124 lines
3.6 KiB
Python
124 lines
3.6 KiB
Python
from collections import OrderedDict
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from migen.fhdl.std import *
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from migen.fhdl.module import FinalizeError
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from migen.fhdl.visit import NodeTransformer
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class AnonymousState:
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pass
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# do not use namedtuple here as it inherits tuple
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# and the latter is used elsewhere in FHDL
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class NextState:
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def __init__(self, state):
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self.state = state
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class _LowerNextState(NodeTransformer):
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def __init__(self, next_state_signal, encoding, aliases):
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self.next_state_signal = next_state_signal
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self.encoding = encoding
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self.aliases = aliases
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def visit_unknown(self, node):
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if isinstance(node, NextState):
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try:
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actual_state = self.aliases[node.state]
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except KeyError:
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actual_state = node.state
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return self.next_state_signal.eq(self.encoding[actual_state])
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else:
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return node
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class FSM(Module):
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def __init__(self, reset_state=None):
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self.actions = OrderedDict()
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self.state_aliases = dict()
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self.reset_state = reset_state
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self.before_entering_signals = OrderedDict()
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self.before_leaving_signals = OrderedDict()
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self.after_entering_signals = OrderedDict()
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self.after_leaving_signals = OrderedDict()
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def act(self, state, *statements):
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if self.finalized:
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raise FinalizeError
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if state not in self.actions:
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self.actions[state] = []
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self.actions[state] += statements
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def delayed_enter(self, name, target, delay):
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if self.finalized:
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raise FinalizeError
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if delay:
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state = name
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for i in range(delay):
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if i == delay - 1:
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next_state = target
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else:
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next_state = AnonymousState()
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self.act(state, NextState(next_state))
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state = next_state
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else:
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self.state_aliases[name] = target
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def ongoing(self, state):
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is_ongoing = Signal()
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self.act(state, is_ongoing.eq(1))
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return is_ongoing
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def _get_signal(self, d, state):
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if state not in self.actions:
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self.actions[state] = []
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try:
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return d[state]
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except KeyError:
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is_el = Signal()
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d[state] = is_el
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return is_el
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def before_entering(self, state):
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return self._get_signal(self.before_entering_signals, state)
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def before_leaving(self, state):
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return self._get_signal(self.before_leaving_signals, state)
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def after_entering(self, state):
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signal = self._get_signal(self.after_entering_signals, state)
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self.sync += signal.eq(self.before_entering(state))
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return signal
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def after_leaving(self, state):
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signal = self._get_signal(self.after_leaving_signals, state)
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self.sync += signal.eq(self.before_leaving(state))
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return signal
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def do_finalize(self):
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nstates = len(self.actions)
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if self.reset_state is None:
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reset_state = next(iter(self.actions.keys()))
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else:
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reset_state = self.reset_state
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self.encoding = dict((s, n) for n, s in enumerate(self.actions.keys()))
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self.state = Signal(max=nstates, reset=self.encoding[reset_state])
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self.next_state = Signal(max=nstates)
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lns = _LowerNextState(self.next_state, self.encoding, self.state_aliases)
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cases = dict((self.encoding[k], lns.visit(v)) for k, v in self.actions.items() if v)
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self.comb += [
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self.next_state.eq(self.state),
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Case(self.state, cases)
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]
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self.sync += self.state.eq(self.next_state)
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# drive entering/leaving signals
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for state, signal in self.before_leaving_signals.items():
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encoded = self.encoding[state]
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self.comb += signal.eq((self.state == encoded) & ~(self.next_state == encoded))
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if reset_state in self.after_entering_signals:
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self.after_entering_signals[reset_state].reset = 1
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for state, signal in self.before_entering_signals.items():
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encoded = self.encoding[state]
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self.comb += signal.eq(~(self.state == encoded) & (self.next_state == encoded))
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