hw/i2c/bitbang_i2c.c

   1 /*
   2  * Bit-Bang i2c emulation extracted from
   3  * Marvell MV88W8618 / Freecom MusicPal emulation.
   4  *
   5  * Copyright (c) 2008 Jan Kiszka
   6  *
   7  * This code is licensed under the GNU GPL v2.
   8  *
   9  * Contributions after 2012-01-13 are licensed under the terms of the
  10  * GNU GPL, version 2 or (at your option) any later version.
  11  */
  12
  13 #include "qemu/osdep.h"
  14 #include "hw/irq.h"
  15 #include "hw/i2c/bitbang_i2c.h"
  16 #include "hw/sysbus.h"
  17 #include "qemu/module.h"
  18 #include "qom/object.h"
  19
  20 //#define DEBUG_BITBANG_I2C
  21
  22 #ifdef DEBUG_BITBANG_I2C
  23 #define DPRINTF(fmt, ...) \
  24 do { printf("bitbang_i2c: " fmt , ## __VA_ARGS__); } while (0)
  25 #else
  26 #define DPRINTF(fmt, ...) do {} while(0)
  27 #endif
  28
  29 static void bitbang_i2c_enter_stop(bitbang_i2c_interface *i2c)
  30 {
  31     DPRINTF("STOP\n");
  32     if (i2c->current_addr >= 0)
  33         i2c_end_transfer(i2c->bus);
  34     i2c->current_addr = -1;
  35     i2c->state = STOPPED;
  36 }
  37
  38 /* Set device data pin.  */
  39 static int bitbang_i2c_ret(bitbang_i2c_interface *i2c, int level)
  40 {
  41     i2c->device_out = level;
  42     //DPRINTF("%d %d %d\n", i2c->last_clock, i2c->last_data, i2c->device_out);
  43     return level & i2c->last_data;
  44 }
  45
  46 /* Leave device data pin unodified.  */
  47 static int bitbang_i2c_nop(bitbang_i2c_interface *i2c)
  48 {
  49     return bitbang_i2c_ret(i2c, i2c->device_out);
  50 }
  51
  52 /* Returns data line level.  */
  53 int bitbang_i2c_set(bitbang_i2c_interface *i2c, int line, int level)
  54 {
  55     int data;
  56
  57     if (level != 0 && level != 1) {
  58         abort();
  59     }
  60
  61     if (line == BITBANG_I2C_SDA) {
  62         if (level == i2c->last_data) {
  63             return bitbang_i2c_nop(i2c);
  64         }
  65         i2c->last_data = level;
  66         if (i2c->last_clock == 0) {
  67             return bitbang_i2c_nop(i2c);
  68         }
  69         if (level == 0) {
  70             DPRINTF("START\n");
  71             /* START condition.  */
  72             i2c->state = SENDING_BIT7;
  73             i2c->current_addr = -1;
  74         } else {
  75             /* STOP condition.  */
  76             bitbang_i2c_enter_stop(i2c);
  77         }
  78         return bitbang_i2c_ret(i2c, 1);
  79     }
  80
  81     data = i2c->last_data;
  82     if (i2c->last_clock == level) {
  83         return bitbang_i2c_nop(i2c);
  84     }
  85     i2c->last_clock = level;
  86     if (level == 0) {
  87         /* State is set/read at the start of the clock pulse.
  88            release the data line at the end.  */
  89         return bitbang_i2c_ret(i2c, 1);
  90     }
  91     switch (i2c->state) {
  92     case STOPPED:
  93     case SENT_NACK:
  94         return bitbang_i2c_ret(i2c, 1);
  95
  96     case SENDING_BIT7 ... SENDING_BIT0:
  97         i2c->buffer = (i2c->buffer << 1) | data;
  98         /* will end up in WAITING_FOR_ACK */
  99         i2c->state++;
 100         return bitbang_i2c_ret(i2c, 1);
 101
 102     case WAITING_FOR_ACK:
 103     {
 104         int ret;
 105
 106         if (i2c->current_addr < 0) {
 107             i2c->current_addr = i2c->buffer;
 108             DPRINTF("Address 0x%02x\n", i2c->current_addr);
 109             ret = i2c_start_transfer(i2c->bus, i2c->current_addr >> 1,
 110                                      i2c->current_addr & 1);
 111         } else {
 112             DPRINTF("Sent 0x%02x\n", i2c->buffer);
 113             ret = i2c_send(i2c->bus, i2c->buffer);
 114         }
 115         if (ret) {
 116             /* NACK (either addressing a nonexistent device, or the
 117              * device we were sending to decided to NACK us).
 118              */
 119             DPRINTF("Got NACK\n");
 120             bitbang_i2c_enter_stop(i2c);
 121             return bitbang_i2c_ret(i2c, 1);
 122         }
 123         if (i2c->current_addr & 1) {
 124             i2c->state = RECEIVING_BIT7;
 125         } else {
 126             i2c->state = SENDING_BIT7;
 127         }
 128         return bitbang_i2c_ret(i2c, 0);
 129     }
 130     case RECEIVING_BIT7:
 131         i2c->buffer = i2c_recv(i2c->bus);
 132         DPRINTF("RX byte 0x%02x\n", i2c->buffer);
 133         /* Fall through... */
 134     case RECEIVING_BIT6 ... RECEIVING_BIT0:
 135         data = i2c->buffer >> 7;
 136         /* will end up in SENDING_ACK */
 137         i2c->state++;
 138         i2c->buffer <<= 1;
 139         return bitbang_i2c_ret(i2c, data);
 140
 141     case SENDING_ACK:
 142         i2c->state = RECEIVING_BIT7;
 143         if (data != 0) {
 144             DPRINTF("NACKED\n");
 145             i2c->state = SENT_NACK;
 146             i2c_nack(i2c->bus);
 147         } else {
 148             DPRINTF("ACKED\n");
 149         }
 150         return bitbang_i2c_ret(i2c, 1);
 151     }
 152     abort();
 153 }
 154
 155 void bitbang_i2c_init(bitbang_i2c_interface *s, I2CBus *bus)
 156 {
 157     s->bus = bus;
 158     s->last_data = 1;
 159     s->last_clock = 1;
 160     s->device_out = 1;
 161 }
 162
 163 /* GPIO interface.  */
 164
 165 #define TYPE_GPIO_I2C "gpio_i2c"
 166 OBJECT_DECLARE_SIMPLE_TYPE(GPIOI2CState, GPIO_I2C)
 167
 168 struct GPIOI2CState {
 169     SysBusDevice parent_obj;
 170
 171     MemoryRegion dummy_iomem;
 172     bitbang_i2c_interface bitbang;
 173     int last_level;
 174     qemu_irq out;
 175 };
 176
 177 static void bitbang_i2c_gpio_set(void *opaque, int irq, int level)
 178 {
 179     GPIOI2CState *s = opaque;
 180
 181     level = bitbang_i2c_set(&s->bitbang, irq, level);
 182     if (level != s->last_level) {
 183         s->last_level = level;
 184         qemu_set_irq(s->out, level);
 185     }
 186 }
 187
 188 static void gpio_i2c_init(Object *obj)
 189 {
 190     DeviceState *dev = DEVICE(obj);
 191     GPIOI2CState *s = GPIO_I2C(obj);
 192     SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
 193     I2CBus *bus;
 194
 195     memory_region_init(&s->dummy_iomem, obj, "gpio_i2c", 0);
 196     sysbus_init_mmio(sbd, &s->dummy_iomem);
 197
 198     bus = i2c_init_bus(dev, "i2c");
 199     bitbang_i2c_init(&s->bitbang, bus);
 200
 201     qdev_init_gpio_in(dev, bitbang_i2c_gpio_set, 2);
 202     qdev_init_gpio_out(dev, &s->out, 1);
 203 }
 204
 205 static void gpio_i2c_class_init(ObjectClass *klass, void *data)
 206 {
 207     DeviceClass *dc = DEVICE_CLASS(klass);
 208
 209     set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
 210     dc->desc = "Virtual GPIO to I2C bridge";
 211 }
 212
 213 static const TypeInfo gpio_i2c_info = {
 214     .name          = TYPE_GPIO_I2C,
 215     .parent        = TYPE_SYS_BUS_DEVICE,
 216     .instance_size = sizeof(GPIOI2CState),
 217     .instance_init = gpio_i2c_init,
 218     .class_init    = gpio_i2c_class_init,
 219 };
 220
 221 static void bitbang_i2c_register_types(void)
 222 {
 223     type_register_static(&gpio_i2c_info);
 224 }
 225
 226 type_init(bitbang_i2c_register_types)