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feat(dma): retain per-channel transfer data

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Retain independent known data across DMA blocks. Duplicate mapped halfword sources and select the destination lane for blocked sources below work RAM. Keep cold history diagnostic, commit only successful units, and preserve separate CPU/BIOS history rules.

Add 13 original regressions and pinned source research. CPU resume ownership, general DMA open bus, and IWRAM DMA lane effects remain explicit limits.

Validated on Darwin arm64: 930 workspace and 861 core/demo tests in debug and release, 39 Python tests, native ROM windows, ten window smoke modes, fmt, clippy, and rustdoc. Public ARM/Thumb/memory/BIOS reports match the previous results exactly.
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0xrsydn 2026-10-06 02:14:19 +07:00
commit e72c643640
12 changed files with 465 additions and 24 deletions
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docs/testing.md
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@ -204,6 +204,9 @@ They distinguish wake-up from IF latching and test stale requests, interrupt mas
ARM/Thumb BIOS Stop tests verify caller preservation. Frame-runner tests check prompt stopped results and unchanged output images.
The graphics test verifies BIOS VBlank waiting, one IRQ callback per update, and status restoration before each redraw.
DMA tests cover both widths, all supported address modes, count limits, register masks, enable latches, and repeated transfers.
Original channel-data tests cover word retention, halfword duplication, blocked-source destination lanes, and channel isolation.
They check cold/zero history, cancel/re-enable, source-counter crossings, repeats, priority, failed-unit rollback, and BIOS snapshot isolation.
These tests do not establish general DMA open-bus reads or DMA-to-CPU handoff. See [the research scope](research/dma-data-latches.md).
Tests verify channel priority/preemption, CPU pausing, display/timer progress, IRQ acknowledgement/return, and WAITCNT costs.
Diagnostic tests check failed-unit isolation, retained earlier transfers, unsupported modes, and CPU block-store atomicity.
Graphics startup tests verify that DMA3, not CPU stores or host writes, fills every background pixel.