Corelink DMA Engines

XDMA cannot access the ARM9 bootrom at all.

DmaConfig

Size of struct is 24 bytes.

struct DmaConfig {
    sint8_t channel_sel; // @0 Selects which DMA channel to use: 0-7, -1 = don't care.
    uint8_t endian_swap_size; // @1 Accepted values: 0=none, 2=16bit, 4=32bit, 8=64bit.
    uint8_t flags; // @2 bit0: DST_CFG, bit1: SRC_CFG, bit2: SHALL_BLOCK, bit3: KEEP_ALIVE, bit6: DST_ALT_CFG, bit7: SRC_ALT_CFG
    uint8_t padding;
    DmaSubConfig dst_cfg;
    DmaSubConfig src_cfg;
}

struct DmaSubConfig {
    sint8_t peripheral_id; // @0 If not *_ALT_CFG set, this must be < 0x1E.
    uint8_t burst_size_raw; // (1 << raw size) bytes, bit4 is ignored? // @1 Accepted values: 4=fixed_addr??, 8=increment_addr??, 12=lgy_fb_copy?, 15=userspace_copy? (??)
    sint16_t max_burst_size_bits; // @2 Must be 0 or multiple of 4?
    sint16_t transfer_size?; // @4 Must not be 0 if peripheral_id == 0xFF.
    sint16_t unk4; // @6
    sint16_t transfer_stride?; // @8
}

If SRC_CFG/DST_CFG is set in the flags field, the configuration for src/dst is loaded from src_cfg/dst_cfg respectively. If the *_ALT_CFG flag is set same thing goes, except byte0 of each cfg is forced to 0xFF. ALT_CFG has priority over CFG.

If CFG or ALT_CFG is not set, default configuration is loaded:

.peripheral_id = 0xFF,
.unk2 = 0xF,
.unk3 = 0x80,
.transfer_size = 0,
.unk4 = 0x80,
.unk5 = 0,

Checks suggest that unk2 of DmaSubConfig equalling 4 means NO_INCREMENT (don't increment after read/write).

If SHALL_BLOCK is set, the thread will sleep until the DMA engine is ready. If not set, the SVC will return 0xD04007F0 if the DMA channel is busy.

The generated bytecode starts with a FLUSHP on the peripheral_ids for src/dst (if specified). After that, it always moves 0 into DAR. Then it moves the src/dst addresses into SAR/DAR respectively...

CDMA Peripheral IDs

ID	Module	Description
0x2	camera (cam)	Camera Port 1
0x3	camera (cam)	Camera Port 2
0x4	nwm	?
0x5	nwm	?
0x6	camera (y2r)	SetSendingY
0x7	camera (y2r)	SetSendingU
0x8	camera (y2r)	SetSendingV
0x9	camera (y2r)	SetSendingYUYV
0xA	camera (y2r)	SetReceiving
0xB	fs	HASH
0xD	TwlBg	LGYFB0/1
0xE	TwlBg	LGYFB0/1
0x12	mvd	?
0x13	mvd	?
0x14	mvd	?
0x15	mvd	?
0x16	mvd	?
0x17	mvd	?
0x18	mvd	?
0x19	mvd	?
0x1A	mvd	?

XDMA Peripheral IDs

ID	Module	Description
7	Process9	SHA