drm/amdgpu: handle CPU access for split VRAM buffers (v2)

This avoids merging them together on page fault.

v2: squash in 64-bit division fix

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_object.c

@@ -927,8 +927,7 @@ int amdgpu_bo_fault_reserve_notify(struct ttm_buffer_object *bo)
 	size = bo->mem.num_pages << PAGE_SHIFT;
 	offset = bo->mem.start << PAGE_SHIFT;
 	/* TODO: figure out how to map scattered VRAM to the CPU */
-	if ((offset + size) <= adev->mc.visible_vram_size &&
-	    (abo->flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS))
+	if ((offset + size) <= adev->mc.visible_vram_size)
 		return 0;
 
 	/* Can't move a pinned BO to visible VRAM */
@@ -936,7 +935,6 @@ int amdgpu_bo_fault_reserve_notify(struct ttm_buffer_object *bo)
 		return -EINVAL;
 
 	/* hurrah the memory is not visible ! */
-	abo->flags |= AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS;
 	amdgpu_ttm_placement_from_domain(abo, AMDGPU_GEM_DOMAIN_VRAM);
 	lpfn =	adev->mc.visible_vram_size >> PAGE_SHIFT;
 	for (i = 0; i < abo->placement.num_placement; i++) {

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c

@@ -529,9 +529,6 @@ static int amdgpu_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_mem_
 	case TTM_PL_TT:
 		break;
 	case TTM_PL_VRAM:
-		if (mem->start == AMDGPU_BO_INVALID_OFFSET)
-			return -EINVAL;
-
 		mem->bus.offset = mem->start << PAGE_SHIFT;
 		/* check if it's visible */
 		if ((mem->bus.offset + mem->bus.size) > adev->mc.visible_vram_size)
@@ -549,6 +546,17 @@ static void amdgpu_ttm_io_mem_free(struct ttm_bo_device *bdev, struct ttm_mem_re
 {
 }
 
+static unsigned long amdgpu_ttm_io_mem_pfn(struct ttm_buffer_object *bo,
+					   unsigned long page_offset)
+{
+	struct drm_mm_node *mm = bo->mem.mm_node;
+	uint64_t size = mm->size;
+	unsigned long offset = page_offset;
+
+	page_offset = do_div(offset, size);
+	return (bo->mem.bus.base >> PAGE_SHIFT) + mm->start + page_offset;
+}
+
 /*
  * TTM backend functions.
  */
@@ -1064,7 +1072,7 @@ static struct ttm_bo_driver amdgpu_bo_driver = {
 	.fault_reserve_notify = &amdgpu_bo_fault_reserve_notify,
 	.io_mem_reserve = &amdgpu_ttm_io_mem_reserve,
 	.io_mem_free = &amdgpu_ttm_io_mem_free,
-	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
+	.io_mem_pfn = amdgpu_ttm_io_mem_pfn,
 };
 
 int amdgpu_ttm_init(struct amdgpu_device *adev)