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