From 334f00e24ed55a3e259d1a9d42c4530a770b9a56 Mon Sep 17 00:00:00 2001
From: notaz <notasas@gmail.com>
Date: Wed, 4 Oct 2017 02:58:48 +0300
Subject: [PATCH] vdp timing hacks

---
 pico/pico_cmn.c  | 34 +++++++++++++++++++++++-----------
 pico/videoport.c | 12 +++++-------
 2 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/pico/pico_cmn.c b/pico/pico_cmn.c
index 01d57a72..0907b930 100644
--- a/pico/pico_cmn.c
+++ b/pico/pico_cmn.c
@@ -68,10 +68,28 @@ static void do_hint(struct PicoVideo *pv)
   }
 }
 
+static void do_timing_hacks_as(struct PicoVideo *pv, int vdp_slots)
+{
+  pv->lwrite_cnt += vdp_slots - Pico.m.dma_xfers * 2; // wrong *2
+  if (pv->lwrite_cnt > vdp_slots)
+    pv->lwrite_cnt = vdp_slots;
+  else if (pv->lwrite_cnt < 0)
+    pv->lwrite_cnt = 0;
+  if (Pico.m.dma_xfers)
+    SekCyclesBurn(CheckDMA());
+}
+
+static void do_timing_hacks_vb(void)
+{
+  if (Pico.m.dma_xfers)
+    SekCyclesBurn(CheckDMA());
+}
+
 static int PicoFrameHints(void)
 {
   struct PicoVideo *pv = &Pico.video;
   int line_sample = Pico.m.pal ? 68 : 93;
+  int vdp_slots = (Pico.video.reg[12] & 1) ? 18 : 16;
   int lines, y, lines_vis, skip;
   int vcnt_wrap, vcnt_adj;
   unsigned int cycles;
@@ -112,13 +130,6 @@ static int PicoFrameHints(void)
     if ((y == 224 && !(pv->reg[1] & 8)) || y == 240)
       break;
 
-    // VDP FIFO
-    pv->lwrite_cnt -= 12;
-    if (pv->lwrite_cnt <= 0) {
-      pv->lwrite_cnt = 0;
-      Pico.video.status |= SR_EMPT;
-    }
-
     PAD_DELAY();
 
     // H-Interrupts:
@@ -160,7 +171,7 @@ static int PicoFrameHints(void)
 
     // Run scanline:
     line_base_cycles = SekCyclesDone();
-    if (Pico.m.dma_xfers) SekCyclesBurn(CheckDMA());
+    do_timing_hacks_as(pv, vdp_slots);
     CPUS_RUN(CYCLES_M68K_LINE);
 
     if (PicoLineHook) PicoLineHook();
@@ -202,7 +213,7 @@ static int PicoFrameHints(void)
   // also delay between F bit (bit 7) is set in SR and IRQ happens (Ex-Mutants)
   // also delay between last H-int and V-int (Golden Axe 3)
   line_base_cycles = SekCyclesDone();
-  if (Pico.m.dma_xfers) SekCyclesBurn(CheckDMA());
+  do_timing_hacks_vb();
   CPUS_RUN(CYCLES_M68K_VINT_LAG);
 
   if (pv->reg[1] & 0x20) {
@@ -266,7 +277,7 @@ static int PicoFrameHints(void)
 
     // Run scanline:
     line_base_cycles = SekCyclesDone();
-    if (Pico.m.dma_xfers) SekCyclesBurn(CheckDMA());
+    do_timing_hacks_vb();
     CPUS_RUN(CYCLES_M68K_LINE);
 
     if (PicoLineHook) PicoLineHook();
@@ -278,6 +289,7 @@ static int PicoFrameHints(void)
   // last scanline
   Pico.m.scanline = y;
   pv->v_counter = 0xff;
+  pv->lwrite_cnt = 0;
 
   PAD_DELAY();
 
@@ -289,7 +301,7 @@ static int PicoFrameHints(void)
 
   // Run scanline:
   line_base_cycles = SekCyclesDone();
-  if (Pico.m.dma_xfers) SekCyclesBurn(CheckDMA());
+  do_timing_hacks_as(pv, vdp_slots);
   CPUS_RUN(CYCLES_M68K_LINE);
 
   if (PicoLineHook) PicoLineHook();
diff --git a/pico/videoport.c b/pico/videoport.c
index 1f57f2d4..4da3ce3a 100644
--- a/pico/videoport.c
+++ b/pico/videoport.c
@@ -377,14 +377,12 @@ PICO_INTERNAL_ASM void PicoVideoWrite(unsigned int a,unsigned short d)
     }
 
     // preliminary FIFO emulation for Chaos Engine, The (E)
-    if (!(pvid->status&8) && (pvid->reg[1]&0x40) && !(PicoOpt&POPT_DIS_VDP_FIFO)) // active display?
+    if (!(pvid->status & SR_VB) && (pvid->reg[1] & 0x40) && !(PicoOpt&POPT_DIS_VDP_FIFO)) // active display?
     {
-      pvid->status&=~0x200; // FIFO no longer empty
-      pvid->lwrite_cnt++;
-      if (pvid->lwrite_cnt >= 4) pvid->status|=0x100; // FIFO full
-      if (pvid->lwrite_cnt >  4) {
-        SekCyclesBurnRun(32); // penalty // 488/12-8
-      }
+      int use = pvid->type == 1 ? 2 : 1;
+      pvid->lwrite_cnt -= use;
+      if (pvid->lwrite_cnt < 0)
+        SekCyclesLeft = 0;
       elprintf(EL_ASVDP, "VDP data write: %04x [%06x] {%i} #%i @ %06x", d, Pico.video.addr,
                Pico.video.type, pvid->lwrite_cnt, SekPc);
     }
-- 
2.39.5