"Unable set up RisingEdge(c) Trigger" with Cadence IUS/Xcelium and VHDL

When I run examples/dff/tests with

make SIM=ius TOPLEVEL_LANG=vhdl COCOTB_LOG_LEVEL=DEBUG COCOTB_SCHEDULER_DEBUG=1 all

I am getting the following output:

     0.00ns DEBUG    cocotb.regression                         regression.py:555  in generate_tests                  Adding generated test "run_test_001" to module "dff_cocotb"
     0.00ns INFO     cocotb.regression                         regression.py:187  in initialise                      Found test dff_cocotb.run_test_001
     0.00ns INFO     cocotb.regression                         regression.py:321  in execute                         Running test 1/1: run_test_001
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:618  in add                             Adding new coroutine run_test_001
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:695  in schedule                        Scheduling coroutine run_test_001 with outcome Value(None)
     0.00ns INFO     ...test.run_test_001.0x7f4ae5046780       decorators.py:253  in _advance                        Starting test: "run_test_001"
                                                                                                                     Description: Automatically generated test
                                                                                                                     
                                                                                                                     
     0.00ns DEBUG    ...test.run_test_001.0x7f4ae5046780       decorators.py:258  in _advance                        Sending Value(None)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:701  in schedule                        Coroutine run_test_001 yielded run_test (mode 1)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:645  in _trigger_from_unstarted_coro    Scheduling nested coroutine: run_test
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:618  in add                             Adding new coroutine run_test
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:695  in schedule                        Scheduling coroutine run_test with outcome Value(None)
     0.00ns DEBUG    cocotb.c                                      handle.py:84   in __init__                        Created
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:618  in add                             Adding new coroutine start
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:695  in schedule                        Scheduling coroutine start with outcome Value(None)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:695  in schedule                        Scheduling coroutine _do_writes with outcome Value(None)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:701  in schedule                        Coroutine _do_writes yielded _Event (mode 1)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:372  in _event_loop                     Trigger fired: _Event
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:434  in _event_loop                     1 pending coroutines for event _Event
                                                                                                                     	_do_writes
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:441  in _event_loop                     Scheduling coroutine _do_writes
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:695  in schedule                        Scheduling coroutine _do_writes with outcome Value(<cocotb.triggers._Event object at 0x7f4ae491f548>)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:701  in schedule                        Coroutine _do_writes yielded ReadWrite(readwritesync) (mode 1)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:444  in _event_loop                     Scheduled coroutine _do_writes
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:463  in _event_loop                     All coroutines scheduled, handing control back to simulator
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:701  in schedule                        Coroutine start yielded Timer(2500000.00ps) (mode 1)
     0.00ns DEBUG    cocotb.d                                      handle.py:84   in __init__                        Created
     0.00ns DEBUG    cocotb.q                                      handle.py:84   in __init__                        Created
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:618  in add                             Adding new coroutine _monitor_recv
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:695  in schedule                        Scheduling coroutine _monitor_recv with outcome Value(None)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:701  in schedule                        Coroutine _monitor_recv yielded RisingEdge(c) (mode 1)
     0.00ns ERROR    cocotb.RisingEdge.0x7f4ae4925c28              result.py:52   in raise_error                     Unable set up RisingEdge(c) Trigger
                                                                                                                     NoneType: None
                                                                                                                     
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:372  in _event_loop                     Trigger fired: NullTrigger()
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:434  in _event_loop                     1 pending coroutines for event NullTrigger()
                                                                                                                     	_monitor_recv
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:441  in _event_loop                     Scheduling coroutine _monitor_recv
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:695  in schedule                        Scheduling coroutine _monitor_recv with outcome Error(TestError('Unable set up RisingEdge(c) Trigger'))
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:714  in schedule                        Coroutine completed: _monitor_recv
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:491  in unschedule                      TestComplete received: TestError
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:754  in finish_test                     finish_test called with TestError('Unable set up RisingEdge(c) Trigger')
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:780  in cleanup                         Killing start
     0.00ns DEBUG    ..tb.coroutine.start.0x7f4ae4924198       decorators.py:182  in kill                            kill() called on coroutine
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:780  in cleanup                         Killing _do_writes
     0.00ns DEBUG    ..routine._do_writes.0x7f4ae4924278       decorators.py:182  in kill                            kill() called on coroutine
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:780  in cleanup                         Killing run_test_001
     0.00ns DEBUG    ...test.run_test_001.0x7f4ae5046780       decorators.py:182  in kill                            kill() called on coroutine
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:444  in _event_loop                     Scheduled coroutine _monitor_recv
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:276  in _check_termination              Test terminating, scheduling Timer
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:463  in _event_loop                     All coroutines scheduled, handing control back to simulator
     0.00ns INFO     cocotb.scoreboard.dff                     scoreboard.py:216  in add_interface                   Created with reorder_depth 0
     0.00ns DEBUG    cocotb.monitor.BitMonitor                   __init__.py:112  in add_callback                    Adding callback of function check_received_transaction to monitor
     0.00ns DEBUG    cocotb.monitor.BitMonitor                   __init__.py:112  in add_callback                    Adding callback of function model to monitor
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:618  in add                             Adding new coroutine _monitor_recv
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:695  in schedule                        Scheduling coroutine _monitor_recv with outcome Value(None)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:701  in schedule                        Coroutine _monitor_recv yielded RisingEdge(c) (mode 4)
     0.00ns ERROR    cocotb.RisingEdge.0x7f4ae4925c28              result.py:52   in raise_error                     Unable set up RisingEdge(c) Trigger
                                                                                                                     NoneType: None
                                                                                                                     
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:372  in _event_loop                     Trigger fired: NullTrigger()
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:378  in _event_loop                     Ignoring trigger NullTrigger() since we're terminating
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:618  in add                             Adding new coroutine _cr_twiddler
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:695  in schedule                        Scheduling coroutine _cr_twiddler with outcome Value(None)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:695  in schedule                        Scheduling coroutine _do_writes with outcome Value(None)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:701  in schedule                        Coroutine _do_writes yielded _Event (mode 4)
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:372  in _event_loop                     Trigger fired: _Event
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:378  in _event_loop                     Ignoring trigger _Event since we're terminating
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:701  in schedule                        Coroutine _cr_twiddler yielded RisingEdge(c) (mode 4)
     0.00ns ERROR    cocotb.RisingEdge.0x7f4ae4925c28              result.py:52   in raise_error                     Unable set up RisingEdge(c) Trigger
                                                                                                                     NoneType: None
                                                                                                                     
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:372  in _event_loop                     Trigger fired: NullTrigger()
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:378  in _event_loop                     Ignoring trigger NullTrigger() since we're terminating
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:701  in schedule                        Coroutine run_test yielded RisingEdge(c) (mode 4)
     0.00ns ERROR    cocotb.RisingEdge.0x7f4ae4925c28              result.py:52   in raise_error                     Unable set up RisingEdge(c) Trigger
                                                                                                                     NoneType: None
                                                                                                                     
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:372  in _event_loop                     Trigger fired: NullTrigger()
     0.00ns DEBUG    cocotb.scheduler                           scheduler.py:378  in _event_loop                     Ignoring trigger NullTrigger() since we're terminating
     1.00ns DEBUG    cocotb.scheduler                           scheduler.py:303  in begin_test                      begin_test called with trigger: Timer(1000.00ps)
     1.00ns DEBUG    cocotb.scheduler                           scheduler.py:319  in begin_test                      Issue test result to regression object
     1.00ns ERROR    cocotb.regression                         regression.py:300  in handle_result                   Test Failed: run_test_001 (result was TestError)
     1.00ns ERROR    cocotb.regression                         regression.py:207  in tear_down                       Failed 1 out of 1 tests (0 skipped)

(I have modified line 695 of scheduler.py to read self.log.debug("Scheduling coroutine {} with outcome {}".format(coroutine.__name__, send_outcome)) here.)

Any hints as to how to approach debugging this?

[martijnbastiaan]

We’re encountering this issue when using Xcelium too. Because it supports cross-language compilation, you can write a Verilog shim. This makes cocotb talk to the simulator over VPI which doesn’t encounter similar issues as the VHPI codepath.

Workaround example

Click to expand

The following cocotb test case + hdl files work fine in GHDL but fail with Xcelium:

adder.vhdl:

port
  ( clk : in std_logic
  ; a : in signed(31 downto 0)
  ; b : in signed(31 downto 0)
  ; c : out signed(31 downto 0)
  );
end adder;

architecture Behavioral of adder is
begin
  p_add : process(clk)
  begin
    if rising_edge(clk) then
      c <= a + b;
    end if;
  end process p_add;
end Behavioral;

test.py:

import cocotb

from cocotb.clock import Clock
from cocotb.triggers import RisingEdge

@cocotb.test()
async def simple_test(dut):
    clock = Clock(dut.clk, 50, units='ns')
    cocotb.fork(clock.start())

    dut.a.value = 5
    dut.b.value = 7

    # Wait for simulator to start
    await RisingEdge(dut.clk)

    # Latch a+b
    await RisingEdge(dut.clk)

    # a+b on output
    await RisingEdge(dut.clk)

    assert dut.c.value.integer == 12

Makefile:

SIM ?= ghdl
TOPLEVEL_LANG ?= vhdl
MODULE := test

VHDL_SOURCES = adder.vhdl

include $(shell cocotb-config --makefiles)/Makefile.sim

To work around this, add a Verilog shim:

adder_shim.v:

module adder_shim
  ( input         clk
  , input  [31:0] a
  , input  [31:0] b
  , output [31:0] c
  );

  adder d0 (clk, a, b, c);
endmodule

and change your Makefile such that it uses the shim when compiling with Xcelium:

SIM ?= ghdl
TOPLEVEL_LANG ?= vhdl
MODULE := test

VHDL_SOURCES = adder.vhdl

ifneq ($(filter $(SIM),xcelium),)
    VERILOG_SOURCES = adder_shim.v
    TOPLEVEL_LANG := verilog
    TOPLEVEL := adder_shim
else
    TOPLEVEL_LANG := vhdl
    TOPLEVEL := adder
endif

include $(shell cocotb-config --makefiles)/Makefile.sim

[imphil]

To add a bit more context here for people coming to this bug:

• User-visible problem: cocotb users with VHDL toplevel designs cannot use RisingEdge() triggers in Xcelium and IUS.
• Workaround: Use a Verilog toplevel.
• Summary of the underlying issue: Cadence Xcelium and IUS do not support a VHPI feature cocotb relies on to implement RisingEdge triggers.

Steps to reproduce the issue

$ git clone https://github.com/cocotb/cocotb.git
$ python3 -m venv cocotb-venv
$ cd cocotb-venv
$ . bin/activate
$ pip3 install cocotb==1.7.2 pytest
$ make -C ../cocotb/examples/simple_dff SIM=xcelium TOPLEVEL_LANG=vhdl COCOTB_LOG_LEVEL=DEBUG COCOTB_SCHEDULER_DEBUG=1 all

The output will include the following lines:

     0.00ns ERROR    gpi                                VHPI: Registered callback isn't enabled! Got vhpiStateP=vhpiUndefined(1000)
     0.00ns ERROR    gpi                                Failed to register a value change callback

where Xcelium indicates that it does not support the vhpiStateP property of vhpi_get().

Analysis

The calling code in question is vhpi_get(vhpiStateP, new_hdl); at https://github.com/cocotb/cocotb/blob/ac41bea02b9e09a617fca95421f36dac5029d247/cocotb/share/lib/vhpi/VhpiCbHdl.cpp#L452-L458

vhpi_get() obtains the property of an object, in this case of new_hdl, a callback handle. vhpiStateP indicates which type of property we’d like to get: the state of the callback. vhpi_get() should return one of three options: vhpiEnable, vhpiDisable or vhpiMature. Instead, Xcelium returns vhpiUndefined, indicating that it does not support getting the vhpiStateP property from a callback handle.

It should be noted that using vhpiStateP is not really obscure, as seen in the example code in the VHDL IEEE Std 1076-2019 spec section “23.8 vhpi_enable_cb”:

In the following VHPI program, the function vhpi_enable_cb is used to enable a callback that was registered but is disabled.

static vhpiHandleT mylastcbk = 0;

void activate_cbk(vhpiHandle cbHdl) {
  vhpiStateT cbState;
  cbState = vhpi_get(vhpiStateP, cbHdl);
  if (cbState == vhpiDisable)
    vhpi_enable_cb(cbHdl);
  }
}

void register_cbk() {
  vhpiCbDataT cbData;
  vhpiHandleT cbHdl;
  int flags;
  flags = vhpiDisableCb | vhpiReturnCb;
  cbData.reason = vhpiCbEndOfSimulation;
  cbData.cb_rtn = myf;
  cbHdl = vhpi_register_cb(&cbData, flags);
  mylastcbk = cbHdl;
}

int main (int argc, char *argv[] ){
  register_cbk();
  ...
  activate_cbk(mylastcbk);
  return(0);
}