[PATCH 2/6] drm/amdgpu: user temporary GTT as bounce buffer

[Andrey Grodzovsky]

From: Lang Yu <Lang.Yu at amd.com>

Currently, we have a limitted GTT memory size and need a bounce buffer
when doing buffer migration between VRAM and SYSTEM domain.

The problem is under GTT memory pressure we can't do buffer migration
between VRAM and SYSTEM domain. But in some cases we really need that.
Eespecially when validating a VRAM backing store BO which resides in
SYSTEM domain.

v2: still account temporary GTT allocations
v3 (chk): revert to the simpler change for now

Signed-off-by: Lang Yu <Lang.Yu at amd.com>
Signed-off-by: Christian König <christian.koenig at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c | 20 ++++++++++++--------
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c     |  2 +-
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
index ec96e0b26b11..b694dc96b336 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
@@ -132,14 +132,15 @@ static int amdgpu_gtt_mgr_new(struct ttm_resource_manager *man,
 	struct amdgpu_gtt_node *node;
 	int r;
 
-	spin_lock(&mgr->lock);
-	if (tbo->resource && tbo->resource->mem_type != TTM_PL_TT &&
-	    atomic64_read(&mgr->available) < num_pages) {
+	if (!(place->flags & TTM_PL_FLAG_TEMPORARY)) {
+		spin_lock(&mgr->lock);
+		if (atomic64_read(&mgr->available) < num_pages) {
+			spin_unlock(&mgr->lock);
+			return -ENOSPC;
+		}
+		atomic64_sub(num_pages, &mgr->available);
 		spin_unlock(&mgr->lock);
-		return -ENOSPC;
 	}
-	atomic64_sub(num_pages, &mgr->available);
-	spin_unlock(&mgr->lock);
 
 	node = kzalloc(struct_size(node, base.mm_nodes, 1), GFP_KERNEL);
 	if (!node) {
@@ -175,7 +176,8 @@ static int amdgpu_gtt_mgr_new(struct ttm_resource_manager *man,
 	kfree(node);
 
 err_out:
-	atomic64_add(num_pages, &mgr->available);
+	if (!(place->flags & TTM_PL_FLAG_TEMPORARY))
+		atomic64_add(num_pages, &mgr->available);
 
 	return r;
 }
@@ -198,7 +200,9 @@ static void amdgpu_gtt_mgr_del(struct ttm_resource_manager *man,
 	if (drm_mm_node_allocated(&node->base.mm_nodes[0]))
 		drm_mm_remove_node(&node->base.mm_nodes[0]);
 	spin_unlock(&mgr->lock);
-	atomic64_add(res->num_pages, &mgr->available);
+	
+	if (!(res->placement & TTM_PL_FLAG_TEMPORARY))
+		atomic64_add(res->num_pages, &mgr->available);
 
 	kfree(node);
 }
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 80dff29f2bc7..79f875792b30 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -521,7 +521,7 @@ static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
 			hop->fpfn = 0;
 			hop->lpfn = 0;
 			hop->mem_type = TTM_PL_TT;
-			hop->flags = 0;
+			hop->flags = TTM_PL_FLAG_TEMPORARY;
 			return -EMULTIHOP;
 		}
 
-- 
2.25.1