xref: /openbmc/qemu/hw/i2c/core.c (revision eabfeb0c) 
1 /*
2  * QEMU I2C bus interface.
3  *
4  * Copyright (c) 2007 CodeSourcery.
5  * Written by Paul Brook
6  *
7  * This code is licensed under the LGPL.
8  */
9 
10 #include "qemu/osdep.h"
11 #include "hw/i2c/i2c.h"
12 #include "hw/qdev-properties.h"
13 #include "migration/vmstate.h"
14 #include "qapi/error.h"
15 #include "qemu/module.h"
16 #include "trace.h"
17 
18 #define I2C_BROADCAST 0x00
19 
20 static Property i2c_props[] = {
21     DEFINE_PROP_UINT8("address", struct I2CSlave, address, 0),
22     DEFINE_PROP_END_OF_LIST(),
23 };
24 
25 static const TypeInfo i2c_bus_info = {
26     .name = TYPE_I2C_BUS,
27     .parent = TYPE_BUS,
28     .instance_size = sizeof(I2CBus),
29 };
30 
31 static int i2c_bus_pre_save(void *opaque)
32 {
33     I2CBus *bus = opaque;
34 
35     bus->saved_address = -1;
36     if (!QLIST_EMPTY(&bus->current_devs)) {
37         if (!bus->broadcast) {
38             bus->saved_address = QLIST_FIRST(&bus->current_devs)->elt->address;
39         } else {
40             bus->saved_address = I2C_BROADCAST;
41         }
42     }
43 
44     return 0;
45 }
46 
47 static const VMStateDescription vmstate_i2c_bus = {
48     .name = "i2c_bus",
49     .version_id = 1,
50     .minimum_version_id = 1,
51     .pre_save = i2c_bus_pre_save,
52     .fields = (VMStateField[]) {
53         VMSTATE_UINT8(saved_address, I2CBus),
54         VMSTATE_END_OF_LIST()
55     }
56 };
57 
58 /* Create a new I2C bus.  */
59 I2CBus *i2c_init_bus(DeviceState *parent, const char *name)
60 {
61     I2CBus *bus;
62 
63     bus = I2C_BUS(qbus_create(TYPE_I2C_BUS, parent, name));
64     QLIST_INIT(&bus->current_devs);
65     vmstate_register(NULL, VMSTATE_INSTANCE_ID_ANY, &vmstate_i2c_bus, bus);
66     return bus;
67 }
68 
69 void i2c_set_slave_address(I2CSlave *dev, uint8_t address)
70 {
71     dev->address = address;
72 }
73 
74 /* Return nonzero if bus is busy.  */
75 int i2c_bus_busy(I2CBus *bus)
76 {
77     return !QLIST_EMPTY(&bus->current_devs);
78 }
79 
80 /* TODO: Make this handle multiple masters.  */
81 /*
82  * Start or continue an i2c transaction.  When this is called for the
83  * first time or after an i2c_end_transfer(), if it returns an error
84  * the bus transaction is terminated (or really never started).  If
85  * this is called after another i2c_start_transfer() without an
86  * intervening i2c_end_transfer(), and it returns an error, the
87  * transaction will not be terminated.  The caller must do it.
88  *
89  * This corresponds with the way real hardware works.  The SMBus
90  * protocol uses a start transfer to switch from write to read mode
91  * without releasing the bus.  If that fails, the bus is still
92  * in a transaction.
93  */
94 int i2c_start_transfer(I2CBus *bus, uint8_t address, int recv)
95 {
96     BusChild *kid;
97     I2CSlaveClass *sc;
98     I2CNode *node;
99     bool bus_scanned = false;
100 
101     if (address == I2C_BROADCAST) {
102         /*
103          * This is a broadcast, the current_devs will be all the devices of the
104          * bus.
105          */
106         bus->broadcast = true;
107     }
108 
109     /*
110      * If there are already devices in the list, that means we are in
111      * the middle of a transaction and we shouldn't rescan the bus.
112      *
113      * This happens with any SMBus transaction, even on a pure I2C
114      * device.  The interface does a transaction start without
115      * terminating the previous transaction.
116      */
117     if (QLIST_EMPTY(&bus->current_devs)) {
118         QTAILQ_FOREACH(kid, &bus->qbus.children, sibling) {
119             DeviceState *qdev = kid->child;
120             I2CSlave *candidate = I2C_SLAVE(qdev);
121             if ((candidate->address == address) || (bus->broadcast)) {
122                 node = g_malloc(sizeof(struct I2CNode));
123                 node->elt = candidate;
124                 QLIST_INSERT_HEAD(&bus->current_devs, node, next);
125                 if (!bus->broadcast) {
126                     break;
127                 }
128             }
129         }
130         bus_scanned = true;
131     }
132 
133     if (QLIST_EMPTY(&bus->current_devs)) {
134         return 1;
135     }
136 
137     QLIST_FOREACH(node, &bus->current_devs, next) {
138         I2CSlave *s = node->elt;
139         int rv;
140 
141         sc = I2C_SLAVE_GET_CLASS(s);
142         /* If the bus is already busy, assume this is a repeated
143            start condition.  */
144 
145         if (sc->event) {
146             trace_i2c_event("start", s->address);
147             rv = sc->event(s, recv ? I2C_START_RECV : I2C_START_SEND);
148             if (rv && !bus->broadcast) {
149                 if (bus_scanned) {
150                     /* First call, terminate the transfer. */
151                     i2c_end_transfer(bus);
152                 }
153                 return rv;
154             }
155         }
156     }
157     return 0;
158 }
159 
160 void i2c_end_transfer(I2CBus *bus)
161 {
162     I2CSlaveClass *sc;
163     I2CNode *node, *next;
164 
165     QLIST_FOREACH_SAFE(node, &bus->current_devs, next, next) {
166         I2CSlave *s = node->elt;
167         sc = I2C_SLAVE_GET_CLASS(s);
168         if (sc->event) {
169             trace_i2c_event("finish", s->address);
170             sc->event(s, I2C_FINISH);
171         }
172         QLIST_REMOVE(node, next);
173         g_free(node);
174     }
175     bus->broadcast = false;
176 }
177 
178 int i2c_send_recv(I2CBus *bus, uint8_t *data, bool send)
179 {
180     I2CSlaveClass *sc;
181     I2CSlave *s;
182     I2CNode *node;
183     int ret = 0;
184 
185     if (send) {
186         QLIST_FOREACH(node, &bus->current_devs, next) {
187             s = node->elt;
188             sc = I2C_SLAVE_GET_CLASS(s);
189             if (sc->send) {
190                 trace_i2c_send(s->address, *data);
191                 ret = ret || sc->send(s, *data);
192             } else {
193                 ret = -1;
194             }
195         }
196         return ret ? -1 : 0;
197     } else {
198         ret = 0xff;
199         if (!QLIST_EMPTY(&bus->current_devs) && !bus->broadcast) {
200             sc = I2C_SLAVE_GET_CLASS(QLIST_FIRST(&bus->current_devs)->elt);
201             if (sc->recv) {
202                 s = QLIST_FIRST(&bus->current_devs)->elt;
203                 ret = sc->recv(s);
204                 trace_i2c_recv(s->address, ret);
205             }
206         }
207         *data = ret;
208         return 0;
209     }
210 }
211 
212 int i2c_send(I2CBus *bus, uint8_t data)
213 {
214     return i2c_send_recv(bus, &data, true);
215 }
216 
217 uint8_t i2c_recv(I2CBus *bus)
218 {
219     uint8_t data = 0xff;
220 
221     i2c_send_recv(bus, &data, false);
222     return data;
223 }
224 
225 void i2c_nack(I2CBus *bus)
226 {
227     I2CSlaveClass *sc;
228     I2CNode *node;
229 
230     if (QLIST_EMPTY(&bus->current_devs)) {
231         return;
232     }
233 
234     QLIST_FOREACH(node, &bus->current_devs, next) {
235         sc = I2C_SLAVE_GET_CLASS(node->elt);
236         if (sc->event) {
237             trace_i2c_event("nack", node->elt->address);
238             sc->event(node->elt, I2C_NACK);
239         }
240     }
241 }
242 
243 static int i2c_slave_post_load(void *opaque, int version_id)
244 {
245     I2CSlave *dev = opaque;
246     I2CBus *bus;
247     I2CNode *node;
248 
249     bus = I2C_BUS(qdev_get_parent_bus(DEVICE(dev)));
250     if ((bus->saved_address == dev->address) ||
251         (bus->saved_address == I2C_BROADCAST)) {
252         node = g_malloc(sizeof(struct I2CNode));
253         node->elt = dev;
254         QLIST_INSERT_HEAD(&bus->current_devs, node, next);
255     }
256     return 0;
257 }
258 
259 const VMStateDescription vmstate_i2c_slave = {
260     .name = "I2CSlave",
261     .version_id = 1,
262     .minimum_version_id = 1,
263     .post_load = i2c_slave_post_load,
264     .fields = (VMStateField[]) {
265         VMSTATE_UINT8(address, I2CSlave),
266         VMSTATE_END_OF_LIST()
267     }
268 };
269 
270 I2CSlave *i2c_slave_new(const char *name, uint8_t addr)
271 {
272     DeviceState *dev;
273 
274     dev = qdev_new(name);
275     qdev_prop_set_uint8(dev, "address", addr);
276     return I2C_SLAVE(dev);
277 }
278 
279 bool i2c_slave_realize_and_unref(I2CSlave *dev, I2CBus *bus, Error **errp)
280 {
281     return qdev_realize_and_unref(&dev->qdev, &bus->qbus, errp);
282 }
283 
284 I2CSlave *i2c_slave_create_simple(I2CBus *bus, const char *name, uint8_t addr)
285 {
286     I2CSlave *dev = i2c_slave_new(name, addr);
287 
288     i2c_slave_realize_and_unref(dev, bus, &error_abort);
289 
290     return dev;
291 }
292 
293 static void i2c_slave_class_init(ObjectClass *klass, void *data)
294 {
295     DeviceClass *k = DEVICE_CLASS(klass);
296     set_bit(DEVICE_CATEGORY_MISC, k->categories);
297     k->bus_type = TYPE_I2C_BUS;
298     device_class_set_props(k, i2c_props);
299 }
300 
301 static const TypeInfo i2c_slave_type_info = {
302     .name = TYPE_I2C_SLAVE,
303     .parent = TYPE_DEVICE,
304     .instance_size = sizeof(I2CSlave),
305     .abstract = true,
306     .class_size = sizeof(I2CSlaveClass),
307     .class_init = i2c_slave_class_init,
308 };
309 
310 static void i2c_slave_register_types(void)
311 {
312     type_register_static(&i2c_bus_info);
313     type_register_static(&i2c_slave_type_info);
314 }
315 
316 type_init(i2c_slave_register_types)
317