| # Copyright lowRISC contributors. |
| # Licensed under the Apache License, Version 2.0, see LICENSE for details. |
| # SPDX-License-Identifier: Apache-2.0 |
| |
| from .flags import FlagGroups |
| from .wsr import WSRFile |
| |
| |
| class CSRFile: |
| '''A model of the CSR file''' |
| def __init__(self) -> None: |
| self.flags = FlagGroups() |
| |
| self._known_indices = set() |
| self._known_indices.add(0x7c0) # FG0 |
| self._known_indices.add(0x7c1) # FG1 |
| self._known_indices.add(0x7c8) # FLAGS |
| for idx in range(0x7d0, 0x7d8): |
| self._known_indices.add(idx) # MODi |
| self._known_indices.add(0x7d8) # RND_PREFETCH |
| self._known_indices.add(0xfc0) # RND |
| self._known_indices.add(0xfc1) # URND |
| |
| @staticmethod |
| def _get_field(field_idx: int, field_size: int, val: int) -> int: |
| mask = (1 << field_size) - 1 |
| return (val >> (field_size * field_idx)) & mask |
| |
| @staticmethod |
| def _set_field(field_idx: int, field_size: int, field_val: int, |
| old_val: int) -> int: |
| assert 0 <= field_val < (1 << field_size) |
| mask = (1 << field_size) - 1 |
| shift = field_size * field_idx |
| return (old_val & ~(mask << shift)) | (field_val << shift) |
| |
| def check_idx(self, idx: int) -> bool: |
| '''Return True if idx points to a valid CSR; False otherwise.''' |
| return idx in self._known_indices |
| |
| def read_unsigned(self, wsrs: WSRFile, idx: int) -> int: |
| if 0x7c0 <= idx <= 0x7c1: |
| # FG0/FG1 |
| fg = idx - 0x7c0 |
| return self._get_field(fg, 4, self.flags.read_unsigned()) |
| |
| if idx == 0x7c8: |
| # FLAGS register |
| return self.flags.read_unsigned() |
| |
| if 0x7d0 <= idx <= 0x7d7: |
| # MOD0 .. MOD7. MODi is bits [32*(i+1)-1..32*i] |
| mod_n = idx - 0x7d0 |
| return self._get_field(mod_n, 32, wsrs.MOD.read_unsigned()) |
| |
| if idx == 0x7d8: |
| # RND_PREFETCH register |
| return 0 |
| |
| if idx == 0xfc0: |
| # RND register |
| return wsrs.RND.read_u32() |
| |
| if idx == 0xfc1: |
| # URND register |
| return wsrs.URND.read_u32() |
| |
| raise RuntimeError('Unknown CSR index: {:#x}'.format(idx)) |
| |
| def write_unsigned(self, wsrs: WSRFile, idx: int, value: int) -> None: |
| assert 0 <= value < (1 << 32) |
| |
| if 0x7c0 <= idx <= 0x7c1: |
| # FG0/FG1 |
| fg = idx - 0x7c0 |
| old = self.flags.read_unsigned() |
| self.flags.write_unsigned(self._set_field(fg, 4, value & 0xf, old)) |
| return |
| |
| if idx == 0x7c8: |
| # FLAGS register |
| self.flags.write_unsigned(value) |
| return |
| |
| if 0x7d0 <= idx <= 0x7d7: |
| # MOD0 .. MOD7. MODi is bits [32*(i+1)-1..32*i]. read,modify,write. |
| mod_n = idx - 0x7d0 |
| old = wsrs.MOD.read_unsigned() |
| wsrs.MOD.write_unsigned(self._set_field(mod_n, 32, value, old)) |
| return |
| |
| if idx == 0x7d8: |
| # RND_PREFETCH |
| wsrs.RND.request_value() |
| return |
| |
| if idx == 0xfc0: |
| # RND register (which ignores writes) |
| return |
| |
| if idx == 0xfc1: |
| # URND register (which ignores writes) |
| return |
| |
| raise RuntimeError('Unknown CSR index: {:#x}'.format(idx)) |
| |
| def wipe(self) -> None: |
| self.flags.write_unsigned(0) |
