round robin arbiter + auto buffered queue + fixed dcache arbiter

hw/rtl/libs/VX_rr_arbiter.v

@@ -0,0 +1,58 @@
+`include "VX_define.vh"
+
+module VX_rr_arbiter #(
+    parameter N = 0
+) (
+    input  wire                  clk,
+    input  wire                  reset,
+    input  wire [N-1:0]          requests,           
+    output wire [`LOG2UP(N)-1:0] grant_index,
+    output wire [N-1:0]          grant_onehot,   
+    output wire                  grant_valid
+  );
+
+    if (N == 1)  begin
+
+        `UNUSED_VAR (clk)
+        `UNUSED_VAR (reset)
+        
+        assign grant_index  = 0;
+        assign grant_onehot = requests;
+        assign grant_valid  = requests[0];
+
+    end else begin
+
+        reg [`CLOG2(N)-1:0] grant_table [0:N-1];
+        reg [`CLOG2(N)-1:0] state;  
+        reg [N-1:0] grant_onehot_r;
+
+        integer i, j;   
+
+        always @(*) begin
+            for (i = 0; i < N; ++i) begin  
+                grant_table[i] = `CLOG2(N)'(i);    
+                for (j = 0; j < N; ++j) begin    
+                    if (requests[(i+j) % N]) begin                        
+                        grant_table[i] = `CLOG2(N)'((i+j) % N);
+                    end
+                end
+            end
+            grant_onehot_r = N'(0);
+            grant_onehot_r[grant_index] = 1;
+        end  
+
+        always @(posedge clk) begin                       
+            if (reset) begin         
+                state <= 0;
+            end 
+            else begin
+                state <= grant_index;
+            end
+        end      
+
+        assign grant_index  = grant_table[state];
+        assign grant_onehot = grant_onehot_r; 
+        assign grant_valid  = (| requests); 
+    end
+    
+endmodule