ttm: add prime sharing support to TTM (v2)

This adds the ability for ttm common code to take an SG table
and use it as the backing for a slave TTM object.

The drivers can then populate their GTT tables using the SG object.

v2: make sure to setup VM for sg bos as well.

Reviewed-by: Alex Deucher <[e-mail]>
Reviewed-by: Jerome Glisse <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>

drivers/gpu/drm/nouveau/nouveau_bo.c

···
 
 	ret = ttm_bo_init(&dev_priv->ttm.bdev, &nvbo->bo, size,
 			  ttm_bo_type_device, &nvbo->placement,
-			  align >> PAGE_SHIFT, 0, false, NULL, acc_size,
+			  align >> PAGE_SHIFT, 0, false, NULL, acc_size, NULL,
 			  nouveau_bo_del_ttm);
 	if (ret) {
 		/* ttm will call nouveau_bo_del_ttm if it fails.. */

drivers/gpu/drm/radeon/radeon_object.c

···
 	mutex_lock(&rdev->vram_mutex);
 	r = ttm_bo_init(&rdev->mman.bdev, &bo->tbo, size, type,
 			&bo->placement, page_align, 0, !kernel, NULL,
-			acc_size, &radeon_ttm_bo_destroy);
+			acc_size, NULL, &radeon_ttm_bo_destroy);
 	mutex_unlock(&rdev->vram_mutex);
 	if (unlikely(r != 0)) {
 		if (r != -ERESTARTSYS) {

drivers/gpu/drm/ttm/ttm_bo.c

···
 		if (unlikely(bo->ttm == NULL))
 			ret = -ENOMEM;
 		break;
+	case ttm_bo_type_sg:
+		bo->ttm = bdev->driver->ttm_tt_create(bdev, bo->num_pages << PAGE_SHIFT,
+						      page_flags | TTM_PAGE_FLAG_SG,
+						      glob->dummy_read_page);
+		if (unlikely(bo->ttm == NULL)) {
+			ret = -ENOMEM;
+			break;
+		}
+		bo->ttm->sg = bo->sg;
+		break;
 	default:
 		pr_err("Illegal buffer object type\n");
 		ret = -EINVAL;
···
 		bool interruptible,
 		struct file *persistent_swap_storage,
 		size_t acc_size,
+		struct sg_table *sg,
 		void (*destroy) (struct ttm_buffer_object *))
 {
 	int ret = 0;
···
 	bo->seq_valid = false;
 	bo->persistent_swap_storage = persistent_swap_storage;
 	bo->acc_size = acc_size;
+	bo->sg = sg;
 	atomic_inc(&bo->glob->bo_count);
 
 	ret = ttm_bo_check_placement(bo, placement);
···
 	 * For ttm_bo_type_device buffers, allocate
 	 * address space from the device.
 	 */
-	if (bo->type == ttm_bo_type_device) {
+	if (bo->type == ttm_bo_type_device ||
+	    bo->type == ttm_bo_type_sg) {
 		ret = ttm_bo_setup_vm(bo);
 		if (ret)
 			goto out_err;
···
 
 	ret = ttm_bo_init(bdev, bo, size, type, placement, page_alignment,
 				buffer_start, interruptible,
-				persistent_swap_storage, acc_size, NULL);
+			  persistent_swap_storage, acc_size, NULL, NULL);
 	if (likely(ret == 0))
 		*p_bo = bo;
 

drivers/gpu/drm/vmwgfx/vmwgfx_resource.c

···
 	ret = ttm_bo_init(bdev, &vmw_bo->base, size,
 			  ttm_bo_type_device, placement,
 			  0, 0, interruptible,
-			  NULL, acc_size, bo_free);
+			  NULL, acc_size, NULL, bo_free);
 	return ret;
 }
 

include/drm/ttm/ttm_bo_api.h

···
  *
  * @ttm_bo_type_kernel: These buffers are like ttm_bo_type_device buffers,
  * but they cannot be accessed from user-space. For kernel-only use.
+ *
+ * @ttm_bo_type_sg: Buffer made from dmabuf sg table shared with another
+ * driver.
  */
 
 enum ttm_bo_type {
 	ttm_bo_type_device,
-	ttm_bo_type_kernel
+	ttm_bo_type_kernel,
+	ttm_bo_type_sg
 };
 
 struct ttm_tt;
···
 
 	unsigned long offset;
 	uint32_t cur_placement;
+
+	struct sg_table *sg;
 };
 
 /**
···
 			bool interrubtible,
 			struct file *persistent_swap_storage,
 			size_t acc_size,
+			struct sg_table *sg,
 			void (*destroy) (struct ttm_buffer_object *));
 
 /**

include/drm/ttm/ttm_bo_driver.h

···
 #define TTM_PAGE_FLAG_PERSISTENT_SWAP (1 << 5)
 #define TTM_PAGE_FLAG_ZERO_ALLOC      (1 << 6)
 #define TTM_PAGE_FLAG_DMA32           (1 << 7)
+#define TTM_PAGE_FLAG_SG              (1 << 8)
 
 enum ttm_caching_state {
 	tt_uncached,
···
 	struct page **pages;
 	uint32_t page_flags;
 	unsigned long num_pages;
+	struct sg_table *sg; /* for SG objects via dma-buf */
 	struct ttm_bo_global *glob;
 	struct ttm_backend *be;
 	struct file *swap_storage;