vram/MemArbiter: remove unnecessary wires and fields

While iterating many redundant bits were added. This removes them again,
keeping just (I think) the minimum necessary for the arbitrators to work.

experiments/arbiter/Top.bsv

@@ -4,6 +4,7 @@ import MemArbiter::*;
 import Vector::*;
 import DReg::*;
 import DelayLine::*;
+import Connectable::*;
 
 typedef UInt#(2) Addr;
 
@@ -22,70 +23,51 @@ endinterface
 
 (* synthesize, clock_prefix="clk_25mhz", reset_prefix="rst_btn" *)
 module mkTop(Top);
-   Vector#(2, Reg#(Maybe#(MemArbiterWrite#(Addr)))) wrin <- replicateM(mkDReg(tagged Invalid));
-   Vector#(4, Reg#(Maybe#(Addr))) rdin <- replicateM(mkDReg(tagged Invalid));
+   Vector#(6, Reg#(Maybe#(MemArbiterOp#(Addr)))) wrin <- replicateM(mkDReg(tagged Invalid));
 
-   MemArbiter#(Addr) ret <- mkMemArbiter();
+   MemArbiter#(3, Addr) portA <- mkPriorityMemArbiter();
+   MemArbiter#(3, Addr) portB <- mkRoundRobinMemArbiter();
+   mkConnection(portA, portB);
+
+   let arbiters = append(portA.ports, portB.ports);
 
    Reg#(Vector#(6, Bool)) ok <- mkReg(replicate(False));
 
-   rule req_cpu (wrin[0] matches tagged Valid .req);
-      ret.cpu.request(req);
-   endrule
-
-   rule req_debugger (wrin[1] matches tagged Valid .req);
-      ret.debugger.request(req);
-   endrule
-
-   rule req_palette (rdin[0] matches tagged Valid .addr);
-      ret.palette.request(addr);
-   endrule
-
-   rule req_tile1 (rdin[1] matches tagged Valid .addr);
-      ret.tile1.request(addr);
-   endrule
-
-   rule req_tile2 (rdin[2] matches tagged Valid .addr);
-      ret.tile2.request(addr);
-   endrule
-
-   rule req_sprite (rdin[3] matches tagged Valid .addr);
-      ret.sprite.request(addr);
+   for (Integer i=0; i<6; i=i+1) begin
+      rule req (wrin[i] matches tagged Valid .req);
+         arbiters[i].request(req);
       endrule
+   end
 
    rule resp;
-      Vector#(6, Bool) r = newVector;
-      r[0] = ret.cpu.grant();
-      r[1] = ret.debugger.grant();
-      r[2] = ret.palette.grant();
-      r[3] = ret.tile1.grant();
-      r[4] = ret.tile2.grant();
-      r[5] = ret.sprite.grant();
-      ok <= r;
+      function Bool get(MemArbiterServer#(Addr) s);
+         return s.grant();
+      endfunction
+      ok <= map(get, arbiters);
    endrule
 
    method Action cpu(Bool write, Addr addr);
-      wrin[0] <= tagged Valid MemArbiterWrite{write: write, addr: addr};
+      wrin[0] <= tagged Valid MemArbiterOp{write: write, addr: addr};
    endmethod
 
    method Action debugger(Bool write, Addr addr);
-      wrin[1] <= tagged Valid MemArbiterWrite{write: write, addr: addr};
+      wrin[1] <= tagged Valid MemArbiterOp{write: write, addr: addr};
    endmethod
 
    method Action palette(Addr addr);
-      rdin[0] <= tagged Valid addr;
+      wrin[2] <= tagged Valid MemArbiterOp{write: False, addr: addr};
    endmethod
 
    method Action tile1(Addr addr);
-      rdin[1] <= tagged Valid addr;
+      wrin[3] <= tagged Valid MemArbiterOp{write: False, addr: addr};
    endmethod
 
    method Action tile2(Addr addr);
-      rdin[2] <= tagged Valid addr;
+      wrin[4] <= tagged Valid MemArbiterOp{write: False, addr: addr};
    endmethod
 
    method Action sprite(Addr addr);
-      rdin[3] <= tagged Valid addr;
+      wrin[5] <= tagged Valid MemArbiterOp{write: False, addr: addr};
    endmethod
 
    method Bit#(6) grants();

experiments/vram/Top.bsv

@@ -1,12 +1,12 @@
 package Top;
 
-import VRAM::*;
+import VRAMCore::*;
 import ECP5_RAM::*;
 import TriState::*;
 
 (* synthesize *)
-module mkTop(VRAM);
-   let _ret <- mkVRAM(112);
+module mkTop(VRAMCore);
+   let _ret <- mkVRAMCore(112);
    return _ret;
 endmodule
 

vram/MemArbiter.bsv

@@ -3,30 +3,45 @@ package MemArbiter;
 import Connectable::*;
 import Vector::*;
 
-export MemArbiterWrite(..);
+export MemArbiterOp(..);
 export MemArbiterServer(..);
 export MemArbiterClient(..);
-export MemArbiter(..);
-export mkMemArbiter;
+export MemArbiter(..), mkPriorityMemArbiter, mkRoundRobinMemArbiter;
 
-// A MemArbiterServer receives requests for memory access and emits
-// grants.
-interface MemArbiterServer#(type request);
-   method Action request(request req);
+// A MemArbiterOp is an operation that a client is seeking permission
+// to perform.
+typedef struct {
+   Bool write;
+   addr addr;
+} MemArbiterOp#(type addr) deriving (Bits, Eq, FShow);
+
+function Bool mem_ops_conflict(Maybe#(MemArbiterOp#(addr)) a, Maybe#(MemArbiterOp#(addr)) b)
+   provisos(Eq#(addr));
+
+   if (a matches tagged Valid .ar &&& b matches tagged Valid .br &&& ar.addr == br.addr)
+      return ar.write || br.write;
+   else
+      return False;
+endfunction
+
+// A MemArbiterServer receives requests and emits grants.
+(* always_ready *)
+interface MemArbiterServer#(type addr);
+   method Action request(MemArbiterOp#(addr) req);
    method Bool grant();
 endinterface
 
-// A MemArbiterClient emits requests for memory access and emits
-// grants.
-interface MemArbiterClient#(type request);
-   method request request();
+// A MemArbiterClient emits requests and receives grants.
+interface MemArbiterClient#(type addr);
+   method Maybe#(MemArbiterOp#(addr)) request();
    method Action grant();
 endinterface
 
-instance Connectable#(MemArbiterClient#(req), MemArbiterServer#(req));
-   module mkConnection(MemArbiterClient#(req) client, MemArbiterServer#(req) server, Empty ifc);
-      rule send_request;
-         server.request(client.request());
+// Arbiter clients and servers can be connected in the obvious way.
+instance Connectable#(MemArbiterClient#(addr), MemArbiterServer#(addr));
+   module mkConnection(MemArbiterClient#(addr) client, MemArbiterServer#(addr) server, Empty ifc);
+      rule send_request (client.request matches tagged Valid .req);
+         server.request(req);
       endrule
 
       rule send_grant (server.grant());
@@ -35,157 +50,173 @@ instance Connectable#(MemArbiterClient#(req), MemArbiterServer#(req));
    endmodule
 endinstance
 
-typedef struct {
-   Bool write;
-   addr addr;
-} MemArbiterWrite#(type addr) deriving (Bits, Eq);
+// A MemArbiter manages concurrent access to a memory port.
+interface MemArbiter#(numeric type num_clients, type addr);
+   // ports allow clients to request memory access.
+   interface Vector#(num_clients, MemArbiterServer#(addr)) ports;
 
-// A MemArbiter manages concurrent access to memory ports.
-interface MemArbiter#(type addr);
-   interface MemArbiterServer#(MemArbiterWrite#(addr)) cpu;
-   interface MemArbiterServer#(MemArbiterWrite#(addr)) debugger;
-   interface MemArbiterServer#(addr) palette;
-
-   interface MemArbiterServer#(addr) tile1;
-   interface MemArbiterServer#(addr) tile2;
-   interface MemArbiterServer#(addr) sprite;
+   // The following methods are to support arbiter chaining.
+   //
+   // Suppose you're arbitrating access to a dual-port
+   // memory. Typically, such a memory specifies that if one port is
+   // writing to an address, the other must not concurrently read or
+   // write that same address. This means the arbiters attached to
+   // each memory port must cooperate to avoid simultaneously granting
+   // conflicting requests from their clients.
+   //
+   // Calling conflict prevents the arbiter from granting a concurrent
+   // request that would result in a write-write, read-write or
+   // write-read conflict. granted_op emits the operation that the
+   // arbiter is granting, if any.
+   //
+   // MemArbiter intances are Connectable: mkConnection(a, b) gives
+   // conflict priority to a. That is, b only grants requests that
+   // don't conflict with a's grant.
+   (* always_ready *)
+   method Action conflict(MemArbiterOp#(addr) conflict);
+   method MemArbiterOp#(addr) granted_op();
 endinterface
 
-// mkMemArbiter builds a GARY memory arbiter.
-//
-// Port A arbitrates with strict priority: CPU requests go first, then
-// the debugger, then the palette DAC.
-//
-// Port B does round-robin arbitration, giving each client a fair
-// share of memory access.
-module mkMemArbiter(MemArbiter#(addr))
+instance Connectable#(MemArbiter#(m, addr), MemArbiter#(n, addr));
+   module mkConnection(MemArbiter#(m, addr) a, MemArbiter#(n, addr) b, Empty ifc);
+      (* fire_when_enabled *)
+      rule forward_conflict;
+         b.conflict(a.granted_op);
+      endrule
+   endmodule
+endinstance
+
+// mkPriorityMemArbiter returns a MemArbiter that gives priority to
+// lower numbered ports.
+module mkPriorityMemArbiter(MemArbiter#(num_clients, addr))
    provisos (Bits#(addr, _),
              Eq#(addr),
-            Alias#(write_req, MemArbiterWrite#(addr)));
+             Min#(num_clients, 1, 1));
 
-   //////
-   // Port A users
+   Vector#(num_clients, RWire#(MemArbiterOp#(addr))) reqs <- replicateM(mkRWire());
+   Wire#(Vector#(num_clients, Bool)) grants <- mkBypassWire();
 
-   RWire#(write_req) cpu_req <- mkRWire();
-   RWire#(write_req) debugger_req <- mkRWire();
-   PulseWire palette_req <- mkPulseWire();
+   RWire#(MemArbiterOp#(addr)) conflict_in <- mkRWire();
+   RWire#(MemArbiterOp#(addr)) granted_op_out <- mkRWire();
 
-   PulseWire cpu_ok <- mkPulseWire();
-   PulseWire debugger_ok <- mkPulseWire();
-   PulseWire palette_ok <- mkPulseWire();
+   (* no_implicit_conditions, fire_when_enabled *)
+   rule grant_requests;
+      Vector#(num_clients, Bool) grant = replicate(False);
+      Bool done = False;
 
-   // Address written to by port A, if any. Used to block port B
-   // clients that are trying to read the same address.
-   RWire#(addr) written_addr <- mkRWire();
-
-   // We could be fancy with rule conditions to express the priorities
-   // between clients, but Bluespec has the preempts annotation to
-   // express the ranking directly.
-   (* preempts = "grant_cpu, (grant_debugger, grant_palette)" *)
-   (* preempts = "grant_debugger, grant_palette" *)
-
-   (* fire_when_enabled *)
-   rule grant_cpu (cpu_req.wget matches tagged Valid .req);
-      cpu_ok.send();
-      if (req.write)
-         written_addr.wset(req.addr);
-   endrule
-
-   rule grant_debugger (debugger_req.wget matches tagged Valid .req);
-      debugger_ok.send();
-      if (req.write)
-         written_addr.wset(req.addr);
-   endrule
-
-   rule grant_palette (palette_req);
-      palette_ok.send();
-   endrule
-
-   //////
-   // Port B users
-
-   Vector#(3, RWire#(addr)) portB_req <- replicateM(mkRWire);
-   Wire#(Vector#(3, Bool)) portB_grant <- mkBypassWire();
-
-   Vector#(3, Bool) init = replicate(False); init[0] = True;
-   Reg#(Vector#(3, Bool)) priority_vec <- mkReg(init);
-
-   rule grant_portB;
-      Vector#(3, Bool) grants = replicate(False);
-      Bool port_available = False;
-
-      // This algorithm is a little mystifying at first glance, but it
-      // works. priority_vec has one bool per client, only one of
-      // which is True. That True bit identifies the client with the
-      // highest priority on the next request.
-      //
-      // This loop goes through each client twice, using
-      // port_available to track whether a client can grab the port or
-      // not. When we start iterating, the port is marked unavailable
-      // until we reach the top priority client, at which point we
-      // mark the port available and keep scanning. That effectively
-      // makes the search for a requesting client start at the top
-      // priority one.
-      //
-      // As we loop back around a second time, the availability bool
-      // gets reset again, but if you take the example of the True bit
-      // being in the middle of the vector, and consider cases where
-      // the first requestor is before/after that starting point,
-      // you'll see that it all works out, and at the end of the loop
-      // we have a new bit vector where only one client is True - the
-      // one whose request is granted.
-      for (Integer i = 0; i < 6; i=i+1) begin
-         Integer idx = i % 3;
-         if (priority_vec[idx])
-            port_available = True;
-         let req = portB_req[idx].wget();
-         if (port_available && isValid(req) && req != written_addr.wget()) begin
-            port_available = False;
-            grants[idx] = True;
+      for (Integer i=0; i<valueOf(num_clients); i=i+1) begin
+         if (reqs[i].wget() matches tagged Valid .req &&&
+             !mem_ops_conflict(conflict_in.wget(), reqs[i].wget()) &&&
+             !done) begin
+                       done = True;
+                       grant[i] = True;
+                       granted_op_out.wset(req);
                     end
       end
-      portB_grant <= grants;
-      // If we granted a request, the grantee becomes the lowest
-      // priority client for the next round of requests. If nobody
-      // requested anything, keep the same priority as before.
-      if (any(id, grants))
-         priority_vec <= rotateR(grants);
+
+      grants <= grant;
    endrule
 
-   //////
-   // External interface
+   Vector#(num_clients, MemArbiterServer#(addr)) _ifcs = newVector();
+   for (Integer i=0; i<valueOf(num_clients); i=i+1)
+      _ifcs[i] = (interface MemArbiterServer#(addr);
+                     method request = reqs[i].wset;
+                     method grant = grants[i];
+                  endinterface);
 
-   interface MemArbiterServer cpu;
-      method request = cpu_req.wset;
-      method grant = cpu_ok;
-   endinterface
-
-   interface MemArbiterServer debugger;
-      method request = debugger_req.wset;
-      method grant = debugger_ok;
-   endinterface
-
-   interface MemArbiterServer palette;
-      method Action request(addr);
-         palette_req.send();
+   interface ports = _ifcs;
+   method conflict = conflict_in.wset;
+   method MemArbiterOp#(addr) granted_op() if (granted_op_out.wget() matches tagged Valid .op);
+      return op;
    endmethod
-      method grant = palette_ok;
-   endinterface
+endmodule
 
-   interface MemArbiterServer tile1;
-      method request = portB_req[0].wset;
-      method grant = portB_grant[0];
-   endinterface
+typedef struct {
+   Vector#(n, Bool) grant_vec;
+   Maybe#(MemArbiterOp#(addr)) granted_op;
+} GrantResult#(numeric type n, type addr) deriving (Bits, Eq, FShow);
 
-   interface MemArbiterServer tile2;
-      method request = portB_req[1].wset;
-      method grant = portB_grant[1];
-   endinterface
+// select_grant computes which one entry of requests should be
+// granted. Priority order is descending starting from
+// requests[hipri].
+function GrantResult#(n, addr) select_grant(Vector#(n, Maybe#(MemArbiterOp#(addr))) requests,
+                                            UInt#(TLog#(n)) hipri,
+                                            Maybe#(MemArbiterOp#(addr)) conflict)
+   provisos (Eq#(addr));
 
-   interface MemArbiterServer sprite;
-      method request = portB_req[2].wset;
-      method grant = portB_grant[2];
-   endinterface
+   function onehot(idx);
+      let ret = replicate(False);
+      ret[idx] = True;
+      return ret;
+   endfunction
+
+   function GrantResult#(n, addr) do_fold(GrantResult#(n, addr) acc,
+                                          Tuple2#(UInt#(TLog#(n)),
+                                                  Maybe#(MemArbiterOp#(addr))) next);
+      match {.idx, .mreq} = next;
+      if (mreq matches tagged Valid .req &&& acc.granted_op matches tagged Invalid &&& !mem_ops_conflict(conflict, mreq))
+         return GrantResult{
+            grant_vec: onehot(idx),
+            granted_op: tagged Valid req
+         };
+      else
+         // Previous grant won, not requesting, or request not satisfiable.
+         return acc;
+   endfunction
+
+   let in = zip(map(fromInteger, genVector()), requests);
+   let rot = rotateBy(in, fromInteger(valueOf(n)-1)-hipri+1);
+   let seed = GrantResult{
+      grant_vec: replicate(False),
+      granted_op: tagged Invalid
+   };
+   return foldl(do_fold, seed, rot);
+endfunction
+
+module mkRoundRobinMemArbiter(MemArbiter#(num_clients, addr))
+   provisos (Bits#(addr, _),
+             Eq#(addr),
+             Min#(num_clients, 1, 1));
+
+   Vector#(num_clients, RWire#(MemArbiterOp#(addr))) reqs <- replicateM(mkRWire);
+   Wire#(Vector#(num_clients, Bool)) grants <- mkBypassWire();
+
+   RWire#(MemArbiterOp#(addr)) conflict_in <- mkRWire();
+   RWire#(MemArbiterOp#(addr)) granted_op_out <- mkRWire();
+
+   // high_prio is the index of the client that should be first in
+   // line to receive access. Every time we grant access to a client,
+   // the one after that in sequence becomes high_prio in the next
+   // round.
+   Reg#(UInt#(TLog#(num_clients))) high_prio <- mkReg(0);
+
+   function Maybe#(_t) get_mreq(RWire#(_t) w);
+      return w.wget();
+   endfunction
+
+   rule grant;
+      let in = map(get_mreq, reqs);
+      let res = select_grant(in, high_prio, conflict_in.wget());
+
+      grants <= res.grant_vec;
+      if (res.granted_op matches tagged Valid .op) begin
+         granted_op_out.wset(op);
+         high_prio <= validValue(findElem(True, rotateR(res.grant_vec)));
+      end
+   endrule
+
+   Vector#(num_clients, MemArbiterServer#(addr)) _ifcs = newVector();
+   for (Integer i=0; i<valueOf(num_clients); i=i+1)
+      _ifcs[i] = (interface MemArbiterServer#(addr);
+                     method request = reqs[i].wset;
+                     method grant = grants[i];
+                  endinterface);
+
+   interface ports = _ifcs;
+   method conflict = conflict_in.wset;
+   method MemArbiterOp#(addr) granted_op() if (granted_op_out.wget() matches tagged Valid .op);
+      return op;
+   endmethod
 endmodule
 
 endpackage

vram/MemArbiter_Test.bsv

@@ -14,282 +14,307 @@ typedef UInt#(4) Addr;
 
 typedef struct {
    String name;
-   Maybe#(MemArbiterWrite#(Addr)) cpu;
-   Maybe#(MemArbiterWrite#(Addr)) debugger;
-   Maybe#(Addr) palette;
-   Maybe#(Addr) tile1;
-   Maybe#(Addr) tile2;
-   Maybe#(Addr) sprite;
 
-   Vector#(6, Bool) want;
-} TestCase deriving (Bits, Eq);
+   Vector#(n, Maybe#(MemArbiterOp#(Addr))) reqs;
+   Maybe#(MemArbiterOp#(Addr)) conflict;
 
-function Maybe#(MemArbiterWrite#(Addr)) rwRead(Addr addr);
-   return tagged Valid MemArbiterWrite{write: False, addr: addr};
+   Vector#(n, Bool) want_grants;
+   Maybe#(MemArbiterOp#(Addr)) want_granted_op;
+} TestCase#(numeric type n) deriving (Bits, Eq);
+
+function Maybe#(MemArbiterOp#(Addr)) read(Addr addr);
+   return tagged Valid MemArbiterOp{write: False, addr: addr};
 endfunction
 
-function Maybe#(MemArbiterWrite#(Addr)) rwWrite(Addr addr);
-   return tagged Valid MemArbiterWrite{write: True, addr: addr};
+function Maybe#(MemArbiterOp#(Addr)) write(Addr addr);
+   return tagged Valid MemArbiterOp{write: True, addr: addr};
 endfunction
 
-function Maybe#(Addr) read(Addr addr);
-   return tagged Valid addr;
-endfunction
-
-function Maybe#(t) idle();
+function Maybe#(MemArbiterOp#(Addr)) idle();
    return tagged Invalid;
 endfunction
 
-function Vector#(6, Bool) grant(Integer granted_a, Integer granted_b);
-   let ret = replicate(False);
-   if (granted_a >= 0)
-      ret[granted_a] = True;
-   if (granted_b >= 0)
-      ret[granted_b+3] = True;
-   return ret;
+function Maybe#(MemArbiterOp#(Addr)) noConflict();
+   return tagged Invalid;
 endfunction
 
-function TestCase testCase(String name,
-                           Maybe#(MemArbiterWrite#(Addr)) cpu,
-                           Maybe#(MemArbiterWrite#(Addr)) debugger,
-                           Maybe#(Addr) palette,
-                           Maybe#(Addr) tile1,
-                           Maybe#(Addr) tile2,
-                           Maybe#(Addr) sprite,
-                           Integer portA,
-                           Integer portB);
+function Vector#(n, Bool) grant(Integer granted);
+   function gen(idx);
+      return idx == granted;
+   endfunction
+
+   return genWith(gen);
+endfunction
+
+function Vector#(n, Bool) noGrant();
+   return replicate(False);
+endfunction
+
+function TestCase#(n) testCase(String name,
+                               Vector#(n, Maybe#(MemArbiterOp#(Addr))) reqs,
+                               Maybe#(MemArbiterOp#(Addr)) conflict,
+                               Vector#(n, Bool) want_grants,
+                               Maybe#(MemArbiterOp#(Addr)) want_granted_op);
    return TestCase{
       name: name,
-      cpu: cpu,
-      debugger: debugger,
-      palette: palette,
-      tile1: tile1,
-      tile2: tile2,
-      sprite: sprite,
-      want: grant(portA, portB)
+      reqs: reqs,
+      conflict: conflict,
+      want_grants: want_grants,
+      want_granted_op: want_granted_op
    };
 endfunction
 
-module mkTB();
-   Vector#(29, TestCase) tests = vec(
-      testCase("All idle",
-               idle, idle, idle,
-               idle, idle, idle,
-               -1, -1),
+interface TB;
+   method Action start();
+   (* always_ready *)
+   method Bool done();
+endinterface
 
-      // Single client accesses at a time
-      testCase("CPU read", rwRead(1), idle, idle,
-               idle, idle, idle,
-               0, -1),
-      testCase("CPU write", rwWrite(1), idle, idle,
-               idle, idle, idle,
-               0, -1),
-      testCase("Debugger read",
-               idle, rwRead(1), idle,
-               idle, idle, idle,
-               1, -1),
-      testCase("Debugger write",
-               idle, rwWrite(1), idle,
-               idle, idle, idle,
-               1, -1),
-      testCase("Palette read",
-               idle, idle, read(1),
-               idle, idle, idle,
-               2, -1),
-      testCase("Tile1 read",
-               idle, idle, idle,
-               read(1), idle, idle,
-               -1, 0),
-      testCase("Tile2 read",
-               idle, idle, idle,
-               idle, read(1), idle,
-               -1, 1),
-      testCase("Sprite read",
-               idle, idle, idle,
-               idle, idle, read(1),
-               -1, 2),
+module mkArbiterTB(MemArbiter#(n, Addr) dut, Vector#(m, TestCase#(n)) tests, TB ifc);
+   let cycles <- mkCycleCounter();
 
-      // Strict priority on port A
-      testCase("CPU + Debugger + Palette",
-               rwRead(1), rwRead(2), read(3),
-               idle, idle, idle,
-               0, -1),
-      testCase("CPU + Palette",
-               rwRead(1), idle, read(3),
-               idle, idle, idle,
-               0, -1),
-      testCase("Debugger + Palette",
-               idle, rwRead(2), read(3),
-               idle, idle, idle,
-               1, -1),
+   Reg#(Bit#(TLog#(m))) idx <- mkReg(0);
+   Reg#(Bool) running <- mkReg(False);
 
-      // Round-robin on port B
-      testCase("Sprite read", // to reset round robin
-               idle, idle, idle,
-               idle, idle, read(1),
-               -1, 2),
-      testCase("Tile1 + Tile2 + Sprite",
-               idle, idle, idle,
-               read(1), read(2), read(3),
-               -1, 0),
-      testCase("Tile1 + Tile2 + Sprite",
-               idle, idle, idle,
-               read(1), read(2), read(3),
-               -1, 1),
-      testCase("Tile1 + Tile2 + Sprite",
-               idle, idle, idle,
-               read(1), read(2), read(3),
-               -1, 2),
-      testCase("Tile1 + Tile2 + Sprite",
-               idle, idle, idle,
-               read(1), read(2), read(3),
-               -1, 0),
-      testCase("Tile1 + Sprite",
-               idle, idle, idle,
-               read(1), idle, read(3),
-               -1, 2),
-      testCase("Tile2 + Sprite",
-               idle, idle, idle,
-               idle, read(2), read(3),
-               -1, 1),
-      testCase("Tile2 + Sprite",
-               idle, idle, idle,
-               idle, read(2), read(3),
-               -1, 2),
-
-      // Inter-port conflicts
-      testCase("Read/read, no conflict",
-               rwRead(0), idle, idle,
-               read(0), idle, idle,
-               0, 0),
-      testCase("Write/read, no conflict",
-               rwWrite(1), idle, idle,
-               read(0), idle, idle,
-               0, 0),
-      testCase("Tile1 write conflict",
-               rwWrite(0), idle, idle,
-               read(0), idle, idle,
-               0, -1),
-      testCase("Tile2 write conflict",
-               rwWrite(0), idle, idle,
-               idle, read(0), idle,
-               0, -1),
-      testCase("Sprite write conflict",
-               rwWrite(0), idle, idle,
-               idle, idle, read(0),
-               0, -1),
-      testCase("Tile1 write conflict with debugger",
-               idle, rwWrite(0), idle,
-               read(0), idle, idle,
-               1, -1),
-      testCase("Sprite read", // to reset round robin
-               idle, idle, idle,
-               idle, idle, read(1),
-               -1, 2),
-      testCase("CPU write conflict, other port feasible",
-               rwWrite(0), idle, idle,
-               read(0), read(1), idle,
-               0, 1),
-      testCase("CPU write conflict, conflict resolved",
-               idle, idle, idle,
-               read(0), idle, idle,
-               -1, 0));
-
-   MemArbiter#(Addr) dut <- mkMemArbiter();
-
-   Reg#(UInt#(32)) idx <- mkReg(0);
-
-   rule display_test (idx == 0);
-      $display("RUN TestMemArbiter");
+   for (Integer i=0; i<valueOf(n); i=i+1) begin
+      rule request (running && isValid(tests[idx].reqs[i]));
+         dut.ports[i].request(validValue(tests[idx].reqs[i]));
       endrule
-
-   (* no_implicit_conditions, fire_when_enabled *)
-   rule input_cpu (tests[idx].cpu matches tagged Valid .req);
-      dut.cpu.request(req);
-   endrule
-
-   (* no_implicit_conditions, fire_when_enabled *)
-   rule input_debugger (tests[idx].debugger matches tagged Valid .req);
-      dut.debugger.request(req);
-   endrule
-
-   (* no_implicit_conditions, fire_when_enabled *)
-   rule input_palette (tests[idx].palette matches tagged Valid .addr);
-      dut.palette.request(addr);
-   endrule
-
-   (* no_implicit_conditions, fire_when_enabled *)
-   rule input_tile1 (tests[idx].tile1 matches tagged Valid .addr);
-      dut.tile1.request(addr);
-   endrule
-
-   (* no_implicit_conditions, fire_when_enabled *)
-   rule input_tile2 (tests[idx].tile2 matches tagged Valid .addr);
-      dut.tile2.request(addr);
-   endrule
-
-   (* no_implicit_conditions, fire_when_enabled *)
-   rule input_sprite (tests[idx].sprite matches tagged Valid .addr);
-      dut.sprite.request(addr);
-   endrule
-
-   function Fmt rw_str(Maybe#(MemArbiterWrite#(Addr)) v);
-      case (v) matches
-         tagged Valid .req: begin
-            if (req.write)
-               return $format("Write(%0d)", req.addr);
-            else
-               return $format("Read(%0d) ", req.addr);
    end
-         tagged Invalid: return $format("Idle    ");
-      endcase
-   endfunction
 
-   function Fmt ro_str(Maybe#(Addr) v);
+   (* no_implicit_conditions, fire_when_enabled *)
+   rule forbid (running && isValid(tests[idx].conflict));
+      dut.conflict(validValue(tests[idx].conflict));
+   endrule
+
+   Wire#(Maybe#(MemArbiterOp#(Addr))) got_granted_op <- mkDWire(tagged Invalid);
+
+   (* fire_when_enabled *)
+   rule collect_granted_op (running);
+      got_granted_op <= tagged Valid dut.granted_op();
+   endrule
+
+   function Fmt req_s(Maybe#(MemArbiterOp#(Addr)) v);
       case (v) matches
-         tagged Valid .addr: return $format("Read(%0d) ", addr);
          tagged Invalid: return $format("Idle");
+         tagged Valid .req &&& req.write: return $format("Write(%0d)", req.addr);
+         tagged Valid .req: return $format("Read(%0d)", req.addr);
       endcase
    endfunction
 
    (* no_implicit_conditions, fire_when_enabled *)
-   rule check_grants;
-      Vector#(6, Bool) gotVec = newVector;
-      gotVec[0] = dut.cpu.grant();
-      gotVec[1] = dut.debugger.grant();
-      gotVec[2] = dut.palette.grant();
-      gotVec[3] = dut.tile1.grant();
-      gotVec[4] = dut.tile2.grant();
-      gotVec[5] = dut.sprite.grant();
-
+   rule check (running);
       let test = tests[idx];
-      let got = pack(reverse(gotVec));
-      let want = pack(reverse(test.want));
+      let reqs = test.reqs;
+      let want_grants = test.want_grants;
+      let want_granted_op = test.want_granted_op;
+      Vector#(n, Bool) got_grants = newVector;
+      for (Integer i=0; i<valueOf(n); i=i+1)
+         got_grants[i] = dut.ports[i].grant();
 
-      $display("RUN %s (%0d)", test.name, idx+1);
-      if (got != want) begin
-         $display("  input: ",
-                  "0:", rw_str(test.cpu), "  1:", rw_str(test.debugger), "  2:", ro_str(test.palette),
-                  "  3:", ro_str(test.tile1), "  4:", ro_str(test.tile2), "  5:", ro_str(test.sprite));
-         $display("  got  : %03b %03b", got[5:3], got[2:0]);
-         $display("  want : %03b %03b", want[5:3], want[2:0]);
-         dynamicAssert(got == want, "wrong arbiter output");
+      $display("RUN %s (%0d)", tests[idx].name, idx);
+      if (got_grants != want_grants || got_granted_op != want_granted_op) begin
+         $display("input:");
+         for (Integer i=0; i<valueOf(n); i=i+1)
+            $display("    ", $format("%0d", i), ": ", req_s(reqs[i]));
+         $display("    conflict: ", fshow(test.conflict));
+
+         $display("  output:");
+         $display("    grants: ", fshow(got_grants));
+         $display("    granted: ", fshow(got_granted_op));
+
+         $display("  want grants: ", fshow(tests[idx].want_grants));
+         $display("  want granted: ", fshow(want_granted_op));
+         dynamicAssert(False, "wrong arbiter output");
       end
+
+      dynamicAssert(cycles == 1, "arbiter took more than 0 cycles");
+
+      $display("OK  %s", tests[idx].name);
+
+      cycles.reset();
+      if (idx == fromInteger(valueOf(m)-1))
+         running <= False;
       else
-         $display("OK  %s", test.name);
+         idx <= idx+1;
    endrule
 
-   (* no_implicit_conditions, fire_when_enabled *)
-   rule advance_test;
-      let next = idx+1;
-      let max = fromInteger(arrayLength(vectorToArray(tests)));
-      if (next == max) begin
-         $display("OK  TestMemArbiter");
-         $finish;
-      end
-      else
-         idx <= next;
-   endrule
+   method Action start() if (!running && idx == 0);
+      cycles.reset();
+      running <= True;
+   endmethod
+
+   method Bool done();
+      return !running && idx != 0;
+   endmethod
+endmodule
+
+module mkTB(Empty);
+   ///////////////////////////////
+   // Strict arbiter
+
+   let strictTests = vec(
+      // Simple grants
+      testCase("All idle",
+               vec(idle, idle, idle), noConflict,
+               noGrant, noConflict),
+      testCase("Port 0 read",
+               vec(read(1), idle, idle), noConflict,
+               grant(0), read(1)),
+      testCase("Port 0 write",
+               vec(write(1), idle, idle), noConflict,
+               grant(0), write(1)),
+      testCase("Port 1 read",
+               vec(idle, read(1), idle), noConflict,
+               grant(1), read(1)),
+      testCase("Port 1 write",
+               vec(idle, write(1), idle), noConflict,
+               grant(1), write(1)),
+      testCase("Port 2 read",
+               vec(idle, idle, read(1)), noConflict,
+               grant(2), read(1)),
+      testCase("Port 2 write",
+               vec(idle, idle, write(1)), noConflict,
+               grant(2), write(1)),
+
+      // Priorities
+      testCase("Port 0+1",
+               vec(read(1), read(2), idle), noConflict,
+               grant(0), read(1)),
+      testCase("Port 0+2",
+               vec(read(1), idle, read(2)), noConflict,
+               grant(0), read(1)),
+      testCase("Port 1+2",
+               vec(idle, read(1), read(2)), noConflict,
+               grant(1), read(1)),
+      testCase("Port 0+1+2",
+               vec(read(1), read(2), read(3)), noConflict,
+               grant(0), read(1)),
+      testCase("Port 0+1+2, overruled writes",
+               vec(read(1), write(1), write(2)), noConflict,
+               grant(0), read(1)),
+
+      // Forbidden addrs
+      testCase("Port 0 read-write denied",
+               vec(read(1), read(2), idle), write(1),
+               grant(1), read(2)),
+      testCase("Port 0 write-write denied",
+               vec(write(1), read(2), idle), write(1),
+               grant(1), read(2)),
+      testCase("Port 0 write-read denied",
+               vec(write(1), read(2), idle), read(1),
+               grant(1), read(2)),
+      testCase("Port 0 no addr match",
+               vec(write(2), idle, idle), write(1),
+               grant(0), write(2)),
+      testCase("Port 0 denied, no alternatives",
+               vec(write(1), idle, idle), write(1),
+               noGrant, noConflict)
+      );
+   MemArbiter#(3, Addr) strict <- mkPriorityMemArbiter();
+   let strictTB <- mkArbiterTB(strict, strictTests);
+
+   ///////////////////////////////
+   // Round-robin arbiter
+   let rrTests = vec(
+      // Simple grants
+      testCase("All idle",
+               vec(idle, idle, idle, idle), noConflict,
+               noGrant, noConflict),
+      testCase("Port 0 read",
+               vec(read(1), idle, idle, idle), noConflict,
+               grant(0), read(1)),
+      testCase("Port 0 write",
+               vec(write(1), idle, idle, idle), noConflict,
+               grant(0), write(1)),
+      testCase("Port 1 read",
+               vec(idle, read(1), idle, idle), noConflict,
+               grant(1), read(1)),
+      testCase("Port 1 write",
+               vec(idle, write(1), idle, idle), noConflict,
+               grant(1), write(1)),
+      testCase("Port 2 read",
+               vec(idle, idle, read(1), idle), noConflict,
+               grant(2), read(1)),
+      testCase("Port 2 write",
+               vec(idle, idle, write(1), idle), noConflict,
+               grant(2), write(1)),
+      testCase("Port 3 read",
+               vec(idle, idle, idle, read(1)), noConflict,
+               grant(3), read(1)),
+      testCase("Port 3 write",
+               vec(idle, idle, idle, write(1)), noConflict,
+               grant(3), write(1)),
+
+      // Priorities
+      testCase("Port 3 to reset RR",
+               vec(idle, idle, idle, read(1)), noConflict,
+               grant(3), read(1)),
+      testCase("Port 0+1 #1",
+               vec(read(1), read(2), idle, idle), noConflict,
+               grant(0), read(1)),
+      testCase("Port 0+1 #2",
+               vec(read(1), read(2), idle, idle), noConflict,
+               grant(1), read(2)),
+      testCase("Port 0+1 #3",
+               vec(read(1), read(2), idle, idle), noConflict,
+               grant(0), read(1)),
+      testCase("Port 0+2 #1",
+               vec(read(1), idle, read(2), idle), noConflict,
+               grant(2), read(2)),
+      testCase("Port 0+2 #2",
+               vec(read(1), idle, read(2), idle), noConflict,
+               grant(0), read(1)),
+      testCase("Port 0+1+2+3 #1",
+               vec(read(1), read(2), read(3), read(4)), noConflict,
+               grant(1), read(2)),
+      testCase("Port 0+1+2+3 #2",
+               vec(read(1), read(2), read(3), read(4)), noConflict,
+               grant(2), read(3)),
+      testCase("Port 0+1+2+3 #3",
+               vec(read(1), read(2), read(3), read(4)), noConflict,
+               grant(3), read(4)),
+      testCase("Port 0+1+2+3 #4",
+               vec(read(1), read(2), read(3), read(4)), noConflict,
+               grant(0), read(1)),
+      testCase("Port 0+1+2+3 #5",
+               vec(read(1), read(2), read(3), read(4)), noConflict,
+               grant(1), read(2)),
+
+      // Forbidden addrs
+      testCase("Port 3 to reset RR",
+               vec(idle, idle, idle, read(1)), noConflict,
+               grant(3), read(1)),
+      testCase("RR with denied writes #1",
+               vec(read(1), write(2), read(3), read(4)), write(3),
+               grant(0), read(1)),
+      testCase("RR with denied writes #2",
+               vec(read(1), write(2), read(3), read(4)), write(3),
+               grant(1), write(2)),
+      testCase("RR with denied writes #3",
+               vec(read(1), write(2), read(3), read(4)), write(3),
+               grant(3), read(4)),
+      testCase("RR with denied writes #4",
+               vec(read(1), write(2), read(3), read(4)), write(3),
+               grant(0), read(1)),
+      testCase("RR with denied writes #5",
+               vec(read(1), write(2), read(3), read(4)), write(3),
+               grant(1), write(2))
+      );
+   MemArbiter#(4, Addr) rr <- mkRoundRobinMemArbiter();
+   let rrTB <- mkArbiterTB(rr, rrTests);
+
+   runTest(100,
+      mkTest("MemArbiter", seq
+         mkTest("MemArbiter/Strict", seq
+            strictTB.start();
+            await(strictTB.done);
+         endseq);
+         mkTest("MemArbiter/RoundRobin", seq
+            rrTB.start();
+            await(rrTB.done);
+         endseq);
+      endseq));
 endmodule
 
 endpackage

vram/VRAMCore.bsv

@@ -1,5 +1,6 @@
-package VRAM;
+package VRAMCore;
 
+import Connectable::*;
 import GetPut::*;
 import ClientServer::*;
 import DReg::*;
@@ -15,11 +16,12 @@ import ECP5_RAM::*;
 
 export VRAMAddr;
 export VRAMData;
-export mkVRAM;
 export VRAMRequest;
 export VRAMResponse;
+export VRAMClient;
 export VRAMServer;
-export VRAM;
+export VRAMCore;
+export mkVRAMCore;
 
 typedef Bit#(8) VRAMData;
 
@@ -133,30 +135,30 @@ typedef struct {
 typedef Server#(VRAMRequest, VRAMResponse) VRAMServer;
 typedef Client#(VRAMRequest, VRAMResponse) VRAMClient;
 
-interface VRAM;
+interface VRAMCore;
    interface VRAMServer portA;
    interface VRAMServer portB;
 endinterface
 
-// mkVRAM creates a dual port VRAM of the specified size, using ECP5
-// EBR memory primitives. The memory size must be a multiple of 4KiB,
-// with a maximum of 128KiB.
+// mkVRAMCore creates a dual port VRAM of the specified size, using
+// ECP5 EBR memory primitives. The memory size must be a multiple of
+// 4KiB, with a maximum of 128KiB.
 //
-// The returned VRAM servers implement flow control. As long as
+// The returned VRAMCore servers implement flow control. As long as
 // responses are processed as soon as they're available, each port can
 // process one memory operation per cycle.
 //
-// The VRAM does not prevent write-write or write-read conflicts
+// The VRAMCore does not prevent write-write or write-read conflicts
 // between the ports. The outcome of a simultaneous write to the same
 // address is unspecified, as is the read output in a simultaneous
 // read and write of the same address. The caller must use external
 // arbitration to avoid such accesses.
-module mkVRAM(Integer num_kilobytes, VRAM ifc);
+module mkVRAMCore(Integer num_kilobytes, VRAMCore ifc);
    if (num_kilobytes > 128)
-      error("maximum VRAM size is 128KiB");
+      error("maximum VRAMCore size is 128KiB");
    let num_bytes = num_kilobytes*1024;
    if (num_bytes % 4096 != 0)
-      error("VRAM must be a multiple of 4096b");
+      error("VRAMCore must be a multiple of 4096b");
    let num_byterams = num_bytes/4096;
    let num_arrays = ceil(fromInteger(num_byterams) / 8);