From 3397941b609cef77086c3225121396e74ce444c2 Mon Sep 17 00:00:00 2001
From: ekeeke <ekeeke31@gmail.com>
Date: Mon, 19 Feb 2024 20:27:54 +0100
Subject: [PATCH] [Core/CD] fixed regression in SUB-CPU synchronization with
 CDC DMA introduced by
 https://github.com/ekeeke/Genesis-Plus-GX/commit/da8e4e547affcbd295d2e3028735b3283ec2c462
 (fixes freezes in Ultraverse Prime and probably other games)

---
 core/cd_hw/cdc.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/core/cd_hw/cdc.c b/core/cd_hw/cdc.c
index 4936233..fb30e53 100644
--- a/core/cd_hw/cdc.c
+++ b/core/cd_hw/cdc.c
@@ -444,8 +444,11 @@ void cdc_dma_update(unsigned int cycles)
     /* SUB-CPU idle on register $04 polling ? */
     if (s68k.stopped & (1<<0x04))
     {
-      /* sync SUB-CPU with CDC DMA */
-      s68k.cycles = cdc.cycles[0];
+      /* sync SUB-CPU with CDC DMA (only if not already ahead) */
+      if (s68k.cycles < cdc.cycles[0])
+      {
+        s68k.cycles = cdc.cycles[0];
+      }
 
       /* restart SUB-CPU */
       s68k.stopped = 0;