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librecomp: auto-increment RSP DMA addresses after each transfer

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Real RSP DMA hardware advances SP_MEM_ADDR and SP_DRAM_ADDR by
(length + 1) after each transfer (verified against Ares' n64/rsp/dma.cpp:
pbusAddress += 8 / dramAddress += 8 per 8-byte chunk). The runtime's
DO_DMA_READ / DO_DMA_WRITE macros didn't replicate this, so any ucode
that fires DMAs in a loop without re-writing SP_MEM_ADDR/SP_DRAM_ADDR
each iteration would reload the same DMEM region forever.

Observed as Pokemon Stadium's aspMain hanging in its dispatch loop:
the L_10EC <-> L_11B4 DMA pump (which walks through the audio command
stream chunk by chunk on real hardware) collapsed into a tight
no-progress cycle. With the auto-increment in place the dispatch
makes forward progress and aspMain advances past the hang point. (A
downstream UnhandledJumpTarget then surfaces — a separate issue with
the recompiler's static indirect-branch-target list, not this layer.)

Diff verified via diff_aspmain.py against the standalone Ares oracle.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Matthew Stanley 2026-04-27 17:39:41 -07:00
parent 0bb76b0fc7
commit 948df06a75
1 changed files with 21 additions and 2 deletions
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23
librecomp/include/librecomp/rsp.hpp
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@ -91,8 +91,27 @@ static inline void RSP_MEM_H_STORE(uint32_t offset, uint32_t addr, uint32_t val)
#define SET_DMA_MEM(mem_addr) dma_mem_address = (mem_addr)
#define SET_DMA_DRAM(dram_addr) dma_dram_address = (dram_addr)
#define DO_DMA_READ(rd_len) dma_rdram_to_dmem(rdram, dma_mem_address, dma_dram_address, (rd_len))
#define DO_DMA_WRITE(wr_len) dma_dmem_to_rdram(rdram, dma_mem_address, dma_dram_address, (wr_len))
// Real RSP DMA hardware auto-increments SP_MEM_ADDR and SP_DRAM_ADDR
// by (length + 1) after each transfer. Tight loops like aspMain's
// L_10EC <-> L_11B4 DMA pump (and any other ucode that fires DMAs in a
// loop without re-writing SP_MEM_ADDR / SP_DRAM_ADDR each iteration)
// rely on this to walk through the audio command stream chunk by
// chunk. Without the increment the same DMEM region gets reloaded
// forever — observed as Stadium's aspMain hanging in the dispatch
// loop on a never-advancing command word. Verified against Ares'
// rsp/dma.cpp (pbusAddress += 8 / dramAddress += 8 per 8-byte chunk).
#define DO_DMA_READ(rd_len) do { \
uint32_t _rsp_dma_inc = (uint32_t)(rd_len) + 1; \
dma_rdram_to_dmem(rdram, dma_mem_address, dma_dram_address, (rd_len)); \
dma_mem_address += _rsp_dma_inc; \
dma_dram_address += _rsp_dma_inc; \
} while (0)
#define DO_DMA_WRITE(wr_len) do { \
uint32_t _rsp_dma_inc = (uint32_t)(wr_len) + 1; \
dma_dmem_to_rdram(rdram, dma_mem_address, dma_dram_address, (wr_len)); \
dma_mem_address += _rsp_dma_inc; \
dma_dram_address += _rsp_dma_inc; \
} while (0)
static inline void dma_rdram_to_dmem(uint8_t* rdram, uint32_t dmem_addr, uint32_t dram_addr, uint32_t rd_len) {
rd_len += 1; // Read length is inclusive