drm/amdgpu: reserve the first 2x512 pages of GART

We want to use them as remap address space.
Signed-off-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

@@ -43,12 +43,15 @@ static int amdgpu_gtt_mgr_init(struct ttm_mem_type_manager *man,
 			       unsigned long p_size)
 {
 	struct amdgpu_gtt_mgr *mgr;
+	uint64_t start, size;
 
 	mgr = kzalloc(sizeof(*mgr), GFP_KERNEL);
 	if (!mgr)
 		return -ENOMEM;
 
-	drm_mm_init(&mgr->mm, 0, p_size);
+	start = AMDGPU_GTT_MAX_TRANSFER_SIZE * AMDGPU_GTT_NUM_TRANSFER_WINDOWS;
+	size = p_size - start;
+	drm_mm_init(&mgr->mm, start, size);
 	spin_lock_init(&mgr->lock);
 	mgr->available = p_size;
 	man->priv = mgr;

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

@@ -34,6 +34,9 @@
 #define AMDGPU_PL_FLAG_GWS		(TTM_PL_FLAG_PRIV << 1)
 #define AMDGPU_PL_FLAG_OA		(TTM_PL_FLAG_PRIV << 2)
 
+#define AMDGPU_GTT_MAX_TRANSFER_SIZE	512
+#define AMDGPU_GTT_NUM_TRANSFER_WINDOWS	2
+
 struct amdgpu_mman {
 	struct ttm_bo_global_ref        bo_global_ref;
 	struct drm_global_reference	mem_global_ref;