lib/sata/link/scrambler.py

   1 from lib.sata.common import *
   2
   3 from migen.fhdl.std import *
   4 from migen.genlib.misc import optree
   5
   6 @DecorateModule(InsertCE)
   7 class Scrambler(Module):
   8         """SATA Scrambler
   9
  10         Implement a SATA Scrambler
  11
  12         Attributes
  13         ----------
  14         value : out
  15                 Scrambled value.
  16         """
  17         def __init__(self):
  18                 self.value = Signal(32)
  19
  20                 ###
  21
  22                 context = Signal(16, reset=0xf0f6)
  23                 next_value = Signal(32)
  24                 self.sync += context.eq(next_value[16:32])
  25
  26                 # XXX: from SATA specification, replace it with
  27                 # a generic implementation using polynoms.
  28                 lfsr_coefs = (
  29                         (15, 13, 4, 0), #0
  30                         (15, 14, 13, 5, 4, 1, 0),
  31                         (14, 13, 6, 5, 4, 2,1, 0),
  32                         (15, 14, 7, 6, 5, 3,2, 1),
  33                         (13, 8, 7, 6, 3, 2, 0),
  34                         (14, 9, 8, 7, 4, 3, 1),
  35                         (15, 10, 9, 8, 5, 4, 2),
  36                         (15, 13, 11, 10, 9, 6, 5, 4, 3, 0),
  37                         (15, 14, 13, 12, 11, 10,7, 6, 5, 1, 0),
  38                         (14, 12, 11, 8, 7, 6, 4, 2, 1, 0),
  39                         (15, 13, 12, 9, 8, 7, 5, 3, 2, 1),
  40                         (15, 14, 10, 9, 8, 6, 3, 2, 0),
  41                         (13, 11, 10, 9, 7, 3, 1, 0),
  42                         (14, 12, 11, 10, 8, 4, 2, 1),
  43                         (15, 13, 12, 11, 9, 5, 3, 2),
  44                         (15, 14, 12, 10, 6, 3, 0),
  45
  46                         (11, 7, 1, 0), #16
  47                         (12, 8, 2, 1),
  48                         (13, 9, 3, 2),
  49                         (14, 10, 4, 3),
  50                         (15, 11, 5, 4),
  51                         (15, 13, 12, 6, 5, 4, 0),
  52                         (15, 14, 7, 6, 5, 4, 1, 0),
  53                         (13, 8, 7, 6, 5, 4, 2, 1, 0),
  54                         (14, 9, 8,7, 6, 5, 3, 2, 1),
  55                         (15, 10, 9, 8, 7, 6, 4, 3, 2),
  56                         (15, 13, 11, 10, 9, 8, 7, 5, 3, 0),
  57                         (15, 14, 13, 12, 11, 10, 9, 8, 6, 1, 0),
  58                         (14, 12, 11, 10, 9, 7, 4, 2, 1, 0),
  59                         (15, 13, 12, 11, 10, 8, 5, 3, 2, 1),
  60                         (15, 14, 12, 11, 9, 6, 3, 2, 0),
  61                         (12, 10, 7, 3, 1, 0),
  62                 )
  63
  64                 for n, coefs in enumerate(lfsr_coefs):
  65                         eq = [context[i] for i in coefs]
  66                         self.comb += next_value[n].eq(optree("^", eq))
  67
  68                 self.comb += self.value.eq(next_value)
  69
  70 @DecorateModule(InsertReset)
  71 class SATAScrambler(Module):
  72         def __init__(self, description):
  73                 self.sink = sink = Sink(description)
  74                 self.source = source = Source(description)
  75
  76                 ###
  77
  78                 self.submodules.scrambler = Scrambler()
  79                 self.comb += [
  80                         self.scrambler.ce.eq(sink.stb & sink.ack),
  81                         Record.connect(sink, source),
  82                         source.d.eq(sink.d ^ self.scrambler.value)
  83                 ]