litesata/core/link/scrambler.py

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