drm/i915/gen8: Pass sg_iter through pte inserts

As a step towards implementing 4 levels, while not discarding the
existing pte insert functions, we need to pass the sg_iter through.
The current function understands to the page directory granularity.
An object's pages may span the page directory, and so using the iter
directly as we write the PTEs allows the iterator to stay coherent
through a VMA insert operation spanning multiple page table levels.

v2: Rebase after s/page_tables/page_table/.
v3: Rebase after Mika's ppgtt cleanup / scratch merge patch series;
updated commit message (s/map/insert).
v4: Rebase.

Reviewed-by: Akash Goel <akash.goel@intel.com> (v3)
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Michel Thierry <michel.thierry@intel.com> (v2+)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -746,7 +746,7 @@ static void gen8_ppgtt_clear_range(struct i915_address_space *vm,
 static void
 gen8_ppgtt_insert_pte_entries(struct i915_address_space *vm,
 			      struct i915_page_directory_pointer *pdp,
-			      struct sg_table *pages,
+			      struct sg_page_iter *sg_iter,
 			      uint64_t start,
 			      enum i915_cache_level cache_level)
 {
@@ -756,11 +756,10 @@ gen8_ppgtt_insert_pte_entries(struct i915_address_space *vm,
 	unsigned pdpe = start >> GEN8_PDPE_SHIFT & GEN8_PDPE_MASK;
 	unsigned pde = start >> GEN8_PDE_SHIFT & GEN8_PDE_MASK;
 	unsigned pte = start >> GEN8_PTE_SHIFT & GEN8_PTE_MASK;
-	struct sg_page_iter sg_iter;
 
 	pt_vaddr = NULL;
 
-	for_each_sg_page(pages->sgl, &sg_iter, pages->nents, 0) {
+	while (__sg_page_iter_next(sg_iter)) {
 		if (WARN_ON(pdpe >= GEN8_LEGACY_PDPES))
 			break;
 
@@ -771,7 +770,7 @@ gen8_ppgtt_insert_pte_entries(struct i915_address_space *vm,
 		}
 
 		pt_vaddr[pte] =
-			gen8_pte_encode(sg_page_iter_dma_address(&sg_iter),
+			gen8_pte_encode(sg_page_iter_dma_address(sg_iter),
 					cache_level, true);
 		if (++pte == GEN8_PTES) {
 			kunmap_px(ppgtt, pt_vaddr);
@@ -797,8 +796,10 @@ static void gen8_ppgtt_insert_entries(struct i915_address_space *vm,
 	struct i915_hw_ppgtt *ppgtt =
 		container_of(vm, struct i915_hw_ppgtt, base);
 	struct i915_page_directory_pointer *pdp = &ppgtt->pdp; /* FIXME: 48b */
+	struct sg_page_iter sg_iter;
 
-	gen8_ppgtt_insert_pte_entries(vm, pdp, pages, start, cache_level);
+	__sg_page_iter_start(&sg_iter, pages->sgl, sg_nents(pages->sgl), 0);
+	gen8_ppgtt_insert_pte_entries(vm, pdp, &sg_iter, start, cache_level);
 }
 
 static void gen8_free_page_tables(struct drm_device *dev,