From: kub <derkub@gmail.com>
Date: Thu, 22 Jun 2023 22:16:47 +0000 (+0002)
Subject: sound, improve ym2612 timers implementation
X-Git-Tag: v2.00~199
X-Git-Url: https://notaz.gp2x.de/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c3d70d1305cdbc6b8c16c63c24efa065c30d9c4f;p=picodrive.git

sound, improve ym2612 timers implementation
---

diff --git a/pico/debug.c b/pico/debug.c
index e8810894..e928d73b 100644
--- a/pico/debug.c
+++ b/pico/debug.c
@@ -406,7 +406,7 @@ void PDebugZ80Frame(void)
   if (PicoIn.sndOut)
     PsndGetSamples(lines);
 
-  timers_cycle();
+  timers_cycle(Pico.t.z80c_aim);
   Pico.t.m68c_aim = Pico.t.m68c_cnt;
 }
 
diff --git a/pico/memory.c b/pico/memory.c
index 3267a16a..a9398b8e 100644
--- a/pico/memory.c
+++ b/pico/memory.c
@@ -1136,31 +1136,26 @@ static int ym2612_write_local(u32 a, u32 d, int is_from_z80)
                                      : ((ym2612.OPN.ST.TA & 0x3fc)|(d&3));
           if (ym2612.OPN.ST.TA != TAnew)
           {
+            int cycles = is_from_z80 ? z80_cyclesDone() : z80_cycles_from_68k();
+            ym2612_sync_timers(cycles, ym2612.OPN.ST.mode, ym2612.OPN.ST.mode);
             //elprintf(EL_STATUS, "timer a set %i", TAnew);
             ym2612.OPN.ST.TA = TAnew;
             //ym2612.OPN.ST.TAC = (1024-TAnew)*18;
             //ym2612.OPN.ST.TAT = 0;
             Pico.t.timer_a_step = TIMER_A_TICK_ZCYCLES * (1024 - TAnew);
-            if (ym2612.OPN.ST.mode & 1) {
-              // this is not right, should really be done on overflow only
-              int cycles = is_from_z80 ? z80_cyclesDone() : z80_cycles_from_68k();
-              Pico.t.timer_a_next_oflow = (cycles << 8) + Pico.t.timer_a_step;
-            }
             elprintf(EL_YMTIMER, "timer a set to %i, %i", 1024 - TAnew, Pico.t.timer_a_next_oflow>>8);
           }
           return 0;
         }
         case 0x26: // timer B
           if (ym2612.OPN.ST.TB != d) {
+            int cycles = is_from_z80 ? z80_cyclesDone() : z80_cycles_from_68k();
+            ym2612_sync_timers(cycles, ym2612.OPN.ST.mode, ym2612.OPN.ST.mode);
             //elprintf(EL_STATUS, "timer b set %i", d);
             ym2612.OPN.ST.TB = d;
             //ym2612.OPN.ST.TBC = (256-d) * 288;
             //ym2612.OPN.ST.TBT  = 0;
             Pico.t.timer_b_step = TIMER_B_TICK_ZCYCLES * (256 - d); // 262800
-            if (ym2612.OPN.ST.mode & 2) {
-              int cycles = is_from_z80 ? z80_cyclesDone() : z80_cycles_from_68k();
-              Pico.t.timer_b_next_oflow = (cycles << 8) + Pico.t.timer_b_step;
-            }
             elprintf(EL_YMTIMER, "timer b set to %i, %i", 256 - d, Pico.t.timer_b_next_oflow>>8);
           }
           return 0;
diff --git a/pico/pico_cmn.c b/pico/pico_cmn.c
index 2be1c47e..2f1747fe 100644
--- a/pico/pico_cmn.c
+++ b/pico/pico_cmn.c
@@ -345,7 +345,7 @@ static int PicoFrameHints(void)
   // get samples from sound chips
   PsndGetSamples(y);
 
-  timers_cycle();
+  timers_cycle(Pico.t.z80c_aim);
 
   pv->hint_cnt = hint;
 
diff --git a/pico/pico_int.h b/pico/pico_int.h
index 055f5ee9..d8b7160b 100644
--- a/pico/pico_int.h
+++ b/pico/pico_int.h
@@ -872,16 +872,18 @@ void ym2612_pack_state(void);
 void ym2612_unpack_state(void);
 
 #define TIMER_NO_OFLOW 0x70000000
-// tA =   72 * (1024 - NA) / M, with M = mclock/2 -> tick = 72 * 2/mclock
-#define TIMER_A_TICK_ZCYCLES  17203 // zcycles = Q8*tick*zclock = Q8*77*2*7/15
-// tB = 1152 * (256 - NA) / M,
-#define TIMER_B_TICK_ZCYCLES 275251 // zcycles = Q8*1152*2*7/15
 
-#define timers_cycle() \
+// NB ~0.2% timers speed up (1/8(A), 2(B) z80 cycles), HACK for A/V sync in OD2
+// tA =    72 * (1024 - TA) / M, with M = mclock/2
+#define TIMER_A_TICK_ZCYCLES (cycles_68k_to_z80(256LL*   72*2)-32) // Q8
+// tB = 16*72 * ( 256 - TB) / M
+#define TIMER_B_TICK_ZCYCLES (cycles_68k_to_z80(256LL*16*72*2)-32*16) // Q8
+
+#define timers_cycle(ticks) \
   if (Pico.t.timer_a_next_oflow > 0 && Pico.t.timer_a_next_oflow < TIMER_NO_OFLOW) \
-    Pico.t.timer_a_next_oflow -= Pico.m.pal ? 70938*256 : 59659*256; \
+    Pico.t.timer_a_next_oflow -= ticks << 8; \
   if (Pico.t.timer_b_next_oflow > 0 && Pico.t.timer_b_next_oflow < TIMER_NO_OFLOW) \
-    Pico.t.timer_b_next_oflow -= Pico.m.pal ? 70938*256 : 59659*256; \
+    Pico.t.timer_b_next_oflow -= ticks << 8; \
   ym2612_sync_timers(0, ym2612.OPN.ST.mode, ym2612.OPN.ST.mode);
 
 #define timers_reset() \