hw/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 #include "hw/hw.h"
  13 #include "hw/bitbang_i2c.h"
  14 #include "hw/sysbus.h"
  15
  16 //#define DEBUG_BITBANG_I2C
  17
  18 #ifdef DEBUG_BITBANG_I2C
  19 #define DPRINTF(fmt, ...) \
  20 do { printf("bitbang_i2c: " fmt , ## __VA_ARGS__); } while (0)
  21 #else
  22 #define DPRINTF(fmt, ...) do {} while(0)
  23 #endif
  24
  25 typedef enum bitbang_i2c_state {
  26     STOPPED = 0,
  27     SENDING_BIT7,
  28     SENDING_BIT6,
  29     SENDING_BIT5,
  30     SENDING_BIT4,
  31     SENDING_BIT3,
  32     SENDING_BIT2,
  33     SENDING_BIT1,
  34     SENDING_BIT0,
  35     WAITING_FOR_ACK,
  36     RECEIVING_BIT7,
  37     RECEIVING_BIT6,
  38     RECEIVING_BIT5,
  39     RECEIVING_BIT4,
  40     RECEIVING_BIT3,
  41     RECEIVING_BIT2,
  42     RECEIVING_BIT1,
  43     RECEIVING_BIT0,
  44     SENDING_ACK,
  45     SENT_NACK
  46 } bitbang_i2c_state;
  47
  48 struct bitbang_i2c_interface {
  49     i2c_bus *bus;
  50     bitbang_i2c_state state;
  51     int last_data;
  52     int last_clock;
  53     int device_out;
  54     uint8_t buffer;
  55     int current_addr;
  56 };
  57
  58 static void bitbang_i2c_enter_stop(bitbang_i2c_interface *i2c)
  59 {
  60     DPRINTF("STOP\n");
  61     if (i2c->current_addr >= 0)
  62         i2c_end_transfer(i2c->bus);
  63     i2c->current_addr = -1;
  64     i2c->state = STOPPED;
  65 }
  66
  67 /* Set device data pin.  */
  68 static int bitbang_i2c_ret(bitbang_i2c_interface *i2c, int level)
  69 {
  70     i2c->device_out = level;
  71     //DPRINTF("%d %d %d\n", i2c->last_clock, i2c->last_data, i2c->device_out);
  72     return level & i2c->last_data;
  73 }
  74
  75 /* Leave device data pin unodified.  */
  76 static int bitbang_i2c_nop(bitbang_i2c_interface *i2c)
  77 {
  78     return bitbang_i2c_ret(i2c, i2c->device_out);
  79 }
  80
  81 /* Returns data line level.  */
  82 int bitbang_i2c_set(bitbang_i2c_interface *i2c, int line, int level)
  83 {
  84     int data;
  85
  86     if (level != 0 && level != 1) {
  87         abort();
  88     }
  89
  90     if (line == BITBANG_I2C_SDA) {
  91         if (level == i2c->last_data) {
  92             return bitbang_i2c_nop(i2c);
  93         }
  94         i2c->last_data = level;
  95         if (i2c->last_clock == 0) {
  96             return bitbang_i2c_nop(i2c);
  97         }
  98         if (level == 0) {
  99             DPRINTF("START\n");
 100             /* START condition.  */
 101             i2c->state = SENDING_BIT7;
 102             i2c->current_addr = -1;
 103         } else {
 104             /* STOP condition.  */
 105             bitbang_i2c_enter_stop(i2c);
 106         }
 107         return bitbang_i2c_ret(i2c, 1);
 108     }
 109
 110     data = i2c->last_data;
 111     if (i2c->last_clock == level) {
 112         return bitbang_i2c_nop(i2c);
 113     }
 114     i2c->last_clock = level;
 115     if (level == 0) {
 116         /* State is set/read at the start of the clock pulse.
 117            release the data line at the end.  */
 118         return bitbang_i2c_ret(i2c, 1);
 119     }
 120     switch (i2c->state) {
 121     case STOPPED:
 122     case SENT_NACK:
 123         return bitbang_i2c_ret(i2c, 1);
 124
 125     case SENDING_BIT7 ... SENDING_BIT0:
 126         i2c->buffer = (i2c->buffer << 1) | data;
 127         /* will end up in WAITING_FOR_ACK */
 128         i2c->state++;
 129         return bitbang_i2c_ret(i2c, 1);
 130
 131     case WAITING_FOR_ACK:
 132         if (i2c->current_addr < 0) {
 133             i2c->current_addr = i2c->buffer;
 134             DPRINTF("Address 0x%02x\n", i2c->current_addr);
 135             i2c_start_transfer(i2c->bus, i2c->current_addr >> 1,
 136                                i2c->current_addr & 1);
 137         } else {
 138             DPRINTF("Sent 0x%02x\n", i2c->buffer);
 139             i2c_send(i2c->bus, i2c->buffer);
 140         }
 141         if (i2c->current_addr & 1) {
 142             i2c->state = RECEIVING_BIT7;
 143         } else {
 144             i2c->state = SENDING_BIT7;
 145         }
 146         return bitbang_i2c_ret(i2c, 0);
 147
 148     case RECEIVING_BIT7:
 149         i2c->buffer = i2c_recv(i2c->bus);
 150         DPRINTF("RX byte 0x%02x\n", i2c->buffer);
 151         /* Fall through... */
 152     case RECEIVING_BIT6 ... RECEIVING_BIT0:
 153         data = i2c->buffer >> 7;
 154         /* will end up in SENDING_ACK */
 155         i2c->state++;
 156         i2c->buffer <<= 1;
 157         return bitbang_i2c_ret(i2c, data);
 158
 159     case SENDING_ACK:
 160         i2c->state = RECEIVING_BIT7;
 161         if (data != 0) {
 162             DPRINTF("NACKED\n");
 163             i2c->state = SENT_NACK;
 164             i2c_nack(i2c->bus);
 165         } else {
 166             DPRINTF("ACKED\n");
 167         }
 168         return bitbang_i2c_ret(i2c, 1);
 169     }
 170     abort();
 171 }
 172
 173 bitbang_i2c_interface *bitbang_i2c_init(i2c_bus *bus)
 174 {
 175     bitbang_i2c_interface *s;
 176
 177     s = g_malloc0(sizeof(bitbang_i2c_interface));
 178
 179     s->bus = bus;
 180     s->last_data = 1;
 181     s->last_clock = 1;
 182     s->device_out = 1;
 183
 184     return s;
 185 }
 186
 187 /* GPIO interface.  */
 188 typedef struct {
 189     SysBusDevice busdev;
 190     MemoryRegion dummy_iomem;
 191     bitbang_i2c_interface *bitbang;
 192     int last_level;
 193     qemu_irq out;
 194 } GPIOI2CState;
 195
 196 static void bitbang_i2c_gpio_set(void *opaque, int irq, int level)
 197 {
 198     GPIOI2CState *s = opaque;
 199
 200     level = bitbang_i2c_set(s->bitbang, irq, level);
 201     if (level != s->last_level) {
 202         s->last_level = level;
 203         qemu_set_irq(s->out, level);
 204     }
 205 }
 206
 207 static int gpio_i2c_init(SysBusDevice *dev)
 208 {
 209     GPIOI2CState *s = FROM_SYSBUS(GPIOI2CState, dev);
 210     i2c_bus *bus;
 211
 212     memory_region_init(&s->dummy_iomem, "gpio_i2c", 0);
 213     sysbus_init_mmio(dev, &s->dummy_iomem);
 214
 215     bus = i2c_init_bus(&dev->qdev, "i2c");
 216     s->bitbang = bitbang_i2c_init(bus);
 217
 218     qdev_init_gpio_in(&dev->qdev, bitbang_i2c_gpio_set, 2);
 219     qdev_init_gpio_out(&dev->qdev, &s->out, 1);
 220
 221     return 0;
 222 }
 223
 224 static void gpio_i2c_class_init(ObjectClass *klass, void *data)
 225 {
 226     DeviceClass *dc = DEVICE_CLASS(klass);
 227     SysBusDeviceClass *k = SYS_BUS_DEVICE_CLASS(klass);
 228
 229     k->init = gpio_i2c_init;
 230     dc->desc = "Virtual GPIO to I2C bridge";
 231 }
 232
 233 static const TypeInfo gpio_i2c_info = {
 234     .name          = "gpio_i2c",
 235     .parent        = TYPE_SYS_BUS_DEVICE,
 236     .instance_size = sizeof(GPIOI2CState),
 237     .class_init    = gpio_i2c_class_init,
 238 };
 239
 240 static void bitbang_i2c_register_types(void)
 241 {
 242     type_register_static(&gpio_i2c_info);
 243 }
 244
 245 type_init(bitbang_i2c_register_types)