drm/i915/gen8: Generalize PTE writing for GEN8 PPGTT

The insert_entries function was the function used to write PTEs. For the
PPGTT it was "hardcoded" to only understand two level page tables, which
was the case for GEN7. We can reuse this for 4 level page tables, and
remove the concept of insert_entries, which was never viable past 2
level page tables anyway, but it requires a bit of rework to make the
function a bit more generic.

v2: Rebase after Mika's ppgtt cleanup / scratch merge patch series.
v3: Rebase after final merged version of Mika's ppgtt/scratch patches.
v4: Check and warn for NULL value of pdp pointer (Akash).

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

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -600,23 +600,23 @@ static int gen8_mm_switch(struct i915_hw_ppgtt *ppgtt,
 	return 0;
 }
 
-static void gen8_ppgtt_clear_range(struct i915_address_space *vm,
-				   uint64_t start,
-				   uint64_t length,
-				   bool use_scratch)
+static void gen8_ppgtt_clear_pte_range(struct i915_address_space *vm,
+				       struct i915_page_directory_pointer *pdp,
+				       uint64_t start,
+				       uint64_t length,
+				       gen8_pte_t scratch_pte)
 {
 	struct i915_hw_ppgtt *ppgtt =
 		container_of(vm, struct i915_hw_ppgtt, base);
-	struct i915_page_directory_pointer *pdp = &ppgtt->pdp; /* FIXME: 48b */
-	gen8_pte_t *pt_vaddr, scratch_pte;
+	gen8_pte_t *pt_vaddr;
 	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;
 	unsigned num_entries = length >> PAGE_SHIFT;
 	unsigned last_pte, i;
 
-	scratch_pte = gen8_pte_encode(px_dma(ppgtt->base.scratch_page),
-				      I915_CACHE_LLC, use_scratch);
+	if (WARN_ON(!pdp))
+		return;
 
 	while (num_entries) {
 		struct i915_page_directory *pd;
@@ -656,14 +656,30 @@ static void gen8_ppgtt_clear_range(struct i915_address_space *vm,
 	}
 }
 
-static void gen8_ppgtt_insert_entries(struct i915_address_space *vm,
-				      struct sg_table *pages,
-				      uint64_t start,
-				      enum i915_cache_level cache_level, u32 unused)
+static void gen8_ppgtt_clear_range(struct i915_address_space *vm,
+				   uint64_t start,
+				   uint64_t length,
+				   bool use_scratch)
 {
 	struct i915_hw_ppgtt *ppgtt =
 		container_of(vm, struct i915_hw_ppgtt, base);
 	struct i915_page_directory_pointer *pdp = &ppgtt->pdp; /* FIXME: 48b */
+
+	gen8_pte_t scratch_pte = gen8_pte_encode(px_dma(vm->scratch_page),
+						 I915_CACHE_LLC, use_scratch);
+
+	gen8_ppgtt_clear_pte_range(vm, pdp, start, length, scratch_pte);
+}
+
+static void
+gen8_ppgtt_insert_pte_entries(struct i915_address_space *vm,
+			      struct i915_page_directory_pointer *pdp,
+			      struct sg_table *pages,
+			      uint64_t start,
+			      enum i915_cache_level cache_level)
+{
+	struct i915_hw_ppgtt *ppgtt =
+		container_of(vm, struct i915_hw_ppgtt, base);
 	gen8_pte_t *pt_vaddr;
 	unsigned pdpe = start >> GEN8_PDPE_SHIFT & GEN8_PDPE_MASK;
 	unsigned pde = start >> GEN8_PDE_SHIFT & GEN8_PDE_MASK;
@@ -700,6 +716,19 @@ static void gen8_ppgtt_insert_entries(struct i915_address_space *vm,
 		kunmap_px(ppgtt, pt_vaddr);
 }
 
+static void gen8_ppgtt_insert_entries(struct i915_address_space *vm,
+				      struct sg_table *pages,
+				      uint64_t start,
+				      enum i915_cache_level cache_level,
+				      u32 unused)
+{
+	struct i915_hw_ppgtt *ppgtt =
+		container_of(vm, struct i915_hw_ppgtt, base);
+	struct i915_page_directory_pointer *pdp = &ppgtt->pdp; /* FIXME: 48b */
+
+	gen8_ppgtt_insert_pte_entries(vm, pdp, pages, start, cache_level);
+}
+
 static void gen8_free_page_tables(struct drm_device *dev,
 				  struct i915_page_directory *pd)
 {