[PATCH v4 4/8] drm/i915: add gen6 ppgtt dummy creation function

[Robert Beckett]

Internal gem objects will soon just be volatile system memory region
objects.
To enable this, create a separate dummy object creation function
for gen6 ppgtt. The object only exists as a fake object pointing to ggtt
and gains no benefit in going via the internal backend.
Instead, create a dummy gem object and avoid having to maintain a custom
ops api in the internal backend, which makes later refactoring easier.

Signed-off-by: Robert Beckett <bob.beckett at collabora.com>
---
 drivers/gpu/drm/i915/gt/gen6_ppgtt.c | 43 ++++++++++++++++++++++++++--
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/gen6_ppgtt.c b/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
index 1bb766c79dcb..f3b660cfeb7f 100644
--- a/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
+++ b/drivers/gpu/drm/i915/gt/gen6_ppgtt.c
@@ -372,6 +372,45 @@ static const struct drm_i915_gem_object_ops pd_dummy_obj_ops = {
 	.put_pages = pd_dummy_obj_put_pages,
 };
 
+static struct drm_i915_gem_object *
+i915_gem_object_create_dummy(struct drm_i915_private *i915, phys_addr_t size)
+{
+	static struct lock_class_key lock_class;
+	struct drm_i915_gem_object *obj;
+	unsigned int cache_level;
+
+	GEM_BUG_ON(!size);
+	GEM_BUG_ON(!IS_ALIGNED(size, PAGE_SIZE));
+
+	if (overflows_type(size, obj->base.size))
+		return ERR_PTR(-E2BIG);
+
+	obj = i915_gem_object_alloc();
+	if (!obj)
+		return ERR_PTR(-ENOMEM);
+
+	drm_gem_private_object_init(&i915->drm, &obj->base, size);
+	i915_gem_object_init(obj, &pd_dummy_obj_ops, &lock_class, 0);
+	obj->mem_flags |= I915_BO_FLAG_STRUCT_PAGE;
+
+	/*
+	 * Mark the object as volatile, such that the pages are marked as
+	 * dontneed whilst they are still pinned. As soon as they are unpinned
+	 * they are allowed to be reaped by the shrinker, and the caller is
+	 * expected to repopulate - the contents of this object are only valid
+	 * whilst active and pinned.
+	 */
+	i915_gem_object_set_volatile(obj);
+
+	obj->read_domains = I915_GEM_DOMAIN_CPU;
+	obj->write_domain = I915_GEM_DOMAIN_CPU;
+
+	cache_level = HAS_LLC(i915) ? I915_CACHE_LLC : I915_CACHE_NONE;
+	i915_gem_object_set_cache_coherency(obj, cache_level);
+
+	return obj;
+}
+
 static struct i915_page_directory *
 gen6_alloc_top_pd(struct gen6_ppgtt *ppgtt)
 {
@@ -383,9 +422,7 @@ gen6_alloc_top_pd(struct gen6_ppgtt *ppgtt)
 	if (unlikely(!pd))
 		return ERR_PTR(-ENOMEM);
 
-	pd->pt.base = __i915_gem_object_create_internal(ppgtt->base.vm.gt->i915,
-							&pd_dummy_obj_ops,
-							I915_PDES * SZ_4K);
+	pd->pt.base = i915_gem_object_create_dummy(ppgtt->base.vm.gt->i915, I915_PDES * SZ_4K);
 	if (IS_ERR(pd->pt.base)) {
 		err = PTR_ERR(pd->pt.base);
 		pd->pt.base = NULL;
-- 
2.25.1