CDROM: Improve accuracy of sector redelivery on DMA complete

Fixes hang in loading in Syphon Filter 2/3.

src/core/cdrom.cpp

@@ -3381,17 +3381,20 @@ void CDROM::CheckForSectorBufferReadComplete()
  {
  sb.position = 0;
  sb.size = 0;
+ }
 
- // Redeliver missed sector on DMA/read complete.
- // I'm still not sure if this is correct behavior.
- SectorBuffer& next_sb = s_sector_buffers[s_current_write_sector_buffer];
- if (next_sb.position == 0 && next_sb.size > 0)
- {
- DEV_LOG("Sending additional INT1 for missed sector in buffer {}", s_current_write_sector_buffer);
- s_current_read_sector_buffer = s_current_write_sector_buffer;
- s_async_response_fifo.Push(s_secondary_status.bits);
- SetAsyncInterrupt(Interrupt::DataReady);
- }
+ // Redeliver missed sector on DMA/read complete.
+ // This would be the main loop checking when the DMA is complete, if there's another sector pending.
+ // Normally, this would happen some time after the DMA actually completes, so we need to put it on a delay.
+ // Otherwise, if games read the header then data out as two separate transfers (which is typical), they'll
+ // get the header for one sector, and the header for the next in the second transfer.
+ SectorBuffer& next_sb = s_sector_buffers[s_current_write_sector_buffer];
+ if (next_sb.position == 0 && next_sb.size > 0 && !HasPendingAsyncInterrupt())
+ {
+ DEV_LOG("Sending additional INT1 for missed sector in buffer {}", s_current_write_sector_buffer);
+ s_async_response_fifo.Push(s_secondary_status.bits);
+ s_pending_async_interrupt = static_cast<u8>(Interrupt::DataReady);
+ s_async_interrupt_event->Schedule(INTERRUPT_DELAY_CYCLES);
  }
 }