@DecorateModule(InsertReset)
@DecorateModule(InsertCE)
 class LFSR(Module):

     def __init__(self, n_out, n_state=31, taps=[27, 30]):
         self.o = Signal(n_out)

         ###

         state = Signal(n_state)
         curval = [state[i] for i in range(n_state)]
         curval += [0]*(n_out - n_state)
         for i in range(n_out):
             nv = ~optree("^", [curval[tap] for tap in taps])
             curval.insert(0, nv)
             curval.pop()

         self.sync += [
             state.eq(Cat(*curval[:n_state])),
             self.o.eq(Cat(*curval))
         ]


 class NandDmaWriter(Module):

     def __init__(self, lasmim, data):
         self._magic = CSRStatus(16)
         self._reset = CSR()
         self._shoot = CSR()
         self.submodules._dma = DMAWriteController(
             dma_lasmi.Writer(lasmim),
             MODE_EXTERNAL)

         ###

         self.comb += self._magic.status.eq(nandread_magic)

         lfsr = LFSR(lasmim.dw)
         self.submodules += lfsr
         self.comb += lfsr.reset.eq(self._reset.re)
         self.data = data

         en = Signal()
         en_counter = Signal(lasmim.aw)
         self.comb += en.eq(en_counter != 0)
         self.sync += [
             If(self._shoot.re,
                en_counter.eq(self._dma.length)
                ).Elif(lfsr.ce,
                       en_counter.eq(en_counter - 1)
                       )
         ]

         self.comb += [
             self._dma.trigger.eq(self._shoot.re),
             self._dma.data.stb.eq(en),
             lfsr.ce.eq(en & self._dma.data.ack),
             # self._dma.data.d.eq(lfsr.o)
             self._dma.data.d.eq(self.data)
         ]

     def get_csrs(self):
         return [self._magic, self._reset, self._shoot] + self._dma.get_csrs()


 class NandDmaReader(Module):

     def __init__(self, lasmim, data):
         self._magic = CSRStatus(16)
         self._reset = CSR()
         self._error_count = CSRStatus(lasmim.aw)
         self.submodules._dma = DMAReadController(
             dma_lasmi.Reader(lasmim),
             MODE_SINGLE_SHOT)

         self.data = data

         ###

         self.comb += self._magic.status.eq(nandread_magic)

         lfsr = LFSR(lasmim.dw)
         self.lfsr = lfsr
         self.submodules += lfsr
         self.comb += lfsr.reset.eq(self._reset.re)

         self.comb += [
             lfsr.ce.eq(self._dma.data.stb),
             self._dma.data.ack.eq(1)
         ]
         err_cnt = self._error_count.status
         self.sync += [
             If(self._reset.re,
                err_cnt.eq(0)
                ).Elif(self._dma.data.stb,
                       If(self._dma.data.d != self.data, err_cnt.eq(err_cnt + 1))
                       ),
             self._dma.data.d[0].eq(1)
         ]

     def get_csrs(self):
         return [
             self._magic,
             self._reset,
             self._error_count] + self._dma.get_csrs()