drm/nouveau: fix dma_address check for CPU/GPU sync

stable inclusion
from stable-5.10.48
commit 45ca6df5df11da7f19c85591e093479d5c60262f
bugzilla: 173268 https://gitee.com/openeuler/kernel/issues/I4DD1K

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=45ca6df5df11da7f19c85591e093479d5c60262f

--------------------------------

[ Upstream commit d3300991 ]

AGP for example doesn't have a dma_address array.
Signed-off-by: NChristian König <christian.koenig@amd.com>
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210614110517.1624-1-christian.koenig@amd.comSigned-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -590,7 +590,7 @@ nouveau_bo_sync_for_device(struct nouveau_bo *nvbo)
 	struct ttm_dma_tt *ttm_dma = (struct ttm_dma_tt *)nvbo->bo.ttm;
 	int i;
 
-	if (!ttm_dma)
+	if (!ttm_dma || !ttm_dma->dma_address)
 		return;
 
 	/* Don't waste time looping if the object is coherent */
@@ -610,7 +610,7 @@ nouveau_bo_sync_for_cpu(struct nouveau_bo *nvbo)
 	struct ttm_dma_tt *ttm_dma = (struct ttm_dma_tt *)nvbo->bo.ttm;
 	int i;
 
-	if (!ttm_dma)
+	if (!ttm_dma || !ttm_dma->dma_address)
 		return;
 
 	/* Don't waste time looping if the object is coherent */