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 <[e-mail]>
Signed-off-by: Ramalingam C <[e-mail]>
Reviewed-by: Thomas Hellstrom <[e-mail]>
Reviewed-by: Andi Shyti <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

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

···
 	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

···
 	 */
 	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

···
 		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;
···
 	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))
···
 		(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

···
 	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

···
 
 	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

···
 	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;
···
 	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;