Qualcomm AI Engine Direct - Fixed the accuracy bug for conv with bias in block quant (#13676)

As title.

cc: @haowhsu-quic

Author: shewu-quic

backends/qualcomm/quantizer/observers/per_block_param_observer.py

@@ -35,6 +35,9 @@ def __init__(
             **kwargs,
         )
         self.block_size = block_size
+        # TODO: expand this when QNN starts to support more configurations
+        self.bitwidth_of_scale = 4
+        self.num_steps = 2**self.bitwidth_of_scale
         self.calibrated = False
 
     def forward(self, input: torch.Tensor):

backends/qualcomm/quantizer/qconfig.py

@@ -1,3 +1,9 @@
+# Copyright (c) Qualcomm Innovation Center, Inc.
+# All rights reserved
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
 from dataclasses import dataclass
 from typing import Any, Callable, Dict, List, Optional, Tuple
 
@@ -49,7 +55,10 @@ def _derive_bias_qparams_fn(
         derived_zero = torch.zeros(derived_scale.size()).to(torch.int32)
         if isinstance(weight_obs_or_fq, PerBlockParamObserver):
             # keep maximum scale of each channel for bias
-            derived_scale = derived_scale.view(derived_scale.size(0), -1).amax(dim=-1)
+            derived_scale = (
+                derived_scale.view(derived_scale.size(0), -1).amax(dim=-1)
+                / weight_obs_or_fq.num_steps
+            )
             derived_zero = derived_zero.view(derived_zero.size(0), -1).amax(dim=-1)
         return (derived_scale, derived_zero)
 

backends/qualcomm/tests/test_qnn_delegate.py

@@ -5552,13 +5552,13 @@ def test_mobilevit_v2(self):
                 self.assertGreaterEqual(msg["top_1"], 50)
                 self.assertGreaterEqual(msg["top_5"], 85)
 
-    def test_mobilevit1(self):
+    def test_mobilevit_v1(self):
         if not self.required_envs([self.image_dataset]):
             self.skipTest("missing required envs")
 
         cmds = [
             "python",
-            f"{self.executorch_root}/examples/qualcomm/oss_scripts/mobilevit1.py",
+            f"{self.executorch_root}/examples/qualcomm/oss_scripts/mobilevit_v1.py",
             "--dataset",
             self.image_dataset,
             "--artifact",