sayma: introduce WRPLL on RTM

artiq/gateware/drtio/wrpll/__init__.py

@@ -1 +1,2 @@
 from artiq.gateware.drtio.wrpll.core import WRPLL
+from artiq.gateware.drtio.wrpll.ddmtd import DDMTDSamplerExtFF, DDMTDSamplerGTP

artiq/gateware/drtio/wrpll/core.py

@@ -23,19 +23,5 @@ class WRPLL(Module, AutoCSR):
 
         ddmtd_counter = Signal(N)
         self.sync.helper += ddmtd_counter.eq(ddmtd_counter + 1)
-        if hasattr(ddmtd_inputs, "rec_clk"):
-            ddmtd_input_rec_clk = ddmtd_inputs.rec_clk
-        else:
-            ddmtd_input_rec_clk = Signal()
-            self.specials += Instance("IBUFDS",
-                i_I=ddmtd_inputs.rec_clk_p, i_IB=ddmtd_inputs.rec_clk_n,
-                o_O=ddmtd_input_rec_clk)
-        if hasattr(ddmtd_inputs, "main_xo"):
-            ddmtd_input_main_xo = ddmtd_inputs.main_xo
-        else:
-            ddmtd_input_main_xo = Signal()
-            self.specials += Instance("IBUFDS",
-                i_I=ddmtd_inputs.main_xo_p, i_IB=ddmtd_inputs.main_xo_n,
-                o_O=ddmtd_input_main_xo)
-        self.submodules.ddmtd_helper = DDMTD(ddmtd_counter, ddmtd_input_rec_clk)
-        self.submodules.ddmtd_main = DDMTD(ddmtd_counter, ddmtd_input_main_xo)
+        self.submodules.ddmtd_helper = DDMTD(ddmtd_counter, ddmtd_inputs.rec_clk)
+        self.submodules.ddmtd_main = DDMTD(ddmtd_counter, ddmtd_inputs.main_xo)

artiq/gateware/drtio/wrpll/ddmtd.py

@@ -3,6 +3,47 @@ from migen.genlib.cdc import PulseSynchronizer, MultiReg
 from misoc.interconnect.csr import *
 
 
+class DDMTDSamplerExtFF(Module):
+    def __init__(self, ddmtd_inputs):
+        # TODO: s/h timing at FPGA pads
+        if hasattr(ddmtd_inputs, "rec_clk"):
+            self.rec_clk = ddmtd_inputs.rec_clk
+        else:
+            self.rec_clk = Signal()
+            self.specials += Instance("IBUFDS",
+                i_I=ddmtd_inputs.rec_clk_p, i_IB=ddmtd_inputs.rec_clk_n,
+                o_O=self.rec_clk)
+        if hasattr(ddmtd_inputs, "main_xo"):
+            self.main_xo = ddmtd_inputs.main_xo
+        else:
+            self.main_xo = Signal()
+            self.specials += Instance("IBUFDS",
+                i_I=ddmtd_inputs.main_xo_p, i_IB=ddmtd_inputs.main_xo_n,
+                o_O=self.main_xo)
+
+
+class DDMTDSamplerGTP(Module):
+    def __init__(self, gtp, main_xo_pads):
+        self.rec_clk = Signal()
+        self.main_xo = Signal()
+
+        # Getting this signal from IBUFDS_GTE2 is problematic because:
+        # 1. the clock gets divided by 2
+        # 2. the transceiver PLL craps out if an improper clock signal is applied,
+        # so we are disabling the buffer until the clock is stable.
+        # 3. UG482 says "The O and ODIV2 outputs are not phase matched to each other",
+        # which may or may not be a problem depending on what it actually means.
+        main_xo_se = Signal()
+        self.specials += Instance("IBUFDS",
+            i_I=main_xo_pads.p, i_IB=main_xo_pads.n,
+            o_O=main_xo_se)
+
+        self.sync.helper += [
+            self.rec_clk.eq(gtp.cd_rtio_rx0.clk),
+            self.main_xo.eq(main_xo_se)
+        ]
+
+
 class DDMTDEdgeDetector(Module):
     def __init__(self, input_signal):
         self.rising = Signal()

artiq/gateware/targets/sayma_amc.py

@@ -19,7 +19,7 @@ from artiq.gateware import jesd204_tools
 from artiq.gateware.rtio.phy import ttl_simple, ttl_serdes_ultrascale, sawg
 from artiq.gateware.drtio.transceiver import gth_ultrascale
 from artiq.gateware.drtio.siphaser import SiPhaser7Series
-from artiq.gateware.drtio.wrpll import WRPLL
+from artiq.gateware.drtio.wrpll import WRPLL, DDMTDSamplerExtFF
 from artiq.gateware.drtio.rx_synchronizer import XilinxRXSynchronizer
 from artiq.gateware.drtio import *
 from artiq.build_soc import *
@@ -136,11 +136,13 @@ class SatelliteBase(MiniSoC):
                 platform.request("ddmtd_main_dcxo_oe").eq(1),
                 platform.request("ddmtd_helper_dcxo_oe").eq(1)
             ]
+            self.submodules.wrpll_sampler = DDMTDSamplerExtFF(
+                platform.request("ddmtd_inputs"))
             self.submodules.wrpll = WRPLL(
                 helper_clk_pads=platform.request("ddmtd_helper_clk"),
                 main_dcxo_i2c=platform.request("ddmtd_main_dcxo_i2c"),
                 helper_dxco_i2c=platform.request("ddmtd_helper_dcxo_i2c"),
-                ddmtd_inputs=platform.request("ddmtd_inputs"))
+                ddmtd_inputs=self.wrpll_sampler)
             self.csr_devices.append("wrpll")
         else:
             self.comb += platform.request("filtered_clk_sel").eq(1)

artiq/gateware/targets/sayma_rtm.py

@@ -19,6 +19,7 @@ from artiq.gateware import rtio
 from artiq.gateware.rtio.phy import ttl_serdes_7series
 from artiq.gateware.drtio.transceiver import gtp_7series
 from artiq.gateware.drtio.siphaser import SiPhaser7Series
+from artiq.gateware.drtio.wrpll import WRPLL, DDMTDSamplerGTP
 from artiq.gateware.drtio.rx_synchronizer import XilinxRXSynchronizer
 from artiq.gateware.drtio import *
 from artiq.build_soc import add_identifier
@@ -73,7 +74,7 @@ class _SatelliteBase(BaseSoC):
     }
     mem_map.update(BaseSoC.mem_map)
 
-    def __init__(self, rtio_clk_freq, **kwargs):
+    def __init__(self, rtio_clk_freq, *, with_wrpll, **kwargs):
         BaseSoC.__init__(self,
                  cpu_type="or1k",
                  **kwargs)
@@ -132,6 +133,22 @@ class _SatelliteBase(BaseSoC):
         self.add_memory_group("drtioaux_mem", ["drtioaux0_mem"])
 
         self.config["RTIO_FREQUENCY"] = str(rtio_clk_freq/1e6)
+        if with_wrpll:
+            self.comb += [
+                platform.request("filtered_clk_sel").eq(0),
+                platform.request("ddmtd_main_dcxo_oe").eq(1),
+                platform.request("ddmtd_helper_dcxo_oe").eq(1)
+            ]
+            self.submodules.wrpll_sampler = DDMTDSamplerGTP(
+                self.drtio_transceiver,
+                platform.request("cdr_clk_clean_fabric"))
+            self.submodules.wrpll = WRPLL(
+                helper_clk_pads=platform.request("ddmtd_helper_clk"),
+                main_dcxo_i2c=platform.request("ddmtd_main_dcxo_i2c"),
+                helper_dxco_i2c=platform.request("ddmtd_helper_dcxo_i2c"),
+                ddmtd_inputs=self.wrpll_sampler)
+            self.csr_devices.append("wrpll")
+        else:
             self.comb += platform.request("filtered_clk_sel").eq(1)
             self.submodules.siphaser = SiPhaser7Series(
                 si5324_clkin=platform.request("si5324_clkin"),
@@ -245,10 +262,12 @@ def main():
     soc_sayma_rtm_args(parser)
     parser.add_argument("--rtio-clk-freq",
         default=150, type=int, help="RTIO clock frequency in MHz")
+    parser.add_argument("--with-wrpll", default=False, action="store_true")
     parser.set_defaults(output_dir=os.path.join("artiq_sayma", "rtm"))
     args = parser.parse_args()
 
-    soc = Satellite(rtio_clk_freq=1e6*args.rtio_clk_freq,
+    soc = Satellite(
+        rtio_clk_freq=1e6*args.rtio_clk_freq, with_wrpll=args.with_wrpll,
         **soc_sayma_rtm_argdict(args))
     builder = SatmanSoCBuilder(soc, **builder_argdict(args))
     try: