feat: add fast-flash support for Verilator simulation and XPI model

- Introduced  target in Makefile to run fast-flash HP Linux userspace acceptance tests with a 7200-second simulation time limit.
- Updated documentation to describe the new fast-flash model and its usage in simulations.
- Implemented Verilator-specific XPI core and fast flash model to handle slot-0 read operations with improved performance.
- Added new tests for the XPI fast flash model to verify protocol compliance and error handling.
- Enhanced existing tests to ensure proper integration of fast-flash features in the HP Linux simulation flow.

tests/test_xpi_fast_flash.py

@@ -0,0 +1,54 @@
+"""Directed verification for the Verilator-only XPI fast flash backend."""
+
+from __future__ import annotations
+
+import os
+import shutil
+import subprocess
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+def test_xpi_fast_flash_model_protocol(tmp_path: Path) -> None:
+    verilator = shutil.which("verilator")
+    if verilator is None:
+        return
+
+    output = tmp_path / "xpi_fast_flash_model_tb"
+    obj_dir = tmp_path / "obj"
+    ccache_dir = tmp_path / "ccache"
+    ccache_dir.mkdir()
+    subprocess.run(
+        [
+            verilator,
+            "--binary",
+            "--timing",
+            "-Wno-fatal",
+            "--top-module",
+            "xpi_fast_flash_model_tb",
+            "-I" + str(ROOT / "rtl/managed/clusterip/common/rtl"),
+            "-I" + str(ROOT / "rtl/ip/storage"),
+            str(ROOT / "rtl/managed/clusterip/common/rtl/utils/register.sv"),
+            str(ROOT / "rtl/ip/storage/xpi_pkg.sv"),
+            str(ROOT / "rtl/mini/dv/verilator/rtl/flash_read_byte_binder.sv"),
+            str(ROOT / "rtl/mini/dv/verilator/rtl/xpi_fast_flash_model.sv"),
+            str(ROOT / "tests/rtl/xpi_fast_flash_model_tb.sv"),
+            str(ROOT / "tests/rtl/xpi_fast_flash_dpi.cpp"),
+            "-Mdir",
+            str(obj_dir),
+            "-o",
+            str(output),
+        ],
+        check=True,
+        text=True,
+        capture_output=True,
+        env={
+            **os.environ,
+            "CCACHE_DIR": str(ccache_dir),
+            "CCACHE_TEMPDIR": str(ccache_dir),
+        },
+    )
+    result = subprocess.run([output], check=True, text=True, capture_output=True)
+    assert "XPI fast flash model test passed" in result.stdout