0xrsydn/gameboy-rust
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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.
This commit is contained in:
0xrsydn 2026-10-06 02:14:19 +07:00
commit e72c643640
12 changed files with 465 additions and 24 deletions
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10
crates/gba-core/src/dma.rs
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@ -1,6 +1,7 @@
//! Four-channel GBA direct memory access (DMA) controller.
//! Transfers are scheduled one data unit at a time. Startup/resumption delays,
//! open-bus latches, sound FIFO, video capture, and Game Pak DRQ are not modeled.
//! CPU bus handoff, sound FIFO, video capture, and Game Pak DRQ are not modeled.
//! Each channel retains known source data across blocks, including blocked reads.
use std::{error::Error, fmt};
@ -65,6 +66,8 @@ struct Channel {
remaining: u32,
active: bool,
first: bool,
// Unknown at synthetic startup. Enable/disable does not reset retained data.
data_latch: Option<u32>,
}
impl Channel {
@ -111,6 +114,7 @@ pub(crate) struct Transfer {
pub destination: u32,
pub width: AccessWidth,
pub first: bool,
pub data_latch: Option<u32>,
}
impl Dma {
@ -199,6 +203,7 @@ impl Dma {
destination: channel.current_destination,
width: channel.width(),
first: channel.first,
data_latch: channel.data_latch,
}));
}
}
@ -206,8 +211,9 @@ impl Dma {
}
/// Commit one successful data unit after its bus cycles. Return completion IRQ bits.
pub(crate) fn complete_unit(&mut self, index: usize) -> u16 {
pub(crate) fn complete_unit(&mut self, index: usize, data_latch: u32) -> u16 {
let channel = &mut self.channels[index];
channel.data_latch = Some(data_latch);
let width = channel.width().bytes();
// The Game Pak source counter increments regardless of source control.
let source_mode = if (0x08..=0x0d).contains(&(channel.current_source >> 24)) {