[PATCH 08/16] drm/i915: align the vma start to the largest gtt page size

[Matthew Auld]

When inserting into a 48bit PPGTT we should the align the vma start
address to the required page size boundary, to guarantee we use said
page size in the gtt. If we are dealing with multiple page-sizes, we
can't guarantee anything and just align to the largest. For soft pinning
we don't force any alignment.

v2: various improvements suggested by Chris

Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_vma.c | 15 +++++++++++++++
 drivers/gpu/drm/i915/i915_vma.h |  1 +
 2 files changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 1aba47024656..15d83c3de4ef 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -471,6 +471,9 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
 	if (ret)
 		return ret;
 
+	vma->page_sizes.phys = obj->mm.page_sizes.phys;
+	vma->page_sizes.sg = obj->mm.page_sizes.sg;
+
 	if (flags & PIN_OFFSET_FIXED) {
 		u64 offset = flags & PIN_OFFSET_MASK;
 		if (!IS_ALIGNED(offset, alignment) ||
@@ -485,6 +488,18 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
 		if (ret)
 			goto err_unpin;
 	} else {
+		/* We only support huge gtt pages through the 48b PPGTT,
+		 * however we also don't want to force any alignment for
+		 * objects which need to be tightly packed into the low 32bits.
+		 */
+		if (end > (1ULL << 32) &&
+		    vma->page_sizes.sg > I915_GTT_PAGE_SIZE) {
+			u64 page_alignment =
+				rounddown_pow_of_two(vma->page_sizes.sg);
+
+			alignment = max(alignment, page_alignment);
+		}
+
 		ret = i915_gem_gtt_insert(vma->vm, &vma->node,
 					  size, alignment, obj->cache_level,
 					  start, end, flags);
diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
index 2e03f81dddbe..ff61acd6e106 100644
--- a/drivers/gpu/drm/i915/i915_vma.h
+++ b/drivers/gpu/drm/i915/i915_vma.h
@@ -51,6 +51,7 @@ struct i915_vma {
 	struct i915_address_space *vm;
 	struct drm_i915_fence_reg *fence;
 	struct sg_table *pages;
+	struct i915_page_sizes page_sizes;
 	void __iomem *iomap;
 	u64 size;
 	u64 display_alignment;
-- 
2.9.4