From: kub <derkub@gmail.com>
Date: Tue, 7 May 2024 21:11:54 +0000 (+0200)
Subject: core z80, bus blocking for VDP DMA
X-Git-Tag: v2.00~64
X-Git-Url: https://notaz.gp2x.de/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ebde43d;p=picodrive.git

core z80, bus blocking for VDP DMA
---

diff --git a/pico/memory.c b/pico/memory.c
index 0c06acae..eca0ba45 100644
--- a/pico/memory.c
+++ b/pico/memory.c
@@ -565,6 +565,7 @@ void NOINLINE ctl_write_z80reset(u32 d)
         pprof_end_sub(m68k);
       }
       Pico.t.z80_busdelay &= 0xff; // also resets bus request
+      Pico.video.status &= ~PVS_Z80WAIT;
       YM2612ResetChip();
       timers_reset();
     }
@@ -1369,8 +1370,10 @@ void PicoWrite16_32x(u32 a, u32 d) {}
 static void access_68k_bus(int delay) // bus delay as Q8
 {
   // TODO: if the 68K is in DMA wait, Z80 has to wait until DMA ends
-  if (Pico.video.status & (PVS_CPUWR|PVS_CPURD))
+  if (Pico.video.status & (PVS_CPUWR|PVS_CPURD)) {
     z80_subCLeft(z80_cyclesLeft); // rather rough on both condition and action
+    Pico.video.status |= PVS_Z80WAIT;
+  }
 
   // 68k bus access delay for z80. The fractional part needs to be accumulated
   // until an additional cycle is full. That is then added to the integer part.
diff --git a/pico/pico_cmn.c b/pico/pico_cmn.c
index af2e598c..cd037899 100644
--- a/pico/pico_cmn.c
+++ b/pico/pico_cmn.c
@@ -125,6 +125,12 @@ static void do_timing_hacks_start(struct PicoVideo *pv)
   int cycles = PicoVideoFIFOHint();
 
   SekCyclesBurn(cycles); // prolong cpu HOLD if necessary
+  if (pv->status & PVS_Z80WAIT) {
+    Pico.t.z80c_cnt += cycles_68k_to_z80(cycles);
+    if (!(pv->status & (PVS_CPUWR|PVS_CPURD)))
+      pv->status &= ~PVS_Z80WAIT;
+  }
+
   // XXX how to handle Z80 bus cycle stealing during DMA correctly?
   if ((Pico.t.z80_buscycles -= cycles) < 0)
     Pico.t.z80_buscycles = 0;
diff --git a/pico/pico_int.h b/pico/pico_int.h
index 995f8c16..49361f14 100644
--- a/pico/pico_int.h
+++ b/pico/pico_int.h
@@ -299,6 +299,7 @@ extern SH2 sh2s[2];
 #define PVS_DMAFILL   (1 << 20) // DMA fill is waiting for fill data
 #define PVS_DMABG     (1 << 21) // background DMA operation is running
 #define PVS_FIFORUN   (1 << 22) // FIFO is processing
+#define PVS_Z80WAIT   (1 << 23) // Z80 blocked by VDP DMA
 
 struct PicoVideo
 {