src/soc/fu/mmu/fsm.py

   1 """
   2 Based on microwatt mmu.vhdl
   3
   4 * https://bugs.libre-soc.org/show_bug.cgi?id=491
   5 * https://bugs.libre-soc.org/show_bug.cgi?id=450
   6 """
   7
   8 from nmigen import Elaboratable, Module, Signal, Shape, unsigned, Cat, Mux
   9 from nmigen import Record, Memory
  10 from nmigen import Const
  11 from soc.fu.mmu.pipe_data import MMUInputData, MMUOutputData, MMUPipeSpec
  12 from nmutil.singlepipe import ControlBase
  13 from nmutil.util import rising_edge
  14
  15 from soc.experiment.mmu import MMU
  16
  17 from openpower.consts import MSR
  18 from openpower.decoder.power_fields import DecodeFields
  19 from openpower.decoder.power_fieldsn import SignalBitRange
  20 from openpower.decoder.power_decoder2 import decode_spr_num
  21 from openpower.decoder.power_enums import MicrOp
  22
  23 from soc.experiment.mem_types import LoadStore1ToMMUType
  24 from soc.experiment.mem_types import MMUToLoadStore1Type
  25
  26 from soc.fu.ldst.loadstore import LoadStore1, TestSRAMLoadStore1
  27 from nmutil.util import Display
  28
  29 class FSMMMUStage(ControlBase):
  30     """FSM MMU
  31
  32     FSM-based MMU: must call set_ldst_interface and pass in an instance
  33     of a LoadStore1.  this to comply with the ConfigMemoryPortInterface API
  34
  35     this Function Unit is extremely unusual in that it actually stores a
  36     "thing" rather than "processes inputs and produces outputs".  hence
  37     why it has to be a FSM.  linking up LD/ST however is going to have
  38     to be done back in Issuer (or Core).  sorted: call set_ldst_interface
  39     """
  40     def __init__(self, pspec):
  41         super().__init__()
  42         self.pspec = pspec
  43
  44         # set up p/n data
  45         self.p.i_data = MMUInputData(pspec)
  46         self.n.o_data = MMUOutputData(pspec)
  47
  48         self.mmu = MMU()
  49
  50         # debugging output for gtkw
  51         self.debug0 = Signal(4)
  52         self.illegal = Signal()
  53
  54         # for SPR field number access
  55         i = self.p.i_data
  56         self.fields = DecodeFields(SignalBitRange, [i.ctx.op.insn])
  57         self.fields.create_specs()
  58
  59     def set_ldst_interface(self, ldst):
  60         """must be called back in Core, after FUs have been set up.
  61         one of those will be the MMU (us!) but the LoadStore1 instance
  62         must be set up in ConfigMemoryPortInterface. sigh.
  63         """
  64         # incoming PortInterface
  65         self.ldst = ldst
  66         self.dcache = self.ldst.dcache
  67         self.pi = self.ldst.pi
  68
  69     def elaborate(self, platform):
  70         assert hasattr(self, "dcache"), "remember to call set_ldst_interface"
  71         m = super().elaborate(platform)
  72         comb, sync = m.d.comb, m.d.sync
  73         dcache = self.dcache
  74
  75         # link mmu and dcache together
  76         m.submodules.mmu = mmu = self.mmu
  77         ldst = self.ldst # managed externally: do not add here
  78         m.d.comb += dcache.m_in.eq(mmu.d_out) # MMUToDCacheType
  79         m.d.comb += mmu.d_in.eq(dcache.m_out) # DCacheToMMUType
  80
  81         l_in, l_out = mmu.l_in, mmu.l_out
  82         d_in, d_out = dcache.d_in, dcache.d_out
  83
  84         # link ldst and MMU together
  85         comb += l_in.eq(ldst.m_out)
  86         comb += ldst.m_in.eq(l_out)
  87
  88         i_data, o_data = self.p.i_data, self.n.o_data
  89         a_i, b_i, o, spr1_o = i_data.ra, i_data.rb, o_data.o, o_data.spr1
  90         op = i_data.ctx.op
  91         spr1_i = i_data.spr1
  92
  93         # busy/done signals
  94         busy = Signal()
  95         done = Signal()
  96         m.d.comb += self.n.o_valid.eq(busy & done)
  97         m.d.comb += self.p.o_ready.eq(~busy)
  98
  99         # take copy of X-Form SPR field
 100         x_fields = self.fields.FormXFX
 101         spr = Signal(len(x_fields.SPR))
 102         comb += spr.eq(decode_spr_num(x_fields.SPR))
 103
 104         # ok so we have to "pulse" the MMU (or dcache) rather than
 105         # hold the valid hi permanently.  guess what this does...
 106         valid = Signal()
 107         blip = Signal()
 108         m.d.comb += blip.eq(rising_edge(m, valid))
 109
 110         with m.If(~busy):
 111             with m.If(self.p.i_valid):
 112                 sync += busy.eq(1)
 113         with m.Else():
 114
 115             # based on the Micro-Op, we work out which of MMU or DCache
 116             # should "action" the operation.  one of MMU or DCache gets
 117             # enabled ("valid") and we twiddle our thumbs until it
 118             # responds ("done").
 119
 120             # WIP: properly implement MicrOp.OP_MTSPR and MicrOp.OP_MFSPR
 121
 122             with m.Switch(op.insn_type):
 123                 with m.Case(MicrOp.OP_MTSPR):
 124                     comb += Display("MMUTEST: OP_MTSPR: spr=%i", spr)
 125                     # despite redirection this FU **MUST** behave exactly
 126                     # like the SPR FU.  this **INCLUDES** updating the SPR
 127                     # regfile because the CSV file entry for OP_MTSPR
 128                     # categorically defines and requires the expectation
 129                     # that the CompUnit **WILL** write to the regfile.
 130                     comb += spr1_o.data.eq(a_i)
 131                     comb += spr1_o.ok.eq(1)
 132                     # subset SPR: first check a few bits
 133                     # XXX NOTE this must now cover **FOUR** values: this
 134                     # test might not be adequate.  DSISR, DAR, PGTBL and PID
 135                     # must ALL be covered here.
 136                     with m.If(~spr[9] & ~spr[5]):
 137                         comb += self.debug0.eq(3)
 138                         #if matched update local cached value
 139                         #commented out because there is a driver conflict
 140                         comb += ldst.sprval_in.eq(a_i)
 141                         comb += ldst.mmu_set_spr.eq(1)
 142                         with m.If(spr[0]):
 143                             comb += ldst.mmu_set_dar.eq(1)
 144                         with m.Else():
 145                             comb += ldst.mmu_set_dsisr.eq(1)
 146                         comb += done.eq(1)
 147                     # pass it over to the MMU instead
 148                     with m.Else():
 149                         # PGTBL and PID
 150                         comb += self.debug0.eq(4)
 151                         # blip the MMU and wait for it to complete
 152                         comb += valid.eq(1)   # start "pulse"
 153                         comb += l_in.valid.eq(blip)   # start
 154                         comb += l_in.mtspr.eq(1)      # mtspr mode
 155                         comb += l_in.sprn.eq(spr)  # which SPR
 156                         comb += l_in.rs.eq(a_i)    # incoming operand (RS)
 157                         comb += done.eq(1) # FIXME l_out.done
 158
 159                 with m.Case(MicrOp.OP_MFSPR):
 160                     comb += Display("MMUTEST: OP_MFSPR: spr=%i returns=%i",
 161                                     spr, spr1_i)
 162                     # partial SPR number decoding perfectly fine
 163                     with m.If(spr[9] | spr[5]):
 164                         # identified as an MMU OP_MFSPR, contact the MMU.
 165                         # interestingly, the read is combinatorial: no need
 166                         # to set "valid", just set the SPR number
 167                         comb += l_in.sprn.eq(spr)  # which SPR
 168                         comb += o.data.eq(l_out.sprval)
 169                     with m.Else():
 170                         # identified as DSISR or DAR.  again: read the SPR
 171                         # directly, combinatorial access
 172                         with m.If(spr[0]):
 173                             comb += o.data.eq(ldst.dar)
 174                         with m.Else():
 175                             comb += o.data.eq(ldst.dsisr)
 176
 177                     comb += o.ok.eq(1)
 178                     comb += done.eq(1)
 179
 180                 with m.Case(MicrOp.OP_TLBIE):
 181                     comb += Display("MMUTEST: OP_TLBIE: insn_bits=%i", spr)
 182                     # pass TLBIE request to MMU (spec: v3.0B p1034)
 183                     # note that the spr is *not* an actual spr number, it's
 184                     # just that those bits happen to match with field bits
 185                     # RIC, PRS, R
 186                     comb += Display("TLBIE: %i %i", spr, l_out.done)
 187                     comb += valid.eq(1)   # start "pulse"
 188                     comb += l_in.valid.eq(blip)   # start
 189                     comb += l_in.tlbie.eq(1)   # mtspr mode
 190                     comb += l_in.sprn.eq(spr)  # use sprn to send insn bits
 191                     comb += l_in.addr.eq(b_i)  # incoming operand (RB)
 192                     comb += done.eq(l_out.done) # zzzz
 193                     comb += self.debug0.eq(2)
 194
 195                 with m.Case(MicrOp.OP_ILLEGAL):
 196                     comb += self.illegal.eq(1)
 197
 198             with m.If(self.n.i_ready & self.n.o_valid):
 199                 sync += busy.eq(0)
 200
 201         return m
 202
 203     def __iter__(self):
 204         yield from self.p
 205         yield from self.n
 206
 207     def ports(self):
 208         return list(self)