Fetch: Fix async reset to actually not do it wrong.

[firearm.git] / ICache.v

diff --git a/ICache.v b/ICache.v
index 43f60281abd93bc5850f147835ff09771ec0caa9..e6754b722acb93829811c7758d64914ecbc538b2 100644 (file)
--- a/ICache.v
+++ b/ICache.v
@@ -32,7 +32,7 @@ module ICache(
        reg [21:0] cache_tags [15:0];
        reg [31:0] cache_data [15:0 /* line */] [15:0 /* word */];
        
-       reg [4:0] i;
+       integer i;
        initial
                for (i = 0; i < 16; i = i + 1)
                begin
@@ -45,11 +45,14 @@ module ICache(
        wire [3:0] rd_idx = rd_addr[9:6];
        wire [21:0] rd_tag = rd_addr[31:10];
        
-       wire cache_hit = cache_valid[rd_idx] && (cache_tags[rd_idx] == rd_tag);
+       reg [31:0] prev_rd_addr = 32'hFFFFFFFF;
        
-       always @(*) begin       /* XXX does this work nowadays? */
+       wire cache_hit = cache_valid[rd_idx] && (cache_tags[rd_idx] == rd_tag);
+
+       wire [31:0] curdata = cache_data[rd_idx][rd_didx_word];
+       always @(*) begin
                rd_wait = rd_req && !cache_hit;
-               rd_data = cache_data[rd_idx][rd_didx_word];
+               rd_data = curdata;
        end
        
        reg [3:0] cache_fill_pos = 0;
@@ -63,15 +66,22 @@ module ICache(
                        bus_rd = 0;
                end
        
-       always @(posedge clk)
-               if (rd_req && !cache_hit) begin
-                       if (bus_ready) begin    /* Started the fill, and we have data. */
+       always @(posedge clk) begin
+               prev_rd_addr <= {rd_addr[31:6], 6'b0};
+               if (cache_fill_pos != 0 && ((prev_rd_addr != {rd_addr[31:6], 6'b0}) || cache_hit))      /* If this wasn't from the same line, or we've moved on somehow, reset the fill circuitry. */
+                       cache_fill_pos <= 0;
+               else if (rd_req && !cache_hit) begin
+                       if (bus_ack && bus_ready) begin /* Started the fill, and we have data. */
+                               $display("ICACHE: FILL: rd addr %08x; bus addr %08x; bus data %08x", rd_addr, bus_addr, bus_rdata);
                                cache_data[rd_idx][cache_fill_pos] <= bus_rdata;
                                cache_fill_pos <= cache_fill_pos + 1;
                                if (cache_fill_pos == 15) begin /* Done? */
                                        cache_tags[rd_idx] <= rd_tag;
                                        cache_valid[rd_idx] <= 1;
-                               end
+                                       $display("ICACHE: Fill complete for line %x, tag %x", rd_idx, rd_tag);
+                               end else
+                                       cache_valid[rd_idx] <= 0;
                        end
                end
+       end
 endmodule