Rework cpuif to support transaction pipelining. Add more docs. update simulator

docs/architecture.rst

@@ -1,26 +1,54 @@
 Register Block Architecture
 ===========================
 
-TODO: Add full block diagram
+The generated register block RTL is organized into several sections.
+Each section is automatically generated based on the source register model and
+is rendered into the output register block SystermVerilog RTL.
+
+.. figure:: diagrams/arch.png
+
+Although it is not completely necessary to know the inner workings of the
+generated RTL, it can be helpful to understand the implications of various
+exporter configuration options.
 
 
 CPU Interface
 -------------
+The CPU interface logic layer provides an abstraction between the
+application-specific bus protocol and the internal register file logic.
+This logic layer normalizes external CPU read & write transactions into a common
+:ref:`cpuif_protocol` that is used to interact with the register file.
 
-TODO: describe boundary signals. Timing diagrams
 
 Address Decode
 --------------
+A common address decode operation is generated which computes individual access
+strobes for each software-accessible register in the design.
+This operation is performed completely combinationally.
 
-TODO: describe boundary signals. Timing diagrams
 
 Field Logic
 -----------
+This layer of the register block implements the storage elements and state-change
+logic for every field in the design. Field state is updated based on address
+decode strobes from software read/write actions, as well as events from the
+hardware interface input struct.
+This section also assigns any hardware interface outputs.
 
-TODO: describe boundary signals. Timing diagrams
 
 Readback
 --------
+The readback layer aggregates and reduces all readable registers into a single
+read response. During a read operation, the same address decode strobes are used
+to select the active register that is being accessed.
+This allows for a simple OR-reduction operation to be used to compute the read
+data response.
 
-TODO: describe boundary signals. Timing diagrams
-Retiming options
+For designs with a large number of software-readable registers, an optional
+fanin re-timing stage can be enabled. This stage is automatically inserted at a
+balanced point in the read-data reduction so that fanin and logic-levels are
+optimally reduced.
+
+A second optional read response retiming register can be enabled in-line with the
+path back to the CPU interface layer. This can be useful if the CPU interface protocol
+used has a fully combinational response path, and needs to be retimed further.

docs/cpuif/internal_protocol.rst

@@ -0,0 +1,228 @@
+.. _cpuif_protocol:
+
+Internal CPUIF Protocol
+=======================
+
+Internally, the regblock generator uses a common CPU interface handshake
+protocol. This strobe-based protocol is designed to add minimal overhead to the
+regblock implementation, while also being flexible enough to support advanced
+features of a variety of bus interface standards.
+
+
+Signal Descriptions
+-------------------
+
+Request
+^^^^^^^
+cpuif_req
+    When asserted, a read or write transfer will be initiated.
+    Denotes that the following signals are valid: ``cpuif_addr``,
+    ``cpuif_req_is_wr``, and ``cpuif_wr_data``.
+
+    A transfer will only initiate if the relevant stall signal is not asserted.
+    If stalled, the request shall be held until accepted. A request's parameters
+    (type, address, etc) shall remain static throughout the stall.
+
+cpuif_addr
+    Byte-address of the transfer.
+
+cpuif_req_is_wr
+    If ``1``, denotes that the current transfer is a write. Otherwise transfer is
+    a read.
+
+cpuif_wr_data
+    Data to be written for the write transfer. This signal is ignored for read
+    transfers.
+
+cpuif_req_stall_rd
+    If asserted, and the next pending request is a read operation, then the
+    transfer will not be accepted until this signal is deasserted.
+
+cpuif_req_stall_wr
+    If asserted, and the next pending request is a read operation, then the
+    transfer will not be accepted until this signal is deasserted.
+
+
+Read Response
+^^^^^^^^^^^^^
+cpuif_rd_ack
+    Single-cycle strobe indicating a read transfer has completed.
+    Qualifies that the following signals are valid: ``cpuif_rd_err`` and
+    ``cpuif_rd_data``
+
+cpuif_rd_err
+    If set, indicates that the read transaction failed and the CPUIF logic
+    should return an error response if possible.
+
+cpuif_rd_data
+    Read data. The width of this is bus is determined by the size of the largest
+    register in the design.
+
+Write Response
+^^^^^^^^^^^^^^
+cpuif_wr_ack
+    Single-cycle strobe indicating a write transfer has completed.
+    Qualifies that the ``cpuif_wr_err`` signal is valid.
+
+cpuif_wr_err
+    If set, indicates that the write transaction failed and the CPUIF logic
+    should return an error response if possible.
+
+
+Transfers
+---------
+
+Transfers have the following characteristics:
+
+* Only one transfer can be initiated per clock-cycle. This is implicit as there
+  is only one set of request signals.
+* The register block implementation shall guarantee that only one response can be
+  asserted in a given clock cycle. Only one ``cpuif_*_ack`` signal can be
+  asserted at a time.
+* Responses shall arrive in the same order as their corresponding request was
+  dispatched.
+
+
+Basic Transfer
+^^^^^^^^^^^^^^
+
+Depending on the configuration of the exported register block, transfers can be
+fully combinational or they may require one or more clock cycles to complete.
+Both are valid and CPU interface logic shall be designed to anticipate either.
+
+.. wavedrom::
+
+    {
+        signal: [
+            {name: 'clk',              wave: 'p....'},
+            {name: 'cpuif_req',        wave: '010..'},
+            {name: 'cpuif_req_is_wr',  wave: 'x2x..'},
+            {name: 'cpuif_addr',       wave: 'x2x..', data: ['A']},
+            {},
+            {name: 'cpuif_*_ack',      wave: '010..'},
+            {name: 'cpuif_*_err',      wave: 'x2x..'},
+        ],
+        foot: {
+            text: "Zero-latency transfer"
+        }
+    }
+
+.. wavedrom::
+
+    {
+        signal: [
+            {name: 'clk',              wave: 'p..|...'},
+            {name: 'cpuif_req',        wave: '010|...'},
+            {name: 'cpuif_req_is_wr',  wave: 'x2x|...'},
+            {name: 'cpuif_addr',       wave: 'x2x|...', data: ['A']},
+            {},
+            {name: 'cpuif_*_ack',      wave: '0..|10.'},
+            {name: 'cpuif_*_err',      wave: 'x..|2x.'},
+        ],
+        foot: {
+            text: "Transfer with non-zero latency"
+        }
+    }
+
+
+Read & Write Transactions
+-------------------------
+
+Waveforms below show the timing relationship of simple read/write transactions.
+For brevity, only showing non-zero latency transfers.
+
+.. wavedrom::
+
+    {
+        signal: [
+            {name: 'clk',              wave: 'p..|...'},
+            {name: 'cpuif_req',        wave: '010|...'},
+            {name: 'cpuif_req_is_wr',  wave: 'x0x|...'},
+            {name: 'cpuif_addr',       wave: 'x3x|...', data: ['A']},
+            {},
+            {name: 'cpuif_rd_ack',     wave: '0..|10.'},
+            {name: 'cpuif_rd_err',     wave: 'x..|0x.'},
+            {name: 'cpuif_rd_data',    wave: 'x..|5x.', data: ['D']},
+        ],
+        foot: {
+            text: "Read Transaction"
+        }
+    }
+
+
+.. wavedrom::
+
+    {
+        signal: [
+            {name: 'clk',              wave: 'p..|...'},
+            {name: 'cpuif_req',        wave: '010|...'},
+            {name: 'cpuif_req_is_wr',  wave: 'x1x|...'},
+            {name: 'cpuif_addr',       wave: 'x3x|...', data: ['A']},
+   			{name: 'cpuif_wr_data',    wave: 'x5x|...', data: ['D']},
+            {},
+            {name: 'cpuif_wr_ack',     wave: '0..|10.'},
+            {name: 'cpuif_wr_err',     wave: 'x..|0x.'},
+        ],
+        foot: {
+            text: "Write Transaction"
+        }
+    }
+
+
+Transaction Pipelining & Stalls
+-------------------------------
+If the CPU interface supports it, read and write operations can be pipelined.
+
+.. wavedrom::
+
+    {
+        signal: [
+            {name: 'clk',              wave: 'p......'},
+            {name: 'cpuif_req',        wave: '01..0..'},
+            {name: 'cpuif_req_is_wr',  wave: 'x0..x..'},
+            {name: 'cpuif_addr',       wave: 'x333x..', data: ['A1', 'A2', 'A3']},
+            {},
+            {name: 'cpuif_rd_ack',     wave: '0.1..0.'},
+            {name: 'cpuif_rd_err',     wave: 'x.0..x.'},
+            {name: 'cpuif_rd_data',    wave: 'x.555x.', data: ['D1', 'D2', 'D3']},
+        ]
+    }
+
+It is very likely that the transfer latency of a read transaction will not
+be the same as a write for a given register block configuration. Typically read
+operations will be more deeply pipelined. This latency asymmetry would create a
+hazard for response collisions.
+
+In order to eliminate this hazard, additional stall signals are provided to delay
+an incoming transfer request if necessary. When asserted, the CPU interface shall
+hold the next pending request until the stall is cleared.
+
+For non-pipelined CPU interfaces that only allow one outstanding transaction at a time,
+these can be safely ignored.
+
+In the following example, the regblock is configured such that:
+
+* A read transaction takes 1 clock cycle to complete
+* A write transaction takes 0 clock cycles to complete
+
+.. wavedrom::
+
+    {
+        signal: [
+            {name: 'clk',                wave: 'p.......'},
+            {name: 'cpuif_req',          wave: '01.....0'},
+            {name: 'cpuif_req_is_wr',    wave: 'x1.0.1.x'},
+            {name: 'cpuif_addr',         wave: 'x33443.x', data: ['W1', 'W2', 'R1', 'R2', 'W3']},
+            {name: 'cpuif_req_stall_wr', wave: '0...1.0.'},
+            {},
+            {name: 'cpuif_rd_ack',       wave: '0...220.', data: ['R1', 'R2']},
+            {name: 'cpuif_wr_ack',       wave: '0220..20', data: ['W1', 'W2', 'W3']},
+
+        ]
+    }
+
+In the above waveform, observe that:
+
+* The ``R2`` read request is not affected by the assertion of the write stall,
+  since the write stall only applies to write requests.
+* The ``W3`` write request is stalled for one cycle, and is accepted once the stall is cleared.

docs/index.rst

@@ -16,7 +16,8 @@ Install from `PyPi`_ using pip
 
 .. code-block:: bash
 
-   python3 -m pip install peakrdl-regblock
+   # NOT RELEASED YET
+   # python3 -m pip install peakrdl-regblock
 
 .. _PyPi: https://pypi.org/project/peakrdl-regblock
 
@@ -47,6 +48,7 @@ Links
    cpuif/addressing
    cpuif/apb3
    cpuif/advanced
+   cpuif/internal_protocol
 
 .. toctree::
    :hidden:

peakrdl/regblock/cpuif/passthrough/__init__.py

@@ -10,6 +10,8 @@ class PassthroughCpuif(CpuifBase):
             "input wire s_cpuif_req_is_wr",
             f"input wire [{self.addr_width-1}:0] s_cpuif_addr",
             f"input wire [{self.data_width-1}:0] s_cpuif_wr_data",
+            "output wire s_cpuif_req_stall_wr",
+            "output wire s_cpuif_req_stall_rd",
             "output wire s_cpuif_rd_ack",
             "output wire s_cpuif_rd_err",
             f"output wire [{self.data_width-1}:0] s_cpuif_rd_data",

peakrdl/regblock/cpuif/passthrough/passthrough_tmpl.sv

@@ -2,6 +2,8 @@ assign cpuif_req = s_cpuif_req;
 assign cpuif_req_is_wr = s_cpuif_req_is_wr;
 assign cpuif_addr = s_cpuif_addr;
 assign cpuif_wr_data = s_cpuif_wr_data;
+assign s_cpuif_req_stall_wr = cpuif_req_stall_wr;
+assign s_cpuif_req_stall_rd = cpuif_req_stall_rd;
 assign s_cpuif_rd_ack = cpuif_rd_ack;
 assign s_cpuif_rd_err = cpuif_rd_err;
 assign s_cpuif_rd_data = cpuif_rd_data;

peakrdl/regblock/exporter.py

@@ -76,6 +76,12 @@ class RegblockExporter:
         if kwargs:
             raise TypeError("got an unexpected keyword argument '%s'" % list(kwargs.keys())[0])
 
+        min_read_latency = 0
+        min_write_latency = 0
+        if retime_read_fanin:
+            min_read_latency += 1
+        if retime_read_response:
+            min_read_latency += 1
 
         # Scan the design for any unsupported features
         # Also collect pre-export information
@@ -114,6 +120,8 @@ class RegblockExporter:
             "readback": self.readback,
             "get_always_ff_event": lambda resetsignal : get_always_ff_event(self.dereferencer, resetsignal),
             "retime_read_response": retime_read_response,
+            "min_read_latency": min_read_latency,
+            "min_write_latency": min_write_latency,
         }
 
         # Write out design

peakrdl/regblock/module_tmpl.sv

@@ -24,6 +24,8 @@ module {{module_name}} (
     logic cpuif_req_is_wr;
     logic [{{cpuif.addr_width-1}}:0] cpuif_addr;
     logic [{{cpuif.data_width-1}}:0] cpuif_wr_data;
+    logic cpuif_req_stall_wr;
+    logic cpuif_req_stall_rd;
 
     logic cpuif_rd_ack;
     logic cpuif_rd_err;
@@ -34,6 +36,40 @@ module {{module_name}} (
 
     {{cpuif.get_implementation()|indent}}
 
+{% if min_read_latency == min_write_latency %}
+    // Read & write latencies are balanced. Stalls not required
+    assign cpuif_req_stall_rd = '0;
+    assign cpuif_req_stall_wr = '0;
+{%- elif min_read_latency > min_write_latency %}
+    // Read latency > write latency. May need to delay next write that follows a read
+    logic [{{min_read_latency - min_write_latency - 1}}:0] cpuif_req_stall_sr;
+    always_ff {{get_always_ff_event(cpuif.reset)}} begin
+        if({{get_resetsignal(cpuif.reset)}}) begin
+            cpuif_req_stall_sr <= '0;
+        end else if(cpuif_req && !cpuif_req_is_wr) begin
+            cpuif_req_stall_sr <= '1;
+        end else begin
+            cpuif_req_stall_sr <= (cpuif_req_stall_sr >> 'd1);
+        end
+    end
+    assign cpuif_req_stall_rd = '0;
+    assign cpuif_req_stall_wr = cpuif_req_stall_sr[0];
+{%- else %}
+    // Write latency > read latency. May need to delay next read that follows a write
+    logic [{{min_write_latency - min_read_latency - 1}}:0] cpuif_req_stall_sr;
+    always_ff {{get_always_ff_event(cpuif.reset)}} begin
+        if({{get_resetsignal(cpuif.reset)}}) begin
+            cpuif_req_stall_sr <= '0;
+        end else if(cpuif_req && cpuif_req_is_wr) begin
+            cpuif_req_stall_sr <= '1;
+        end else begin
+            cpuif_req_stall_sr <= (cpuif_req_stall_sr >> 'd1);
+        end
+    end
+    assign cpuif_req_stall_rd = cpuif_req_stall_sr[0];
+    assign cpuif_req_stall_wr = '0;
+{%- endif %}
+
     //--------------------------------------------------------------------------
     // Address Decode
     //--------------------------------------------------------------------------
@@ -47,15 +83,15 @@ module {{module_name}} (
         {{address_decode.get_implementation()|indent(8)}}
     end
 
-    // Writes are always granted with no error response
-    assign cpuif_wr_ack = cpuif_req & cpuif_req_is_wr;
-    assign cpuif_wr_err = '0;
-
     // Pass down signals to next stage
     assign decoded_req = cpuif_req;
     assign decoded_req_is_wr = cpuif_req_is_wr;
     assign decoded_wr_data = cpuif_wr_data;
 
+    // Writes are always granted with no error response
+    assign cpuif_wr_ack = decoded_req & decoded_req_is_wr;
+    assign cpuif_wr_err = '0;
+
     //--------------------------------------------------------------------------
     // Field logic
     //--------------------------------------------------------------------------

test/README.md

@@ -1,12 +1,14 @@
 
 # Test Dependencies
 
-## ModelSim
+## Questa
 
-Testcases require an installation of ModelSim/QuestaSim, and for `vlog` & `vsim`
+Testcases require an installation of the Questa simulator, and for `vlog` & `vsim`
 commands to be visible via the PATH environment variable.
 
-ModelSim - Intel FPGA Edition can be downloaded for free from https://fpgasoftware.intel.com/ and is sufficient to run unit tests.
+*Questa - Intel FPGA Starter Edition* can be downloaded for free from
+https://fpgasoftware.intel.com/ and is sufficient to run unit tests. You will need
+to generate a free license file to unlock the software: https://licensing.intel.com/psg/s/sales-signup-evaluationlicenses
 
 
 ## Python Packages
@@ -19,7 +21,7 @@ python3 -m pip install test/requirements.txt
 # Running tests
 
 Tests can be launched from the test directory using `pytest`.
-Use `pytest -n auto` to run tests in parallel.
+Use `pytest --workers auto` to run tests in parallel.
 
 To run all tests:
 ```bash

test/lib/cpuifs/apb3/apb3_intf_driver.sv

@@ -40,7 +40,7 @@ interface apb3_intf_driver #(
         input PSLVERR;
     endclocking
 
-    task reset();
+    task automatic reset();
         cb.PSEL <= '0;
         cb.PENABLE <= '0;
         cb.PWRITE <= '0;
@@ -48,7 +48,10 @@ interface apb3_intf_driver #(
         cb.PWDATA <= '0;
     endtask
 
-    task write(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] data);
+    semaphore txn_mutex = new(1);
+
+    task automatic write(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] data);
+        txn_mutex.get();
         ##0;
 
         // Initiate transfer
@@ -66,9 +69,11 @@ interface apb3_intf_driver #(
         // Wait for response
         while(cb.PREADY !== 1'b1) @(cb);
         reset();
+        txn_mutex.put();
     endtask
 
-    task read(logic [ADDR_WIDTH-1:0] addr, output logic [DATA_WIDTH-1:0] data);
+    task automatic read(logic [ADDR_WIDTH-1:0] addr, output logic [DATA_WIDTH-1:0] data);
+        txn_mutex.get();
         ##0;
 
         // Initiate transfer
@@ -89,9 +94,10 @@ interface apb3_intf_driver #(
         assert(!$isunknown(cb.PSLVERR)) else $error("Read from 0x%0x returned X's on PSLVERR", addr);
         data = cb.PRDATA;
         reset();
+        txn_mutex.put();
     endtask
 
-    task assert_read(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] expected_data, logic [DATA_WIDTH-1:0] mask = '1);
+    task automatic assert_read(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] expected_data, logic [DATA_WIDTH-1:0] mask = '1);
         logic [DATA_WIDTH-1:0] data;
         read(addr, data);
         data &= mask;

test/lib/cpuifs/axi4lite/axi4lite_intf_driver.sv

@@ -77,7 +77,7 @@ interface axi4lite_intf_driver #(
         input RRESP;
     endclocking
 
-    task reset();
+    task automatic reset();
         cb.AWVALID <= '0;
         cb.AWADDR <= '0;
         cb.AWPROT <= '0;
@@ -95,13 +95,20 @@ interface axi4lite_intf_driver #(
         @cb;
     end
 
-    task write(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] data);
+    semaphore txn_aw_mutex = new(1);
+    semaphore txn_w_mutex = new(1);
+    semaphore txn_b_mutex = new(1);
+    semaphore txn_ar_mutex = new(1);
+    semaphore txn_r_mutex = new(1);
+
+    task automatic write(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] data);
         bit w_before_aw;
         w_before_aw = $urandom_range(1,0);
-        ##0;
 
         fork
             begin
+                txn_aw_mutex.get();
+                ##0;
                 if(w_before_aw) repeat($urandom_range(2,0)) @cb;
                 cb.AWVALID <= '1;
                 cb.AWADDR <= addr;
@@ -109,9 +116,12 @@ interface axi4lite_intf_driver #(
                 @(cb);
                 while(cb.AWREADY !== 1'b1) @(cb);
                 cb.AWVALID <= '0;
+                txn_aw_mutex.put();
             end
 
             begin
+                txn_w_mutex.get();
+                ##0;
                 if(!w_before_aw) repeat($urandom_range(2,0)) @cb;
                 cb.WVALID <= '1;
                 cb.WDATA <= data;
@@ -120,39 +130,47 @@ interface axi4lite_intf_driver #(
                 while(cb.WREADY !== 1'b1) @(cb);
                 cb.WVALID <= '0;
                 cb.WSTRB <= '0;
+                txn_w_mutex.put();
             end
 
             begin
+                txn_b_mutex.get();
+                @cb;
                 while(cb.BREADY !== 1'b1 && cb.BVALID !== 1'b1) @(cb);
                 assert(!$isunknown(cb.BRESP)) else $error("Read from 0x%0x returned X's on BRESP", addr);
+                txn_b_mutex.put();
             end
         join
     endtask
 
-    task read(logic [ADDR_WIDTH-1:0] addr, output logic [DATA_WIDTH-1:0] data);
-        ##0;
+    task automatic read(logic [ADDR_WIDTH-1:0] addr, output logic [DATA_WIDTH-1:0] data);
 
         fork
             begin
+                txn_ar_mutex.get();
+                ##0;
                 cb.ARVALID <= '1;
                 cb.ARADDR <= addr;
                 cb.ARPROT <= '0;
                 @(cb);
                 while(cb.ARREADY !== 1'b1) @(cb);
                 cb.ARVALID <= '0;
+                txn_ar_mutex.put();
             end
 
             begin
+                txn_r_mutex.get();
                 @cb;
                 while(!(cb.RREADY === 1'b1 && cb.RVALID === 1'b1)) @(cb);
                 assert(!$isunknown(cb.RDATA)) else $error("Read from 0x%0x returned X's on RDATA", addr);
                 assert(!$isunknown(cb.RRESP)) else $error("Read from 0x%0x returned X's on RRESP", addr);
                 data = cb.RDATA;
+                txn_r_mutex.put();
             end
         join
     endtask
 
-    task assert_read(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] expected_data, logic [DATA_WIDTH-1:0] mask = '1);
+    task automatic assert_read(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] expected_data, logic [DATA_WIDTH-1:0] mask = '1);
         logic [DATA_WIDTH-1:0] data;
         read(addr, data);
         data &= mask;

test/lib/cpuifs/passthrough/passthrough_driver.sv

@@ -9,6 +9,8 @@ interface passthrough_driver #(
         output logic m_cpuif_req_is_wr,
         output logic [ADDR_WIDTH-1:0] m_cpuif_addr,
         output logic [DATA_WIDTH-1:0] m_cpuif_wr_data,
+        input wire m_cpuif_req_stall_wr,
+        input wire m_cpuif_req_stall_rd,
         input wire m_cpuif_rd_ack,
         input wire m_cpuif_rd_err,
         input wire [DATA_WIDTH-1:0] m_cpuif_rd_data,
@@ -25,6 +27,8 @@ interface passthrough_driver #(
         output m_cpuif_req_is_wr;
         output m_cpuif_addr;
         output m_cpuif_wr_data;
+        input m_cpuif_req_stall_wr;
+        input m_cpuif_req_stall_rd;
         input m_cpuif_rd_ack;
         input m_cpuif_rd_err;
         input m_cpuif_rd_data;
@@ -32,47 +36,70 @@ interface passthrough_driver #(
         input m_cpuif_wr_err;
     endclocking
 
-    task reset();
+    task automatic reset();
         cb.m_cpuif_req <= '0;
         cb.m_cpuif_req_is_wr <= '0;
         cb.m_cpuif_addr <= '0;
         cb.m_cpuif_wr_data <= '0;
     endtask
 
-    task write(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] data);
-        ##0;
+    semaphore txn_req_mutex = new(1);
+    semaphore txn_resp_mutex = new(1);
 
-        // Initiate transfer
-        cb.m_cpuif_req <= '1;
-        cb.m_cpuif_req_is_wr <= '1;
-        cb.m_cpuif_addr <= addr;
-        cb.m_cpuif_wr_data <= data;
-        @(cb);
-        reset();
+    task automatic write(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] data);
+        fork
+            begin
+                // Initiate transfer
+                txn_req_mutex.get();
+                ##0;
+                cb.m_cpuif_req <= '1;
+                cb.m_cpuif_req_is_wr <= '1;
+                cb.m_cpuif_addr <= addr;
+                cb.m_cpuif_wr_data <= data;
+                @(cb);
+                while(cb.m_cpuif_req_stall_wr !== 1'b0) @(cb);
+                reset();
+                txn_req_mutex.put();
+            end
 
-        // Wait for response
-        while(cb.m_cpuif_wr_ack !== 1'b1) @(cb);
-        reset();
+            begin
+                // Wait for response
+                txn_resp_mutex.get();
+                @cb;
+                while(cb.m_cpuif_wr_ack !== 1'b1) @(cb);
+                txn_resp_mutex.put();
+            end
+        join
     endtask
 
-    task read(logic [ADDR_WIDTH-1:0] addr, output logic [DATA_WIDTH-1:0] data);
-        ##0;
+    task automatic read(logic [ADDR_WIDTH-1:0] addr, output logic [DATA_WIDTH-1:0] data);
+        fork
+            begin
+                // Initiate transfer
+                txn_req_mutex.get();
+                ##0;
+                cb.m_cpuif_req <= '1;
+                cb.m_cpuif_req_is_wr <= '0;
+                cb.m_cpuif_addr <= addr;
+                @(cb);
+                while(cb.m_cpuif_req_stall_rd !== 1'b0) @(cb);
+                reset();
+                txn_req_mutex.put();
+            end
 
-        // Initiate transfer
-        cb.m_cpuif_req <= '1;
-        cb.m_cpuif_req_is_wr <= '0;
-        cb.m_cpuif_addr <= addr;
-        @(cb);
-        reset();
-
-        // Wait for response
-        while(cb.m_cpuif_rd_ack !== 1'b1) @(cb);
-        assert(!$isunknown(cb.m_cpuif_rd_data)) else $error("Read from 0x%0x returned X's on m_cpuif_rd_data", addr);
-        data = cb.m_cpuif_rd_data;
-        reset();
+            begin
+                // Wait for response
+                txn_resp_mutex.get();
+                @cb;
+                while(cb.m_cpuif_rd_ack !== 1'b1) @(cb);
+                assert(!$isunknown(cb.m_cpuif_rd_data)) else $error("Read from 0x%0x returned X's on m_cpuif_rd_data", addr);
+                data = cb.m_cpuif_rd_data;
+                txn_resp_mutex.put();
+            end
+        join
     endtask
 
-    task assert_read(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] expected_data, logic [DATA_WIDTH-1:0] mask = '1);
+    task automatic assert_read(logic [ADDR_WIDTH-1:0] addr, logic [DATA_WIDTH-1:0] expected_data, logic [DATA_WIDTH-1:0] mask = '1);
         logic [DATA_WIDTH-1:0] data;
         read(addr, data);
         data &= mask;

test/lib/cpuifs/passthrough/tb_inst.sv

@@ -3,6 +3,8 @@ wire s_cpuif_req;
 wire s_cpuif_req_is_wr;
 wire [{{exporter.cpuif.addr_width-1}}:0] s_cpuif_addr;
 wire [{{exporter.cpuif.data_width-1}}:0] s_cpuif_wr_data;
+wire s_cpuif_req_stall_wr;
+wire s_cpuif_req_stall_rd;
 wire s_cpuif_rd_ack;
 wire s_cpuif_rd_err;
 wire [{{exporter.cpuif.data_width-1}}:0] s_cpuif_rd_data;
@@ -18,6 +20,8 @@ passthrough_driver #(
     .m_cpuif_req_is_wr(s_cpuif_req_is_wr),
     .m_cpuif_addr(s_cpuif_addr),
     .m_cpuif_wr_data(s_cpuif_wr_data),
+    .m_cpuif_req_stall_wr(s_cpuif_req_stall_wr),
+    .m_cpuif_req_stall_rd(s_cpuif_req_stall_rd),
     .m_cpuif_rd_ack(s_cpuif_rd_ack),
     .m_cpuif_rd_err(s_cpuif_rd_err),
     .m_cpuif_rd_data(s_cpuif_rd_data),

test/lib/regblock_testcase.py

@@ -16,7 +16,7 @@ from peakrdl.regblock import RegblockExporter
 from .cpuifs.base import CpuifTestMode
 from .cpuifs.apb3 import APB3
 
-from .simulators.modelsim import ModelSim
+from .simulators.questa import Questa
 
 
 class RegblockTestCase(unittest.TestCase):
@@ -40,9 +40,9 @@ class RegblockTestCase(unittest.TestCase):
     retime_read_response = False
 
     #: Abort test if it exceeds this number of clock cycles
-    timeout_clk_cycles = 1000
+    timeout_clk_cycles = 5000
 
-    simulator_cls = ModelSim
+    simulator_cls = Questa
 
     #: this gets auto-loaded via the _load_request autouse fixture
     request = None # type: pytest.FixtureRequest

test/lib/simulators/questa.py

@@ -4,27 +4,21 @@ import os
 
 from . import Simulator
 
-class ModelSim(Simulator):
+class Questa(Simulator):
     def compile(self) -> None:
         cmd = [
             "vlog", "-sv", "-quiet", "-l", "build.log",
 
             "+incdir+%s" % os.path.join(os.path.dirname(__file__), ".."),
 
-            # Free version of ModelSim throws errors if generate/endgenerate
-            # blocks are not used.
-            # These have been made optional long ago. Modern versions of SystemVerilog do
-            # not require them and I prefer not to add them.
-            "-suppress", "2720",
-
-            # Ignore noisy warning about vopt-time checking of always_comb/always_latch
-            "-suppress", "2583",
+            # Use strict LRM conformance
+            "-svinputport=net",
 
             # all warnings are errors
             "-warning", "error",
 
-            # except this one.. TODO: figure out if I can avoid this
-            "-suppress", "13314",
+            # Ignore noisy warning about vopt-time checking of always_comb/always_latch
+            "-suppress", "2583",
         ]
 
         # Add source files
@@ -42,6 +36,7 @@ class ModelSim(Simulator):
         # call vsim
         cmd = [
             "vsim", "-quiet",
+            "-voptargs=+acc",
             "-msgmode", "both",
             "-do", "set WildcardFilter [lsearch -not -all -inline $WildcardFilter Memory]",
             "-do", "log -r /*;",

test/requirements.txt

@@ -1,4 +1,4 @@
 pytest
 parameterized
-pytest-xdist
+pytest-parallel
 jinja2-simple-tags

test/test_pipelined_cpuif/regblock.rdl

@@ -0,0 +1,8 @@
+addrmap regblock {
+    default sw=rw;
+    default hw=r;
+
+    reg {
+        field {} x[31:0] = 0;
+    } x[64] @ 0 += 4;
+};

test/test_pipelined_cpuif/tb_template.sv

@@ -0,0 +1,50 @@
+{% extends "lib/tb_base.sv" %}
+
+{% block seq %}
+    {% sv_line_anchor %}
+    ##1;
+    cb.rst <= '0;
+    ##1;
+
+    // Write all regs in parallel burst
+    for(int i=0; i<64; i++) begin
+        fork
+            automatic int i_fk = i;
+            begin
+                cpuif.write(i_fk*4, i_fk + 32'h12340000);
+            end
+        join_none
+    end
+    wait fork;
+
+    // Verify HW value
+    @cb;
+    for(int i=0; i<64; i++) begin
+        assert(cb.hwif_out.x[i].x.value == i + 32'h12340000)
+            else $error("hwif_out.x[i] == 0x%0x. Expected 0x%0x", cb.hwif_out.x[i].x.value, i + 32'h12340000);
+    end
+
+    // Read all regs in parallel burst
+    for(int i=0; i<64; i++) begin
+        fork
+            automatic int i_fk = i;
+            begin
+                cpuif.assert_read(i_fk*4, i_fk + 32'h12340000);
+            end
+        join_none
+    end
+    wait fork;
+
+    // Mix read/writes
+    for(int i=0; i<64; i++) begin
+        fork
+            automatic int i_fk = i;
+            begin
+                cpuif.write(i_fk*4, i_fk + 32'h56780000);
+                cpuif.assert_read(i_fk*4, i_fk + 32'h56780000);
+            end
+        join_none
+    end
+    wait fork;
+
+{% endblock %}

test/test_pipelined_cpuif/testcase.py

@@ -0,0 +1,9 @@
+from parameterized import parameterized_class
+
+from ..lib.regblock_testcase import RegblockTestCase
+from ..lib.test_params import TEST_PARAMS
+
+@parameterized_class(TEST_PARAMS)
+class Test(RegblockTestCase):
+    def test_dut(self):
+        self.run_test()