32x: quirk on rom read 0x1070 when RV=1

fedex81 · Jan 18, 2024 · 92cdfbf · 92cdfbf
1 parent c49f691
commit 92cdfbf
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Showing 2 changed files with 59 additions and 1 deletion.
diff --git a/src/main/java/s32x/bus/S32xBus.java b/src/main/java/s32x/bus/S32xBus.java
@@ -22,6 +22,7 @@
 import java.nio.ByteBuffer;
 
 import static m68k.cpu.Cpu.PC_MASK;
+import static omegadrive.util.BufferUtil.assertionsEnabled;
 import static omegadrive.util.LogHelper.logWarnOnce;
 import static omegadrive.util.Util.th;
 
@@ -135,6 +136,9 @@ private int readAdapterEnOn(int address, Size size) {
                 logWarnOnce(LOG, "Ignoring read access to ROM when RV={}, addr: {} {}", DmaFifo68k.rv, th(address), size);
                 return size.getMask();
             }
+            if (assertionsEnabled && romReadQuirk(address)) {
+                return size.getMask();
+            }
             res = super.read(address, size);
         }
         if (verboseMd) {
@@ -158,6 +162,15 @@ private int readAdapterEnOff(int address, Size size) {
         return res;
     }
 
+    //quirk: https://github.com/viciious/32XDK/wiki/Bugs-and-quirks#about-rom-read-when-rv1
+    private boolean romReadQuirk(int address) {
+        if ((address & 0xFFFF_CFFC) == 0x70 && address > 0x100) {
+            LogHelper.logWarnOnce(LOG, "Unable to read from ROM address: {} when RV=1", th(address));
+            return true;
+        }
+        return false;
+    }
+
     private void writeAdapterEnOn(int address, int data, Size size) {
         if (address >= S32xDict.M68K_START_FRAME_BUFFER && address < S32xDict.M68K_END_FRAME_BUFFER) {
             write32xWord((address & S32xDict.DRAM_MASK) | S32xDict.START_DRAM, data, size);

diff --git a/src/test/java/s32x/RomAccessTest.java b/src/test/java/s32x/RomAccessTest.java
@@ -15,6 +15,7 @@
 
 import static omegadrive.bus.model.GenesisBusProvider.SRAM_LOCK;
 import static omegadrive.util.BufferUtil.CpuDeviceAccess.*;
+import static omegadrive.util.BufferUtil.assertionsEnabled;
 import static omegadrive.util.Util.th;
 import static s32x.MarsRegTestUtil.readBus;
 import static s32x.MarsRegTestUtil.setRv;
@@ -28,10 +29,11 @@
 public class RomAccessTest {
 
     private MarsLauncherHelper.Sh2LaunchContext lc;
+    private static int ROM_SIZE = 0x3100;
 
     @BeforeEach
     public void before() {
-        byte[] rom = new byte[0x1000];
+        byte[] rom = new byte[ROM_SIZE];
         MarsRegTestUtil.fillAsMdRom(rom, true);
         lc = MarsRegTestUtil.createTestInstance(rom);
         lc.s32XMMREG.aden = 1;
@@ -133,6 +135,49 @@ public void testBadAppleSonicAccess() {
     }
 
 
+    @Test
+    public void testRvOn1073Address() {
+        assert assertionsEnabled;
+        int res;
+        int[] addrList = {0x1070, 0x2070, 0x3070};
+        assert addrList[2] + 8 < ROM_SIZE;
+        for (Size size : Size.vals) {
+            for (int addr : addrList) {
+                setRv(lc, 0);
+                res = readBus(lc, M68K, M68K_START_ROM_MIRROR + addr, size);
+                //random values are guaranteed not be 0 or 0xFF
+                Assertions.assertTrue(res != 0 && res != size.getMask(), th(res));
+
+                res = readBus(lc, M68K, M68K_START_ROM_MIRROR_BANK + addr, size);
+                Assertions.assertTrue(res != 0 && res != size.getMask());
+
+                //RV=1, 1070 - 1073 cannot be read correctly, let's assume 0xFF
+                setRv(lc, 1);
+                res = readBus(lc, M68K, addr, size);
+                Assertions.assertTrue(res == size.getMask());
+
+                //106c, 1074 are fine
+                res = readBus(lc, M68K, addr - 4, size);
+                Assertions.assertTrue(res != 0 && res != size.getMask());
+                res = readBus(lc, M68K, addr + 4, size);
+                Assertions.assertTrue(res != 0 && res != size.getMask());
+            }
+        }
+
+        //check 0x70 works ok
+        int addr = 0x70;
+        Size size = Size.WORD;
+        setRv(lc, 0);
+        //hint vector
+        res = readBus(lc, M68K, addr, size);
+        //RV=1, 70 - 73 should be ok
+        setRv(lc, 1);
+        int res2 = readBus(lc, M68K, addr, size);
+        Assertions.assertFalse(res == size.getMask());
+        Assertions.assertEquals(res, res2);
+    }
+
+
     private int readRomToggleRv(CpuDeviceAccess cpu, Sh2Bus sh2Mem, S32xBus mdBus, int addr) {
         int val;
         if (cpu.regSide == BufferUtil.S32xRegSide.SH2) {