Arm backend: Backend test TOSA FP, INT and Ethos-U55/U85 (pytorch#14653)

### Summary
Create arm_ethos_u55 and arm_ethos_u85 test flows and add them to CI
Build a semihosted runner for testing on the Corstone3x0 FVP
And split the arm_tosa test job that tested TOSA-1.0+FP into arm_tosa_fp
and arm_tosa_int to also test TOSA-1.0+INT

### Test plan
This will add new tests for arm_tosa_int arm_ethos_u55 and arm_ethos_u85

cc @digantdesai @freddan80 @per @oscarandersson8218

---------

Signed-off-by: Zingo Andersen <[email protected]>

Author: zingo

.ci/scripts/test_backend.sh

@@ -1,6 +1,7 @@
 #!/usr/bin/env bash
 # Copyright (c) Meta Platforms, Inc. and affiliates.
 # All rights reserved.
+# Copyright 2025 Arm Limited and/or its affiliates.
 #
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
@@ -58,6 +59,12 @@ fi
 if [[ "$FLOW" == *arm* ]]; then
     # Setup ARM deps.
     .ci/scripts/setup-arm-baremetal-tools.sh
+
+    if [[ "$FLOW" == *ethos_u* ]]; then
+        # Prepare a test runner binary that can run on the Corstone-3x0 FVPs
+        backends/arm/scripts/build_executorch.sh
+        backends/arm/test/setup_testing.sh
+    fi
 fi
 
 if [[ $IS_MACOS -eq 1 ]]; then

.github/workflows/test-backend-arm.yml

@@ -23,7 +23,7 @@ jobs:
     uses: ./.github/workflows/_test_backend.yml
     with:
       backend: arm
-      flows: '["arm_tosa"]'
+      flows: '["arm_tosa_fp", "arm_tosa_int", "arm_ethos_u55", "arm_ethos_u85"]'
       ref: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.sha }}
       timeout: 120
       run-linux: true

backends/test/suite/flow.py

@@ -1,3 +1,8 @@
+# Copyright 2025 Arm Limited and/or its affiliates.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
 import logging
 
 from dataclasses import dataclass, field
@@ -122,10 +127,18 @@ def all_flows() -> dict[str, TestFlow]:
         logger.info(f"Skipping QNN flow registration: {e}")
 
     try:
-        from executorch.backends.test.suite.flows.arm import ARM_TOSA_FLOW
+        from executorch.backends.test.suite.flows.arm import (
+            ARM_ETHOS_U55_FLOW,
+            ARM_ETHOS_U85_FLOW,
+            ARM_TOSA_FP_FLOW,
+            ARM_TOSA_INT_FLOW,
+        )
 
         flows += [
-            ARM_TOSA_FLOW,
+            ARM_TOSA_FP_FLOW,
+            ARM_TOSA_INT_FLOW,
+            ARM_ETHOS_U55_FLOW,
+            ARM_ETHOS_U85_FLOW,
         ]
     except Exception as e:
         logger.info(f"Skipping ARM flow registration: {e}")

backends/test/suite/flows/arm.py

@@ -1,24 +1,72 @@
+# Copyright 2025 Arm Limited and/or its affiliates.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+
+from executorch.backends.arm.quantizer import (
+    get_symmetric_quantization_config,
+    TOSAQuantizer,
+)
 from executorch.backends.arm.test import common
 from executorch.backends.arm.test.tester.arm_tester import ArmTester
 from executorch.backends.test.suite.flow import TestFlow
+from executorch.backends.xnnpack.test.tester.tester import Quantize
 
 
-def _create_arm_tester_tosa_fp(*args, **kwargs) -> ArmTester:
-    kwargs["compile_spec"] = common.get_tosa_compile_spec(tosa_spec="TOSA-1.0+FP")
+def _create_tosa_flow(
+    name,
+    compile_spec,
+    quantize: bool = False,
+    symmetric_io_quantization: bool = False,
+    per_channel_quantization: bool = True,
+) -> TestFlow:
 
-    return ArmTester(
-        *args,
-        **kwargs,
-    )
+    def _create_arm_tester(*args, **kwargs) -> ArmTester:
+        kwargs["compile_spec"] = compile_spec
 
+        return ArmTester(
+            *args,
+            **kwargs,
+        )
+
+    # Create and configure quantizer to use in the flow
+    def create_quantize_stage() -> Quantize:
+        quantizer = TOSAQuantizer(compile_spec)
+        quantization_config = get_symmetric_quantization_config(
+            is_per_channel=per_channel_quantization
+        )
+        if symmetric_io_quantization:
+            quantizer.set_io(quantization_config)
+        return Quantize(quantizer, quantization_config)
 
-def _create_tosa_flow() -> TestFlow:
     return TestFlow(
-        "arm_tosa",
+        name,
         backend="arm",
-        tester_factory=_create_arm_tester_tosa_fp,
+        tester_factory=_create_arm_tester,
         supports_serialize=False,
+        quantize=quantize,
+        quantize_stage_factory=create_quantize_stage if quantize else None,
     )
 
 
-ARM_TOSA_FLOW = _create_tosa_flow()
+ARM_TOSA_FP_FLOW = _create_tosa_flow(
+    "arm_tosa_fp", common.get_tosa_compile_spec(tosa_spec="TOSA-1.0+FP")
+)
+ARM_TOSA_INT_FLOW = _create_tosa_flow(
+    "arm_tosa_int",
+    common.get_tosa_compile_spec(tosa_spec="TOSA-1.0+INT"),
+    quantize=True,
+)
+
+ARM_ETHOS_U55_FLOW = _create_tosa_flow(
+    "arm_ethos_u55",
+    common.get_u55_compile_spec(),
+    quantize=True,
+)
+
+ARM_ETHOS_U85_FLOW = _create_tosa_flow(
+    "arm_ethos_u85",
+    common.get_u85_compile_spec(),
+    quantize=True,
+)