experiments/primitive_ram: customize the clock/reset of one of the RAM ports

Callers can still specify whacky cross-domain RAMs in the cfg, but the
default is what you usually want: a dual-port RAM with both ports in the
caller's clock/reset domain.

experiments/primitive_ram/Top.bsv

@@ -2,13 +2,19 @@ package Top;
 
 import ECP5_RAM::*;
 
-(* synthesize *)
-module mkTop(ECP5_EBRCorePort#(Bit#(12), Bit#(8)));
-   let clk <- exposeCurrentClock;
-   let rstN <- exposeCurrentReset;
+(* always_enabled *)
+interface Top;
+   method Action put(UInt#(3) select, Bool write, Bit#(12) address, Bit#(4) data);
+   method Bit#(4) read();
+endinterface
 
-   ECP5_EBRPortConfig cfg = defaultValue;
-   ECP5_EBRCore#(Bit#(12), Bit#(8), UInt#(12), UInt#(8)) ram <- mkECP5_EBRCoreByte(cfg, cfg);
+(* synthesize *)
+module mkTop(Clock extClk, Reset extRst, Top ifc);
+   ECP5_EBRPortConfig cfgA = defaultValue;
+   cfgA.clk = tagged Valid extClk;
+   cfgA.rstN = tagged Valid extRst;
+   ECP5_EBRPortConfig cfgB = defaultValue;
+   ECP5_EBRCore#(Bit#(12), Bit#(4), UInt#(12), UInt#(4)) ram <- mkECP5_EBRCore(cfgA, cfgB);
 
    method put = ram.portA.put;
    method read = ram.portA.read;

lib/ECP5_RAM.bsv

@@ -17,8 +17,12 @@ typedef enum {
 
 // ECP5_EBRPortConfig is the static configuration of an EBR port.
 typedef struct {
-   Clock clk;
-   Reset rstN;
+   // clk, if specified, is the Clock to use for the port. If
+   // unspecified, uses the module default clock.
+   Maybe#(Clock) clk;
+   // rstN, if specified, is the Reset to use for the port. If
+   // unspecified, uses the module default reset.
+   Maybe#(Reset) rstN;
    // By default, ECP5 EBRs only register the input address and write
    // data, giving a 1-cycle latency for operations. If
    // registered_output is true, the output value is also registered,
@@ -34,8 +38,8 @@ typedef struct {
 
 instance DefaultValue#(ECP5_EBRPortConfig);
    defaultValue = ECP5_EBRPortConfig{
-      clk: noClock,
-      rstN: noReset,
+      clk: defaultValue,
+      rstN: defaultValue,
       registered_output: False,
       chip_select_addr: 0,
       write_mode: Normal
@@ -68,14 +72,34 @@ import "BVI" ECP5_RAM =
                                Integer portB_width)
       (ECP5_EBRCoreInner);
 
+      let defClk <- exposeCurrentClock;
+      let defRstN <- exposeCurrentReset;
+
+      let portA_bsv_clock = case (port_a.clk) matches
+                               tagged Invalid: defClk;
+                               tagged Valid .clk: clk;
+                            endcase;
+      let portA_bsv_rstN = case (port_a.rstN) matches
+                              tagged Invalid: defRstN;
+                              tagged Valid .rstN: rstN;
+                           endcase;
+      let portB_bsv_clock = case (port_b.clk) matches
+                               tagged Invalid: defClk;
+                               tagged Valid .clk: clk;
+                            endcase;
+      let portB_bsv_rstN = case (port_b.rstN) matches
+                              tagged Invalid: defRstN;
+                              tagged Valid .rstN: rstN;
+                           endcase;
+
       default_clock no_clock;
       default_reset no_reset;
 
-      input_clock portA_clk(CLKA, (* unused *)CLKA_GATE)  = port_a.clk;
-      input_reset portA_rstN(RSTA) clocked_by(portA_clk) = port_a.rstN;
+      input_clock portA_clk(CLKA, (* unused *)CLKA_GATE)  = portA_bsv_clock;
+      input_reset portA_rstN(RSTA) clocked_by(portA_clk) = portA_bsv_rstN;
 
-      input_clock portB_clk(CLKB, (* unused *)CLKB_GATE)  = port_b.clk;
-      input_reset portB_rstN(RSTB) clocked_by(portB_clk) = port_b.rstN;
+      input_clock portB_clk(CLKB, (* unused *)CLKB_GATE)  = portB_bsv_clock;
+      input_reset portB_rstN(RSTB) clocked_by(portB_clk) = portB_bsv_rstN;
 
       parameter DATA_WIDTH_A = portA_width;
       parameter REGMODE_A = port_a.registered_output ? "OUTREG" : "NOREG";

lib/ECP5_RAM.v

@@ -160,7 +160,7 @@ module ECP5_RAM(CLKA,
                                         .CSA2(CSA[2]),
                                         .CSA1(CSA[1]),
                                         .CSA0(CSA[0]),
-                                        .RSTB(RSTA),
+                                        .RSTB(RSTB),
                                         .DOB17(DOB[17]),
                                         .DOB16(DOB[16]),
                                         .DOB15(DOB[15]),