Corelink DMA Engines

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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: ???, bit6: DST_ALT_CFG, bit7: SRC_ALT_CFG
    uint8_t padding;
    DmaSubConfig dst_cfg;
    DmaSubConfig src_cfg;
}
struct DmaSubConfig {
    uint8_t peripheral_id; // @0
    uint8_t unk2; // @1 Accepted values: 4, 8, 12, 15
    uint16_t unk3; // @2
    uint16_t transfer_size?; // @4
    uint16_t unk4; // @6
    uint16_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...

ARM11 Peripheral IDs

ID Module Description
0x2 camera (cam) ?
0x3 camera (cam) ?
0x6 camera (y2r) SetSendingY
0x7 camera (y2r) SetSendingU
0x8 camera (y2r) SetSendingV
0x9 camera (y2r) SetSendingYUYV
0xA camera (y2r) SetReceiving
0xE TwlBg LGYFB0/1
0xD TwlBg LGYFB0/1