Add partial implementation of CRI interface
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rtio/cri.py
126
rtio/cri.py
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from nmigen import *
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from nmigen.utils import *
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from nmigen.hdl.rec import *
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"""Common RTIO Interface"""
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# CRI write happens in 3 cycles:
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# 1. set timestamp and channel
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# 2. set other payload elements and issue write command
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# 3. check status
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commands = {
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"nop": 0,
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"write": 1,
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# i_status should have the "wait for status" bit set until
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# an event is available, or timestamp is reached.
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"read": 2,
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# targets must assert o_buffer_space_valid in response
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# to this command
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"get_buffer_space": 3
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}
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layout = [
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("cmd", 2, DIR_FANOUT),
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# 8 MSBs of chan_sel = routing destination
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# 16 LSBs of chan_sel = channel within the destination
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("chan_sel", 24, DIR_FANOUT),
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("o_timestamp", 64, DIR_FANOUT),
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("o_data", 512, DIR_FANOUT),
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("o_address", 8, DIR_FANOUT),
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# o_status bits:
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# <0:wait> <1:underflow> <2:destination unreachable>
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("o_status", 3, DIR_FANIN),
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# pessimistic estimate of the number of outputs events that can be
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# written without waiting.
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# this feature may be omitted on systems without DRTIO.
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("o_buffer_space_valid", 1, DIR_FANIN),
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("o_buffer_space", 16, DIR_FANIN),
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("i_timeout", 64, DIR_FANOUT),
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("i_data", 32, DIR_FANIN),
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("i_timestamp", 64, DIR_FANIN),
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# i_status bits:
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# <0:wait for event (command timeout)> <1:overflow> <2:wait for status>
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# <3:destination unreachable>
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# <0> and <1> are mutually exclusive. <1> has higher priority.
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("i_status", 4, DIR_FANIN),
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]
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class Interface(Record):
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def __init__(self, **kwargs):
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super().__init__(layout, **kwargs)
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# Skip KernelInitiator for now
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class CRIDecoder(Elaboratable):
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def __init__(self, slaves=2, master=None, mode="async", enable_routing=False):
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if isinstance(slaves, int):
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slaves = [Interface() for _ in range(slaves)]
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if master is None:
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master = Interface()
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self.slaves = slaves
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self.master = master
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self.mode = mode
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self.enable_routing = enable_routing
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def elaborate(self, platform):
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m = Module()
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# routing
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if self.enable_routing:
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destination_unreachable = Interface()
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m.d.comb += destination_unreachable.o_status.eq(4)
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m.d.comb += destination_unreachable.i_status.eq(8)
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self.slaves = self.slaves[:]
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self.slaves.append(destination_unreachable)
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target_len = 2 ** (len(slaves) - 1).bit_length()
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self.slaves += [destination_unreachable] * (target_len - len(slaves))
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slave_bits = bits_for(len(self.slaves) - 1)
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selected = Signal(slave_bits)
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if self.enable_routing:
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routing_table = Memory(slave_bits, 256)
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if self.mode == "async":
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rtp_decoder_rdport = routing_table.read_port()
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rtp_decoder_wrport = routing_table.write_port()
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elif self.mode == "sync":
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rtp_decoder_rdport = routing_table.read_port(clock_domain="rtio")
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rtp_decoder_wrport = routing_tables.write_port(clock_domain="rtio")
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else:
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raise ValueError
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m.submodules.rtp_decoder_rdport = rtp_decoder_rdport
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m.submodules.rtp_decoder_wrport = rtp_decoder_wrport
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m.d.comb += rtp_decoder_rdport.addr.eq(self.master.chan_sel[16:])
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m.d.comb += selected.eq(rtp_decoder_rdport.data)
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else:
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m.d.sync += selected.eq(self.master.chan_sel[16:])
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# master -> slave
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for n, slave in enumerate(self.slaves):
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for name, size, direction in layout:
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if direction == DIR_FANOUT and name != "cmd":
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m.d.comb += getattr(slave, name).eq(getattr(self.master, name))
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with m.If(selected == n):
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m.d.comb += slave.cmd.eq(self.master.cmd)
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# slave -> master
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with m.Switch(selected):
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for n, slave in enumerate(self.slaves):
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with m.Case(n):
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for name, size, direction in layout:
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if direction == DIR_FANIN:
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m.d.comb += getattr(self.master, name).eq(getattr(slave, name))
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return m
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# TODO: CRISwitch
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# TODO: CRIInterconnectShared
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# TODO: RoutingTableAccess
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