feat: add HP mailbox and PLIC tests; enhance existing test coverage

- Updated axi4_interconnect_tb to include an additional master and issue high-priority access tests.
- Introduced hp_mailbox_tb for testing the HP mailbox functionality, including register and doorbell operations.
- Added plic_tb to validate PLIC priority, claim, and completion mechanisms.
- Enhanced pll_ctrl_tb to initialize additional system control signals.
- Updated soc_irq_topology_tb to account for new IRQ sources and validate IRQ signal behavior.
- Improved sysctrl_tb to include tests for HP lifecycle control and status registers.
- Added tests for HP boot bundle layout, CRC, and payload validation.
- Introduced test_hp_mailbox.py for RTL regression testing of the HP mailbox.
- Added test_hp_platform.py to validate HP platform configuration and generated-source boundaries.
- Enhanced test_librelane_flow.py to ensure correct signal placement in chip configuration.
- Added performance log tests to validate LP and HP coremark ratios.
- Updated test_soc_topology.py to reflect changes in IRQ and peripheral mappings.

tests/test_axi4.py

@@ -12,6 +12,49 @@ from pathlib import Path
 ROOT = Path(__file__).resolve().parents[1]
 
 
+def test_axi4_downsizer_preserves_bursts_lanes_and_backpressure(
+    tmp_path: Path,
+) -> None:
+    verilator = shutil.which("verilator")
+    if verilator is None:
+        return
+
+    output = tmp_path / "axi4_downsizer_64to32_tb"
+    ccache_tmp = tmp_path / "ccache"
+    ccache_tmp.mkdir()
+    subprocess.run(
+        [
+            verilator,
+            "--binary",
+            "--timing",
+            "-Wno-fatal",
+            "--top-module",
+            "axi4_downsizer_64to32_tb",
+            "-I" + str(ROOT / "rtl/managed/clusterip/common/rtl"),
+            "-I" + str(ROOT / "rtl/managed/clusterip/common/rtl/interface"),
+            str(ROOT / "rtl/managed/clusterip/common/rtl/interface/axi4_if.sv"),
+            str(ROOT / "rtl/managed/clusterip/common/rtl/utils/register.sv"),
+            str(ROOT / "rtl/managed/clusterip/common/rtl/interface/axi4_addr_gen.sv"),
+            str(ROOT / "rtl/mini/top/axi4_downsizer_64to32.sv"),
+            str(ROOT / "tests/rtl/axi4_downsizer_64to32_tb.sv"),
+            "-Mdir",
+            str(tmp_path / "obj"),
+            "-o",
+            str(output),
+        ],
+        check=True,
+        text=True,
+        capture_output=True,
+        env={
+            **os.environ,
+            "CCACHE_DIR": str(ccache_tmp),
+            "CCACHE_TEMPDIR": str(ccache_tmp),
+        },
+    )
+    result = subprocess.run([output], check=True, text=True, capture_output=True)
+    assert "AXI4 64-to-32 downsizer test passed" in result.stdout
+
+
 def test_axi4_word_bridge_supports_bursts_backpressure_and_errors(tmp_path: Path) -> None:
     verilator = shutil.which("verilator")
     if verilator is None: