litex/misoclib/mem/sdram/frontend/dma_lasmi.py

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from migen.fhdl.std import *
from migen.flow.actor import *
from migen.genlib.fifo import SyncFIFO
2015-04-13 10:47:22 -04:00
class Reader(Module):
def __init__(self, lasmim, fifo_depth=None):
self.address = Sink([("a", lasmim.aw)])
self.data = Source([("d", lasmim.dw)])
self.busy = Signal()
###
if fifo_depth is None:
fifo_depth = lasmim.req_queue_size + lasmim.read_latency + 2
# request issuance
request_enable = Signal()
request_issued = Signal()
self.comb += [
lasmim.we.eq(0),
lasmim.stb.eq(self.address.stb & request_enable),
lasmim.adr.eq(self.address.a),
self.address.ack.eq(lasmim.req_ack & request_enable),
request_issued.eq(lasmim.stb & lasmim.req_ack)
]
# FIFO reservation level counter
# incremented when data is planned to be queued
# decremented when data is dequeued
data_dequeued = Signal()
rsv_level = Signal(max=fifo_depth+1)
self.sync += [
If(request_issued,
If(~data_dequeued, rsv_level.eq(rsv_level + 1))
).Elif(data_dequeued,
rsv_level.eq(rsv_level - 1)
)
]
self.comb += [
self.busy.eq(rsv_level != 0),
request_enable.eq(rsv_level != fifo_depth)
]
# FIFO
fifo = SyncFIFO(lasmim.dw, fifo_depth)
self.submodules += fifo
self.comb += [
fifo.din.eq(lasmim.dat_r),
fifo.we.eq(lasmim.dat_r_ack),
self.data.stb.eq(fifo.readable),
fifo.re.eq(self.data.ack),
self.data.d.eq(fifo.dout),
data_dequeued.eq(self.data.stb & self.data.ack)
]
class Writer(Module):
def __init__(self, lasmim, fifo_depth=None):
self.address_data = Sink([("a", lasmim.aw), ("d", lasmim.dw)])
self.busy = Signal()
###
if fifo_depth is None:
fifo_depth = lasmim.req_queue_size + lasmim.write_latency + 2
fifo = SyncFIFO(lasmim.dw, fifo_depth)
self.submodules += fifo
self.comb += [
lasmim.we.eq(1),
lasmim.stb.eq(fifo.writable & self.address_data.stb),
lasmim.adr.eq(self.address_data.a),
self.address_data.ack.eq(fifo.writable & lasmim.req_ack),
fifo.we.eq(self.address_data.stb & lasmim.req_ack),
fifo.din.eq(self.address_data.d)
]
self.comb += [
If(lasmim.dat_w_ack,
fifo.re.eq(1),
lasmim.dat_we.eq(2**(lasmim.dw//8)-1),
lasmim.dat_w.eq(fifo.dout)
),
self.busy.eq(fifo.readable)
]