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asmicon: fix and simplify refresh grant logic

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This commit is contained in:
Sebastien Bourdeauducq 2012-08-04 22:59:21 +02:00
parent ea4c214790
commit a5d6ced181
2 changed files with 7 additions and 24 deletions
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2
milkymist/asmicon/bankmachine.py
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@ -294,7 +294,7 @@ class BankMachine:
self.cmd.ras_n.eq(0)
)
fsm.act(fsm.REFRESH,
self.refresh_gnt.eq(1),
self.refresh_gnt.eq(precharge_ok),
track_close.eq(1),
If(~self.refresh_req, fsm.next_state(fsm.REGULAR))
)

29
milkymist/asmicon/multiplexer.py
View file

@ -1,5 +1,3 @@
import math
from migen.fhdl.structure import *
from migen.corelogic.roundrobin import *
from migen.corelogic.misc import optree
@ -212,27 +210,11 @@ class Multiplexer:
write_time_en, max_write_time = anti_starvation(self.timing_settings.write_time)
# Refresh
refresh_w_ok = Signal()
t_unsafe_refresh = 2 + self.timing_settings.tWR - 1
unsafe_refresh_count = Signal(BV(bits_for(t_unsafe_refresh)))
comb.append(refresh_w_ok.eq(unsafe_refresh_count == 0))
sync += [
If(choose_req.cmd.stb & choose_req.cmd.ack & choose_req.cmd.is_write,
unsafe_refresh_count.eq(t_unsafe_refresh)
).Elif(~refresh_w_ok,
unsafe_refresh_count.eq(unsafe_refresh_count-1)
)
]
# Reads cannot conflict with refreshes, since we have one idle cycle
# (all bank machines in refresh state) before the PRECHARGE ALL command
# from the refresher.
comb += [bm.refresh_req.eq(self.refresher.req)
for bm in self.bank_machines]
comb.append(
self.refresher.ack.eq(optree("&",
[bm.refresh_gnt for bm in self.bank_machines]) \
& refresh_w_ok)
)
go_to_refresh = Signal()
comb.append(go_to_refresh.eq(
optree("&", [bm.refresh_gnt for bm in self.bank_machines])))
# Datapath
datapath = _Datapath(self.timing_settings, choose_req.cmd, self.dfi, self.hub)
@ -253,7 +235,7 @@ class Multiplexer:
# TODO: switch only after several cycles of ~read_available?
If(~read_available | max_read_time, fsm.next_state(fsm.RTW))
),
If(self.refresher.ack, fsm.next_state(fsm.REFRESH))
If(go_to_refresh, fsm.next_state(fsm.REFRESH))
)
fsm.act(fsm.WRITE,
write_time_en.eq(1),
@ -265,10 +247,11 @@ class Multiplexer:
If(read_available,
If(~write_available | max_write_time, fsm.next_state(fsm.WTR))
),
If(self.refresher.ack, fsm.next_state(fsm.REFRESH))
If(go_to_refresh, fsm.next_state(fsm.REFRESH))
)
fsm.act(fsm.REFRESH,
steerer.sel[0].eq(STEER_REFRESH),
self.refresher.ack.eq(1),
If(~self.refresher.req, fsm.next_state(fsm.READ))
)