litesata/frontend/arbiter.py

   1 from litesata.common import *
   2 from litesata.frontend.common import *
   3
   4 from migen.genlib.roundrobin import *
   5
   6 class LiteSATAArbiter(Module):
   7         def __init__(self, users, master):
   8                 self.rr = RoundRobin(len(users))
   9                 self.submodules += self.rr
  10                 self.grant = self.rr.grant
  11                 cases = {}
  12                 for i, slave in enumerate(users):
  13                         sink, source = slave.sink, slave.source
  14                         start = Signal()
  15                         done = Signal()
  16                         ongoing = Signal()
  17                         self.comb += [
  18                                 start.eq(sink.stb & sink.sop),
  19                                 done.eq(source.stb & source.last & source.eop & source.ack)
  20                         ]
  21                         self.sync += \
  22                                 If(start,
  23                                         ongoing.eq(1)
  24                                 ).Elif(done,
  25                                         ongoing.eq(0)
  26                                 )
  27                         self.comb += self.rr.request[i].eq((start | ongoing) & ~done)
  28                         cases[i] = [users[i].connect(master)]
  29                 self.comb += Case(self.grant, cases)