+
+   if (irb->need_map_upsample) {
+      intel_renderbuffer_upsample(brw, irb);
+      irb->need_map_upsample = false;
+   }
+
+   if (irb->singlesample_mt_is_tmp)
+      intel_miptree_release(&irb->singlesample_mt);
 }
 
 
@@ -788,16 +872,6 @@ intel_blit_framebuffer(struct gl_context *ctx,
 }
 
 /**
- * This is a no-op except on multisample buffers shared with DRI2.
- */
-void
-intel_renderbuffer_set_needs_downsample(struct intel_renderbuffer *irb)
-{
-   if (irb->mt && irb->mt->singlesample_mt)
-      irb->mt->need_downsample = true;
-}
-
-/**
  * Does the renderbuffer have hiz enabled?
  */
 bool
diff --git a/src/mesa/drivers/dri/i965/intel_fbo.h b/src/mesa/drivers/dri/i965/intel_fbo.h
index 45e2cd89d9e..b8db7e2d73f 100644
--- a/src/mesa/drivers/dri/i965/intel_fbo.h
+++ b/src/mesa/drivers/dri/i965/intel_fbo.h
@@ -49,7 +49,26 @@ struct intel_texture_image;
 struct intel_renderbuffer
 {
    struct swrast_renderbuffer Base;
-   struct intel_mipmap_tree *mt; /**< The renderbuffer storage. */
+   /**
+    * The real renderbuffer storage.
+    *
+    * This is multisampled if NumSamples is > 1.
+    */
+   struct intel_mipmap_tree *mt;
+
+   /**
+    * Downsampled contents for window-system MSAA renderbuffers.
+    *
+    * For window system MSAA color buffers, the singlesample_mt is shared with
+    * other processes in DRI2 (and in DRI3, it's the image buffer managed by
+    * glx_dri3.c), while mt is private to our process.  To do a swapbuffers,
+    * we have to downsample out of mt into singlesample_mt.  For depth and
+    * stencil buffers, the singlesample_mt is also private, and since we don't
+    * expect to need to do resolves (except if someone does a glReadPixels()
+    * or glCopyTexImage()), we just temporarily allocate singlesample_mt when
+    * asked to map the renderbuffer.
+    */
+   struct intel_mipmap_tree *singlesample_mt;
 
    /**
     * \name Miptree view
@@ -74,6 +93,24 @@ struct intel_renderbuffer
    /** \} */
 
    GLuint draw_x, draw_y; /**< Offset of drawing within the region */
+
+   /**
+    * Set to true at every draw call, to indicate if a window-system
+    * renderbuffer needs to be downsampled before using singlesample_mt.
+    */
+   bool need_downsample;
+
+   /**
+    * Set to true when doing an intel_renderbuffer_map()/unmap() that requires
+    * an upsample at the end.
+    */
+   bool need_map_upsample;
+
+   /**
+    * Set to true if singlesample_mt is temporary storage that persists only
+    * for the duration of a mapping.
+    */
+   bool singlesample_mt_is_tmp;
 };
 
 
@@ -157,9 +194,6 @@ intel_renderbuffer_get_tile_offsets(struct intel_renderbuffer *irb,
                                          tile_x, tile_y);
 }
 
-void
-intel_renderbuffer_set_needs_downsample(struct intel_renderbuffer *irb);
-
 bool
 intel_renderbuffer_has_hiz(struct intel_renderbuffer *irb);
 
@@ -195,6 +229,14 @@ void intel_renderbuffer_move_to_temp(struct brw_context *brw,
                                      struct intel_renderbuffer *irb,
                                      bool invalidate);
 
+void
+intel_renderbuffer_downsample(struct brw_context *brw,
+                              struct intel_renderbuffer *irb);
+
+void
+intel_renderbuffer_upsample(struct brw_context *brw,
+                            struct intel_renderbuffer *irb);
+
 unsigned
 intel_quantize_num_samples(struct intel_screen *intel, unsigned num_samples);
 
diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
index c5c8a362f9d..dcc8b6e2c5b 100644
--- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
+++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
@@ -728,10 +728,9 @@ intel_update_winsys_renderbuffer_miptree(struct brw_context *intel,
       return NULL;
    }
 
-   multisample_mt->singlesample_mt = singlesample_mt;
-   multisample_mt->need_downsample = false;
-
+   irb->need_downsample = false;
    irb->mt = multisample_mt;
+   irb->singlesample_mt = singlesample_mt;
 }
 
 struct intel_mipmap_tree*
@@ -799,7 +798,6 @@ intel_miptree_release(struct intel_mipmap_tree **mt)
       intel_miptree_release(&(*mt)->stencil_mt);
       intel_miptree_release(&(*mt)->hiz_mt);
       intel_miptree_release(&(*mt)->mcs_mt);
-      intel_miptree_release(&(*mt)->singlesample_mt);
       intel_resolve_map_clear(&(*mt)->hiz_map);
 
       for (i = 0; i < MAX_TEXTURE_LEVELS; i++) {
@@ -1547,7 +1545,7 @@ intel_offset_S8(uint32_t stride, uint32_t x, uint32_t y, bool swizzled)
    return u;
 }
 
-static void
+void
 intel_miptree_updownsample(struct brw_context *brw,
                            struct intel_mipmap_tree *src,
                            struct intel_mipmap_tree *dst)
@@ -1573,49 +1571,6 @@ intel_miptree_updownsample(struct brw_context *brw,
    }
 }
 
-static void
-assert_is_flat(struct intel_mipmap_tree *mt)
-{
-   assert(mt->target == GL_TEXTURE_2D ||
-          mt->target == GL_TEXTURE_2D_MULTISAMPLE);
-   assert(mt->first_level == 0);
-   assert(mt->last_level == 0);
-}
-
-/**
- * \brief Downsample from mt to mt->singlesample_mt.
- *
- * If the miptree needs no downsample, then skip.
- */
-void
-intel_miptree_downsample(struct brw_context *brw,
-                         struct intel_mipmap_tree *mt)
-{
-   /* Only flat, renderbuffer-like miptrees are supported. */
-   assert_is_flat(mt);
-
-   if (!mt->need_downsample)
-      return;
-   intel_miptree_updownsample(brw, mt, mt->singlesample_mt);
-   mt->need_downsample = false;
-}
-
-/**
- * \brief Upsample from mt->singlesample_mt to mt.
- *
- * The upsample is done unconditionally.
- */
-void
-intel_miptree_upsample(struct brw_context *brw,
-                       struct intel_mipmap_tree *mt)
-{
-   /* Only flat, renderbuffer-like miptrees are supported. */
-   assert_is_flat(mt);
-   assert(!mt->need_downsample);
-
-   intel_miptree_updownsample(brw, mt->singlesample_mt, mt);
-}
-
 void *
 intel_miptree_map_raw(struct brw_context *brw, struct intel_mipmap_tree *mt)
 {
@@ -2164,18 +2119,18 @@ can_blit_slice(struct intel_mipmap_tree *mt,
    return true;
 }
 
-static void
-intel_miptree_map_singlesample(struct brw_context *brw,
-                               struct intel_mipmap_tree *mt,
-                               unsigned int level,
-                               unsigned int slice,
-                               unsigned int x,
-                               unsigned int y,
-                               unsigned int w,
-                               unsigned int h,
-                               GLbitfield mode,
-                               void **out_ptr,
-                               int *out_stride)
+void
+intel_miptree_map(struct brw_context *brw,
+                  struct intel_mipmap_tree *mt,
+                  unsigned int level,
+                  unsigned int slice,
+                  unsigned int x,
+                  unsigned int y,
+                  unsigned int w,
+                  unsigned int h,
+                  GLbitfield mode,
+                  void **out_ptr,
+                  int *out_stride)
 {
    struct intel_miptree_map *map;
 
@@ -2228,11 +2183,11 @@ intel_miptree_map_singlesample(struct brw_context *brw,
       intel_miptree_release_map(mt, level, slice);
 }
 
-static void
-intel_miptree_unmap_singlesample(struct brw_context *brw,
-                                 struct intel_mipmap_tree *mt,
-                                 unsigned int level,
-                                 unsigned int slice)
+void
+intel_miptree_unmap(struct brw_context *brw,
+                    struct intel_mipmap_tree *mt,
+                    unsigned int level,
+                    unsigned int slice)
 {
    struct intel_miptree_map *map = mt->level[level].slice[slice].map;
 
@@ -2263,127 +2218,3 @@ intel_miptree_unmap_singlesample(struct brw_context *brw,
 
    intel_miptree_release_map(mt, level, slice);
 }
-
-static void
-intel_miptree_map_multisample(struct brw_context *brw,
-                              struct intel_mipmap_tree *mt,
-                              unsigned int level,
-                              unsigned int slice,
-                              unsigned int x,
-                              unsigned int y,
-                              unsigned int w,
-                              unsigned int h,
-                              GLbitfield mode,
-                              void **out_ptr,
-                              int *out_stride)
-{
-   struct gl_context *ctx = &brw->ctx;
-   struct intel_miptree_map *map;
-
-   assert(mt->num_samples > 1);
-
-   /* Only flat, renderbuffer-like miptrees are supported. */
-   if (mt->target != GL_TEXTURE_2D_MULTISAMPLE ||
-       mt->first_level != 0 ||
-       mt->last_level != 0) {
-      _mesa_problem(ctx, "attempt to map a multisample miptree for "
-                    "which (target, first_level, last_level != "
-                    "(GL_TEXTURE_2D, 0, 0)");
-      goto fail;
-   }
-
-   map = intel_miptree_attach_map(mt, level, slice, x, y, w, h, mode);
-   if (!map)
-      goto fail;
-
-   if (!mt->singlesample_mt) {
-      mt->singlesample_mt =
-         intel_miptree_create_for_renderbuffer(brw,
-                                               mt->format,
-                                               mt->logical_width0,
-                                               mt->logical_height0,
-                                               0 /*num_samples*/);
-      if (!mt->singlesample_mt)
-         goto fail;
-
-      map->singlesample_mt_is_tmp = true;
-      mt->need_downsample = true;
-   }
-
-   intel_miptree_downsample(brw, mt);
-   intel_miptree_map_singlesample(brw, mt->singlesample_mt,
-                                  level, slice,
-                                  x, y, w, h,
-                                  mode,
-                                  out_ptr, out_stride);
-   return;
-
-fail:
-   intel_miptree_release_map(mt, level, slice);
-   *out_ptr = NULL;
-   *out_stride = 0;
-}
-
-static void
-intel_miptree_unmap_multisample(struct brw_context *brw,
-                                struct intel_mipmap_tree *mt,
-                                unsigned int level,
-                                unsigned int slice)
-{
-   struct intel_miptree_map *map = mt->level[level].slice[slice].map;
-
-   assert(mt->num_samples > 1);
-
-   if (!map)
-      return;
-
-   intel_miptree_unmap_singlesample(brw, mt->singlesample_mt, level, slice);
-
-   mt->need_downsample = false;
-   if (map->mode & GL_MAP_WRITE_BIT)
-      intel_miptree_upsample(brw, mt);
-
-   if (map->singlesample_mt_is_tmp)
-      intel_miptree_release(&mt->singlesample_mt);
-
-   intel_miptree_release_map(mt, level, slice);
-}
-
-void
-intel_miptree_map(struct brw_context *brw,
-		  struct intel_mipmap_tree *mt,
-		  unsigned int level,
-		  unsigned int slice,
-		  unsigned int x,
-		  unsigned int y,
-		  unsigned int w,
-		  unsigned int h,
-		  GLbitfield mode,
-		  void **out_ptr,
-		  int *out_stride)
-{
-   if (mt->num_samples <= 1)
-      intel_miptree_map_singlesample(brw, mt,
-                                     level, slice,
-                                     x, y, w, h,
-                                     mode,
-                                     out_ptr, out_stride);
-   else
-      intel_miptree_map_multisample(brw, mt,
-                                    level, slice,
-                                    x, y, w, h,
-                                    mode,
-                                    out_ptr, out_stride);
-}
-
-void
-intel_miptree_unmap(struct brw_context *brw,
-		    struct intel_mipmap_tree *mt,
-		    unsigned int level,
-		    unsigned int slice)
-{
-   if (mt->num_samples <= 1)
-      intel_miptree_unmap_singlesample(brw, mt, level, slice);
-   else
-      intel_miptree_unmap_multisample(brw, mt, level, slice);
-}
diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.h b/src/mesa/drivers/dri/i965/intel_mipmap_tree.h
index 753e938d625..aa3247bcf77 100644
--- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.h
+++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.h
@@ -93,12 +93,6 @@ struct intel_miptree_map {
    void *ptr;
    /** Stride of the mapping. */
    int stride;
-
-   /**
-    * intel_mipmap_tree::singlesample_mt is temporary storage that persists
-    * only for the duration of the map.
-    */
-   bool singlesample_mt_is_tmp;
 };
 
 /**
@@ -371,50 +365,6 @@ struct intel_mipmap_tree
    uint32_t offset;
 
    /**
-    * \brief Singlesample miptree.
-    *
-    * This is used under two cases.
-    *
-    * --- Case 1: As persistent singlesample storage for multisample window
-    *  system front and back buffers ---
-    *
-    * Suppose that the window system FBO was created with a multisample
-    * config.  Let `back_irb` be the `intel_renderbuffer` for the FBO's back
-    * buffer. Then `back_irb` contains two miptrees: a parent multisample
-    * miptree (back_irb->mt) and a child singlesample miptree
-    * (back_irb->mt->singlesample_mt).  The DRM buffer shared with DRI2
-    * belongs to `back_irb->mt->singlesample_mt` and contains singlesample
-    * data.  The singlesample miptree is created at the same time as and
-    * persists for the lifetime of its parent multisample miptree.
-    *
-    * When access to the singlesample data is needed, such as at
-    * eglSwapBuffers and glReadPixels, an automatic downsample occurs from
-    * `back_rb->mt` to `back_rb->mt->singlesample_mt` when necessary.
-    *
-    * This description of the back buffer applies analogously to the front
-    * buffer.
-    *
-    *
-    * --- Case 2: As temporary singlesample storage for mapping multisample
-    *  miptrees ---
-    *
-    * Suppose the intel_miptree_map is called on a multisample miptree, `mt`,
-    * for which case 1 does not apply (that is, `mt` does not belong to
-    * a front or back buffer).  Then `mt->singlesample_mt` is null at the
-    * start of the call. intel_miptree_map will create a temporary
-    * singlesample miptree, store it at `mt->singlesample_mt`, downsample from
-    * `mt` to `mt->singlesample_mt` if necessary, then map
-    * `mt->singlesample_mt`. The temporary miptree is later deleted during
-    * intel_miptree_unmap.
-    */
-   struct intel_mipmap_tree *singlesample_mt;
-
-   /**
-    * \brief A downsample is needed from this miptree to singlesample_mt.
-    */
-   bool need_downsample;
-
-   /**
     * \brief HiZ miptree
     *
     * The hiz miptree contains the miptree's hiz buffer. To allocate the hiz
@@ -699,12 +649,9 @@ intel_miptree_make_shareable(struct brw_context *brw,
                              struct intel_mipmap_tree *mt);
 
 void
-intel_miptree_downsample(struct brw_context *brw,
-                         struct intel_mipmap_tree *mt);
-
-void
-intel_miptree_upsample(struct brw_context *brw,
-                       struct intel_mipmap_tree *mt);
+intel_miptree_updownsample(struct brw_context *brw,
+                           struct intel_mipmap_tree *src,
+                           struct intel_mipmap_tree *dst);
 
 void brw_miptree_layout(struct brw_context *brw, struct intel_mipmap_tree *mt);