diff options
Diffstat (limited to 'hw/bitbang_i2c.c')
| -rw-r--r-- | hw/bitbang_i2c.c | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/hw/bitbang_i2c.c b/hw/bitbang_i2c.c new file mode 100644 index 0000000000..9ab04cc42e --- /dev/null +++ b/hw/bitbang_i2c.c @@ -0,0 +1,179 @@ +/* + * Bit-Bang i2c emulation extracted from + * Marvell MV88W8618 / Freecom MusicPal emulation. + * + * Copyright (c) 2008 Jan Kiszka + * + * This code is licenced under the GNU GPL v2. + */ +#include "hw.h" +#include "i2c.h" +#include "sysbus.h" + +typedef enum bitbang_i2c_state { + STOPPED = 0, + INITIALIZING, + 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 +} bitbang_i2c_state; + +typedef struct bitbang_i2c_interface { + SysBusDevice busdev; + i2c_bus *bus; + bitbang_i2c_state state; + int last_data; + int last_clock; + uint8_t buffer; + int current_addr; + qemu_irq out; +} bitbang_i2c_interface; + +static void bitbang_i2c_enter_stop(bitbang_i2c_interface *i2c) +{ + if (i2c->current_addr >= 0) + i2c_end_transfer(i2c->bus); + i2c->current_addr = -1; + i2c->state = STOPPED; +} + +static void bitbang_i2c_gpio_set(void *opaque, int irq, int level) +{ + bitbang_i2c_interface *i2c = opaque; + int data; + int clock; + int data_goes_up; + int data_goes_down; + int clock_goes_up; + int clock_goes_down; + + /* get pins states */ + data = i2c->last_data; + clock = i2c->last_clock; + + if (irq == 0) + data = level; + if (irq == 1) + clock = level; + + /* compute pins changes */ + data_goes_up = data == 1 && i2c->last_data == 0; + data_goes_down = data == 0 && i2c->last_data == 1; + clock_goes_up = clock == 1 && i2c->last_clock == 0; + clock_goes_down = clock == 0 && i2c->last_clock == 1; + + if (data_goes_up == 0 && data_goes_down == 0 && + clock_goes_up == 0 && clock_goes_down == 0) + return; + + if (!i2c) + return; + + if ((RECEIVING_BIT7 > i2c->state && i2c->state > RECEIVING_BIT0) + || i2c->state == WAITING_FOR_ACK) + qemu_set_irq(i2c->out, 0); + + switch (i2c->state) { + case STOPPED: + if (data_goes_down && clock == 1) + i2c->state = INITIALIZING; + break; + + case INITIALIZING: + if (clock_goes_down && data == 0) + i2c->state = SENDING_BIT7; + else + bitbang_i2c_enter_stop(i2c); + break; + + case SENDING_BIT7 ... SENDING_BIT0: + if (clock_goes_down) { + i2c->buffer = (i2c->buffer << 1) | data; + /* will end up in WAITING_FOR_ACK */ + i2c->state++; + } else if (data_goes_up && clock == 1) + bitbang_i2c_enter_stop(i2c); + break; + + case WAITING_FOR_ACK: + if (clock_goes_down) { + if (i2c->current_addr < 0) { + i2c->current_addr = i2c->buffer; + i2c_start_transfer(i2c->bus, (i2c->current_addr & 0xfe) / 2, + i2c->buffer & 1); + } else + i2c_send(i2c->bus, i2c->buffer); + if (i2c->current_addr & 1) { + i2c->state = RECEIVING_BIT7; + i2c->buffer = i2c_recv(i2c->bus); + } else + i2c->state = SENDING_BIT7; + } else if (data_goes_up && clock == 1) + bitbang_i2c_enter_stop(i2c); + break; + + case RECEIVING_BIT7 ... RECEIVING_BIT0: + qemu_set_irq(i2c->out, i2c->buffer >> 7); + if (clock_goes_down) { + /* will end up in SENDING_ACK */ + i2c->state++; + i2c->buffer <<= 1; + } else if (data_goes_up && clock == 1) + bitbang_i2c_enter_stop(i2c); + break; + + case SENDING_ACK: + if (clock_goes_down) { + i2c->state = RECEIVING_BIT7; + if (data == 0) + i2c->buffer = i2c_recv(i2c->bus); + else + i2c_nack(i2c->bus); + } else if (data_goes_up && clock == 1) + bitbang_i2c_enter_stop(i2c); + break; + } + + i2c->last_data = data; + i2c->last_clock = clock; +} + +static void bitbang_i2c_init(SysBusDevice *dev) +{ + bitbang_i2c_interface *s = FROM_SYSBUS(bitbang_i2c_interface, dev); + i2c_bus *bus; + + sysbus_init_mmio(dev, 0x0, 0); + + bus = i2c_init_bus(&dev->qdev, "i2c"); + s->bus = bus; + + s->last_data = 1; + s->last_clock = 1; + + qdev_init_gpio_in(&dev->qdev, bitbang_i2c_gpio_set, 2); + qdev_init_gpio_out(&dev->qdev, &s->out, 1); +} + +static void bitbang_i2c_register(void) +{ + sysbus_register_dev("bitbang_i2c", + sizeof(bitbang_i2c_interface), bitbang_i2c_init); +} + +device_init(bitbang_i2c_register) |