From 018f6d1b5227114e906bb0bb403bf9363c496bde Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Tue, 11 Oct 2016 17:59:22 +0800
Subject: [PATCH] drtio: implement basic IOT

---
 artiq/gateware/drtio/core.py |  4 +-
 artiq/gateware/drtio/iot.py  | 71 +++++++++++++++++++++++++++++++++++-
 2 files changed, 71 insertions(+), 4 deletions(-)

diff --git a/artiq/gateware/drtio/core.py b/artiq/gateware/drtio/core.py
index d8bd1d165..1063822d4 100644
--- a/artiq/gateware/drtio/core.py
+++ b/artiq/gateware/drtio/core.py
@@ -4,13 +4,13 @@ from artiq.gateware.drtio import link_layer, rt_packets, iot
 
 
 class DRTIOSatellite(Module):
-    def __init__(self, transceiver, channels, full_ts_width=63, fine_ts_width=3):
+    def __init__(self, transceiver, channels, fine_ts_width=3, full_ts_width=63):
         self.submodules.link_layer = link_layer.LinkLayer(
             transceiver.encoder, transceiver.decoders)
         self.submodules.rt_packets = rt_packets.RTPacketSatellite(
             self.link_layer)
         self.submodules.iot = iot.IOT(
-            self.rt_packets, channels, full_ts_width, fine_ts_width)
+            self.rt_packets, channels, fine_ts_width, full_ts_width)
 
 
 class DRTIOMaster(Module):
diff --git a/artiq/gateware/drtio/iot.py b/artiq/gateware/drtio/iot.py
index 93e008796..5416893fa 100644
--- a/artiq/gateware/drtio/iot.py
+++ b/artiq/gateware/drtio/iot.py
@@ -1,9 +1,76 @@
 from migen import *
 from migen.genlib.fifo import SyncFIFOBuffered
+from migen.genlib.record import *
 
 from artiq.gateware.rtio import rtlink
 
 
 class IOT(Module):
-    def __init__(self, rt_packets, channels, full_ts_width, fine_ts_width):
-        pass
+    def __init__(self, rt_packets, channels, max_fine_ts_width, full_ts_width):
+        tsc = Signal(full_ts_width - max_fine_ts_width)
+        self.sync += \
+            If(rt_packets.tsc_load,
+                tsc.eq(rt_packets.tsc_value)
+            ).Else(
+                tsc.eq(tsc + 1)
+            )
+
+        for n, channel in enumerate(channels):
+            data_width = rtlink.get_data_width(channel.interface)
+            address_width = rtlink.get_address_width(channel.interface)
+            fine_ts_width = rtlink.get_fine_ts_width(channel.interface)
+            assert fine_ts_width <= max_fine_ts_width
+
+            # FIFO
+            ev_layout = []
+            if data_width:
+                ev_layout.append(("data", data_width))
+            if address_width:
+                ev_layout.append(("address", address_width))
+            ev_layout.append(("timestamp", len(tsc) + fine_ts_width))
+
+            fifo = SyncFIFOBuffered(layout_len(ev_layout), channel.ofifo_depth)
+            self.submodules += fifo
+            fifo_in = Record(ev_layout)
+            fifo_out = Record(ev_layout)
+            self.comb += [
+                fifo.din.eq(fifo_in.raw_bits()),
+                fifo_out.raw_bits().eq(fifo.dout)
+            ]
+
+            # FIFO write
+            self.comb += fifo.we.eq(rt_packets.write_stb)
+            self.sync += \
+                If(rt_packets.write_stb,
+                    If(rt_packets.write_overflow_ack,
+                        rt_packets.write_overflow.eq(0)),
+                    If(~fifo.writable, rt_packets.write_overflow.eq(1)),
+                    If(rt_packets.write_underflow_ack,
+                        rt_packets.write_underflow.eq(0)),
+                    If(rt_packets.timestamp[max_fine_ts_width:] < (tsc + 4),
+                        rt_packets.write_underflow.eq(1)
+                    )
+                )
+            if data_width:
+                self.comb += fifo_in.data.eq(rt_packets.write_data)
+            if address_width:
+                self.comb += fifo_in.address.eq(rt_packets.write_address)
+            self.comb += fifo_in.timestamp.eq(
+                rt_packets.timestamp[max_fine_ts_width-fine_ts_width:])
+
+            # FIFO read
+            self.sync += [
+                fifo.re.eq(0),
+                interface.stb.eq(0),
+                If(fifo.readable &
+                   (fifo_out.timestamp[fine_ts_width:] == tsc),
+                    fifo.re.eq(1),
+                    interface.stb.eq(1)
+                )
+            ]
+            if data_width:
+                self.sync += interface.data.eq(fifo_out.data)
+            if address_width:
+                self.sync += interface.address.eq(fifo_out.address)
+            if fine_ts_width:
+                self.sync += interface.fine_ts.eq(fifo_out.timestamp[:fine_ts_width])