cdrom: add a timing hack

notaz/pcsx_rearmed#267

diff --git a/libpcsxcore/cdrom.c b/libpcsxcore/cdrom.c
index 41dc151..12945d6 100644 (file)
--- a/libpcsxcore/cdrom.c
+++ b/libpcsxcore/cdrom.c
@@ -578,6 +578,27 @@ static int cdrSeekTime(unsigned char *target)
        return seekTime;
 }
 
+static u32 cdrAlignTimingHack(u32 cycles)
+{
+       /*
+        * timing hack for T'ai Fu - Wrath of the Tiger:
+        * The game has a bug where it issues some cdc commands from a low priority
+        * vint handler, however there is a higher priority default bios handler
+        * that acks the vint irq and returns, so game's handler is not reached
+        * (see bios irq handler chains at e004 and the game's irq handling func
+        * at 80036810). For the game to work, vint has to arrive after the bios
+        * vint handler rejects some other irq (of which only cd and rcnt2 are
+        * active), but before the game's handler loop reads I_STAT. The time
+        * window for this is quite small (~1k cycles of so). Apparently this
+        * somehow happens naturally on the real hardware.
+        */
+       u32 vint_rel = rcnts[3].cycleStart + 63000 - psxRegs.cycle;
+       vint_rel += PSXCLK / 60;
+       while ((s32)(vint_rel - cycles) < 0)
+               vint_rel += PSXCLK / 60;
+       return vint_rel;
+}
+
 static void cdrUpdateTransferBuf(const u8 *buf);
 static void cdrReadInterrupt(void);
 static void cdrPrepCdda(s16 *buf, int samples);
@@ -637,7 +658,7 @@ void cdrPlayReadInterrupt(void)
 void cdrInterrupt(void) {
        int start_rotating = 0;
        int error = 0;
-       unsigned int seekTime = 0;
+       u32 cycles, seekTime = 0;
        u32 second_resp_time = 0;
        const void *buf;
        u8 ParamC;
@@ -1116,7 +1137,10 @@ void cdrInterrupt(void) {
                        ReadTrack(cdr.SetSectorPlay);
                        cdr.LocL[0] = LOCL_INVALID;
 
-                       CDRPLAYREAD_INT(((cdr.Mode & 0x80) ? (cdReadTime) : cdReadTime * 2) + seekTime, 1);
+                       cycles = (cdr.Mode & 0x80) ? cdReadTime : cdReadTime * 2;
+                       cycles += seekTime;
+                       cycles = cdrAlignTimingHack(cycles);
+                       CDRPLAYREAD_INT(cycles, 1);
 
                        SetPlaySeekRead(cdr.StatP, STATUS_SEEK);
                        start_rotating = 1;