[PATCH 2/2] drm/ttm: make TT creation purely optional

[Christian König]

We only need the page array when the BO is about to be accessed.

So not only populate, but also create it on demand.

Signed-off-by: Christian König <christian.koenig at amd.com>
---
 drivers/gpu/drm/ttm/ttm_bo.c      | 26 ++++----------------------
 drivers/gpu/drm/ttm/ttm_bo_util.c |  9 +++++++--
 drivers/gpu/drm/ttm/ttm_bo_vm.c   |  5 +++++
 3 files changed, 16 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 15f9b19fa00d..0e0a9dadf3ed 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -667,13 +667,8 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
 	placement.num_busy_placement = 0;
 	bdev->driver->evict_flags(bo, &placement);
 
-	if (!placement.num_placement && !placement.num_busy_placement) {
-		ret = ttm_bo_pipeline_gutting(bo);
-		if (ret)
-			return ret;
-
-		return ttm_tt_create(bo, false);
-	}
+	if (!placement.num_placement && !placement.num_busy_placement)
+		return ttm_bo_pipeline_gutting(bo);
 
 	evict_mem = bo->mem;
 	evict_mem.mm_node = NULL;
@@ -1200,13 +1195,8 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
 	/*
 	 * Remove the backing store if no placement is given.
 	 */
-	if (!placement->num_placement && !placement->num_busy_placement) {
-		ret = ttm_bo_pipeline_gutting(bo);
-		if (ret)
-			return ret;
-
-		return ttm_tt_create(bo, false);
-	}
+	if (!placement->num_placement && !placement->num_busy_placement)
+		return ttm_bo_pipeline_gutting(bo);
 
 	/*
 	 * Check whether we need to move buffer.
@@ -1223,14 +1213,6 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
 		ttm_flag_masked(&bo->mem.placement, new_flags,
 				~TTM_PL_MASK_MEMTYPE);
 	}
-	/*
-	 * We might need to add a TTM.
-	 */
-	if (bo->mem.mem_type == TTM_PL_SYSTEM && bo->ttm == NULL) {
-		ret = ttm_tt_create(bo, true);
-		if (ret)
-			return ret;
-	}
 	return 0;
 }
 EXPORT_SYMBOL(ttm_bo_validate);
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index 52d2b71f1588..f8414f820350 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -580,12 +580,17 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 		.interruptible = false,
 		.no_wait_gpu = false
 	};
-	struct ttm_tt *ttm = bo->ttm;
+	struct ttm_tt *ttm;
 	pgprot_t prot;
 	int ret;
 
-	BUG_ON(!ttm);
+	if (!bo->ttm) {
+		ret = ttm_tt_create(bo, true);
+		if (ret)
+			return ret;
+	}
 
+	ttm = bo->ttm;
 	ret = ttm_tt_populate(ttm, &ctx);
 	if (ret)
 		return ret;
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 0ad30b112982..bdfed6725d6f 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -349,6 +349,11 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
 
 		};
 
+		if (!bo->ttm && ttm_tt_create(bo, true)) {
+			ret = VM_FAULT_OOM;
+			goto out_io_unlock;
+		}
+
 		ttm = bo->ttm;
 		if (ttm_tt_populate(bo->ttm, &ctx)) {
 			ret = VM_FAULT_OOM;
-- 
2.17.1