src/soc/simple/issuer.py

   1 """simple core issuer
   2
   3 not in any way intended for production use.  this runs a FSM that:
   4
   5 * reads the Program Counter from StateRegs
   6 * reads an instruction from a fixed-size Test Memory
   7 * issues it to the Simple Core
   8 * waits for it to complete
   9 * increments the PC
  10 * does it all over again
  11
  12 the purpose of this module is to verify the functional correctness
  13 of the Function Units in the absolute simplest and clearest possible
  14 way, and to at provide something that can be further incrementally
  15 improved.
  16 """
  17
  18 from nmigen import (Elaboratable, Module, Signal, ClockSignal, ResetSignal,
  19                     ClockDomain, DomainRenamer)
  20 from nmigen.cli import rtlil
  21 from nmigen.cli import main
  22 import sys
  23
  24 from soc.decoder.power_decoder import create_pdecode
  25 from soc.decoder.power_decoder2 import PowerDecode2
  26 from soc.decoder.decode2execute1 import Data
  27 from soc.experiment.testmem import TestMemory # test only for instructions
  28 from soc.regfile.regfiles import StateRegs
  29 from soc.simple.core import NonProductionCore
  30 from soc.config.test.test_loadstore import TestMemPspec
  31 from soc.config.ifetch import ConfigFetchUnit
  32 from soc.decoder.power_enums import MicrOp
  33 from soc.debug.dmi import CoreDebug, DMIInterface
  34 from soc.config.state import CoreState
  35
  36 from nmutil.util import rising_edge
  37
  38
  39 class TestIssuer(Elaboratable):
  40     """TestIssuer - reads instructions from TestMemory and issues them
  41
  42     efficiency and speed is not the main goal here: functional correctness is.
  43     """
  44     def __init__(self, pspec):
  45         # main instruction core
  46         self.core = core = NonProductionCore(pspec)
  47
  48         # instruction decoder
  49         pdecode = create_pdecode()
  50         self.pdecode2 = PowerDecode2(pdecode)   # decoder
  51
  52         # Test Instruction memory
  53         self.imem = ConfigFetchUnit(pspec).fu
  54         # one-row cache of instruction read
  55         self.iline = Signal(64) # one instruction line
  56         self.iprev_adr = Signal(64) # previous address: if different, do read
  57
  58         # DMI interface
  59         self.dbg = CoreDebug()
  60
  61         # instruction go/monitor
  62         self.pc_o = Signal(64, reset_less=True)
  63         self.pc_i = Data(64, "pc_i") # set "ok" to indicate "please change me"
  64         self.core_bigendian_i = Signal()
  65         self.busy_o = Signal(reset_less=True)
  66         self.memerr_o = Signal(reset_less=True)
  67
  68         # FAST regfile read /write ports for PC and MSR
  69         self.state_r_pc = self.core.regs.rf['state'].r_ports['cia'] # PC rd
  70         self.state_w_pc = self.core.regs.rf['state'].w_ports['d_wr1'] # PC wr
  71         self.state_r_msr = self.core.regs.rf['state'].r_ports['msr'] # MSR rd
  72
  73         # DMI interface access
  74         intrf = self.core.regs.rf['int']
  75         self.int_r = intrf.r_ports['dmi'] # INT read
  76
  77         # hack method of keeping an eye on whether branch/trap set the PC
  78         self.state_nia = self.core.regs.rf['state'].w_ports['nia']
  79         self.state_nia.wen.name = 'state_nia_wen'
  80
  81     def elaborate(self, platform):
  82         m = Module()
  83         comb, sync = m.d.comb, m.d.sync
  84
  85         m.submodules.core = core = DomainRenamer("coresync")(self.core)
  86         m.submodules.imem = imem = self.imem
  87         m.submodules.dbg = dbg = self.dbg
  88
  89         # instruction decoder
  90         pdecode = create_pdecode()
  91         m.submodules.dec2 = pdecode2 = self.pdecode2
  92
  93         # convenience
  94         dmi = dbg.dmi
  95         d_reg = dbg.dbg_gpr
  96         intrf = self.core.regs.rf['int']
  97
  98         # clock delay power-on reset
  99         cd_por  = ClockDomain(reset_less=True)
 100         cd_sync = ClockDomain()
 101         core_sync = ClockDomain("coresync")
 102         m.domains += cd_por, cd_sync, core_sync
 103
 104         delay = Signal(range(4), reset=3)
 105         with m.If(delay != 0):
 106             m.d.por += delay.eq(delay - 1)
 107         comb += cd_por.clk.eq(ClockSignal())
 108         comb += core_sync.clk.eq(ClockSignal())
 109         # power-on reset delay
 110         comb += core.core_reset_i.eq(delay != 0 | dbg.core_rst_o)
 111
 112         # busy/halted signals from core
 113         comb += self.busy_o.eq(core.busy_o)
 114         comb += pdecode2.dec.bigendian.eq(self.core_bigendian_i)
 115
 116         # current state (MSR/PC at the moment
 117         cur_state = CoreState("cur")
 118
 119         # temporary hack: says "go" immediately for both address gen and ST
 120         l0 = core.l0
 121         ldst = core.fus.fus['ldst0']
 122         st_go_edge = rising_edge(m, ldst.st.rel_o)
 123         m.d.comb += ldst.ad.go_i.eq(ldst.ad.rel_o) # link addr-go direct to rel
 124         m.d.comb += ldst.st.go_i.eq(st_go_edge) # link store-go to rising rel
 125
 126         # PC and instruction from I-Memory
 127         pc_changed = Signal() # note write to PC
 128         comb += self.pc_o.eq(cur_state.pc)
 129         ilatch = Signal(32)
 130
 131         # next instruction (+4 on current)
 132         nia = Signal(64, reset_less=True)
 133         comb += nia.eq(cur_state.pc + 4)
 134
 135         # read the PC
 136         pc = Signal(64, reset_less=True)
 137         with m.If(self.pc_i.ok):
 138             # incoming override (start from pc_i)
 139             comb += pc.eq(self.pc_i.data)
 140         with m.Else():
 141             # otherwise read StateRegs regfile for PC
 142             comb += self.state_r_pc.ren.eq(1<<StateRegs.PC)
 143             comb += pc.eq(self.state_r_pc.data_o)
 144
 145         # don't write pc every cycle
 146         sync += self.state_w_pc.wen.eq(0)
 147         sync += self.state_w_pc.data_i.eq(0)
 148
 149         # don't read msr every cycle
 150         sync += self.state_r_msr.ren.eq(0)
 151
 152         # connect up debug signals
 153         # TODO comb += core.icache_rst_i.eq(dbg.icache_rst_o)
 154         comb += core.core_stopped_i.eq(dbg.core_stop_o)
 155         comb += dbg.terminate_i.eq(core.core_terminate_o)
 156         comb += dbg.state.pc.eq(pc)
 157         comb += dbg.state.msr.eq(cur_state.msr)
 158
 159         # temporaries
 160         core_busy_o = core.busy_o                 # core is busy
 161         core_ivalid_i = core.ivalid_i             # instruction is valid
 162         core_issue_i = core.issue_i               # instruction is issued
 163         dec_opcode_i = pdecode2.dec.raw_opcode_in # raw opcode
 164
 165         insn_type = core.e.do.insn_type
 166         insn_state = pdecode2.state
 167
 168         # actually use a nmigen FSM for the first time (w00t)
 169         # this FSM is perhaps unusual in that it detects conditions
 170         # then "holds" information, combinatorially, for the core
 171         # (as opposed to using sync - which would be on a clock's delay)
 172         # this includes the actual opcode, valid flags and so on.
 173         with m.FSM() as fsm:
 174
 175             # waiting (zzz)
 176             with m.State("IDLE"):
 177                 sync += pc_changed.eq(0)
 178                 sync += core.e.eq(0)
 179                 with m.If(~dbg.core_stop_o & ~core.core_reset_i):
 180                     # instruction allowed to go: start by reading the PC
 181                     # capture the PC and also drop it into Insn Memory
 182                     # we have joined a pair of combinatorial memory
 183                     # lookups together.  this is Generally Bad.
 184                     comb += self.imem.a_pc_i.eq(pc)
 185                     comb += self.imem.a_valid_i.eq(1)
 186                     comb += self.imem.f_valid_i.eq(1)
 187                     sync += cur_state.pc.eq(pc)
 188
 189                     # read MSR, latch it, and put it in decode "state"
 190                     sync += self.state_r_msr.ren.eq(1<<StateRegs.MSR)
 191                     sync += cur_state.msr.eq(self.state_r_msr.data_o)
 192
 193                     m.next = "INSN_READ" # move to "wait for bus" phase
 194
 195             # dummy pause to find out why simulation is not keeping up
 196             with m.State("INSN_READ"):
 197                 with m.If(self.imem.f_busy_o): # zzz...
 198                     # busy: stay in wait-read
 199                     comb += self.imem.a_valid_i.eq(1)
 200                     comb += self.imem.f_valid_i.eq(1)
 201                 with m.Else():
 202                     # not busy: instruction fetched
 203                     f_instr_o = self.imem.f_instr_o
 204                     if f_instr_o.width == 32:
 205                         insn = f_instr_o
 206                     else:
 207                         insn = f_instr_o.word_select(cur_state.pc[2], 32)
 208                     comb += dec_opcode_i.eq(insn) # actual opcode
 209                     sync += core.e.eq(pdecode2.e)
 210                     sync += ilatch.eq(insn) # latch current insn
 211                     # also drop PC and MSR into decode "state"
 212                     sync += insn_state.eq(cur_state)
 213                     m.next = "INSN_START" # move to "start"
 214
 215             # waiting for instruction bus (stays there until not busy)
 216             with m.State("INSN_START"):
 217                 comb += core_ivalid_i.eq(1) # instruction is valid
 218                 comb += core_issue_i.eq(1)  # and issued
 219
 220
 221                 m.next = "INSN_ACTIVE" # move to "wait completion"
 222
 223             # instruction started: must wait till it finishes
 224             with m.State("INSN_ACTIVE"):
 225                 with m.If(insn_type != MicrOp.OP_NOP):
 226                     comb += core_ivalid_i.eq(1) # instruction is valid
 227                 with m.If(self.state_nia.wen):
 228                     sync += pc_changed.eq(1)
 229                 with m.If(~core_busy_o): # instruction done!
 230                     # ok here we are not reading the branch unit.  TODO
 231                     # this just blithely overwrites whatever pipeline
 232                     # updated the PC
 233                     with m.If(~pc_changed):
 234                         sync += self.state_w_pc.wen.eq(1<<StateRegs.PC)
 235                         sync += self.state_w_pc.data_i.eq(nia)
 236                     sync += core.e.eq(0)
 237                     m.next = "IDLE" # back to idle
 238
 239         # this bit doesn't have to be in the FSM: connect up to read
 240         # regfiles on demand from DMI
 241
 242         with m.If(d_reg.req): # request for regfile access being made
 243             # TODO: error-check this
 244             # XXX should this be combinatorial?  sync better?
 245             if intrf.unary:
 246                 comb += self.int_r.ren.eq(1<<d_reg.addr)
 247             else:
 248                 comb += self.int_r.addr.eq(d_reg.addr)
 249                 comb += self.int_r.ren.eq(1)
 250             comb += d_reg.data.eq(self.int_r.data_o)
 251             comb += d_reg.ack.eq(1)
 252
 253         return m
 254
 255     def __iter__(self):
 256         yield from self.pc_i.ports()
 257         yield self.pc_o
 258         yield self.memerr_o
 259         yield from self.core.ports()
 260         yield from self.imem.ports()
 261         yield self.core_bigendian_i
 262         yield self.busy_o
 263
 264     def ports(self):
 265         return list(self)
 266
 267     def external_ports(self):
 268         return self.pc_i.ports() + [self.pc_o,
 269                                     self.memerr_o,
 270                                     self.core_bigendian_i,
 271                                     ClockSignal(),
 272                                     ResetSignal(),
 273                                     self.busy_o,
 274                                     ] + \
 275                 list(self.dbg.dmi.ports()) + \
 276                 list(self.imem.ibus.fields.values()) + \
 277                 list(self.core.l0.cmpi.lsmem.lsi.dbus.fields.values())
 278
 279     def ports(self):
 280         return list(self)
 281
 282
 283 if __name__ == '__main__':
 284     units = {'alu': 1, 'cr': 1, 'branch': 1, 'trap': 1, 'logical': 1,
 285              'spr': 1,
 286              'div': 1,
 287              'mul': 1,
 288              'shiftrot': 1
 289             }
 290     pspec = TestMemPspec(ldst_ifacetype='bare_wb',
 291                          imem_ifacetype='bare_wb',
 292                          addr_wid=48,
 293                          mask_wid=8,
 294                          reg_wid=64,
 295                          units=units)
 296     dut = TestIssuer(pspec)
 297     vl = main(dut, ports=dut.ports(), name="test_issuer")
 298
 299     if len(sys.argv) == 1:
 300         vl = rtlil.convert(dut, ports=dut.external_ports(), name="test_issuer")
 301         with open("test_issuer.il", "w") as f:
 302             f.write(vl)