From 6a88229e6ac5fc36ab73b11312604ec8e711bcdd Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Thu, 20 Oct 2016 23:37:59 +0800
Subject: [PATCH] drtio: CrossDomainRequest

---
 artiq/gateware/drtio/rt_packets.py           | 33 +++++++++++++
 artiq/test/gateware/drtio/test_rt_packets.py | 49 ++++++++++++++++++++
 2 files changed, 82 insertions(+)

diff --git a/artiq/gateware/drtio/rt_packets.py b/artiq/gateware/drtio/rt_packets.py
index 93e7781eb..b243f4065 100644
--- a/artiq/gateware/drtio/rt_packets.py
+++ b/artiq/gateware/drtio/rt_packets.py
@@ -2,6 +2,8 @@ from types import SimpleNamespace
 
 from migen import *
 from migen.genlib.fsm import *
+from migen.genlib.fifo import AsyncFIFO
+from migen.genlib.cdc import PulseSynchronizer, NoRetiming
 
 
 def layout_len(l):
@@ -311,3 +313,34 @@ class RTPacketSatellite(Module):
             tx_dp.stb.eq(1),
             If(tx_dp.done, NextState("IDLE"))
         )
+
+
+class _CrossDomainRequest(Module):
+    def __init__(self, domain,
+                 req_stb, req_ack, req_data,
+                 srv_stb, srv_ack, srv_data):
+        dsync = getattr(self.sync, domain)
+
+        request = PulseSynchronizer("sys", domain)
+        reply = PulseSynchronizer(domain, "sys")
+        self.submodules += request, reply
+
+        ongoing = Signal()
+        self.comb += request.i.eq(~ongoing & req_stb)
+        self.sync += [
+            req_ack.eq(reply.o),
+            If(req_stb, ongoing.eq(1)),
+            If(req_ack, ongoing.eq(0))
+        ]
+        if req_data is not None:
+            srv_data_r = Signal.like(srv_data)
+            dsync += If(srv_stb & srv_ack, srv_data_r.eq(srv_data))
+            self.specials += NoRetiming(srv_data_r)
+            self.sync += If(reply.o, req_data.eq(srv_data_r))
+        dsync += [
+            If(request.o, srv_stb.eq(1)),
+            If(srv_ack, srv_stb.eq(0))
+        ]
+        self.comb += reply.i.eq(srv_stb & srv_ack)
+
+
diff --git a/artiq/test/gateware/drtio/test_rt_packets.py b/artiq/test/gateware/drtio/test_rt_packets.py
index 8709c596b..b1168d424 100644
--- a/artiq/test/gateware/drtio/test_rt_packets.py
+++ b/artiq/test/gateware/drtio/test_rt_packets.py
@@ -1,9 +1,11 @@
 import unittest
 from types import SimpleNamespace
+import random
 
 from migen import *
 
 from artiq.gateware.drtio.rt_packets import *
+from artiq.gateware.drtio.rt_packets import _CrossDomainRequest
 
 
 class PacketInterface:
@@ -119,3 +121,50 @@ class TestSatellite(unittest.TestCase):
                     yield
             run_simulation(dut, [send(), receive()])
             self.assertEqual(tx_times, rx_times)
+
+
+class TestCrossDomainRequest(unittest.TestCase):
+    def test_cross_domain_request(self):
+        for sys_freq in 3, 6, 11:
+            for srv_freq in 3, 6, 11:
+                prng = random.Random(1)
+
+                req_stb = Signal()
+                req_ack = Signal()
+                req_data = Signal(8)
+                srv_stb = Signal()
+                srv_ack = Signal()
+                srv_data = Signal(8)
+                test_seq = [93, 92, 19, 39, 91, 30, 12, 91, 38, 42]
+                received_seq = []
+
+                def requester():
+                    for i in range(len(test_seq)):
+                        yield req_stb.eq(1)
+                        yield
+                        while not (yield req_ack):
+                            yield
+                        received_seq.append((yield req_data))
+                        yield req_stb.eq(0)
+                        for j in range(prng.randrange(0, 10)):
+                            yield
+
+                def server():
+                    for data in test_seq:
+                        while not (yield srv_stb):
+                            yield
+                        for j in range(prng.randrange(0, 10)):
+                            yield
+                        yield srv_data.eq(data)
+                        yield srv_ack.eq(1)
+                        yield
+                        yield srv_ack.eq(0)
+                        yield
+
+                dut = _CrossDomainRequest("srv",
+                         req_stb, req_ack, req_data,
+                         srv_stb, srv_ack, srv_data)
+                run_simulation(dut,
+                    {"sys": requester(), "srv": server()},
+                    {"sys": sys_freq, "srv": srv_freq})
+                self.assertEqual(test_seq, received_seq)