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/*
* Bit-Bang i2c emulation extracted from
* Marvell MV88W8618 / Freecom MusicPal emulation.
*
* Copyright (c) 2008 Jan Kiszka
*
* This code is licensed under the GNU GPL v2.
*/
#include "hw.h"
#include "bitbang_i2c.h"
#include "sysbus.h"
//#define DEBUG_BITBANG_I2C
#ifdef DEBUG_BITBANG_I2C
#define DPRINTF(fmt, ...) \
do { printf("bitbang_i2c: " fmt , ## __VA_ARGS__); } while (0)
#else
#define DPRINTF(fmt, ...) do {} while(0)
#endif
typedef enum bitbang_i2c_state {
STOPPED = 0,
SENDING_BIT7,
SENDING_BIT6,
SENDING_BIT5,
SENDING_BIT4,
SENDING_BIT3,
SENDING_BIT2,
SENDING_BIT1,
SENDING_BIT0,
WAITING_FOR_ACK,
RECEIVING_BIT7,
RECEIVING_BIT6,
RECEIVING_BIT5,
RECEIVING_BIT4,
RECEIVING_BIT3,
RECEIVING_BIT2,
RECEIVING_BIT1,
RECEIVING_BIT0,
SENDING_ACK,
SENT_NACK
} bitbang_i2c_state;
struct bitbang_i2c_interface {
i2c_bus *bus;
bitbang_i2c_state state;
int last_data;
int last_clock;
int device_out;
uint8_t buffer;
int current_addr;
};
static void bitbang_i2c_enter_stop(bitbang_i2c_interface *i2c)
{
DPRINTF("STOP\n");
if (i2c->current_addr >= 0)
i2c_end_transfer(i2c->bus);
i2c->current_addr = -1;
i2c->state = STOPPED;
}
/* Set device data pin. */
static int bitbang_i2c_ret(bitbang_i2c_interface *i2c, int level)
{
i2c->device_out = level;
//DPRINTF("%d %d %d\n", i2c->last_clock, i2c->last_data, i2c->device_out);
return level & i2c->last_data;
}
/* Leave device data pin unodified. */
static int bitbang_i2c_nop(bitbang_i2c_interface *i2c)
{
return bitbang_i2c_ret(i2c, i2c->device_out);
}
/* Returns data line level. */
int bitbang_i2c_set(bitbang_i2c_interface *i2c, int line, int level)
{
int data;
if (level != 0 && level != 1) {
abort();
}
if (line == BITBANG_I2C_SDA) {
if (level == i2c->last_data) {
return bitbang_i2c_nop(i2c);
}
i2c->last_data = level;
if (i2c->last_clock == 0) {
return bitbang_i2c_nop(i2c);
}
if (level == 0) {
DPRINTF("START\n");
/* START condition. */
i2c->state = SENDING_BIT7;
i2c->current_addr = -1;
} else {
/* STOP condition. */
bitbang_i2c_enter_stop(i2c);
}
return bitbang_i2c_ret(i2c, 1);
}
data = i2c->last_data;
if (i2c->last_clock == level) {
return bitbang_i2c_nop(i2c);
}
i2c->last_clock = level;
if (level == 0) {
/* State is set/read at the start of the clock pulse.
release the data line at the end. */
return bitbang_i2c_ret(i2c, 1);
}
switch (i2c->state) {
case STOPPED:
case SENT_NACK:
return bitbang_i2c_ret(i2c, 1);
case SENDING_BIT7 ... SENDING_BIT0:
i2c->buffer = (i2c->buffer << 1) | data;
/* will end up in WAITING_FOR_ACK */
i2c->state++;
return bitbang_i2c_ret(i2c, 1);
case WAITING_FOR_ACK:
if (i2c->current_addr < 0) {
i2c->current_addr = i2c->buffer;
DPRINTF("Address 0x%02x\n", i2c->current_addr);
i2c_start_transfer(i2c->bus, i2c->current_addr >> 1,
i2c->current_addr & 1);
} else {
DPRINTF("Sent 0x%02x\n", i2c->buffer);
i2c_send(i2c->bus, i2c->buffer);
}
if (i2c->current_addr & 1) {
i2c->state = RECEIVING_BIT7;
} else {
i2c->state = SENDING_BIT7;
}
return bitbang_i2c_ret(i2c, 0);
case RECEIVING_BIT7:
i2c->buffer = i2c_recv(i2c->bus);
DPRINTF("RX byte 0x%02x\n", i2c->buffer);
/* Fall through... */
case RECEIVING_BIT6 ... RECEIVING_BIT0:
data = i2c->buffer >> 7;
/* will end up in SENDING_ACK */
i2c->state++;
i2c->buffer <<= 1;
return bitbang_i2c_ret(i2c, data);
case SENDING_ACK:
i2c->state = RECEIVING_BIT7;
if (data != 0) {
DPRINTF("NACKED\n");
i2c->state = SENT_NACK;
i2c_nack(i2c->bus);
} else {
DPRINTF("ACKED\n");
}
return bitbang_i2c_ret(i2c, 1);
}
abort();
}
bitbang_i2c_interface *bitbang_i2c_init(i2c_bus *bus)
{
bitbang_i2c_interface *s;
s = g_malloc0(sizeof(bitbang_i2c_interface));
s->bus = bus;
s->last_data = 1;
s->last_clock = 1;
s->device_out = 1;
return s;
}
/* GPIO interface. */
typedef struct {
SysBusDevice busdev;
MemoryRegion dummy_iomem;
bitbang_i2c_interface *bitbang;
int last_level;
qemu_irq out;
} GPIOI2CState;
static void bitbang_i2c_gpio_set(void *opaque, int irq, int level)
{
GPIOI2CState *s = opaque;
level = bitbang_i2c_set(s->bitbang, irq, level);
if (level != s->last_level) {
s->last_level = level;
qemu_set_irq(s->out, level);
}
}
static int gpio_i2c_init(SysBusDevice *dev)
{
GPIOI2CState *s = FROM_SYSBUS(GPIOI2CState, dev);
i2c_bus *bus;
memory_region_init(&s->dummy_iomem, "gpio_i2c", 0);
sysbus_init_mmio(dev, &s->dummy_iomem);
bus = i2c_init_bus(&dev->qdev, "i2c");
s->bitbang = bitbang_i2c_init(bus);
qdev_init_gpio_in(&dev->qdev, bitbang_i2c_gpio_set, 2);
qdev_init_gpio_out(&dev->qdev, &s->out, 1);
return 0;
}
static SysBusDeviceInfo gpio_i2c_info = {
.init = gpio_i2c_init,
.qdev.name = "gpio_i2c",
.qdev.desc = "Virtual GPIO to I2C bridge",
.qdev.size = sizeof(GPIOI2CState),
};
static void bitbang_i2c_register(void)
{
sysbus_register_withprop(&gpio_i2c_info);
}
device_init(bitbang_i2c_register)
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