xref: /openbmc/qemu/hw/i2c/core.c (revision ad66b5cb)
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 "qemu/main-loop.h"
17 #include "trace.h"
18 
19 #define I2C_BROADCAST 0x00
20 
21 static Property i2c_props[] = {
22     DEFINE_PROP_UINT8("address", struct I2CSlave, address, 0),
23     DEFINE_PROP_END_OF_LIST(),
24 };
25 
26 static const TypeInfo i2c_bus_info = {
27     .name = TYPE_I2C_BUS,
28     .parent = TYPE_BUS,
29     .instance_size = sizeof(I2CBus),
30 };
31 
32 static int i2c_bus_pre_save(void *opaque)
33 {
34     I2CBus *bus = opaque;
35 
36     bus->saved_address = -1;
37     if (!QLIST_EMPTY(&bus->current_devs)) {
38         if (!bus->broadcast) {
39             bus->saved_address = QLIST_FIRST(&bus->current_devs)->elt->address;
40         } else {
41             bus->saved_address = I2C_BROADCAST;
42         }
43     }
44 
45     return 0;
46 }
47 
48 static const VMStateDescription vmstate_i2c_bus = {
49     .name = "i2c_bus",
50     .version_id = 1,
51     .minimum_version_id = 1,
52     .pre_save = i2c_bus_pre_save,
53     .fields = (VMStateField[]) {
54         VMSTATE_UINT8(saved_address, I2CBus),
55         VMSTATE_END_OF_LIST()
56     }
57 };
58 
59 /* Create a new I2C bus.  */
60 I2CBus *i2c_init_bus(DeviceState *parent, const char *name)
61 {
62     I2CBus *bus;
63 
64     bus = I2C_BUS(qbus_new(TYPE_I2C_BUS, parent, name));
65     QLIST_INIT(&bus->current_devs);
66     QSIMPLEQ_INIT(&bus->pending_masters);
67     vmstate_register(NULL, VMSTATE_INSTANCE_ID_ANY, &vmstate_i2c_bus, bus);
68     return bus;
69 }
70 
71 void i2c_slave_set_address(I2CSlave *dev, uint8_t address)
72 {
73     dev->address = address;
74 }
75 
76 /* Return nonzero if bus is busy.  */
77 int i2c_bus_busy(I2CBus *bus)
78 {
79     return !QLIST_EMPTY(&bus->current_devs) || bus->bh;
80 }
81 
82 bool i2c_scan_bus(I2CBus *bus, uint8_t address, bool broadcast,
83                   I2CNodeList *current_devs)
84 {
85     BusChild *kid;
86 
87     QTAILQ_FOREACH(kid, &bus->qbus.children, sibling) {
88         DeviceState *qdev = kid->child;
89         I2CSlave *candidate = I2C_SLAVE(qdev);
90         I2CSlaveClass *sc = I2C_SLAVE_GET_CLASS(candidate);
91 
92         if (sc->match_and_add(candidate, address, broadcast, current_devs)) {
93             if (!broadcast) {
94                 return true;
95             }
96         }
97     }
98 
99     /*
100      * If broadcast was true, and the list was full or empty, return true. If
101      * broadcast was false, return false.
102      */
103     return broadcast;
104 }
105 
106 /* TODO: Make this handle multiple masters.  */
107 /*
108  * Start or continue an i2c transaction.  When this is called for the
109  * first time or after an i2c_end_transfer(), if it returns an error
110  * the bus transaction is terminated (or really never started).  If
111  * this is called after another i2c_start_transfer() without an
112  * intervening i2c_end_transfer(), and it returns an error, the
113  * transaction will not be terminated.  The caller must do it.
114  *
115  * This corresponds with the way real hardware works.  The SMBus
116  * protocol uses a start transfer to switch from write to read mode
117  * without releasing the bus.  If that fails, the bus is still
118  * in a transaction.
119  *
120  * @event must be I2C_START_RECV or I2C_START_SEND.
121  */
122 static int i2c_do_start_transfer(I2CBus *bus, uint8_t address,
123                                  enum i2c_event event)
124 {
125     I2CSlaveClass *sc;
126     I2CNode *node;
127     bool bus_scanned = false;
128 
129     if (address == I2C_BROADCAST) {
130         /*
131          * This is a broadcast, the current_devs will be all the devices of the
132          * bus.
133          */
134         bus->broadcast = true;
135     }
136 
137     /*
138      * If there are already devices in the list, that means we are in
139      * the middle of a transaction and we shouldn't rescan the bus.
140      *
141      * This happens with any SMBus transaction, even on a pure I2C
142      * device.  The interface does a transaction start without
143      * terminating the previous transaction.
144      */
145     if (QLIST_EMPTY(&bus->current_devs)) {
146         /* Disregard whether devices were found. */
147         (void)i2c_scan_bus(bus, address, bus->broadcast, &bus->current_devs);
148         bus_scanned = true;
149     }
150 
151     if (QLIST_EMPTY(&bus->current_devs)) {
152         return 1;
153     }
154 
155     QLIST_FOREACH(node, &bus->current_devs, next) {
156         I2CSlave *s = node->elt;
157         int rv;
158 
159         sc = I2C_SLAVE_GET_CLASS(s);
160         /* If the bus is already busy, assume this is a repeated
161            start condition.  */
162 
163         if (sc->event) {
164             trace_i2c_event(event == I2C_START_SEND ? "start" : "start_async",
165                             s->address);
166             rv = sc->event(s, event);
167             if (rv && !bus->broadcast) {
168                 if (bus_scanned) {
169                     /* First call, terminate the transfer. */
170                     i2c_end_transfer(bus);
171                 }
172                 return rv;
173             }
174         }
175     }
176     return 0;
177 }
178 
179 int i2c_start_transfer(I2CBus *bus, uint8_t address, bool is_recv)
180 {
181     return i2c_do_start_transfer(bus, address, is_recv
182                                                ? I2C_START_RECV
183                                                : I2C_START_SEND);
184 }
185 
186 void i2c_bus_master(I2CBus *bus, QEMUBH *bh)
187 {
188     I2CPendingMaster *node = g_new(struct I2CPendingMaster, 1);
189     node->bh = bh;
190 
191     QSIMPLEQ_INSERT_TAIL(&bus->pending_masters, node, entry);
192 }
193 
194 void i2c_schedule_pending_master(I2CBus *bus)
195 {
196     I2CPendingMaster *node;
197 
198     if (i2c_bus_busy(bus)) {
199         /* someone is already controlling the bus; wait for it to release it */
200         return;
201     }
202 
203     if (QSIMPLEQ_EMPTY(&bus->pending_masters)) {
204         return;
205     }
206 
207     node = QSIMPLEQ_FIRST(&bus->pending_masters);
208     bus->bh = node->bh;
209 
210     QSIMPLEQ_REMOVE_HEAD(&bus->pending_masters, entry);
211     g_free(node);
212 
213     qemu_bh_schedule(bus->bh);
214 }
215 
216 void i2c_bus_release(I2CBus *bus)
217 {
218     bus->bh = NULL;
219 
220     i2c_schedule_pending_master(bus);
221 }
222 
223 int i2c_start_recv(I2CBus *bus, uint8_t address)
224 {
225     return i2c_do_start_transfer(bus, address, I2C_START_RECV);
226 }
227 
228 int i2c_start_send(I2CBus *bus, uint8_t address)
229 {
230     return i2c_do_start_transfer(bus, address, I2C_START_SEND);
231 }
232 
233 int i2c_start_send_async(I2CBus *bus, uint8_t address)
234 {
235     return i2c_do_start_transfer(bus, address, I2C_START_SEND_ASYNC);
236 }
237 
238 void i2c_end_transfer(I2CBus *bus)
239 {
240     I2CSlaveClass *sc;
241     I2CNode *node, *next;
242 
243     QLIST_FOREACH_SAFE(node, &bus->current_devs, next, next) {
244         I2CSlave *s = node->elt;
245         sc = I2C_SLAVE_GET_CLASS(s);
246         if (sc->event) {
247             trace_i2c_event("finish", s->address);
248             sc->event(s, I2C_FINISH);
249         }
250         QLIST_REMOVE(node, next);
251         g_free(node);
252     }
253     bus->broadcast = false;
254 }
255 
256 int i2c_send(I2CBus *bus, uint8_t data)
257 {
258     I2CSlaveClass *sc;
259     I2CSlave *s;
260     I2CNode *node;
261     int ret = 0;
262 
263     QLIST_FOREACH(node, &bus->current_devs, next) {
264         s = node->elt;
265         sc = I2C_SLAVE_GET_CLASS(s);
266         if (sc->send) {
267             trace_i2c_send(s->address, data);
268             ret = ret || sc->send(s, data);
269         } else {
270             ret = -1;
271         }
272     }
273 
274     return ret ? -1 : 0;
275 }
276 
277 int i2c_send_async(I2CBus *bus, uint8_t data)
278 {
279     I2CNode *node = QLIST_FIRST(&bus->current_devs);
280     I2CSlave *slave = node->elt;
281     I2CSlaveClass *sc = I2C_SLAVE_GET_CLASS(slave);
282 
283     if (!sc->send_async) {
284         return -1;
285     }
286 
287     trace_i2c_send_async(slave->address, data);
288 
289     sc->send_async(slave, data);
290 
291     return 0;
292 }
293 
294 uint8_t i2c_recv(I2CBus *bus)
295 {
296     uint8_t data = 0xff;
297     I2CSlaveClass *sc;
298     I2CSlave *s;
299 
300     if (!QLIST_EMPTY(&bus->current_devs) && !bus->broadcast) {
301         sc = I2C_SLAVE_GET_CLASS(QLIST_FIRST(&bus->current_devs)->elt);
302         if (sc->recv) {
303             s = QLIST_FIRST(&bus->current_devs)->elt;
304             data = sc->recv(s);
305             trace_i2c_recv(s->address, data);
306         }
307     }
308 
309     return data;
310 }
311 
312 void i2c_nack(I2CBus *bus)
313 {
314     I2CSlaveClass *sc;
315     I2CNode *node;
316 
317     if (QLIST_EMPTY(&bus->current_devs)) {
318         return;
319     }
320 
321     QLIST_FOREACH(node, &bus->current_devs, next) {
322         sc = I2C_SLAVE_GET_CLASS(node->elt);
323         if (sc->event) {
324             trace_i2c_event("nack", node->elt->address);
325             sc->event(node->elt, I2C_NACK);
326         }
327     }
328 }
329 
330 void i2c_ack(I2CBus *bus)
331 {
332     if (!bus->bh) {
333         return;
334     }
335 
336     trace_i2c_ack();
337 
338     qemu_bh_schedule(bus->bh);
339 }
340 
341 static int i2c_slave_post_load(void *opaque, int version_id)
342 {
343     I2CSlave *dev = opaque;
344     I2CBus *bus;
345     I2CNode *node;
346 
347     bus = I2C_BUS(qdev_get_parent_bus(DEVICE(dev)));
348     if ((bus->saved_address == dev->address) ||
349         (bus->saved_address == I2C_BROADCAST)) {
350         node = g_new(struct I2CNode, 1);
351         node->elt = dev;
352         QLIST_INSERT_HEAD(&bus->current_devs, node, next);
353     }
354     return 0;
355 }
356 
357 const VMStateDescription vmstate_i2c_slave = {
358     .name = "I2CSlave",
359     .version_id = 1,
360     .minimum_version_id = 1,
361     .post_load = i2c_slave_post_load,
362     .fields = (VMStateField[]) {
363         VMSTATE_UINT8(address, I2CSlave),
364         VMSTATE_END_OF_LIST()
365     }
366 };
367 
368 I2CSlave *i2c_slave_new(const char *name, uint8_t addr)
369 {
370     DeviceState *dev;
371 
372     dev = qdev_new(name);
373     qdev_prop_set_uint8(dev, "address", addr);
374     return I2C_SLAVE(dev);
375 }
376 
377 bool i2c_slave_realize_and_unref(I2CSlave *dev, I2CBus *bus, Error **errp)
378 {
379     return qdev_realize_and_unref(&dev->qdev, &bus->qbus, errp);
380 }
381 
382 I2CSlave *i2c_slave_create_simple(I2CBus *bus, const char *name, uint8_t addr)
383 {
384     I2CSlave *dev = i2c_slave_new(name, addr);
385 
386     i2c_slave_realize_and_unref(dev, bus, &error_abort);
387 
388     return dev;
389 }
390 
391 static bool i2c_slave_match(I2CSlave *candidate, uint8_t address,
392                             bool broadcast, I2CNodeList *current_devs)
393 {
394     if ((candidate->address == address) || (broadcast)) {
395         I2CNode *node = g_new(struct I2CNode, 1);
396         node->elt = candidate;
397         QLIST_INSERT_HEAD(current_devs, node, next);
398         return true;
399     }
400 
401     /* Not found and not broadcast. */
402     return false;
403 }
404 
405 static void i2c_slave_class_init(ObjectClass *klass, void *data)
406 {
407     DeviceClass *k = DEVICE_CLASS(klass);
408     I2CSlaveClass *sc = I2C_SLAVE_CLASS(klass);
409     set_bit(DEVICE_CATEGORY_MISC, k->categories);
410     k->bus_type = TYPE_I2C_BUS;
411     device_class_set_props(k, i2c_props);
412     sc->match_and_add = i2c_slave_match;
413 }
414 
415 static const TypeInfo i2c_slave_type_info = {
416     .name = TYPE_I2C_SLAVE,
417     .parent = TYPE_DEVICE,
418     .instance_size = sizeof(I2CSlave),
419     .abstract = true,
420     .class_size = sizeof(I2CSlaveClass),
421     .class_init = i2c_slave_class_init,
422 };
423 
424 static void i2c_slave_register_types(void)
425 {
426     type_register_static(&i2c_bus_info);
427     type_register_static(&i2c_slave_type_info);
428 }
429 
430 type_init(i2c_slave_register_types)
431