retroSoC/physical/librelane/tiny/scripts/generate_sdc.py

#!/usr/bin/env python3
"""Generate pad-aware timing constraints for the Tiny IHP130 Chip flow."""

from __future__ import annotations

import argparse
import json
import sys
from pathlib import Path


ROOT = Path(__file__).resolve().parents[4]
sys.path.insert(0, str(ROOT))
from scripts.rtl.generate_pin_map import Pad, ihp130_pad_instance, read_map  # noqa: E402
from scripts.check_clock_reset_domains import validate  # noqa: E402
from scripts.setup_helpers import atomic_write  # noqa: E402


CLOCK_PADS = {
    "external": "extclk_i_pad",
    "jtag": "jtag_tck_i_pad",
}
RESET_PADS = {"ext_rst_n_i_pad", "jtag_trst_n_i_pad"}
IHP130_SYSTEM_CLOCK_PIN = "u_clock_buffer.u_sg13g2_buf_1/X"
JTAG_PERIOD_NS = 100.0


def positive_integer(value: str) -> int:
    parsed = int(value)
    if parsed <= 0:
        raise argparse.ArgumentTypeError("value must be positive")
    return parsed


def timing_clock(pad: Pad) -> str:
    if pad.name.startswith("jtag_"):
        return "jtag"
    return "external"


def logical_directions(pad: Pad) -> tuple[bool, bool]:
    input_kinds = {"tri_input", "schmitt_input"}
    output_kinds = {"tri_output", "peripheral_output"}
    bidir_kinds = {"full", "peripheral_bidir", "xpi_data"}
    if pad.kind in input_kinds:
        return True, False
    if pad.kind in output_kinds:
        return False, True
    if pad.kind in bidir_kinds:
        return True, True
    return False, False


def render(args: argparse.Namespace) -> str:
    validate(args.domains, ROOT)
    pads, _ = read_map(args.pin_map)
    by_name = {pad.name: pad for pad in pads}
    for name in CLOCK_PADS.values():
        if name not in by_name:
            raise ValueError(f"clock PAD is missing from the pin map: {name}")

    periods = {
        "external": 1_000_000_000 / args.ext_clk_hz,
        "jtag": JTAG_PERIOD_NS,
    }
    groups: dict[str, dict[str, list[str]]] = {
        name: {"inputs": [], "outputs": []} for name in periods
    }
    excluded = set(CLOCK_PADS.values()) | RESET_PADS
    for pad in pads:
        if pad.name in excluded:
            continue
        is_input, is_output = logical_directions(pad)
        clock = timing_clock(pad)
        if is_input:
            groups[clock]["inputs"].append(pad.name)
        if is_output:
            groups[clock]["outputs"].append(pad.name)

    lines = [
        "# Generated by physical/librelane/tiny/scripts/generate_sdc.py; do not edit.",
        "current_design $::env(DESIGN_NAME)",
        "set_units -time ns",
        "",
        "proc require_pins {label name} {",
        "  set objects [get_pins -quiet $name]",
        '  if {$objects eq ""} { error "required SDC pin is missing: $label ($name)" }',
        "  return $objects",
        "}",
        "proc require_ports {label name} {",
        "  set objects [get_ports -quiet $name]",
        '  if {$objects eq ""} { error "required SDC port is missing: $label ($name)" }',
        "  return $objects",
        "}",
        "",
    ]
    for name, pad_name in CLOCK_PADS.items():
        instance = ihp130_pad_instance(by_name[pad_name])
        if instance is None:
            raise ValueError(f"clock PAD has no IHP130 physical instance: {pad_name}")
        lines.append(
            f'set clk_{name}_pin [require_pins "clock {name}" {{{instance}/p2c}}]'
        )
        lines.append(
            f"create_clock -name clk_{name} -period {periods[name]:.12g} $clk_{name}_pin"
        )
        lines.append("")

    lines.extend(
        [
            f'set clk_system_pin [require_pins "clock system" {{{IHP130_SYSTEM_CLOCK_PIN}}}]',
            "create_generated_clock -name clk_system -source $clk_external_pin "
            "-divide_by 1 $clk_system_pin",
            "",
            "set_clock_groups -name retrosoc_async -asynchronous \\",
            "  -group [get_clocks {clk_external clk_system}] \\",
            "  -group [get_clocks {clk_jtag}]",
            "",
            "set all_retrosoc_clocks [get_clocks {clk_external clk_system clk_jtag}]",
            "set_clock_uncertainty -setup 0.2 $all_retrosoc_clocks",
            "set_clock_uncertainty -hold 0.1 $all_retrosoc_clocks",
            "set_clock_transition 0.1 $all_retrosoc_clocks",
            "set_timing_derate -early 0.95",
            "set_timing_derate -late 1.05",
            "set_max_fanout 10 [current_design]",
            "",
        ]
    )

    for reset in sorted(RESET_PADS):
        lines.extend(
            [
                f'set reset_{reset} [require_ports "reset {reset}" {{{reset}}}]',
                f"set_false_path -from $reset_{reset}",
                "",
            ]
        )

    for clock, port_groups in groups.items():
        delay = periods[clock] * 0.2
        for direction, ports in port_groups.items():
            if not ports:
                continue
            variable = f"{clock}_{direction}"
            lines.append(f"set {variable} [get_ports {{{' '.join(ports)}}}]")
            if direction == "inputs":
                lines.append(f"set_input_delay -min 0 -clock clk_{clock} ${variable}")
                lines.append(f"set_input_delay -max {delay:.12g} -clock clk_{clock} ${variable}")
            else:
                lines.append(f"set_output_delay -min 0 -clock clk_{clock} ${variable}")
                lines.append(f"set_output_delay -max {delay:.12g} -clock clk_{clock} ${variable}")
                lines.append(f"set_load 0.006 ${variable}")
            lines.append("")
    return "\n".join(lines)


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--domains", type=Path, required=True)
    parser.add_argument("--pin-map", type=Path, required=True)
    parser.add_argument("--ext-clk-hz", type=positive_integer, required=True)
    parser.add_argument("--output", type=Path, required=True)
    args = parser.parse_args()
    try:
        atomic_write(args.output, render(args))
    except (OSError, ValueError, json.JSONDecodeError) as error:
        parser.error(str(error))
    return 0


if __name__ == "__main__":
    raise SystemExit(main())