debugger: start of a debugger client that uses the serial debug gateware

IT WORKS!

blinky/Blinky.bsv

@@ -0,0 +1,26 @@
+package Blinky;
+
+import Strobe::*;
+
+(* always_ready *)
+interface Blinky;
+   method Bool led_on();
+endinterface
+
+// mkBlinky returns a module that toggles its output approximately
+// once a second. It's intended to be wired to an LED as a basic "are
+// you alive" indicator.
+module mkBlinky(Integer clock_frequency, Blinky ifc);
+   let strobe <- mkStrobe(clock_frequency, 1);
+
+   Reg#(Bool) out <- mkReg(False);
+
+   (* no_implicit_conditions,fire_when_enabled *)
+   rule increment (strobe);
+      out <= !out;
+   endrule
+
+   method led_on = out._read;
+endmodule
+
+endpackage

debugger/main.go

@@ -0,0 +1,105 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"sync"
+	"time"
+
+	"go.bug.st/serial"
+)
+
+const portDev = "/dev/ttyUSB0"
+
+func main() {
+	dbg, err := Open()
+	if err != nil {
+		log.Fatalf("connecting to debugger: %v", err)
+	}
+	defer dbg.Close()
+
+	fmt.Println("Writing...")
+	if err := dbg.Write(0x42, 123); err != nil {
+		log.Fatalf("writing to memory: %v", err)
+	}
+	v, err := dbg.Read(0x42)
+	if err != nil {
+		log.Fatalf("reading from memory: %v", err)
+	}
+	fmt.Printf("addr 0: %02x\n", v)
+}
+
+type Debugger struct {
+	port serial.Port
+	mu   sync.Mutex
+}
+
+func Open() (*Debugger, error) {
+	mode := &serial.Mode{
+		BaudRate: 115_200,
+	}
+	port, err := serial.Open(portDev, mode)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Debugger{port: port}, nil
+}
+
+func (d *Debugger) Close() error {
+	d.mu.Lock() // note, deliberately no unlocking, to poison.
+	return d.port.Close()
+}
+
+func encode(addr int, write bool, data byte) [4]byte {
+	writeVal := uint8(0)
+	if write {
+		writeVal = 1
+	}
+	var ret [4]byte
+	ret[3] = data
+	ret[2] = byte(addr<<1) | writeVal
+	ret[1] = byte(addr >> 7)
+	ret[0] = byte(addr >> 15)
+	return ret
+}
+
+func (d *Debugger) Read(addr int) (byte, error) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	if addr >= 2<<17 {
+		return 0, fmt.Errorf("read %d out of bounds", addr)
+	}
+
+	packet := encode(addr, false, 0)
+	fmt.Printf("Writing: %02x %02x %02x %02x\n", packet[0], packet[1], packet[2], packet[3])
+	if _, err := d.port.Write(packet[:]); err != nil {
+		return 0, err
+	}
+
+	d.port.SetReadTimeout(2 * time.Second)
+
+	n, err := d.port.Read(packet[:1])
+	if err != nil {
+		return 0, err
+	} else if n == 0 {
+		return 0, errors.New("no read")
+	}
+	return packet[0], nil
+}
+
+func (d *Debugger) Write(addr int, val byte) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	if addr >= 2<<17 {
+		return fmt.Errorf("write %d out of bounds", addr)
+	}
+
+	packet := encode(addr, true, val)
+	fmt.Printf("Writing: %02x %02x %02x %02x\n", packet[0], packet[1], packet[2], packet[3])
+	if _, err := d.port.Write(packet[:]); err != nil {
+		return err
+	}
+	return nil
+}

go.mod

@@ -0,0 +1,9 @@
+module git.sentinel65x.com/dave/gary
+
+go 1.22.6
+
+require (
+	github.com/creack/goselect v0.1.2 // indirect
+	go.bug.st/serial v1.6.2 // indirect
+	golang.org/x/sys v0.0.0-20220829200755-d48e67d00261 // indirect
+)

go.sum

@@ -0,0 +1,6 @@
+github.com/creack/goselect v0.1.2 h1:2DNy14+JPjRBgPzAd1thbQp4BSIihxcBf0IXhQXDRa0=
+github.com/creack/goselect v0.1.2/go.mod h1:a/NhLweNvqIYMuxcMOuWY516Cimucms3DglDzQP3hKY=
+go.bug.st/serial v1.6.2 h1:kn9LRX3sdm+WxWKufMlIRndwGfPWsH1/9lCWXQCasq8=
+go.bug.st/serial v1.6.2/go.mod h1:UABfsluHAiaNI+La2iESysd9Vetq7VRdpxvjx7CmmOE=
+golang.org/x/sys v0.0.0-20220829200755-d48e67d00261 h1:v6hYoSR9T5oet+pMXwUWkbiVqx/63mlHjefrHmxwfeY=
+golang.org/x/sys v0.0.0-20220829200755-d48e67d00261/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

hardware/ulx3s/Top.bsv

@@ -4,23 +4,24 @@ import Connectable::*;
 import GetPut::*;
 import ClientServer::*;
 
+import Blinky::*;
 import PackUnpack::*;
 import UART::*;
 import VRAM::*;
 
 module mkUARTDebugger(Integer clock_frequency, Integer uart_bitrate, VRAMServer mem, UART_PHY ifc);
-   UART _uart <- mkUART(clock_frequency, uart_bitrate);
+   UART uart <- mkUART(clock_frequency, uart_bitrate);
-   disableFlowControl(_uart); // Can't do hardware flow control on ULX3S
+   disableFlowControl(uart); // Can't do hardware flow control on ULX3S
 
-   Server#(Bit#(8), VRAMRequest) _decode <- mkUnpacker();
+   Server#(Bit#(8), VRAMRequest) decode <- mkUnpacker();
-   Server#(VRAMResponse, Bit#(8)) _encode <- mkPacker();
+   Server#(VRAMResponse, Bit#(8)) encode <- mkPacker();
 
-   mkConnection(_uart.receive, _decode.request);
+   mkConnection(uart.receive, decode.request);
-   mkConnection(_decode.response, mem.request);
+   mkConnection(decode.response, mem.request);
-   mkConnection(mem.response, _encode.request);
+   mkConnection(mem.response, encode.request);
-   mkConnection(_encode.response, _uart.send);
+   mkConnection(encode.response, uart.send);
 
-   return _uart.phy;
+   return uart.phy;
 endmodule
 
 interface Top;
@@ -28,20 +29,28 @@ interface Top;
    method Action debugger_rx_in((* port="serial_in" *) bit b);
    (* always_ready,result="debug_serial_out" *)
    method bit debugger_tx_out();
+
+   (* always_ready *)
+   method Bool led();
 endinterface
 
 (* synthesize *)
 module mkTop(Top);
    ////////////
    // Memory
-   VRAM mem <- mkVRAM(128);
+   VRAM mem <- mkVRAM(4);
 
    ////////////
-   // Debug interface
+   // Debugging
    let debugger <- mkUARTDebugger(25_000_000, 115_200, mem.debugger);
+   let blinky <- mkBlinky(25_000_000);
 
+   ////////////
+   // External interface
    method debugger_rx_in = debugger.rx_in;
    method debugger_tx_out = debugger.tx_out;
+
+   method led = blinky.led_on;
 endmodule
 
 endpackage

hardware/ulx3s/pin_map.lpf

@@ -14,3 +14,6 @@ LOCATE COMP "debug_serial_out" SITE "L4"; # FPGA transmits to ftdi
 LOCATE COMP "debug_serial_in" SITE "M1"; # FPGA receives from ftdi
 IOBUF  PORT "debug_serial_out" PULLMODE=UP IO_TYPE=LVCMOS33 DRIVE=4;
 IOBUF  PORT "debug_serial_in" PULLMODE=UP IO_TYPE=LVCMOS33;
+
+LOCATE COMP "led" SITE "B2";
+IOBUF  PORT "led" PULLMODE=NONE IO_TYPE=LVCMOS33 DRIVE=4;

lib/ECP5_RAM.v

@@ -42,7 +42,7 @@ module ECP5_RAM#(
           .REGMODE_B(REGMODE_B),
           .WRITEMODE_B(WRITEMODE_B),
           .CSDECODE_B(CSDECODE_B)
-          ) ram(.CLKA(CLKA), .RSTA(RSTA), .CEA(CEA), .OCEA(OCEA), .WEA(WEA),
+          ) ram(.CLKA(CLKA), .RSTA(!RSTA), .CEA(CEA), .OCEA(OCEA), .WEA(WEA),
                 .CSA2(CSA[2]), .CSA1(CSA[1]), .CSA0(CSA[0]),
                 .ADA13(ADA[13]), .ADA12(ADA[12]), .ADA11(ADA[11]), .ADA10(ADA[10]), .ADA9(ADA[9]),
                 .ADA8(ADA[8]),   .ADA7(ADA[7]),   .ADA6(ADA[6]),   .ADA5(ADA[5]),   .ADA4(ADA[4]),
@@ -56,7 +56,7 @@ module ECP5_RAM#(
                 .DOA7(DOA[7]),   .DOA6(DOA[6]),   .DOA5(DOA[5]),   .DOA4(DOA[4]),   .DOA3(DOA[3]),
                 .DOA2(DOA[2]),   .DOA1(DOA[1]),   .DOA0(DOA[0]),
 
-                .CLKB(CLKB), .RSTB(RSTB), .CEB(CEB), .OCEB(OCEB), .WEB(WEB),
+                .CLKB(CLKB), .RSTB(!RSTB), .CEB(CEB), .OCEB(OCEB), .WEB(WEB),
                 .CSA2(CSA[2]), .CSA1(CSA[1]), .CSA0(CSA[0]),
                 .ADB13(ADB[13]), .ADB12(ADB[12]), .ADB11(ADB[11]), .ADB10(ADB[10]), .ADB9(ADB[9]),
                 .ADB8(ADB[8]),   .ADB7(ADB[7]),   .ADB6(ADB[6]),   .ADB5(ADB[5]),   .ADB4(ADB[4]),

vram/VRAM.bsv

@@ -16,6 +16,8 @@ export VRAMAddr, VRAMData, VRAMRequest(..), VRAMResponse(..);
 export VRAMServer(..);
 export VRAM(..), mkVRAM;
 
+export mkArbitratedVRAMServers;
+
 // A VRAMServer is a memory port.
 typedef Server#(VRAMRequest, VRAMResponse) VRAMServer;
 
@@ -44,9 +46,12 @@ module mkArbitratedVRAMServers(VRAMServer ram, MemArbiter#(n, VRAMAddr) arb, Vec
    (* fire_when_enabled *)
    rule submit (awaiting_response[1] matches tagged Invalid);
       let port = arb.granted_port();
-      ram.request.put(requests[port].first);
+      let req = requests[port].first;
+      ram.request.put(req);
       requests[port].deq();
-      awaiting_response[1] <= tagged Valid port;
+      // Only reads generate a response.
+      if (req.data matches tagged Invalid)
+         awaiting_response[1] <= tagged Valid port;
    endrule
 
    (* fire_when_enabled *)

vram/VRAMCore.bsv

@@ -28,11 +28,11 @@ typedef EBR#(ByteAddr, VRAMData, ByteAddr, VRAMData) ByteRAM;
 typedef struct {
    VRAMAddr addr;
    Maybe#(VRAMData) data;
-} VRAMRequest deriving (Bits, Eq);
+} VRAMRequest deriving (Bits, Eq, FShow);
 
 typedef struct {
    VRAMData data;
-} VRAMResponse deriving (Bits, Eq);
+} VRAMResponse deriving (Bits, Eq, FShow);
 
 module mkNibbleRAM_ECP5(ChipAddr chip_addr, EBR#(ByteAddr, Bit#(4), ByteAddr, Bit#(4)) ifc);
    EBRPortConfig cfg = defaultValue;

vram/VRAM_Test.bsv

@@ -0,0 +1,136 @@
+package VRAM_Test;
+
+import Assert::*;
+import StmtFSM::*;
+import GetPut::*;
+import ClientServer::*;
+import Connectable::*;
+import Vector::*;
+
+import MemArbiter::*;
+import Testing::*;
+import VRAM::*;
+
+interface FakeVRAM;
+   interface VRAMServer server;
+   method Action next_response(VRAMResponse resp);
+   method Maybe#(VRAMRequest) last_request();
+endinterface
+
+module mkFakeVRAM(FakeVRAM);
+   Reg#(Maybe#(VRAMRequest)) req <- mkReg(tagged Invalid);
+   Reg#(Maybe#(VRAMResponse)) resp <- mkReg(tagged Invalid);
+
+   interface VRAMServer server;
+      interface Put request;
+         method Action put(r);
+            req <= tagged Valid r;
+         endmethod
+      endinterface
+      interface Get response;
+         method ActionValue#(VRAMResponse) get() if (resp matches tagged Valid .respval &&& req matches tagged Valid .reqval &&& reqval.data matches tagged Invalid);
+            resp <= tagged Invalid;
+            return respval;
+         endmethod
+      endinterface
+   endinterface
+   method Action next_response(r) if (resp matches tagged Invalid);
+      resp <= tagged Valid r;
+   endmethod
+   method Maybe#(VRAMRequest) last_request();
+      return req;
+   endmethod
+endmodule
+
+module mkArbitratedVRAMServersTest(FSM);
+   let testflags <- mkTestFlags();
+   let cycles <- mkCycleCounter();
+
+   let vram <- mkFakeVRAM();
+   MemArbiter#(3, VRAMAddr) arb <- mkPriorityMemArbiter();
+
+   Vector#(3, VRAMServer) ports <- mkArbitratedVRAMServers(vram.server, arb);
+
+   function Action check_read(VRAMServer port, VRAMAddr want_addr, VRAMData want_data);
+      return action
+                let want_request = VRAMRequest{addr: want_addr, data: tagged Invalid};
+                if (testflags.verbose)
+                   $display("Last received VRAM request: ", fshow(vram.last_request), " want ", fshow(want_request));
+                dynamicAssert(vram.last_request == tagged Valid want_request, "wrong request seen by vram for read");
+
+                let got <- port.response.get();
+                if (testflags.verbose)
+                   $display("VRAM.read() = %0d, want %0d", got.data, want_data);
+                dynamicAssert(got.data == want_data, "wrong data seen in vram read");
+             endaction;
+   endfunction
+
+   function Action check_write(VRAMAddr want_addr, VRAMData data);
+      return action
+                let want = VRAMRequest{addr: want_addr, data: tagged Valid data};
+                if (testflags.verbose)
+                   $display("Last received VRAM request: ", fshow(vram.last_request), " want ", fshow(want));
+                dynamicAssert(vram.last_request == tagged Valid want, "wrong request seen by vram for write");
+             endaction;
+   endfunction
+
+   let fsm <- mkFSM(seq
+      // Single write
+      ports[1].request.put(VRAMRequest{addr: 123, data: tagged Valid 42});
+      check_write(123, 42);
+
+      // Single read
+      vram.next_response(VRAMResponse{data: 23});
+      ports[1].request.put(VRAMRequest{addr: 124, data: tagged Invalid});
+      check_read(ports[1], 124, 23);
+
+      // Concurrent ops, process port 1 response first to check
+      // buffering allows port 0 op to finish and port 1 to proceed
+      vram.next_response(VRAMResponse{data: 11});
+      par
+         vram.next_response(VRAMResponse{data: 66});
+         ports[0].request.put(VRAMRequest{addr: 123, data: tagged Invalid});
+         ports[1].request.put(VRAMRequest{addr: 125, data: tagged Invalid});
+      endpar
+      check_read(ports[1], 125, 66);
+      check_read(ports[0], 125, 11); // note, 125 because the last op is still port 1's read
+   endseq);
+   return fsm;
+endmodule
+
+module mkTestFull(FSM);
+   let testflags <- mkTestFlags();
+
+   let dut <- mkVRAM(4);
+
+   let fsm <- mkFSM(seq
+      dut.cpu.request.put(VRAMRequest{addr: 1, data: tagged Valid 42});
+      dut.cpu.request.put(VRAMRequest{addr: 1, data: tagged Invalid});
+      action
+         let resp <- dut.cpu.response.get();
+         if (testflags.verbose)
+            $display("vram read: ", fshow(resp));
+         dynamicAssert(resp.data == 42, "wrong data read after writing");
+      endaction
+   endseq);
+   return fsm;
+endmodule
+
+module mkTB();
+   let testGlue <- mkArbitratedVRAMServersTest();
+   let testFull <- mkTestFull();
+
+   runTest(100,
+      mkTest("VRAM", seq
+         mkTest("VRAM/Glue", seq
+            testGlue.start();
+            await(testGlue.done);
+         endseq);
+         mkTest("VRAM/Full", seq
+            testFull.start();
+            await(testFull.done);
+         endseq);
+      endseq));
+endmodule
+
+endpackage