litex/lib/sata/link/scrambler.py

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from migen.fhdl.std import *
from migen.genlib.misc import optree
@DecorateModule(InsertReset)
@DecorateModule(InsertCE)
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class Scrambler(Module):
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"""SATA Scrambler
Implement a SATA Scrambler
Attributes
----------
value : out
Scrambled value.
"""
def __init__(self):
self.value = Signal(32)
###
context = Signal(16, reset=0xf0f6)
next_value = Signal(32)
self.sync += context.eq(next_value[16:32])
# from SATA specification, if possible replace it
# with a generic implementation using polynoms.
lfsr_coefs = (
(15, 13, 4, 0), #0
(15, 14, 13, 5, 4, 1, 0),
(14, 13, 6, 5, 4, 2,1, 0),
(15, 14, 7, 6, 5, 3,2, 1),
(13, 8, 7, 6, 3, 2, 0),
(14, 9, 8, 7, 4, 3, 1),
(15, 10, 9, 8, 5, 4, 2),
(15, 13, 11, 10, 9, 6, 5, 4, 3, 0),
(15, 14, 13, 12, 11, 10,7, 6, 5, 1, 0),
(14, 12, 11, 8, 7, 6, 4, 2, 1, 0),
(15, 13, 12, 9, 8, 7, 5, 3, 2, 1),
(15, 14, 10, 9, 8, 6, 3, 2, 0),
(13, 11, 10, 9, 7, 3, 1, 0),
(14, 12, 11, 10, 8, 4, 2, 1),
(15, 13, 12, 11, 9, 5, 3, 2),
(15, 14, 12, 10, 6, 3, 0),
(11, 7, 1, 0), #16
(12, 8, 2, 1),
(13, 9, 3, 2),
(14, 10, 4, 3),
(15, 11, 5, 4),
(15, 13, 12, 6, 5, 4, 0),
(15, 14, 7, 6, 5, 4, 1, 0),
(13, 8, 7, 6, 5, 4, 2, 1, 0),
(14, 9, 8,7, 6, 5, 3, 2, 1),
(15, 10, 9, 8, 7, 6, 4, 3, 2),
(15, 13, 11, 10, 9, 8, 7, 5, 3, 0),
(15, 14, 13, 12, 11, 10, 9, 8, 6, 1, 0),
(14, 12, 11, 10, 9, 7, 4, 2, 1, 0),
(15, 13, 12, 11, 10, 8, 5, 3, 2, 1),
(15, 14, 12, 11, 9, 6, 3, 2, 0),
(12, 10, 7, 3, 1, 0),
)
for n, coefs in enumerate(lfsr_coefs):
eq = [context[i] for i in coefs]
self.comb += next_value[n].eq(optree("^", eq))
self.comb += self.value.eq(next_value)
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class SATAScrambler(Module):
def __init__(self, layout):
self.sink = sink = Sink(layout)
self.source = source = Source(layout)
###
self.submodules.scrambler = Scrambler()
ongoing = Signal()
self.sync += [
If(sink.stb & sink.ack,
If(sink.eop,
ongoing.eq(0)
).Elsif(sink.sop,
ongoing.eq(1)
)
)
]
self.comb += [
self.scrambler.ce.eq(sink.stb & (sink.sop | ongoing)),
self.scrambler.reset.eq(~ongoing),
Record.connect(sink, source),
source.d.eq(sink.d ^ self.scrambler.value)
]