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from functools import partial
from migen.fhdl.structure import *
from migen.corelogic import roundrobin, multimux
from migen.bus.simple import Simple, get_sig_name
_desc = [
(True, "adr", 32),
(True, "dat", 32),
(False, "dat", 32),
(True, "sel", 4),
(True, "cyc", 1),
(True, "stb", 1),
(False, "ack", 1),
(True, "we", 1),
(True, "cti", 3),
(True, "bte", 2),
(False, "err", 1)
]
class Master(Simple):
def __init__(self, name=""):
Simple.__init__(self, _desc, False, name)
class Slave(Simple):
def __init__(self, name=""):
Simple.__init__(self, _desc, True, name)
class Arbiter:
def __init__(self, masters, target):
self.masters = masters
self.target = target
self.rr = roundrobin.Inst(len(self.masters))
def get_fragment(self):
comb = []
# mux master->slave signals
m2s_names = [get_sig_name(x, False) for x in _desc if x[0]]
m2s_masters = [[getattr(m, name) for name in m2s_names] for m in self.masters]
m2s_target = [getattr(self.target, name) for name in m2s_names]
comb += multimux.multimux(self.rr.grant, m2s_masters, m2s_target)
# connect slave->master signals
s2m_names = [get_sig_name(x, False) for x in _desc if not x[0]]
for name in s2m_names:
source = getattr(self.target, name)
i = 0
for m in self.masters:
dest = getattr(m, name)
if name == "ack_i" or name == "err_i":
comb.append(dest.eq(source & (self.rr.grant == Constant(i, self.rr.grant.bv))))
else:
comb.append(dest.eq(source))
i += 1
# connect bus requests to round-robin selector
reqs = [m.cyc_o for m in self.masters]
comb.append(self.rr.request.eq(Cat(*reqs)))
return Fragment(comb) + self.rr.get_fragment()
class Decoder:
# slaves is a list of pairs:
# 0) structure.Constant defining address (always decoded on the upper bits)
# Slaves can have differing numbers of address bits, but addresses
# must not conflict.
# 1) wishbone.Slave reference
# Addresses are decoded from bit 31-offset and downwards.
# register adds flip-flops after the address comparators. Improves timing,
# but breaks Wishbone combinatorial feedback.
def __init__(self, master, slaves, offset=0, register=False):
self.master = master
self.slaves = slaves
self.offset = offset
self.register = register
addresses = [slave[0] for slave in self.slaves]
maxbits = max([bits_for(addr) for addr in addresses])
def mkconst(x):
if isinstance(x, int):
return Constant(x, BV(maxbits))
else:
return x
self.addresses = list(map(mkconst, addresses))
ns = len(self.slaves)
d = partial(declare_signal, self)
d("_slave_sel", BV(ns))
d("_slave_sel_r", BV(ns))
def get_fragment(self):
comb = []
sync = []
# decode slave addresses
i = 0
hi = self.master.adr_o.bv.width - self.offset
for addr in self.addresses:
comb.append(self._slave_sel[i].eq(
self.master.adr_o[hi-addr.bv.width:hi] == addr))
i += 1
if self.register:
sync.append(self._slave_sel_r.eq(self._slave_sel))
else:
comb.append(self._slave_sel_r.eq(self._slave_sel))
# connect master->slaves signals except cyc
m2s_names = [(get_sig_name(x, False), get_sig_name(x, True))
for x in _desc if x[0] and x[1] != "cyc"]
comb += [getattr(slave[1], name[1]).eq(getattr(self.master, name[0]))
for name in m2s_names for slave in self.slaves]
# combine cyc with slave selection signals
i = 0
for slave in self.slaves:
comb.append(slave[1].cyc_i.eq(self.master.cyc_o & self._slave_sel[i]))
i += 1
# generate master ack (resp. err) by ORing all slave acks (resp. errs)
ackv = Constant(0)
errv = Constant(0)
for slave in self.slaves:
ackv = ackv | slave[1].ack_o
errv = errv | slave[1].err_o
comb.append(self.master.ack_i.eq(ackv))
comb.append(self.master.err_i.eq(errv))
# mux (1-hot) slave data return
i = 0
datav = Constant(0, self.master.dat_i.bv)
for slave in self.slaves:
datav = datav | (Replicate(self._slave_sel_r[i], self.master.dat_i.bv.width) & slave[1].dat_o)
i += 1
comb.append(self.master.dat_i.eq(datav))
return Fragment(comb, sync)
class InterconnectShared:
def __init__(self, masters, slaves, offset=0, register=False):
self._shared = Master("shr")
self._arbiter = Arbiter(masters, self._shared)
self._decoder = Decoder(self._shared, slaves, offset, register)
self.addresses = self._decoder.addresses
def get_fragment(self):
return self._arbiter.get_fragment() + self._decoder.get_fragment()
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