drm/ttm: make TT creation purely optional v3

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

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

v2: move NULL check into ttm_tt_create()
v3: fix the occurrence in ttm_bo_kmap_ttm as well

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Link: https://patchwork.freedesktop.org/patch/373182/

4 files changed, 22 insertions, 31 deletions

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 2da8dbd2553b..0c13fe96c7e3 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -292,12 +292,11 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
 	 */
 
 	if (!(new_man->flags & TTM_MEMTYPE_FLAG_FIXED)) {
-		if (bo->ttm == NULL) {
-			bool zero = !(old_man->flags & TTM_MEMTYPE_FLAG_FIXED);
-			ret = ttm_tt_create(bo, zero);
-			if (ret)
-				goto out_err;
-		}
+		bool zero = !(old_man->flags & TTM_MEMTYPE_FLAG_FIXED);
+
+		ret = ttm_tt_create(bo, zero);
+		if (ret)
+			goto out_err;
 
 		ret = ttm_tt_set_placement_caching(bo->ttm, mem->placement);
 		if (ret)
@@ -660,13 +659,8 @@ 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;
@@ -1195,13 +1189,8 @@ 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.
@@ -1218,14 +1207,6 @@ 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 f09b096ba4fd..5e0f3a9caedc 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -532,12 +532,15 @@ 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);
+	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 a43aa7275f12..82b893d4249f 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 (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;
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index 2ec448e1d663..e25d4097aa16 100644
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -50,6 +50,9 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc)
 
 	dma_resv_assert_held(bo->base.resv);
 
+	if (bo->ttm)
+		return 0;
+
 	if (bdev->need_dma32)
 		page_flags |= TTM_PAGE_FLAG_DMA32;
 
@@ -67,7 +70,6 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc)
 		page_flags |= TTM_PAGE_FLAG_SG;
 		break;
 	default:
-		bo->ttm = NULL;
 		pr_err("Illegal buffer object type\n");
 		return -EINVAL;
 	}