soc: reprogrammable identifier

artiq/build_soc.py

@@ -1,7 +1,8 @@
 import os
 import subprocess
 
-from misoc.cores import identifier
+from migen import *
+from misoc.interconnect.csr import *
 from misoc.integration.builder import *
 
 from artiq.gateware.amp import AMPSoC
@@ -22,11 +23,39 @@ def get_identifier_string(soc, suffix="", add_class_name=True):
     return r
 
 
+class ReprogrammableIdentifier(Module, AutoCSR):
+    def __init__(self, ident):
+        self.address = CSRStorage(8)
+        self.data = CSRStatus(8)
+
+        contents = list(ident.encode())
+        l = len(contents)
+        if l > 255:
+            raise ValueError("Identifier string must be 255 characters or less")
+        contents.insert(0, l)
+
+        init_params = {i: 0 for i in range(0x40)}
+        for i, c in enumerate(contents):
+            # 0x38 was determined empirically. Another Xilinx mystery.
+            row = 0x38 + i//32
+            col = 8*(i % 32)
+            init_params[row] |= c << col
+        init_params = {"p_INIT_{:02X}".format(k): v for k, v in init_params.items()}
+
+        self.specials += Instance("RAMB18E1", name="identifier_str",
+            i_ADDRARDADDR=Cat(C(0, 3), self.address.storage),
+            i_CLKARDCLK=ClockSignal(),
+            o_DOADO=self.data.status,
+            i_ENARDEN=1,
+            p_READ_WIDTH_A=9,
+            **init_params)
+
+
 def add_identifier(soc, *args, **kwargs):
     if hasattr(soc, "identifier"):
         raise ValueError
     identifier_str = get_identifier_string(soc, *args, **kwargs)
-    soc.submodules.identifier = identifier.Identifier(identifier_str)
+    soc.submodules.identifier = ReprogrammableIdentifier(identifier_str)
     soc.config["IDENTIFIER_STR"] = identifier_str