1 /*
2 * Multiplexed I2C bus driver.
3 *
4 * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
5 * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
6 * Copyright (c) 2009-2010 NSN GmbH & Co KG <michael.lawnick.ext@nsn.com>
7 *
8 * Simplifies access to complex multiplexed I2C bus topologies, by presenting
9 * each multiplexed bus segment as an additional I2C adapter.
10 * Supports multi-level mux'ing (mux behind a mux).
11 *
12 * Based on:
13 * i2c-virt.c from Kumar Gala <galak@kernel.crashing.org>
14 * i2c-virtual.c from Ken Harrenstien, Copyright (c) 2004 Google, Inc.
15 * i2c-virtual.c from Brian Kuschak <bkuschak@yahoo.com>
16 *
17 * This file is licensed under the terms of the GNU General Public
18 * License version 2. This program is licensed "as is" without any
19 * warranty of any kind, whether express or implied.
20 */
21
22 #include <linux/acpi.h>
23 #include <linux/i2c.h>
24 #include <linux/i2c-mux.h>
25 #include <linux/kernel.h>
26 #include <linux/module.h>
27 #include <linux/of.h>
28 #include <linux/slab.h>
29 #include <linux/sysfs.h>
30
31 /* multiplexer per channel data */
32 struct i2c_mux_priv {
33 struct i2c_adapter adap;
34 struct i2c_algorithm algo;
35 struct i2c_mux_core *muxc;
36 u32 chan_id;
37 };
38
__i2c_mux_master_xfer(struct i2c_adapter * adap,struct i2c_msg msgs[],int num)39 static int __i2c_mux_master_xfer(struct i2c_adapter *adap,
40 struct i2c_msg msgs[], int num)
41 {
42 struct i2c_mux_priv *priv = adap->algo_data;
43 struct i2c_mux_core *muxc = priv->muxc;
44 struct i2c_adapter *parent = muxc->parent;
45 int ret;
46
47 /* Switch to the right mux port and perform the transfer. */
48
49 ret = muxc->select(muxc, priv->chan_id);
50 if (ret >= 0)
51 ret = __i2c_transfer(parent, msgs, num);
52 if (muxc->deselect)
53 muxc->deselect(muxc, priv->chan_id);
54
55 return ret;
56 }
57
i2c_mux_master_xfer(struct i2c_adapter * adap,struct i2c_msg msgs[],int num)58 static int i2c_mux_master_xfer(struct i2c_adapter *adap,
59 struct i2c_msg msgs[], int num)
60 {
61 struct i2c_mux_priv *priv = adap->algo_data;
62 struct i2c_mux_core *muxc = priv->muxc;
63 struct i2c_adapter *parent = muxc->parent;
64 int ret;
65
66 /* Switch to the right mux port and perform the transfer. */
67
68 ret = muxc->select(muxc, priv->chan_id);
69 if (ret >= 0)
70 ret = i2c_transfer(parent, msgs, num);
71 if (muxc->deselect)
72 muxc->deselect(muxc, priv->chan_id);
73
74 return ret;
75 }
76
__i2c_mux_smbus_xfer(struct i2c_adapter * adap,u16 addr,unsigned short flags,char read_write,u8 command,int size,union i2c_smbus_data * data)77 static int __i2c_mux_smbus_xfer(struct i2c_adapter *adap,
78 u16 addr, unsigned short flags,
79 char read_write, u8 command,
80 int size, union i2c_smbus_data *data)
81 {
82 struct i2c_mux_priv *priv = adap->algo_data;
83 struct i2c_mux_core *muxc = priv->muxc;
84 struct i2c_adapter *parent = muxc->parent;
85 int ret;
86
87 /* Select the right mux port and perform the transfer. */
88
89 ret = muxc->select(muxc, priv->chan_id);
90 if (ret >= 0)
91 ret = __i2c_smbus_xfer(parent, addr, flags,
92 read_write, command, size, data);
93 if (muxc->deselect)
94 muxc->deselect(muxc, priv->chan_id);
95
96 return ret;
97 }
98
i2c_mux_smbus_xfer(struct i2c_adapter * adap,u16 addr,unsigned short flags,char read_write,u8 command,int size,union i2c_smbus_data * data)99 static int i2c_mux_smbus_xfer(struct i2c_adapter *adap,
100 u16 addr, unsigned short flags,
101 char read_write, u8 command,
102 int size, union i2c_smbus_data *data)
103 {
104 struct i2c_mux_priv *priv = adap->algo_data;
105 struct i2c_mux_core *muxc = priv->muxc;
106 struct i2c_adapter *parent = muxc->parent;
107 int ret;
108
109 /* Select the right mux port and perform the transfer. */
110
111 ret = muxc->select(muxc, priv->chan_id);
112 if (ret >= 0)
113 ret = i2c_smbus_xfer(parent, addr, flags,
114 read_write, command, size, data);
115 if (muxc->deselect)
116 muxc->deselect(muxc, priv->chan_id);
117
118 return ret;
119 }
120
121 /* Return the parent's functionality */
i2c_mux_functionality(struct i2c_adapter * adap)122 static u32 i2c_mux_functionality(struct i2c_adapter *adap)
123 {
124 struct i2c_mux_priv *priv = adap->algo_data;
125 struct i2c_adapter *parent = priv->muxc->parent;
126
127 return parent->algo->functionality(parent);
128 }
129
130 /* Return all parent classes, merged */
i2c_mux_parent_classes(struct i2c_adapter * parent)131 static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent)
132 {
133 unsigned int class = 0;
134
135 do {
136 class |= parent->class;
137 parent = i2c_parent_is_i2c_adapter(parent);
138 } while (parent);
139
140 return class;
141 }
142
i2c_mux_lock_bus(struct i2c_adapter * adapter,unsigned int flags)143 static void i2c_mux_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
144 {
145 struct i2c_mux_priv *priv = adapter->algo_data;
146 struct i2c_adapter *parent = priv->muxc->parent;
147
148 rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
149 if (!(flags & I2C_LOCK_ROOT_ADAPTER))
150 return;
151 i2c_lock_bus(parent, flags);
152 }
153
i2c_mux_trylock_bus(struct i2c_adapter * adapter,unsigned int flags)154 static int i2c_mux_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
155 {
156 struct i2c_mux_priv *priv = adapter->algo_data;
157 struct i2c_adapter *parent = priv->muxc->parent;
158
159 if (!rt_mutex_trylock(&parent->mux_lock))
160 return 0; /* mux_lock not locked, failure */
161 if (!(flags & I2C_LOCK_ROOT_ADAPTER))
162 return 1; /* we only want mux_lock, success */
163 if (i2c_trylock_bus(parent, flags))
164 return 1; /* parent locked too, success */
165 rt_mutex_unlock(&parent->mux_lock);
166 return 0; /* parent not locked, failure */
167 }
168
i2c_mux_unlock_bus(struct i2c_adapter * adapter,unsigned int flags)169 static void i2c_mux_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
170 {
171 struct i2c_mux_priv *priv = adapter->algo_data;
172 struct i2c_adapter *parent = priv->muxc->parent;
173
174 if (flags & I2C_LOCK_ROOT_ADAPTER)
175 i2c_unlock_bus(parent, flags);
176 rt_mutex_unlock(&parent->mux_lock);
177 }
178
i2c_parent_lock_bus(struct i2c_adapter * adapter,unsigned int flags)179 static void i2c_parent_lock_bus(struct i2c_adapter *adapter,
180 unsigned int flags)
181 {
182 struct i2c_mux_priv *priv = adapter->algo_data;
183 struct i2c_adapter *parent = priv->muxc->parent;
184
185 rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
186 i2c_lock_bus(parent, flags);
187 }
188
i2c_parent_trylock_bus(struct i2c_adapter * adapter,unsigned int flags)189 static int i2c_parent_trylock_bus(struct i2c_adapter *adapter,
190 unsigned int flags)
191 {
192 struct i2c_mux_priv *priv = adapter->algo_data;
193 struct i2c_adapter *parent = priv->muxc->parent;
194
195 if (!rt_mutex_trylock(&parent->mux_lock))
196 return 0; /* mux_lock not locked, failure */
197 if (i2c_trylock_bus(parent, flags))
198 return 1; /* parent locked too, success */
199 rt_mutex_unlock(&parent->mux_lock);
200 return 0; /* parent not locked, failure */
201 }
202
i2c_parent_unlock_bus(struct i2c_adapter * adapter,unsigned int flags)203 static void i2c_parent_unlock_bus(struct i2c_adapter *adapter,
204 unsigned int flags)
205 {
206 struct i2c_mux_priv *priv = adapter->algo_data;
207 struct i2c_adapter *parent = priv->muxc->parent;
208
209 i2c_unlock_bus(parent, flags);
210 rt_mutex_unlock(&parent->mux_lock);
211 }
212
i2c_root_adapter(struct device * dev)213 struct i2c_adapter *i2c_root_adapter(struct device *dev)
214 {
215 struct device *i2c;
216 struct i2c_adapter *i2c_root;
217
218 /*
219 * Walk up the device tree to find an i2c adapter, indicating
220 * that this is an i2c client device. Check all ancestors to
221 * handle mfd devices etc.
222 */
223 for (i2c = dev; i2c; i2c = i2c->parent) {
224 if (i2c->type == &i2c_adapter_type)
225 break;
226 }
227 if (!i2c)
228 return NULL;
229
230 /* Continue up the tree to find the root i2c adapter */
231 i2c_root = to_i2c_adapter(i2c);
232 while (i2c_parent_is_i2c_adapter(i2c_root))
233 i2c_root = i2c_parent_is_i2c_adapter(i2c_root);
234
235 return i2c_root;
236 }
237 EXPORT_SYMBOL_GPL(i2c_root_adapter);
238
i2c_mux_alloc(struct i2c_adapter * parent,struct device * dev,int max_adapters,int sizeof_priv,u32 flags,int (* select)(struct i2c_mux_core *,u32),int (* deselect)(struct i2c_mux_core *,u32))239 struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
240 struct device *dev, int max_adapters,
241 int sizeof_priv, u32 flags,
242 int (*select)(struct i2c_mux_core *, u32),
243 int (*deselect)(struct i2c_mux_core *, u32))
244 {
245 struct i2c_mux_core *muxc;
246 size_t mux_size;
247
248 mux_size = struct_size(muxc, adapter, max_adapters);
249 muxc = devm_kzalloc(dev, size_add(mux_size, sizeof_priv), GFP_KERNEL);
250 if (!muxc)
251 return NULL;
252 if (sizeof_priv)
253 muxc->priv = &muxc->adapter[max_adapters];
254
255 muxc->parent = parent;
256 muxc->dev = dev;
257 if (flags & I2C_MUX_LOCKED)
258 muxc->mux_locked = true;
259 if (flags & I2C_MUX_ARBITRATOR)
260 muxc->arbitrator = true;
261 if (flags & I2C_MUX_GATE)
262 muxc->gate = true;
263 muxc->select = select;
264 muxc->deselect = deselect;
265 muxc->max_adapters = max_adapters;
266
267 return muxc;
268 }
269 EXPORT_SYMBOL_GPL(i2c_mux_alloc);
270
271 static const struct i2c_lock_operations i2c_mux_lock_ops = {
272 .lock_bus = i2c_mux_lock_bus,
273 .trylock_bus = i2c_mux_trylock_bus,
274 .unlock_bus = i2c_mux_unlock_bus,
275 };
276
277 static const struct i2c_lock_operations i2c_parent_lock_ops = {
278 .lock_bus = i2c_parent_lock_bus,
279 .trylock_bus = i2c_parent_trylock_bus,
280 .unlock_bus = i2c_parent_unlock_bus,
281 };
282
i2c_mux_add_adapter(struct i2c_mux_core * muxc,u32 force_nr,u32 chan_id,unsigned int class)283 int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
284 u32 force_nr, u32 chan_id,
285 unsigned int class)
286 {
287 struct i2c_adapter *parent = muxc->parent;
288 struct i2c_mux_priv *priv;
289 char symlink_name[20];
290 int ret;
291
292 if (muxc->num_adapters >= muxc->max_adapters) {
293 dev_err(muxc->dev, "No room for more i2c-mux adapters\n");
294 return -EINVAL;
295 }
296
297 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
298 if (!priv)
299 return -ENOMEM;
300
301 /* Set up private adapter data */
302 priv->muxc = muxc;
303 priv->chan_id = chan_id;
304
305 /* Need to do algo dynamically because we don't know ahead
306 * of time what sort of physical adapter we'll be dealing with.
307 */
308 if (parent->algo->master_xfer) {
309 if (muxc->mux_locked)
310 priv->algo.master_xfer = i2c_mux_master_xfer;
311 else
312 priv->algo.master_xfer = __i2c_mux_master_xfer;
313 }
314 if (parent->algo->master_xfer_atomic)
315 priv->algo.master_xfer_atomic = priv->algo.master_xfer;
316
317 if (parent->algo->smbus_xfer) {
318 if (muxc->mux_locked)
319 priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
320 else
321 priv->algo.smbus_xfer = __i2c_mux_smbus_xfer;
322 }
323 if (parent->algo->smbus_xfer_atomic)
324 priv->algo.smbus_xfer_atomic = priv->algo.smbus_xfer;
325
326 priv->algo.functionality = i2c_mux_functionality;
327
328 /* Now fill out new adapter structure */
329 snprintf(priv->adap.name, sizeof(priv->adap.name),
330 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
331 priv->adap.owner = THIS_MODULE;
332 priv->adap.algo = &priv->algo;
333 priv->adap.algo_data = priv;
334 priv->adap.dev.parent = &parent->dev;
335 priv->adap.retries = parent->retries;
336 priv->adap.timeout = parent->timeout;
337 priv->adap.quirks = parent->quirks;
338 if (muxc->mux_locked)
339 priv->adap.lock_ops = &i2c_mux_lock_ops;
340 else
341 priv->adap.lock_ops = &i2c_parent_lock_ops;
342
343 /* Sanity check on class */
344 if (i2c_mux_parent_classes(parent) & class)
345 dev_err(&parent->dev,
346 "Segment %d behind mux can't share classes with ancestors\n",
347 chan_id);
348 else
349 priv->adap.class = class;
350
351 /*
352 * Try to populate the mux adapter's of_node, expands to
353 * nothing if !CONFIG_OF.
354 */
355 if (muxc->dev->of_node) {
356 struct device_node *dev_node = muxc->dev->of_node;
357 struct device_node *mux_node, *child = NULL;
358 u32 reg;
359
360 if (muxc->arbitrator)
361 mux_node = of_get_child_by_name(dev_node, "i2c-arb");
362 else if (muxc->gate)
363 mux_node = of_get_child_by_name(dev_node, "i2c-gate");
364 else
365 mux_node = of_get_child_by_name(dev_node, "i2c-mux");
366
367 if (mux_node) {
368 /* A "reg" property indicates an old-style DT entry */
369 if (!of_property_read_u32(mux_node, "reg", ®)) {
370 of_node_put(mux_node);
371 mux_node = NULL;
372 }
373 }
374
375 if (!mux_node)
376 mux_node = of_node_get(dev_node);
377 else if (muxc->arbitrator || muxc->gate)
378 child = of_node_get(mux_node);
379
380 if (!child) {
381 for_each_child_of_node(mux_node, child) {
382 ret = of_property_read_u32(child, "reg", ®);
383 if (ret)
384 continue;
385 if (chan_id == reg)
386 break;
387 }
388 }
389
390 priv->adap.dev.of_node = child;
391 of_node_put(mux_node);
392 }
393
394 /*
395 * Associate the mux channel with an ACPI node.
396 */
397 if (has_acpi_companion(muxc->dev))
398 acpi_preset_companion(&priv->adap.dev,
399 ACPI_COMPANION(muxc->dev),
400 chan_id);
401
402 if (force_nr) {
403 priv->adap.nr = force_nr;
404 ret = i2c_add_numbered_adapter(&priv->adap);
405 if (ret < 0) {
406 dev_err(&parent->dev,
407 "failed to add mux-adapter %u as bus %u (error=%d)\n",
408 chan_id, force_nr, ret);
409 goto err_free_priv;
410 }
411 } else {
412 ret = i2c_add_adapter(&priv->adap);
413 if (ret < 0) {
414 dev_err(&parent->dev,
415 "failed to add mux-adapter %u (error=%d)\n",
416 chan_id, ret);
417 goto err_free_priv;
418 }
419 }
420
421 WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
422 "mux_device"),
423 "can't create symlink to mux device\n");
424
425 snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
426 WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
427 symlink_name),
428 "can't create symlink to channel %u\n", chan_id);
429 dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
430 i2c_adapter_id(&priv->adap));
431
432 muxc->adapter[muxc->num_adapters++] = &priv->adap;
433 return 0;
434
435 err_free_priv:
436 kfree(priv);
437 return ret;
438 }
439 EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
440
i2c_mux_del_adapters(struct i2c_mux_core * muxc)441 void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
442 {
443 char symlink_name[20];
444
445 while (muxc->num_adapters) {
446 struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
447 struct i2c_mux_priv *priv = adap->algo_data;
448 struct device_node *np = adap->dev.of_node;
449
450 muxc->adapter[muxc->num_adapters] = NULL;
451
452 snprintf(symlink_name, sizeof(symlink_name),
453 "channel-%u", priv->chan_id);
454 sysfs_remove_link(&muxc->dev->kobj, symlink_name);
455
456 sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
457 i2c_del_adapter(adap);
458 of_node_put(np);
459 kfree(priv);
460 }
461 }
462 EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
463
464 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
465 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
466 MODULE_LICENSE("GPL v2");
467
