Add rtio.sed.layouts

README.md

@@ -8,7 +8,7 @@ Formally verified implementation of the ARTIQ RTIO core in nMigen
 - [ ] Implement the core in nMigen
 - - [x] `rtio.cri` (`Interface` and `CRIDecoder` only)
 - - [x] `rtio.rtlink`
-- - [ ] `rtio.sed.layouts`
+- - [x] `rtio.sed.layouts`
 - - [ ] `rtio.sed.output_network`
 - - [ ] `rtio.sed.output_driver`
 - [ ] Add suitable assertions for verification (BMC / unbounded proof?)

rtio/sed/layouts.py

@@ -1 +1,78 @@
+from nmigen import *
+from nmigen.utils import *
+from nmigen.hdl.rec import *
 
+from rtio import rtlink
+
+def fifo_payload(channels):
+    address_width = max(rtlink.get_address_width(channel.interface.o)
+                        for channel in channels)
+    data_width = max(rtlink.get_data_width(channel.interface.o)
+                     for channel in channels)
+
+    layout = [
+        ("channel", bits_for(len(channels)-1)),
+        ("timestamp", 64)
+    ]
+    if address_width:
+        layout.append(("address", address_width))
+    if data_width:
+        layout.append(("data", data_width))
+
+    return layout
+
+
+def seqn_width(lane_count, fifo_depth):
+    # There must be a unique sequence number for every possible event in every FIFO.
+    # Plus 2 bits to detect and handle wraparounds.
+    return bits_for(lane_count*fifo_depth-1) + 2
+
+
+def fifo_ingress(seqn_width, layout_payload):
+    return [
+        ("we", 1, DIR_FANOUT),
+        ("writable", 1, DIR_FANIN),
+        ("seqn", seqn_width, DIR_FANOUT),
+        ("payload", [(a, b, DIR_FANOUT) for a, b in layout_payload])
+    ]
+
+
+def fifo_egress(seqn_width, layout_payload):
+    return [
+        ("re", 1, DIR_FANIN),
+        ("readable", 1, DIR_FANOUT),
+        ("seqn", seqn_width, DIR_FANOUT),
+        ("payload", [(a, b, DIR_FANOUT) for a, b in layout_payload])
+    ]
+
+
+# We use glbl_fine_ts_width in the output network so that collisions due
+# to insufficiently increasing timestamps are always reliably detected.
+# We can still have undetected collisions on the address by making it wrap
+# around, but those are more rare and easier to debug, and addresses are
+# not normally exposed directly to the ARTIQ user.
+def output_network_payload(channels, glbl_fine_ts_width):
+    address_width = max(rtlink.get_address_width(channel.interface.o)
+                        for channel in channels)
+    data_width = max(rtlink.get_data_width(channel.interface.o)
+                     for channel in channels)
+
+    layout = [("channel", bits_for(len(channels)-1))]
+    if glbl_fine_ts_width:
+        layout.append(("fine_ts", glbl_fine_ts_width))
+    if address_width:
+        layout.append(("address", address_width))
+    if data_width:
+        layout.append(("data", data_width))
+
+    return layout
+
+
+def output_network_node(seqn_width, layout_payload):
+    return [
+        ("valid", 1),
+        ("seqn", seqn_width),
+        ("replace_occured", 1),
+        ("nondata_replace_occured", 1),
+        ("payload", layout_payload)
+    ]