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asmicon: bank machine (untested)
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Sebastien Bourdeauducq
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Mar 17, 2012
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Original file line number | Diff line number | Diff line change |
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@@ -1,8 +1,246 @@ | ||
from migen.fhdl.structure import * | ||
from migen.bus.asmibus import * | ||
from migen.corelogic.roundrobin import * | ||
from migen.corelogic.fsm import FSM | ||
from migen.corelogic.misc import multimux, optree | ||
|
||
from milkymist.asmicon.multiplexer import * | ||
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# Row:Bank:Col address mapping | ||
class _AddressSlicer: | ||
def __init__(self, geom_settings, address_align): | ||
self.geom_settings = geom_settings | ||
self.address_align = address_align | ||
|
||
self._b1 = self.geom_settings.col_a - self.address_align | ||
self._b2 = self._b1 + self.geom_settings.row_a | ||
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def bank(self, address): | ||
return address[self._b2:] | ||
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def row(self, address): | ||
return address[self._b1:self._b2] | ||
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def col(self, address): | ||
return Cat(Constant(0, BV(self.address_align)), address[:self._b1]) | ||
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class _Selector: | ||
def __init__(self, slicer, bankn, slots): | ||
self.slicer = slicer | ||
self.bankn = bankn | ||
self.slots = slots | ||
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self.nslots = len(self.slots) | ||
self.stb = Signal() | ||
self.ack = Signal() | ||
self.tag = Signal(BV(bits_for(self.nslots-1))) | ||
self.adr = Signal(self.slots[0].adr.bv) | ||
self.we = Signal() | ||
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||
def get_fragment(self): | ||
comb = [] | ||
sync = [] | ||
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# List outstanding requests for our bank | ||
outstandings = [] | ||
for slot in self.slots: | ||
outstanding = Signal() | ||
comb.append(outstanding.eq( | ||
self.slicer.bank(slot.adr) == self.bankn & \ | ||
slot.state == SLOT_PENDING | ||
)) | ||
outstandings.append(outstanding) | ||
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# Row tracking | ||
openrow_r = Signal(BV(self.slicer.geom_settings.row_a)) | ||
openrow_n = Signal(BV(self.slicer.geom_settings.row_a)) | ||
openrow = Signal(BV(self.slicer.geom_settings.row_a)) | ||
comb += [ | ||
openrow_n.eq(self.slicer.row(self.adr)), | ||
If(self.stb, | ||
openrow.eq(openrow_n) | ||
).Else( | ||
openrow.eq(openrow_r) | ||
) | ||
] | ||
sync += [ | ||
If(self.stb & self.ack, | ||
openrow_r.eq(openrow_n) | ||
) | ||
] | ||
hits = [] | ||
for slot in self.slots: | ||
hit = Signal() | ||
comb.append(hit.eq(self.slicer.row(slot.adr) == openrow)) | ||
hits.append(hit) | ||
|
||
# Determine best request | ||
rr = RoundRobin(self.nslots, SP_CE) | ||
has_hit = Signal() | ||
comb.append(has_hit.eq(optree("|", hits))) | ||
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best_hit = [rr.request[i].eq(hit & os) | ||
for i, (hit, os) in enumerate(zip(hits, outstandings))] | ||
best_fallback = [rr.request[i].eq(os) | ||
for i, os in enumerate(outstandings)] | ||
select_stmt = If(has_hit, | ||
*best_hit | ||
).Else( | ||
*best_fallback | ||
) | ||
|
||
if self.slots[0].time: | ||
# Implement anti-starvation timer | ||
has_mature = Signal() | ||
comb.append(has_mature.eq(optree("|", [slot.mature for slot in self.slots]))) | ||
best_mature = [rr.request[i].eq(slot.mature & os) | ||
for i, (slot, os) in enumerate(zip(self.slots, outstandings))] | ||
select_stmt = If(has_mature, *best_mature).Else(select_stmt) | ||
comb.append(select_stmt) | ||
|
||
# Multiplex | ||
state = Signal(BV(2)) | ||
mux_outputs = [state, self.adr, self.we] | ||
mux_inputs = [[slot.state, slot.adr, slot.we] | ||
for slot in self.slots] | ||
comb += multimux(rr.grant, mux_inputs, mux_outputs) | ||
comb += [ | ||
self.stb.eq(state == SLOT_PENDING), | ||
rr.ce.eq(self.ack), | ||
self.tag.eq(rr.grant) | ||
] | ||
comb += [slot.process.eq(rr.grant == i & self.ack) | ||
for i, slot in enumerate(self.slots)] | ||
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return Fragment(comb, sync) + rr.get_fragment() | ||
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class _Buffer: | ||
def __init__(self, source): | ||
self.source = source | ||
|
||
self.stb = Signal() | ||
self.ack = Signal() | ||
self.tag = Signal(self.source.tag.bv) | ||
self.adr = Signal(self.source.adr.bv) | ||
self.we = Signal() | ||
|
||
def get_fragment(self): | ||
en = Signal() | ||
comb = [ | ||
en.eq(self.ack | ~self.stb), | ||
self.source.ack.eq(en) | ||
] | ||
sync = [ | ||
If(en, | ||
self.stb.eq(self.source.stb), | ||
self.tag.eq(self.source.tag), | ||
self.adr.eq(self.source.adr), | ||
self.we.eq(self.source.we) | ||
) | ||
] | ||
return Fragment(comb, sync) | ||
|
||
class BankMachine: | ||
def __init__(self, geom_settings, timing_settings, address_align, bankn, slots): | ||
pass | ||
self.geom_settings = geom_settings | ||
self.timing_settings = timing_settings | ||
self.address_align = address_align | ||
self.bankn = bankn | ||
self.slots = slots | ||
|
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self.refresh_req = Signal() | ||
self.refresh_gnt = Signal() | ||
self.cmd_request = CommandRequestRW(geom_settings.mux_a, geom_settings.bank_a, | ||
bits_for(len(slots)-1)) | ||
|
||
def get_fragment(self): | ||
return Fragment() | ||
comb = [] | ||
sync = [] | ||
|
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# Sub components | ||
slicer = _AddressSlicer(self.geom_settings, self.address_align) | ||
selector = _Selector(slicer, self.bankn, self.slots) | ||
buf = _Buffer(selector) | ||
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# Row tracking | ||
has_openrow = Signal() | ||
openrow = Signal(BV(self.geom_settings.row_a)) | ||
hit = Signal() | ||
comb.append(hit.eq(openrow == slicer.row(buf.adr))) | ||
track_open = Signal() | ||
track_close = Signal() | ||
sync += [ | ||
If(track_open, | ||
has_openrow.eq(1), | ||
openrow.eq(slicer.row(buf.adr)) | ||
), | ||
If(track_close, | ||
has_openrow.eq(0) | ||
) | ||
] | ||
|
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# Address generation | ||
s_row_adr = Signal() | ||
comb += [ | ||
self.cmd_request.ba.eq(self.bankn), | ||
If(s_row_adr, | ||
self.cmd_request.a.eq(slicer.row(buf.adr)) | ||
).Else( | ||
self.cmd_request.a.eq(slicer.col(buf.adr)) | ||
) | ||
] | ||
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||
comb.append(self.cmd_request.tag.eq(buf.tag)) | ||
|
||
# Control and command generation FSM | ||
fsm = FSM("REGULAR", "PRECHARGE", "ACTIVATE", "REFRESH", delayed_enters=[ | ||
("TRP", "ACTIVATE", self.timing_settings.tRP-1), | ||
("TRCD", "REGULAR", self.timing_settings.tRCD-1) | ||
]) | ||
fsm.act(fsm.REGULAR, | ||
If(self.refresh_req, | ||
fsm.next_state(fsm.REFRESH) | ||
).Elif(buf.stb, | ||
If(has_openrow, | ||
If(hit, | ||
self.cmd_request.stb.eq(1), | ||
buf.ack.eq(self.cmd_request.ack), | ||
self.cmd_request.is_read.eq(~buf.we), | ||
self.cmd_request.is_write.eq(buf.we), | ||
self.cmd_request.cas_n.eq(0), | ||
self.cmd_request.we_n.eq(~buf.we) | ||
).Else( | ||
fsm.next_state(fsm.PRECHARGE) | ||
) | ||
).Else( | ||
fsm.next_state(fsm.ACTIVATE) | ||
) | ||
) | ||
) | ||
fsm.act(fsm.PRECHARGE, | ||
# Notes: | ||
# 1. we are presenting the column address, A10 is always low | ||
# 2. since we always go to the ACTIVATE state, we do not need | ||
# to assert track_close. | ||
self.cmd_request.stb.eq(1), | ||
If(self.cmd_request.ack, fsm.next_state(fsm.TRP)), | ||
self.cmd_request.ras_n.eq(0), | ||
self.cmd_request.we_n.eq(0) | ||
) | ||
fsm.act(fsm.ACTIVATE, | ||
s_row_adr.eq(1), | ||
track_open.eq(1), | ||
self.cmd_request.stb.eq(1), | ||
If(self.cmd_request.ack, fsm.next_state(fsm.TRCD)), | ||
self.cmd_request.ras_n.eq(0) | ||
) | ||
fsm.act(fsm.REFRESH, | ||
self.refresh_gnt.eq(1), | ||
track_close.eq(1), | ||
If(~self.refresh_req, fsm.next_state(fsm.REGULAR)) | ||
) | ||
|
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return Fragment(comb, sync) + \ | ||
selector.get_fragment() + \ | ||
buf.get_fragment() + \ | ||
fsm.get_fragment() |
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