G2 bus memory interface. More...

#include <sys/cdefs.h>
#include <stdint.h>
#include <arch/irq.h>
#include <arch/types.h>
#include <dc/fifo.h>

Data Structures
struct	g2_ctx_t
	G2 context. More...

Macros
#define	G2_DMA_TO_G2 0
	G2Bus DMA direction.

#define	G2_DMA_TO_SH4 1

List of G2 Bus channels
AICA (SPU) is channel 0, BBA uses channel 1. CH2_DMA_G2CHN and CH3_DMA_G2CHN are not currently tied to any specific device. Note A change in the implementation has rendered _DMA_MODE and _DMA_SHCHN obsolete. In the current implementation, _DMA_MODE should always be set to zero (representing CPU_TRIGGER). There is also no involvement of SH4-DMA with G2-DMA; therefore, the _DMA_SHCHN values have been deprecated.
#define	G2_DMA_CHAN_SPU 0
	AICA: G2 channel 0.

#define	G2_DMA_CHAN_BBA 1
	BBA: G2 channel 1.

#define	G2_DMA_CHAN_CH2 2
	CH2: G2 channel 2.

#define	G2_DMA_CHAN_CH3 3
	CH3: G2 channel 3.

Typedefs
typedef void(*	g2_dma_callback_t) (void *data)
	G2Bus DMA interrupt callback type.

Functions
int	g2_dma_transfer (void sh4, void g2bus, size_t length, uint32_t block, g2_dma_callback_t callback, void *cbdata, uint32_t dir, uint32_t mode, uint32_t g2chn, uint32_t sh4chn)
	Perform a DMA transfer between SH-4 RAM and G2 Bus.

int	g2_dma_init (void)
	Initialize DMA support.

void	g2_dma_shutdown (void)
	Shutdown DMA support.

static g2_ctx_t	g2_lock (void)
	Disable IRQs and G2 DMA.

static void	g2_unlock (g2_ctx_t ctx)
	Enable IRQs and G2 DMA.

uint8_t	g2_read_8 (uintptr_t address)
	Read one byte from G2.

void	g2_write_8 (uintptr_t address, uint8_t value)
	Write a single byte to G2.

uint16	g2_read_16 (uintptr_t address)
	Read one 16-bit word from G2.

void	g2_write_16 (uintptr_t address, uint16_t value)
	Write a 16-bit word to G2.

uint32_t	g2_read_32 (uintptr_t address)
	Read one 32-bit dword from G2.

void	g2_write_32 (uintptr_t address, uint32_t value)
	Write a 32-bit dword to G2.

void	g2_read_block_8 (uint8_t *output, uintptr_t address, size_t amt)
	Read a block of bytes from G2.

void	g2_write_block_8 (const uint8_t *input, uintptr_t address, size_t amt)
	Write a block of bytes to G2.

void	g2_read_block_16 (uint16_t *output, uintptr_t address, size_t amt)
	Read a block of words from G2.

void	g2_write_block_16 (const uint16_t *input, uintptr_t address, size_t amt)
	Write a block of words to G2.

void	g2_read_block_32 (uint32_t *output, uintptr_t address, size_t amt)
	Read a block of dwords from G2.

void	g2_write_block_32 (const uint32_t *input, uintptr_t address, size_t amt)
	Write a block of dwords to G2.

void	g2_memset_8 (uintptr_t address, uint8_t c, size_t amt)
	Set a block of bytes to G2.

void	g2_fifo_wait (void)
	Wait for the G2 write FIFO to empty.

Detailed Description

G2 bus memory interface.

This file provides low-level support for accessing devices on the G2 bus in the Dreamcast. The G2 bus contains the AICA, as well as the expansion port. Generally, you won't be dealing with things at this level, but rather on the level of the device you're actually interested in working with. Most of the expansion port devices (the modem, bba, and lan adapter) all have their own drivers that work off of this functionality.

The G2 bus is notoroiously picky about a lot of things. You have to be careful to use the right access size for whatever you're working with. Also you can't be doing PIO and DMA at the same time. Finally, there's a FIFO to contend with when you're doing PIO stuff as well. Generally, G2 is a pain in the rear, so you really do want to be using the higher-level stuff related to each device if at all possible!

Author: Megan Potter; Andy Barajas

Data Structures

Macros

Typedefs

Functions

Detailed Description