1 files changed, 60 insertions, 0 deletions
diff --git a/ethosu/vela/insert_dma.py b/ethosu/vela/insert_dma.py
new file mode 100644
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+++ b/ethosu/vela/insert_dma.py
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+# Copyright (C) 2020 Arm Limited or its affiliates. All rights reserved.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the License); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an AS IS BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+# Description:
+# Insert DMA operations into the graph for transfering weights.
+
+from .nn_graph import Operation, MemArea, TensorPurpose, NpuBlockType
+from . import rewrite_graph
+
+
+def insert_dma_cmd(op, arch):
+    if op.type == "DMA":
+        return op # Already rewritten
+    for idx, tens in enumerate(op.inputs):
+
+        if tens.mem_area in (MemArea.Dram, MemArea.OffChipFlash) and tens.mem_area != arch.fast_storage_mem_area:
+            if tens.purpose == TensorPurpose.Weights:
+                only_vector_product_consumers = True
+                for oper in tens.consumers():
+                    if oper is None or oper.attrs.get("npu_block_type") != NpuBlockType.VectorProduct:
+                        only_vector_product_consumers = False
+                        break
+
+                # Tensor products has no need for DMA, tensors are only read once and can be in flash.
+                # Other operations re-reads tensors, this is better done from SRAM.
+                if not only_vector_product_consumers:
+                    # Insert a DMA command here, as well as a new tensor situated in SRAM of the same size.
+                    new_tens = tens.clone_into_fast_storage(arch)
+                    dma_cmd = Operation("DMA", tens.ops[0].name + "_dma")
+                    dma_cmd.inputs = [tens]
+                    dma_cmd.outputs = [new_tens]
+                    dma_cmd.attrs["source"] = tens.mem_area
+                    dma_cmd.attrs["destination"] = new_tens.mem_area
+                    dma_cmd.run_on_npu = True
+                    new_tens.ops = [dma_cmd]
+                    op.inputs[idx] = new_tens
+    return op
+
+
+def insert_dma_commands(nng, arch, verbose_graph=False):
+
+    for idx, sg in enumerate(nng.subgraphs):
+        nng.subgraphs[idx] = rewrite_graph.rewrite_graph_pre_order(sg, arch, [], [insert_dma_cmd])
+    if verbose_graph:
+        nng.print_graph()
+    return nng