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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.
*
* Contributions after 2012-01-13 are licensed under the terms of the
* GNU GPL, version 2 or (at your option) any later version.
*/
#include "qemu/osdep.h"
#include "hw/irq.h"
#include "hw/i2c/bitbang_i2c.h"
#include "hw/sysbus.h"
#include "qemu/module.h"
#include "qom/object.h"
#include "trace.h"
/* bitbang_i2c_state enum to name */
static const char * const sname[] = {
#define NAME(e) [e] = stringify(e)
NAME(STOPPED),
[SENDING_BIT7] = "SENDING_BIT7 (START)",
NAME(SENDING_BIT6),
NAME(SENDING_BIT5),
NAME(SENDING_BIT4),
NAME(SENDING_BIT3),
NAME(SENDING_BIT2),
NAME(SENDING_BIT1),
NAME(SENDING_BIT0),
NAME(WAITING_FOR_ACK),
[RECEIVING_BIT7] = "RECEIVING_BIT7 (ACK)",
NAME(RECEIVING_BIT6),
NAME(RECEIVING_BIT5),
NAME(RECEIVING_BIT4),
NAME(RECEIVING_BIT3),
NAME(RECEIVING_BIT2),
NAME(RECEIVING_BIT1),
NAME(RECEIVING_BIT0),
NAME(SENDING_ACK),
NAME(SENT_NACK)
#undef NAME
};
static void bitbang_i2c_set_state(bitbang_i2c_interface *i2c,
bitbang_i2c_state state)
{
trace_bitbang_i2c_state(sname[i2c->state], sname[state]);
i2c->state = state;
}
static void bitbang_i2c_enter_stop(bitbang_i2c_interface *i2c)
{
if (i2c->current_addr >= 0)
i2c_end_transfer(i2c->bus);
i2c->current_addr = -1;
bitbang_i2c_set_state(i2c, STOPPED);
}
/* Set device data pin. */
static int bitbang_i2c_ret(bitbang_i2c_interface *i2c, int level)
{
trace_bitbang_i2c_data(i2c->last_clock, i2c->last_data,
i2c->device_out, level);
i2c->device_out = level;
return level & i2c->last_data;
}
/* Leave device data pin unmodified. */
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) {
/* START condition. */
bitbang_i2c_set_state(i2c, 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 */
bitbang_i2c_set_state(i2c, i2c->state + 1);
return bitbang_i2c_ret(i2c, 1);
case WAITING_FOR_ACK:
{
int ret;
if (i2c->current_addr < 0) {
i2c->current_addr = i2c->buffer;
trace_bitbang_i2c_addr(i2c->current_addr);
ret = i2c_start_transfer(i2c->bus, i2c->current_addr >> 1,
i2c->current_addr & 1);
} else {
trace_bitbang_i2c_send(i2c->buffer);
ret = i2c_send(i2c->bus, i2c->buffer);
}
if (ret) {
/* NACK (either addressing a nonexistent device, or the
* device we were sending to decided to NACK us).
*/
bitbang_i2c_set_state(i2c, SENT_NACK);
bitbang_i2c_enter_stop(i2c);
return bitbang_i2c_ret(i2c, 1);
}
if (i2c->current_addr & 1) {
bitbang_i2c_set_state(i2c, RECEIVING_BIT7);
} else {
bitbang_i2c_set_state(i2c, SENDING_BIT7);
}
return bitbang_i2c_ret(i2c, 0);
}
case RECEIVING_BIT7:
i2c->buffer = i2c_recv(i2c->bus);
trace_bitbang_i2c_recv(i2c->buffer);
/* Fall through... */
case RECEIVING_BIT6 ... RECEIVING_BIT0:
data = i2c->buffer >> 7;
/* will end up in SENDING_ACK */
bitbang_i2c_set_state(i2c, i2c->state + 1);
i2c->buffer <<= 1;
return bitbang_i2c_ret(i2c, data);
case SENDING_ACK:
if (data != 0) {
bitbang_i2c_set_state(i2c, SENT_NACK);
i2c_nack(i2c->bus);
} else {
bitbang_i2c_set_state(i2c, RECEIVING_BIT7);
}
return bitbang_i2c_ret(i2c, 1);
}
abort();
}
void bitbang_i2c_init(bitbang_i2c_interface *s, I2CBus *bus)
{
s->bus = bus;
s->last_data = 1;
s->last_clock = 1;
s->device_out = 1;
}
/* GPIO interface. */
OBJECT_DECLARE_SIMPLE_TYPE(GPIOI2CState, GPIO_I2C)
struct GPIOI2CState {
/*< private >*/
SysBusDevice parent_obj;
/*< public >*/
bitbang_i2c_interface bitbang;
int last_level;
qemu_irq out;
};
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 void gpio_i2c_init(Object *obj)
{
DeviceState *dev = DEVICE(obj);
GPIOI2CState *s = GPIO_I2C(obj);
I2CBus *bus;
bus = i2c_init_bus(dev, "i2c");
bitbang_i2c_init(&s->bitbang, bus);
qdev_init_gpio_in(dev, bitbang_i2c_gpio_set, 2);
qdev_init_gpio_out(dev, &s->out, 1);
}
static void gpio_i2c_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
dc->desc = "Virtual GPIO to I2C bridge";
}
static const TypeInfo gpio_i2c_info = {
.name = TYPE_GPIO_I2C,
.parent = TYPE_SYS_BUS_DEVICE,
.instance_size = sizeof(GPIOI2CState),
.instance_init = gpio_i2c_init,
.class_init = gpio_i2c_class_init,
};
static void bitbang_i2c_register_types(void)
{
type_register_static(&gpio_i2c_info);
}
type_init(bitbang_i2c_register_types)
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