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CDROM: Handle BFRD clears inbetween DMA transfers

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Fixes disc detection in Metal Gear Solid: Special Missions.
This commit is contained in:
Stenzek 2024-07-19 15:31:50 +10:00
parent f0945ca3ca
commit 6a920b268e
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1 changed files with 15 additions and 4 deletions
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19
src/core/cdrom.cpp
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@ -1006,10 +1006,21 @@ void CDROM::WriteRegister(u32 offset, u8 value)
s_request_register.bits = rr.bits;
if (s_request_register.BFRD)
SectorBuffer& sb = s_sector_buffers[s_current_read_sector_buffer];
DEBUG_LOG("{} BFRD buffer={} pos={} size={}", s_request_register.BFRD ? "Set" : "Clear",
s_current_read_sector_buffer, sb.position, sb.size);
if (!s_request_register.BFRD)
{
const SectorBuffer& sb = s_sector_buffers[s_current_read_sector_buffer];
DEV_LOG("BFRD buffer={} pos={} size={}", s_current_read_sector_buffer, sb.position, sb.size);
// Clearing BFRD needs to reset the position of the current buffer.
// Metal Gear Solid: Special Missions (PAL) clears BFRD inbetween two DMAs during its disc detection, and needs
// the buffer to reset. But during the actual game, it doesn't clear, and needs the pointer to increment.
sb.position = 0;
}
else
{
if (sb.size == 0)
WARNING_LOG("Setting BFRD without a buffer ready.");
}
UpdateStatusRegister();
@ -2991,7 +3002,7 @@ ALWAYS_INLINE_RELEASE void CDROM::ProcessDataSector(const u8* raw_sector, const
// TODO: How does XA relate to this buffering?
SectorBuffer* sb = &s_sector_buffers[sb_num];
if (sb->position == 0 && sb->size == 0)
if (sb->position == 0 && sb->size > 0)
{
DEV_LOG("Sector buffer {} was not read, previous sector dropped",
(s_current_write_sector_buffer - 1) % NUM_SECTOR_BUFFERS);