Implement broken copper dma request (even to even cycle)

diff --git a/custom.cpp b/custom.cpp
index 640a551edc692c6626378e51a0b618a80cf68034..405586342bbcf53250ab995697e0d8953c65cc38 100644 (file)
--- a/custom.cpp
+++ b/custom.cpp
@@ -746,6 +746,7 @@ struct copper {
        bool blitwait;
        bool cycle_alloc;
        bool validmove;
+       uaecptr dummyip;
 };
 
 static struct copper cop_state;
@@ -8917,16 +8918,30 @@ static uae_u64 fetch64(struct rgabuf *r)
 
 static void process_copper(struct rgabuf *r)
 {
+       uaecptr ip = cop_state.ip;
+       bool brokencycle = false;
+
 #ifdef DEBUGGER
        uae_u16 reg = r->reg;
+#endif
+
+       if (r->alloc == -2 || r->alloc == 2) {
+               ip = 0;
+               brokencycle = true;
+#ifdef DEBUGGER
+               reg = 0x1fe;
+#endif
+       }
+
+#ifdef DEBUGGER
        if (debug_dma) {
                if (memwatch_enabled) {
-                       debug_getpeekdma_chipram(cop_state.ip, MW_MASK_COPPER, reg);
+                       debug_getpeekdma_chipram(ip, MW_MASK_COPPER, reg);
                }
        }
 #endif
 
-       uae_u16 data = chipmem_wget_indirect(cop_state.ip);
+       uae_u16 data = chipmem_wget_indirect(ip);
 
 #ifdef DEBUGGER
        if (debug_dma) {
@@ -8943,7 +8958,10 @@ static void process_copper(struct rgabuf *r)
                if (cop_state.strobe & 3) {
                        m = 6;
                }
-               record_dma_read(reg, cop_state.ip, DMARECORD_COPPER, m);
+               if (brokencycle) {
+                       m = 7;
+               }
+               record_dma_read(reg, ip, DMARECORD_COPPER, m);
        }
        if (debug_dma) {
                record_dma_read_value(data);
@@ -8953,6 +8971,10 @@ static void process_copper(struct rgabuf *r)
        }
 #endif
 
+       if (brokencycle) {
+               return;
+       }
+
        if (cop_state.load2) {
                cop_state.ir[1] = data;
                cop_state.load2 = false;
@@ -9012,7 +9034,7 @@ static void process_copper(struct rgabuf *r)
 
 }
 
-static void alloc_copper_cycle(void)
+static struct rgabuf *alloc_copper_cycle(void)
 {
        struct rgabuf *rga = write_rga(RGA_SLOT_IN, CYCLE_COPPER, 0x8c, &cop_state.ip);
        if (!cop_state.cycle_alloc) {
@@ -9020,6 +9042,19 @@ static void alloc_copper_cycle(void)
                // mark copper allocated cycle as not actually allocated. Conflict possible!
                rga->alloc = -1;
        }
+       return rga;
+}
+// Address zero broken dma copper request
+static struct rgabuf *alloc_copper_cycle_dummy(void)
+{
+       cop_state.dummyip = 0;
+       struct rgabuf *rga = write_rga(RGA_SLOT_IN, CYCLE_COPPER, 0x8c, &cop_state.dummyip);
+       if (!cop_state.cycle_alloc) {
+               rga->alloc = -2;
+       } else {
+               rga->alloc = 2;
+       }
+       return rga;
 }
 
 static void generate_copper(void)
@@ -9029,7 +9064,7 @@ static void generate_copper(void)
        bool ena_odd = !bus_allocated && (agnus_hpos & 1) == COPPER_CYCLE_POLARITY && dma;
        bool act_even = (agnus_hpos & 1) != COPPER_CYCLE_POLARITY && dma;
        bool idle = !cop_state.irload1 && !cop_state.irload2 && !cop_state.start;
-       bool allocated = false;
+       struct rgabuf *rga = NULL;
 
        if (ena_odd) {
 
@@ -9078,27 +9113,24 @@ static void generate_copper(void)
 
                        // If MOVE: IR1 state
                        if (cop_state.validmove && !cop_state.irload1) {
-                               alloc_copper_cycle();
+                               rga = alloc_copper_cycle();
                                cop_state.load1 = true;
-                               allocated = true;
                                cop_state.irload1 = 1;
                        }
                }
 
                if (cop_state.irload1 == 2) {
-                       alloc_copper_cycle();
+                       rga = alloc_copper_cycle();
                        cop_state.load2 = true;
-                       allocated = true;
                        cop_state.irload1 = 0;
                        cop_state.irload2 = 1;
                        cop_state.validmove = cop_state.inst == COP_INS_MOVE && !test_copper_dangerous(cop_state.ir[0], true);
                }
 
                if (cop_state.start == 2) {
-                       alloc_copper_cycle();
+                       rga = alloc_copper_cycle();
                        cop_state.strobe = 0;
                        cop_state.load1 = true;
-                       allocated = true;
                        cop_state.start = 0;
                        cop_state.irload1 = 1;
 
@@ -9116,11 +9148,27 @@ static void generate_copper(void)
                                }
                        }
 #endif
-
                }
 
        }
 
+       // Copper bug: even to even line horizontal position condition (PAL 226 to 0, VHPOSW tricks)
+       // triggers condition that enables copper DMA request output (if activated previously)
+       // This DMA request is not fully working and does not select copper pointer
+       // causing it to do DMA from address 0.
+       // I assume it happens because there is very short even->odd transition in
+       // horizontal counter bit 0 before new even value is loaded.
+       if (!(agnus_hpos & 1) && !(agnus_hpos_prev & 1)) {
+               if (!rga) {
+                       if (cop_state.irload1 == 1 || cop_state.start == 1) {
+                               rga = alloc_copper_cycle_dummy();
+                       }
+                       if (cop_state.irload2 == 1 && cop_state.validmove && !cop_state.irload1) {
+                               rga = alloc_copper_cycle_dummy();
+                       }
+               }
+       }
+
        if (cop_state.startstrobe) {
                // Copper state machine restart after COPxJMP strobe
                if (cop_state.startstrobe & 8) {
@@ -9140,8 +9188,8 @@ static void generate_copper(void)
        if (cop_state.strobe) {
                // Initial DMA request after COPxJMP strobe
                if (ena_odd) {
-                       if (!allocated) {
-                               alloc_copper_cycle();
+                       if (!rga) {
+                               rga = alloc_copper_cycle();
                        }
                        cop_state.start = 1;
                }