[microNPU][ETHOSU] Fix minimum buffer size (#15104)

Fix minimum buffer size for DMA operations according to alignment.

python/tvm/relay/backend/contrib/ethosu/tir_to_cs_translator.py

@@ -926,17 +926,20 @@ def _create_npu_dma_op(serial_copy):
     """This is a helper function to capture the list of arguments
     to create a NpuDmaOperation object"""
     data_type_bytes = np.iinfo(np.dtype(serial_copy.read_address.dtype)).bits // 8
+    length = int(serial_copy.length.value) * data_type_bytes
+    # The buffer size in bytes must be at least 16 bytes
+    length = max(length, 16)
     src = vapi.NpuAddressRange(
         # region will be updated later
         region=0,
         address=serial_copy.read_address,
-        length=int(serial_copy.length.value) * data_type_bytes,
+        length=length,
     )
     dest = vapi.NpuAddressRange(
         # region will be updated later
         region=0,
         address=serial_copy.write_address,
-        length=int(serial_copy.length.value) * data_type_bytes,
+        length=length,
     )
     return vapi.NpuDmaOperation(src, dest)
 
@@ -1076,7 +1079,6 @@ def _create_npu_op_binary_elementwise(serial_binary_elementwise: spec.SerialBina
 def translate_ethosu_unary_elementwise(
     tir_extern_call: tvm.tir.Call,
 ) -> vapi.NpuElementWiseOperation:
-
     """This function will translate a tir extern_call
     as produced by Relay to TIR compilation.
     Parameters

tests/python/contrib/test_ethosu/test_tir_to_cs_translator.py

@@ -84,6 +84,26 @@ def main(placeholder_3: T.Buffer((8192,), "int8"), ethosu_conv2d_1: T.Buffer((20
 # fmt: on
 
 
+# fmt: off
+"""A tir test case with copy operation having a buffer size less than the minimum for a DMA operation"""
+@tvm.script.ir_module
+class CopyLessMinimal:
+    @T.prim_func
+    def main(ethos_u_0_i0: T.Buffer((1, 4), "int8"), ethosu_write: T.Buffer((1, 4), "int8")):
+        T.func_attr({"from_legacy_te_schedule": T.bool(True), "global_symbol": "main", "tir.noalias": T.bool(True)})
+        p1_global = T.allocate([4], "int8", "global", annotations={"disable_lower_builtin": T.bool(True)})
+        ethosu_write_1 = T.allocate([4], "int8", "global", annotations={"disable_lower_builtin": T.bool(True)})
+        p1 = T.Buffer((4,), "int8")
+        p1_global_1 = T.Buffer((4,), "int8", data=p1_global)
+        T.call_extern("handle", "ethosu_copy", p1[0], 4, p1_global_1[0])
+        ethos_u_0_i0_1 = T.Buffer((4,), "int8", data=ethos_u_0_i0.data)
+        ethosu_write_2 = T.Buffer((4,), "int8", data=ethosu_write_1, align=4)
+        T.call_extern("handle", "ethosu_binary_elementwise", "int8", 1, 1, 4, 1, 0, 1, ethos_u_0_i0_1[0], 0, 0, 0, T.float32(0.0039170472882688046), -128, "NHWC", 1, 1, 1, "int8", 1, 1, 4, 1, 0, 1, p1_global_1[0], 0, 0, 0, T.float32(0.0028046639636158943), -128, "NHWC", 1, 1, 1, "int8", 1, 1, 4, 1, 0, 1, ethosu_write_2[0], 0, 0, 0, T.float32(0.0067217112518846989), -128, "NHWC", 1, 1, 1, "ADD", 0, "NONE", 0, 0, "TFL", 0, 0, 0, 0, 0, 0)
+        ethosu_write_3 = T.Buffer((4,), "int8", data=ethosu_write.data)
+        T.call_extern("handle", "ethosu_identity", "int8", 1, 4, 1, 1, 0, 4, ethosu_write_2[0], 0, 0, 0, T.float32(1), 0, "NHWC", 1, 1, 1, "int8", 1, 4, 1, 1, 0, 4, ethosu_write_3[0], 0, 0, 0, T.float32(1), 0, "NHWC", 1, 1, 1, "AVG", 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, "NONE", 0, 0, "TFL", "NONE", 0, 0, 0)
+# fmt: on
+
+
 # fmt: off
 """A TIR test module of weight streaming"""
 @tvm.script.ir_module
@@ -658,6 +678,21 @@ def populate_ethosu_copy_calls(stmt):
                 },
             ],
         },
+        {
+            # Mod contains a copy operation with a buffer size of 4 bytes and it should be replaced by 16
+            "tir_module": CopyLessMinimal,
+            "param_dict": {
+                1: np.random.randint(np.iinfo("int8").min, np.iinfo("int8").max, [1, 4], "int8"),
+            },
+            # Reference outputs
+            "ref": [
+                {
+                    "src": "p1",
+                    "dest": "p1_global_1",
+                    "length": 16,
+                },
+            ],
+        },
     ]
 
     for test_case in test_cases: