litex/misoc/cores/sdram_model.py

192 lines
6.5 KiB
Python

# This file is Copyright (c) 2015 Florent Kermarrec <florent@enjoy-digital.fr>
# License: BSD
# SDRAM simulation PHY at DFI level
# tested with SDR/DDR/DDR2/LPDDR/DDR3
# TODO:
# - add $display support to Migen and manage timing violations?
from migen import *
from migen.fhdl.specials import *
from misoc.mem.sdram.phy.dfi import *
from misoc.mem import sdram
class Bank(Module):
def __init__(self, data_width, nrows, ncols, burst_length):
self.activate = Signal()
self.activate_row = Signal(max=nrows)
self.precharge = Signal()
self.write = Signal()
self.write_col = Signal(max=ncols)
self.write_data = Signal(data_width)
self.write_mask = Signal(data_width//8)
self.read = Signal()
self.read_col = Signal(max=ncols)
self.read_data = Signal(data_width)
###
active = Signal()
row = Signal(max=nrows)
self.sync += \
If(self.precharge,
active.eq(0),
).Elif(self.activate,
active.eq(1),
row.eq(self.activate_row)
)
self.specials.mem = mem = Memory(data_width, nrows*ncols//burst_length)
self.specials.write_port = write_port = mem.get_port(write_capable=True,
we_granularity=8)
self.specials.read_port = read_port = mem.get_port(async_read=True)
self.comb += [
If(active,
write_port.adr.eq(row*ncols | self.write_col),
write_port.dat_w.eq(self.write_data),
write_port.we.eq(Replicate(self.write, data_width//8) & ~self.write_mask),
If(self.read,
read_port.adr.eq(row*ncols | self.read_col),
self.read_data.eq(read_port.dat_r)
)
)
]
class DFIPhase(Module):
def __init__(self, dfi, n):
phase = getattr(dfi, "p"+str(n))
self.bank = phase.bank
self.address = phase.address
self.wrdata = phase.wrdata
self.wrdata_mask = phase.wrdata_mask
self.rddata = phase.rddata
self.rddata_valid = phase.rddata_valid
self.activate = Signal()
self.precharge = Signal()
self.write = Signal()
self.read = Signal()
###
self.comb += [
If(~phase.cs_n & ~phase.ras_n & phase.cas_n,
self.activate.eq(phase.we_n),
self.precharge.eq(~phase.we_n)
),
If(~phase.cs_n & phase.ras_n & ~phase.cas_n,
self.write.eq(~phase.we_n),
self.read.eq(phase.we_n)
)
]
class SDRAMPHYSim(Module):
def __init__(self, module, settings):
if settings.memtype in ["SDR"]:
burst_length = settings.nphases*1 # command multiplication*SDR
elif settings.memtype in ["DDR", "LPDDR", "DDR2", "DDR3"]:
burst_length = settings.nphases*2 # command multiplication*DDR
addressbits = module.geom_settings.addressbits
bankbits = module.geom_settings.bankbits
rowbits = module.geom_settings.rowbits
colbits = module.geom_settings.colbits
self.settings = settings
self.module = module
self.dfi = Interface(addressbits, bankbits, self.settings.dfi_databits, self.settings.nphases)
###
nbanks = 2**bankbits
nrows = 2**rowbits
ncols = 2**colbits
data_width = self.settings.dfi_databits*self.settings.nphases
# DFI phases
phases = [DFIPhase(self.dfi, n) for n in range(self.settings.nphases)]
self.submodules += phases
# banks
banks = [Bank(data_width, nrows, ncols, burst_length) for i in range(nbanks)]
self.submodules += banks
# connect DFI phases to banks (cmds, write datapath)
for nb, bank in enumerate(banks):
# bank activate
activates = Signal(len(phases))
cases = {}
for np, phase in enumerate(phases):
self.comb += activates[np].eq(phase.activate)
cases[2**np] = [
bank.activate.eq(phase.bank == nb),
bank.activate_row.eq(phase.address)
]
self.comb += Case(activates, cases)
# bank precharge
precharges = Signal(len(phases))
cases = {}
for np, phase in enumerate(phases):
self.comb += precharges[np].eq(phase.precharge)
cases[2**np] = [
bank.precharge.eq((phase.bank == nb) | phase.address[10])
]
self.comb += Case(precharges, cases)
# bank writes
writes = Signal(len(phases))
cases = {}
for np, phase in enumerate(phases):
self.comb += writes[np].eq(phase.write)
cases[2**np] = [
bank.write.eq(phase.bank == nb),
bank.write_col.eq(phase.address)
]
self.comb += Case(writes, cases)
self.comb += [
bank.write_data.eq(Cat(*[phase.wrdata for phase in phases])),
bank.write_mask.eq(Cat(*[phase.wrdata_mask for phase in phases]))
]
# bank reads
reads = Signal(len(phases))
cases = {}
for np, phase in enumerate(phases):
self.comb += reads[np].eq(phase.read)
cases[2**np] = [
bank.read.eq(phase.bank == nb),
bank.read_col.eq(phase.address)
]
self.comb += Case(reads, cases)
# connect banks to DFI phases (cmds, read datapath)
banks_read = Signal()
banks_read_data = Signal(data_width)
self.comb += [
banks_read.eq(optree("|", [bank.read for bank in banks])),
banks_read_data.eq(optree("|", [bank.read_data for bank in banks]))
]
# simulate read latency
for i in range(self.settings.read_latency):
new_banks_read = Signal()
new_banks_read_data = Signal(data_width)
self.sync += [
new_banks_read.eq(banks_read),
new_banks_read_data.eq(banks_read_data)
]
banks_read = new_banks_read
banks_read_data = new_banks_read_data
self.comb += [
Cat(*[phase.rddata_valid for phase in phases]).eq(banks_read),
Cat(*[phase.rddata for phase in phases]).eq(banks_read_data)
]