src/experiment/compalu.py

   1 from nmigen.compat.sim import run_simulation
   2 from nmigen.cli import verilog, rtlil
   3 from nmigen import Module, Signal, Elaboratable
   4
   5 from nmutil.latch import SRLatch, latchregister
   6
   7
   8 class ComputationUnitNoDelay(Elaboratable):
   9     def __init__(self, rwid, opwid, alu):
  10         self.rwid = rwid
  11         self.alu = alu
  12
  13         self.go_rd_i = Signal(reset_less=True) # go read in
  14         self.go_wr_i = Signal(reset_less=True) # go write in
  15         self.issue_i = Signal(reset_less=True) # fn issue in
  16
  17         self.oper_i = Signal(opwid, reset_less=True) # opcode in
  18         self.src1_i = Signal(rwid, reset_less=True) # oper1 in
  19         self.src2_i = Signal(rwid, reset_less=True) # oper2 in
  20
  21         self.busy_o = Signal(reset_less=True) # fn busy out
  22         self.data_o = Signal(rwid, reset_less=True) # Dest out
  23         self.req_rel_o = Signal(reset_less=True) # release request out (valid_o)
  24
  25     def elaborate(self, platform):
  26         m = Module()
  27         m.submodules.alu = self.alu
  28         m.submodules.src_l = src_l = SRLatch(sync=False)
  29         m.submodules.opc_l = opc_l = SRLatch(sync=False)
  30         m.submodules.req_l = req_l = SRLatch(sync=False)
  31
  32         # This is fascinating and very important to observe that this
  33         # is in effect a "3-way revolving door".  At no time may all 3
  34         # latches be set at the same time.
  35
  36         # opcode latch (not using go_rd_i)
  37         m.d.comb += opc_l.s.eq(self.go_wr_i)
  38         m.d.comb += opc_l.r.eq(self.issue_i)
  39
  40         # src operand latch (not using go_wr_i)
  41         m.d.comb += src_l.s.eq(self.issue_i)
  42         m.d.comb += src_l.r.eq(self.go_rd_i)
  43
  44         # dest operand latch (not using issue_i)
  45         m.d.comb += req_l.s.eq(self.go_rd_i)
  46         m.d.comb += req_l.r.eq(self.go_wr_i)
  47
  48         # XXX
  49         # XXX NOTE: sync on req_rel_o and data_o due to simulation lock-up
  50         # XXX
  51
  52         # outputs
  53         m.d.comb += self.busy_o.eq(opc_l.qn) # busy out
  54         m.d.comb += self.req_rel_o.eq(req_l.q & opc_l.qn) # request release out
  55
  56         # create a latch/register for src1/src2
  57         latchregister(m, self.src1_i, self.alu.a, src_l.q)
  58         latchregister(m, self.src2_i, self.alu.b, src_l.q)
  59         with m.If(src_l.qn):
  60             m.d.comb += self.alu.op.eq(self.oper_i)
  61
  62         if False:
  63             data_o = Signal(self.rwid, reset_less=True) # Dest register
  64             data_r = Signal(self.rwid, reset_less=True) # Dest register
  65             with m.If(req_l.q):
  66                 m.d.comb += data_o.eq(self.alu.o)
  67                 m.d.sync += data_r.eq(self.alu.o)
  68             with m.Else():
  69                 m.d.comb += data_o.eq(data_r)
  70             #with m.If(self.go_wr_i):
  71                 #m.d.comb += self.data_o.eq(data_o)
  72
  73
  74         # create a latch/register for the operand
  75         #latchregister(m, self.oper_i, self.alu.op, opc_l.q)
  76
  77         # and one for the output from the ALU
  78         data_o = Signal(self.rwid, reset_less=True) # Dest register
  79         latchregister(m, self.alu.o, data_o, req_l.q)
  80
  81         with m.If(self.go_wr_i):
  82             m.d.comb += self.data_o.eq(data_o)
  83
  84         return m
  85
  86 def scoreboard_sim(dut):
  87     yield dut.dest_i.eq(1)
  88     yield dut.issue_i.eq(1)
  89     yield
  90     yield dut.issue_i.eq(0)
  91     yield
  92     yield dut.src1_i.eq(1)
  93     yield dut.issue_i.eq(1)
  94     yield
  95     yield
  96     yield
  97     yield dut.issue_i.eq(0)
  98     yield
  99     yield dut.go_read_i.eq(1)
 100     yield
 101     yield dut.go_read_i.eq(0)
 102     yield
 103     yield dut.go_write_i.eq(1)
 104     yield
 105     yield dut.go_write_i.eq(0)
 106     yield
 107
 108 def test_scoreboard():
 109     dut = Scoreboard(32, 8)
 110     vl = rtlil.convert(dut, ports=dut.ports())
 111     with open("test_scoreboard.il", "w") as f:
 112         f.write(vl)
 113
 114     run_simulation(dut, scoreboard_sim(dut), vcd_name='test_scoreboard.vcd')
 115
 116 if __name__ == '__main__':
 117     test_scoreboard()