drm/i915: Not all mappable regions require GTT fence regions

Combining map_and_fenceable revealed a bug in
i915_gem_object_gtt_size() in that it always computed the appropriate
fence size for the object regardless of tiling state which caused us to
over-allocate linear buffers when binding to the GTT.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index d196895..8e3f1de 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -41,9 +41,6 @@ struct change_domains {
        uint32_t flush_rings;
 };
 
-static uint32_t i915_gem_get_gtt_alignment(struct drm_i915_gem_object *obj);
-static uint32_t i915_gem_get_gtt_size(struct drm_i915_gem_object *obj);
-
 static int i915_gem_object_flush_gpu_write_domain(struct drm_i915_gem_object *obj,
                                                  bool pipelined);
 static void i915_gem_object_flush_gtt_write_domain(struct drm_i915_gem_object *obj);
@@ -1443,6 +1440,28 @@ i915_gem_free_mmap_offset(struct drm_i915_gem_object *obj)
        list->map = NULL;
 }
 
+static uint32_t
+i915_gem_get_gtt_size(struct drm_i915_gem_object *obj)
+{
+       struct drm_device *dev = obj->base.dev;
+       uint32_t size;
+
+       if (INTEL_INFO(dev)->gen >= 4 ||
+           obj->tiling_mode == I915_TILING_NONE)
+               return obj->base.size;
+
+       /* Previous chips need a power-of-two fence region when tiling */
+       if (INTEL_INFO(dev)->gen == 3)
+               size = 1024*1024;
+       else
+               size = 512*1024;
+
+       while (size < obj->base.size)
+               size <<= 1;
+
+       return size;
+}
+
 /**
  * i915_gem_get_gtt_alignment - return required GTT alignment for an object
  * @obj: object to check
@@ -1505,34 +1524,6 @@ i915_gem_get_unfenced_gtt_alignment(struct drm_i915_gem_object *obj)
        return tile_height * obj->stride * 2;
 }
 
-static uint32_t
-i915_gem_get_gtt_size(struct drm_i915_gem_object *obj)
-{
-       struct drm_device *dev = obj->base.dev;
-       uint32_t size;
-
-       /*
-        * Minimum alignment is 4k (GTT page size), but might be greater
-        * if a fence register is needed for the object.
-        */
-       if (INTEL_INFO(dev)->gen >= 4)
-               return obj->base.size;
-
-       /*
-        * Previous chips need to be aligned to the size of the smallest
-        * fence register that can contain the object.
-        */
-       if (INTEL_INFO(dev)->gen == 3)
-               size = 1024*1024;
-       else
-               size = 512*1024;
-
-       while (size < obj->base.size)
-               size <<= 1;
-
-       return size;
-}
-
 /**
  * i915_gem_mmap_gtt_ioctl - prepare an object for GTT mmap'ing
  * @dev: DRM device