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frontend/avalon: Clearly separate Data/Control-paths and add TODO.

This commit is contained in:
Florent Kermarrec 2023-05-31 19:02:53 +02:00
parent a86bd6c3d0
commit 1b7435c6d5
1 changed files with 68 additions and 76 deletions
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144
litedram/frontend/avalon.py
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@ -2,10 +2,15 @@
# This file is part of LiteDRAM.
#
# Copyright (c) 2023 Hans Baier <hansfbaier@gmail.com>
# Copyright (c) 2023 Florent Kermarrec <florent@enjoy-digital.fr>
# SPDX-License-Identifier: BSD-2-Clause
"""AvalonMM frontend for LiteDRAM"""
# TODO:
# - Try to merge SINGLE-WRITE/BURST-WRITE (Consider single access as a 1 word burst).
# - Try to merge SINGLE-READ /BURST-READ (Consider single access as a 1 word burst).
from math import log2
from migen import *
@ -48,81 +53,15 @@ class LiteDRAMAvalonMM2Native(LiteXModule):
burst_count = Signal(9)
address = Signal(port.address_width)
address_offset = Signal(port.address_width)
latch = Signal()
cmd_ready_seen = Signal()
cmd_ready_count = Signal(9)
self.comb += address_offset.eq(base_address >> log2_int(port.data_width//8))
# Layouts.
# Write Data-path.
wdata_layout = [
("data", avalon_data_width),
("byteenable", avalon_data_width//8),
]
self.sync += [
If(latch,
burst_count.eq(avalon.burstcount),
address.eq(avalon.address - address_offset),
)
]
# FSM.
self.fsm = fsm = FSM(reset_state="START")
fsm.act("START",
avalon.waitrequest.eq(1),
NextValue(cmd_ready_seen, 0),
# Start of Access.
If(avalon.read | avalon.write,
latch.eq(1),
# Burst Access.
If(avalon.burstcount > 1,
If(avalon.write,
NextState("BURST_WRITE")
),
If(avalon.read,
avalon.waitrequest.eq(0),
NextValue(cmd_ready_count, avalon.burstcount),
NextState("BURST_READ")
)
# Single Access.
).Else(
port.cmd.addr.eq(avalon.address - address_offset),
port.cmd.we.eq(avalon.write),
port.cmd.valid.eq(1),
port.cmd.last.eq(1),
If(port.cmd.ready,
avalon.waitrequest.eq(0),
If(port.cmd.we,
NextState("SINGLE_WRITE")
).Else(
NextState("SINGLE_READ")
)
)
)
)
)
fsm.act("SINGLE_WRITE",
avalon.waitrequest.eq(1),
If(port.wdata.valid & port.wdata.ready,
NextState("START")
)
)
fsm.act("SINGLE_READ",
avalon.waitrequest.eq(1),
port.rdata.ready.eq(1),
If(port.rdata.valid,
avalon.readdata.eq(port.rdata.data),
avalon.readdatavalid.eq(1),
NextState("START")
)
)
# Write Data-Path.
self.wdata_fifo = wdata_fifo = stream.SyncFIFO(wdata_layout, max_burst_length)
self.comb += [
wdata_fifo.sink.payload.data.eq(avalon.writedata),
@ -135,7 +74,65 @@ class LiteDRAMAvalonMM2Native(LiteXModule):
wdata_fifo.source.ready.eq(port.wdata.ready),
]
fsm.act("BURST_WRITE",
# Read Data-path.
self.comb += [
port.rdata.ready.eq(1),
avalon.readdata.eq(port.rdata.data),
avalon.readdatavalid.eq(port.rdata.valid),
]
# Control-Path.
self.fsm = fsm = FSM(reset_state="IDLE")
fsm.act("IDLE",
avalon.waitrequest.eq(1),
NextValue(cmd_ready_seen, 0),
# Start of Access.
If(avalon.read | avalon.write,
NextValue(burst_count, avalon.burstcount),
NextValue(address, avalon.address - address_offset),
# Burst Access.
If(avalon.burstcount > 1,
If(avalon.write,
NextState("BURST-WRITE")
),
If(avalon.read,
avalon.waitrequest.eq(0),
NextValue(cmd_ready_count, avalon.burstcount),
NextState("BURST-READ")
)
# Single Access.
).Else(
port.cmd.addr.eq(avalon.address - address_offset),
port.cmd.we.eq(avalon.write),
port.cmd.valid.eq(1),
port.cmd.last.eq(1),
If(port.cmd.ready,
avalon.waitrequest.eq(0),
If(port.cmd.we,
NextState("SINGLE-WRITE")
).Else(
NextState("SINGLE-READ")
)
)
)
)
)
fsm.act("SINGLE-WRITE",
avalon.waitrequest.eq(1),
If(port.wdata.valid & port.wdata.ready,
NextState("IDLE")
)
)
fsm.act("SINGLE-READ",
avalon.waitrequest.eq(1),
If(port.rdata.valid,
NextState("IDLE")
)
)
fsm.act("BURST-WRITE",
avalon.waitrequest.eq(1),
port.cmd.addr.eq(address),
port.cmd.we.eq(1),
@ -152,21 +149,16 @@ class LiteDRAMAvalonMM2Native(LiteXModule):
avalon.waitrequest.eq(1),
# Wait for the FIFO to be empty
If((~port.cmd.valid) & (~wdata_fifo.source.valid),
NextState("START")
NextState("IDLE")
)
),
)
fsm.act("BURST_READ",
fsm.act("BURST-READ",
avalon.waitrequest.eq(1),
port.cmd.addr.eq(address),
port.cmd.we.eq(0),
port.cmd.valid.eq(~cmd_ready_seen),
port.rdata.ready.eq(1),
avalon.readdata.eq(port.rdata.data),
avalon.readdatavalid.eq(port.rdata.valid),
If(port.cmd.ready,
If(cmd_ready_count == 1,
NextValue(cmd_ready_seen, 1)
@ -177,7 +169,7 @@ class LiteDRAMAvalonMM2Native(LiteXModule):
If(port.rdata.valid,
If(burst_count == 1,
NextState("START")
NextState("IDLE")
),
NextValue(burst_count, burst_count - 1)
)