drm/i915/gtt/xehpsdv: move scratch page to system memory

On some platforms the hw has dropped support for 4K GTT pages when
dealing with LMEM, and due to the design of 64K GTT pages in the hw, we
can only mark the *entire* page-table as operating in 64K GTT mode,
since the enable bit is still on the pde, and not the pte. And since we
we still need to allow 4K GTT pages for SMEM objects, we can't have a
"normal" 4K page-table with scratch pointing to LMEM, since that's
undefined from the hw pov. The simplest solution is to just move the 64K
scratch page to SMEM on such platforms and call it a day, since that
should work for all configurations.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Thomas Hellstrom <thomas.hellstrom@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211208141613.7251-4-ramalingam.c@intel.com

drivers/gpu/drm/i915/gt/gen6_ppgtt.c

@@ -454,6 +454,7 @@ struct i915_ppgtt *gen6_ppgtt_create(struct intel_gt *gt)
 	ppgtt->base.vm.cleanup = gen6_ppgtt_cleanup;
 
 	ppgtt->base.vm.alloc_pt_dma = alloc_pt_dma;
+	ppgtt->base.vm.alloc_scratch_dma = alloc_pt_dma;
 	ppgtt->base.vm.pte_encode = ggtt->vm.pte_encode;
 
 	err = gen6_ppgtt_init_scratch(ppgtt);

drivers/gpu/drm/i915/gt/gen8_ppgtt.c

@@ -776,10 +776,29 @@ struct i915_ppgtt *gen8_ppgtt_create(struct intel_gt *gt,
 	 */
 	ppgtt->vm.has_read_only = !IS_GRAPHICS_VER(gt->i915, 11, 12);
 
-	if (HAS_LMEM(gt->i915))
+	if (HAS_LMEM(gt->i915)) {
 		ppgtt->vm.alloc_pt_dma = alloc_pt_lmem;
-	else
+
+		/*
+		 * On some platforms the hw has dropped support for 4K GTT pages
+		 * when dealing with LMEM, and due to the design of 64K GTT
+		 * pages in the hw, we can only mark the *entire* page-table as
+		 * operating in 64K GTT mode, since the enable bit is still on
+		 * the pde, and not the pte. And since we still need to allow
+		 * 4K GTT pages for SMEM objects, we can't have a "normal" 4K
+		 * page-table with scratch pointing to LMEM, since that's
+		 * undefined from the hw pov. The simplest solution is to just
+		 * move the 64K scratch page to SMEM on such platforms and call
+		 * it a day, since that should work for all configurations.
+		 */
+		if (HAS_64K_PAGES(gt->i915))
+			ppgtt->vm.alloc_scratch_dma = alloc_pt_dma;
+		else
+			ppgtt->vm.alloc_scratch_dma = alloc_pt_lmem;
+	} else {
 		ppgtt->vm.alloc_pt_dma = alloc_pt_dma;
+		ppgtt->vm.alloc_scratch_dma = alloc_pt_dma;
+	}
 
 	err = gen8_init_scratch(&ppgtt->vm);
 	if (err)

drivers/gpu/drm/i915/gt/intel_ggtt.c

@@ -924,6 +924,7 @@ static int gen8_gmch_probe(struct i915_ggtt *ggtt)
 		size = gen8_get_total_gtt_size(snb_gmch_ctl);
 
 	ggtt->vm.alloc_pt_dma = alloc_pt_dma;
+	ggtt->vm.alloc_scratch_dma = alloc_pt_dma;
 	ggtt->vm.lmem_pt_obj_flags = I915_BO_ALLOC_PM_EARLY;
 
 	ggtt->vm.total = (size / sizeof(gen8_pte_t)) * I915_GTT_PAGE_SIZE;
@@ -1077,6 +1078,7 @@ static int gen6_gmch_probe(struct i915_ggtt *ggtt)
 	ggtt->vm.total = (size / sizeof(gen6_pte_t)) * I915_GTT_PAGE_SIZE;
 
 	ggtt->vm.alloc_pt_dma = alloc_pt_dma;
+	ggtt->vm.alloc_scratch_dma = alloc_pt_dma;
 
 	ggtt->vm.clear_range = nop_clear_range;
 	if (!HAS_FULL_PPGTT(i915) || intel_scanout_needs_vtd_wa(i915))
@@ -1129,6 +1131,7 @@ static int i915_gmch_probe(struct i915_ggtt *ggtt)
 		(struct resource)DEFINE_RES_MEM(gmadr_base, ggtt->mappable_end);
 
 	ggtt->vm.alloc_pt_dma = alloc_pt_dma;
+	ggtt->vm.alloc_scratch_dma = alloc_pt_dma;
 
 	if (needs_idle_maps(i915)) {
 		drm_notice(&i915->drm,

drivers/gpu/drm/i915/gt/intel_gtt.c

@@ -301,7 +301,7 @@ int setup_scratch_page(struct i915_address_space *vm)
 	do {
 		struct drm_i915_gem_object *obj;
 
-		obj = vm->alloc_pt_dma(vm, size);
+		obj = vm->alloc_scratch_dma(vm, size);
 		if (IS_ERR(obj))
 			goto skip;
 

drivers/gpu/drm/i915/gt/intel_gtt.h

@@ -268,6 +268,8 @@ struct i915_address_space {
 
 	struct drm_i915_gem_object *
 		(*alloc_pt_dma)(struct i915_address_space *vm, int sz);
+	struct drm_i915_gem_object *
+		(*alloc_scratch_dma)(struct i915_address_space *vm, int sz);
 
 	u64 (*pte_encode)(dma_addr_t addr,
 			  enum i915_cache_level level,

drivers/gpu/drm/i915/selftests/mock_gtt.c

@@ -78,6 +78,7 @@ struct i915_ppgtt *mock_ppgtt(struct drm_i915_private *i915, const char *name)
 	i915_address_space_init(&ppgtt->vm, VM_CLASS_PPGTT);
 
 	ppgtt->vm.alloc_pt_dma = alloc_pt_dma;
+	ppgtt->vm.alloc_scratch_dma = alloc_pt_dma;
 
 	ppgtt->vm.clear_range = mock_clear_range;
 	ppgtt->vm.insert_page = mock_insert_page;
@@ -118,6 +119,7 @@ void mock_init_ggtt(struct drm_i915_private *i915, struct i915_ggtt *ggtt)
 	ggtt->vm.total = 4096 * PAGE_SIZE;
 
 	ggtt->vm.alloc_pt_dma = alloc_pt_dma;
+	ggtt->vm.alloc_scratch_dma = alloc_pt_dma;
 
 	ggtt->vm.clear_range = mock_clear_range;
 	ggtt->vm.insert_page = mock_insert_page;