litex/migen/bus/asmibus.py

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from migen.fhdl.structure import *
from migen.corelogic.misc import optree
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from migen.bus.transactions import *
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from migen.sim.generic import Proxy
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class FinalizeError(Exception):
pass
(SLOT_EMPTY, SLOT_PENDING, SLOT_PROCESSING) = range(3)
class Slot:
def __init__(self, aw, time):
self.state = Signal(BV(2))
self.we = Signal()
self.adr = Signal(BV(aw))
self.time = time
if self.time:
self._counter = Signal(BV(bits_for(time)))
self.mature = Signal()
self.allocate = Signal()
self.allocate_we = Signal()
self.allocate_adr = Signal(BV(aw))
self.process = Signal()
self.call = Signal()
def get_fragment(self):
comb = []
sync = [
If(self.allocate,
self.state.eq(SLOT_PENDING),
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self.we.eq(self.allocate_we),
self.adr.eq(self.allocate_adr)
),
If(self.process, self.state.eq(SLOT_PROCESSING)),
If(self.call, self.state.eq(SLOT_EMPTY))
]
if self.time:
comb += [
self.mature.eq(self._counter == 0)
]
sync += [
If(self.allocate,
self._counter.eq(self.time)
).Elif(self._counter != 0,
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self._counter.eq(self._counter - 1)
)
]
return Fragment(comb, sync)
class Port:
def __init__(self, hub, nslots):
self.hub = hub
self.slots = [Slot(self.hub.aw, self.hub.time) for i in range(nslots)]
self.finalized = False
# request issuance
self.adr = Signal(BV(self.hub.aw))
self.we = Signal()
self.stb = Signal()
# tag_issue is created by finalize()
self.ack = Signal()
# request completion
self.call = Signal()
# tag_call is created by finalize()
self.dat_r = Signal(BV(self.hub.dw))
self.dat_w = Signal(BV(self.hub.dw))
self.dat_wm = Signal(BV(self.hub.dw//8))
def finalize(self, tagbits, base):
if self.finalized:
raise FinalizeError
self.finalized = True
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self.tagbits = tagbits
self.base = base
nslots = len(self.slots)
if nslots > 1:
self.tag_issue = Signal(BV(bits_for(nslots-1)))
self.tag_call = Signal(BV(tagbits))
def get_call_expression(self, slotn=0):
if not self.finalized:
raise FinalizeError
return self.call \
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& (self.tag_call == Constant(self.base + slotn, BV(self.tagbits)))
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def get_fragment(self):
if not self.finalized:
raise FinalizeError
slots_fragment = sum([s.get_fragment() for s in self.slots], Fragment())
comb = []
sync = []
# allocate
for s in self.slots:
comb += [
s.allocate_we.eq(self.we),
s.allocate_adr.eq(self.adr)
]
choose_slot = None
for s in reversed(self.slots):
choose_slot = If(s.state == SLOT_EMPTY,
s.allocate.eq(self.stb)
).Else(choose_slot)
comb.append(choose_slot)
comb.append(self.ack.eq(optree("|",
[s.state == SLOT_EMPTY for s in self.slots])))
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# call
comb += [s.call.eq(self.get_call_expression(n))
for n, s in enumerate(self.slots)]
return slots_fragment + Fragment(comb, sync)
class Hub:
def __init__(self, aw, dw, time=0):
self.aw = aw
self.dw = dw
self.time = time
self.ports = []
self.finalized = False
self.call = Signal()
# tag_call is created by finalize()
self.dat_r = Signal(BV(self.dw))
self.dat_w = Signal(BV(self.dw))
self.dat_wm = Signal(BV(self.dw//8))
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def get_port(self, nslots=1):
if self.finalized:
raise FinalizeError
new_port = Port(self, nslots)
self.ports.append(new_port)
return new_port
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def finalize(self):
if self.finalized:
raise FinalizeError
self.finalized = True
nslots = sum([len(port.slots) for port in self.ports])
tagbits = bits_for(nslots-1)
base = 0
for port in self.ports:
port.finalize(tagbits, base)
base += len(port.slots)
self.tag_call = Signal(BV(tagbits))
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def get_slots(self):
if not self.finalized:
raise FinalizeError
return sum([port.slots for port in self.ports], [])
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def get_fragment(self):
if not self.finalized:
raise FinalizeError
ports = sum([port.get_fragment() for port in self.ports], Fragment())
comb = []
for port in self.ports:
comb += [
port.call.eq(self.call),
port.tag_call.eq(self.tag_call),
port.dat_r.eq(self.dat_r)
]
comb += [
self.dat_w.eq(optree("|", [port.dat_w for port in self.ports])),
self.dat_wm.eq(optree("|", [port.dat_wm for port in self.ports]))
]
return ports + Fragment(comb)
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class Tap:
def __init__(self, hub, handler=print):
self.hub = hub
self.handler = handler
self.tag_to_transaction = dict()
self.transaction = None
def do_simulation(self, s):
hub = Proxy(s, self.hub)
# Pull any data announced in the previous cycle.
if isinstance(self.transaction, TWrite):
self.transaction.data = hub.dat_w
self.transaction.sel = ~hub.dat_wm
self.handler(self.transaction)
self.transaction = None
if isinstance(self.transaction, TRead):
self.transaction.data = hub.dat_r
self.handler(self.transaction)
self.transaction = None
# Tag issue. Transaction objects are created here
# and placed into the tag_to_transaction dictionary.
for tag, slot in enumerate(self.hub.get_slots()):
if s.rd(slot.allocate):
adr = s.rd(slot.allocate_adr)
we = s.rd(slot.allocate_we)
if we:
transaction = TWrite(adr)
else:
transaction = TRead(adr)
transaction.latency = s.cycle_counter
self.tag_to_transaction[tag] = transaction
# Tag call.
if hub.call:
transaction = self.tag_to_transaction[hub.tag_call]
transaction.latency = s.cycle_counter - transaction.latency + 1
self.transaction = transaction
def get_fragment(self):
return Fragment(sim=[self.do_simulation])
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class Initiator:
def __init__(self, port, generator):
self.port = port
self.generator = generator
self.done = False
self._exe = None
def _execute(self, s, port, generator):
while True:
transaction = next(generator)
transaction_start = s.cycle_counter
if transaction is None:
yield
else:
# tag phase
s.wr(port.adr, transaction.address)
if isinstance(transaction, TWrite):
s.wr(port.we, 1)
else:
s.wr(port.we, 0)
s.wr(port.stb, 1)
yield
while not s.rd(port.ack):
yield
if hasattr(port, "tag_issue"):
tag = s.rd(port.tag_issue)
else:
tag = 0
tag += port.base
s.wr(port.stb, 0)
# data phase
while not (s.rd(port.call) and (s.rd(port.tag_call) == tag)):
yield
if isinstance(transaction, TWrite):
s.wr(port.dat_w, transaction.data)
s.wr(port.dat_wm, ~transaction.sel)
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yield
s.wr(port.dat_w, 0)
s.wr(port.dat_wm, 0)
else:
yield
transaction.data = s.rd(port.dat_r)
transaction.latency = s.cycle_counter - transaction_start - 1
def do_simulation(self, s):
if not self.done:
if self._exe is None:
self._exe = self._execute(s, self.port, self.generator)
try:
next(self._exe)
except StopIteration:
self.done = True
def get_fragment(self):
return Fragment(sim=[self.do_simulation])
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class TargetModel:
def __init__(self):
self.last_slot = 0
def read(self, address):
return 0
def write(self, address, data, mask):
pass
# Round-robin scheduling.
def select_slot(self, pending_slots):
if not pending_slots:
return -1
self.last_slot += 1
if self.last_slot > max(pending_slots):
self.last_slot = 0
while self.last_slot not in pending_slots:
self.last_slot += 1
return self.last_slot
class Target:
def __init__(self, hub, model):
self.hub = hub
self.model = model
self._calling_tag = -1
self._write_request_d = -1
self._write_request = -1
self._read_request = -1
def do_simulation(self, s):
slots = self.hub.get_slots()
# Data I/O
if self._write_request >= 0:
self.model.write(self._write_request,
s.rd(self.hub.dat_w), s.rd(self.hub.dat_wm))
if self._read_request >= 0:
s.wr(self.hub.dat_r, self.model.read(self._read_request))
# Request pipeline
self._read_request = -1
self._write_request = self._write_request_d
self._write_request_d = -1
# Examine pending slots and possibly choose one.
# Note that we do not use the SLOT_PROCESSING state here.
# Selected slots are immediately called.
pending_slots = set()
for tag, slot in enumerate(slots):
if tag != self._calling_tag and s.rd(slot.state) == SLOT_PENDING:
pending_slots.add(tag)
slot_to_call = self.model.select_slot(pending_slots)
# Call slot.
if slot_to_call >= 0:
slot = slots[slot_to_call]
s.wr(self.hub.call, 1)
s.wr(self.hub.tag_call, slot_to_call)
self._calling_tag = slot_to_call
if s.rd(slot.we):
self._write_request_d = s.rd(slot.adr)
else:
self._read_request = s.rd(slot.adr)
else:
s.wr(self.hub.call, 0)
self._calling_tag = -1
def get_fragment(self):
return Fragment(sim=[self.do_simulation])