src/soc/fu/spr/main_stage.py

   1 """SPR Pipeline
   2
   3 * https://bugs.libre-soc.org/show_bug.cgi?id=348
   4 * https://libre-soc.org/openpower/isa/sprset/
   5 """
   6
   7 from nmigen import (Module, Signal, Cat)
   8 from nmutil.pipemodbase import PipeModBase
   9 from soc.fu.spr.pipe_data import SPRInputData, SPROutputData
  10 from openpower.decoder.power_enums import MicrOp, SPRfull, SPRreduced, XER_bits
  11
  12 from openpower.decoder.power_fields import DecodeFields
  13 from openpower.decoder.power_fieldsn import SignalBitRange
  14 from openpower.decoder.power_decoder2 import decode_spr_num
  15
  16
  17 class SPRMainStage(PipeModBase):
  18     def __init__(self, pspec):
  19         super().__init__(pspec, "spr_main")
  20         # test if regfiles are reduced
  21         self.regreduce_en = (hasattr(pspec, "regreduce") and
  22                              (pspec.regreduce == True))
  23
  24         self.fields = DecodeFields(SignalBitRange, [self.i.ctx.op.insn])
  25         self.fields.create_specs()
  26
  27     def ispec(self):
  28         return SPRInputData(self.pspec)
  29
  30     def ospec(self):
  31         return SPROutputData(self.pspec)
  32
  33     def elaborate(self, platform):
  34         if self.regreduce_en:
  35             SPR = SPRreduced
  36         else:
  37             SPR = SPRfull
  38         m = Module()
  39         comb = m.d.comb
  40         op = self.i.ctx.op
  41
  42         # convenience variables
  43         a_i, spr1_i, fast1_i = self.i.a, self.i.spr1, self.i.fast1
  44         so_i, ov_i, ca_i = self.i.xer_so, self.i.xer_ov, self.i.xer_ca
  45         so_o, ov_o, ca_o = self.o.xer_so, self.o.xer_ov, self.o.xer_ca
  46         o, spr1_o, fast1_o = self.o.o, self.o.spr1, self.o.fast1
  47         state1_i, state1_o = self.i.state1, self.o.state1
  48
  49         # take copy of D-Form TO field
  50         x_fields = self.fields.FormXFX
  51         spr = Signal(len(x_fields.SPR))
  52         comb += spr.eq(decode_spr_num(x_fields.SPR))
  53
  54         # TODO: some #defines for the bits n stuff.
  55         with m.Switch(op.insn_type):
  56             #### MTSPR ####
  57             with m.Case(MicrOp.OP_MTSPR):
  58                 with m.Switch(spr):
  59                     # fast SPRs first
  60                     with m.Case(SPR.DEC, SPR.TB):
  61                         comb += state1_o.data.eq(a_i)
  62                         comb += state1_o.ok.eq(1)
  63
  64                     # state SPRs second
  65                     with m.Case(SPR.CTR, SPR.LR, SPR.TAR, SPR.SRR0,
  66                                 SPR.SRR1, SPR.XER, SPR.DEC, SPR.TB):
  67                         comb += fast1_o.data.eq(a_i)
  68                         comb += fast1_o.ok.eq(1)
  69                         # XER is constructed
  70                         with m.If(spr == SPR.XER):
  71                             # sticky
  72                             comb += so_o.data.eq(a_i[63-XER_bits['SO']])
  73                             comb += so_o.ok.eq(1)
  74                             # overflow
  75                             comb += ov_o.data[0].eq(a_i[63-XER_bits['OV']])
  76                             comb += ov_o.data[1].eq(a_i[63-XER_bits['OV32']])
  77                             comb += ov_o.ok.eq(1)
  78                             # carry
  79                             comb += ca_o.data[0].eq(a_i[63-XER_bits['CA']])
  80                             comb += ca_o.data[1].eq(a_i[63-XER_bits['CA32']])
  81                             comb += ca_o.ok.eq(1)
  82
  83                     # slow SPRs TODO
  84                     with m.Default():
  85                         comb += spr1_o.data.eq(a_i)
  86                         comb += spr1_o.ok.eq(1)
  87
  88             # move from SPRs
  89             with m.Case(MicrOp.OP_MFSPR):
  90                 comb += o.ok.eq(1)
  91                 with m.Switch(spr):
  92                     # state SPRs first
  93                     with m.Case(SPR.DEC, SPR.TB):
  94                         comb += o.data.eq(fast1_i)
  95
  96                     # fast SPRs second
  97                     with m.Case(SPR.CTR, SPR.LR, SPR.TAR, SPR.SRR0, SPR.SRR1,
  98                                 SPR.XER):
  99                         comb += o.data.eq(fast1_i)
 100                         with m.If(spr == SPR.XER):
 101                             # bits 0:31 and 35:43 are treated as reserved
 102                             # and return 0s when read using mfxer
 103                             comb += o[32:64].eq(0)       # MBS0 bits 0-31
 104                             comb += o[63-43:64-35].eq(0)  # MSB0 bits 35-43
 105                             # sticky
 106                             comb += o[63-XER_bits['SO']].eq(so_i)
 107                             # overflow
 108                             comb += o[63-XER_bits['OV']].eq(ov_i[0])
 109                             comb += o[63-XER_bits['OV32']].eq(ov_i[1])
 110                             # carry
 111                             comb += o[63-XER_bits['CA']].eq(ca_i[0])
 112                             comb += o[63-XER_bits['CA32']].eq(ca_i[1])
 113                     with m.Case(SPR.TBU):
 114                         comb += o.data[0:32].eq(fast1_i[32:64])
 115
 116                     # slow SPRs TODO
 117                     with m.Default():
 118                         comb += o.data.eq(spr1_i)
 119
 120         comb += self.o.ctx.eq(self.i.ctx)
 121
 122         return m