diff options
Diffstat (limited to 'hw/i2c/bitbang_i2c.c')
| -rw-r--r-- | hw/i2c/bitbang_i2c.c | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/hw/i2c/bitbang_i2c.c b/hw/i2c/bitbang_i2c.c new file mode 100644 index 000000000..e9a0612a0 --- /dev/null +++ b/hw/i2c/bitbang_i2c.c @@ -0,0 +1,226 @@ +/* + * 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" + +//#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 + +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: + { + int ret; + + if (i2c->current_addr < 0) { + i2c->current_addr = i2c->buffer; + DPRINTF("Address 0x%02x\n", i2c->current_addr); + ret = i2c_start_transfer(i2c->bus, i2c->current_addr >> 1, + i2c->current_addr & 1); + } else { + DPRINTF("Sent 0x%02x\n", 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). + */ + DPRINTF("Got NACK\n"); + bitbang_i2c_enter_stop(i2c); + return bitbang_i2c_ret(i2c, 1); + } + 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(); +} + +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. */ + +#define TYPE_GPIO_I2C "gpio_i2c" +OBJECT_DECLARE_SIMPLE_TYPE(GPIOI2CState, GPIO_I2C) + +struct GPIOI2CState { + SysBusDevice parent_obj; + + MemoryRegion dummy_iomem; + 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); + SysBusDevice *sbd = SYS_BUS_DEVICE(obj); + I2CBus *bus; + + memory_region_init(&s->dummy_iomem, obj, "gpio_i2c", 0); + sysbus_init_mmio(sbd, &s->dummy_iomem); + + 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) |