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
i2c_mux_lock_bus(struct i2c_adapter * adapter,unsigned int flags)130 static void i2c_mux_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
131 {
132 struct i2c_mux_priv *priv = adapter->algo_data;
133 struct i2c_adapter *parent = priv->muxc->parent;
134
135 rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
136 if (!(flags & I2C_LOCK_ROOT_ADAPTER))
137 return;
138 i2c_lock_bus(parent, flags);
139 }
140
i2c_mux_trylock_bus(struct i2c_adapter * adapter,unsigned int flags)141 static int i2c_mux_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
142 {
143 struct i2c_mux_priv *priv = adapter->algo_data;
144 struct i2c_adapter *parent = priv->muxc->parent;
145
146 if (!rt_mutex_trylock(&parent->mux_lock))
147 return 0; /* mux_lock not locked, failure */
148 if (!(flags & I2C_LOCK_ROOT_ADAPTER))
149 return 1; /* we only want mux_lock, success */
150 if (i2c_trylock_bus(parent, flags))
151 return 1; /* parent locked too, success */
152 rt_mutex_unlock(&parent->mux_lock);
153 return 0; /* parent not locked, failure */
154 }
155
i2c_mux_unlock_bus(struct i2c_adapter * adapter,unsigned int flags)156 static void i2c_mux_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
157 {
158 struct i2c_mux_priv *priv = adapter->algo_data;
159 struct i2c_adapter *parent = priv->muxc->parent;
160
161 if (flags & I2C_LOCK_ROOT_ADAPTER)
162 i2c_unlock_bus(parent, flags);
163 rt_mutex_unlock(&parent->mux_lock);
164 }
165
i2c_parent_lock_bus(struct i2c_adapter * adapter,unsigned int flags)166 static void i2c_parent_lock_bus(struct i2c_adapter *adapter,
167 unsigned int flags)
168 {
169 struct i2c_mux_priv *priv = adapter->algo_data;
170 struct i2c_adapter *parent = priv->muxc->parent;
171
172 rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
173 i2c_lock_bus(parent, flags);
174 }
175
i2c_parent_trylock_bus(struct i2c_adapter * adapter,unsigned int flags)176 static int i2c_parent_trylock_bus(struct i2c_adapter *adapter,
177 unsigned int flags)
178 {
179 struct i2c_mux_priv *priv = adapter->algo_data;
180 struct i2c_adapter *parent = priv->muxc->parent;
181
182 if (!rt_mutex_trylock(&parent->mux_lock))
183 return 0; /* mux_lock not locked, failure */
184 if (i2c_trylock_bus(parent, flags))
185 return 1; /* parent locked too, success */
186 rt_mutex_unlock(&parent->mux_lock);
187 return 0; /* parent not locked, failure */
188 }
189
i2c_parent_unlock_bus(struct i2c_adapter * adapter,unsigned int flags)190 static void i2c_parent_unlock_bus(struct i2c_adapter *adapter,
191 unsigned int flags)
192 {
193 struct i2c_mux_priv *priv = adapter->algo_data;
194 struct i2c_adapter *parent = priv->muxc->parent;
195
196 i2c_unlock_bus(parent, flags);
197 rt_mutex_unlock(&parent->mux_lock);
198 }
199
i2c_root_adapter(struct device * dev)200 struct i2c_adapter *i2c_root_adapter(struct device *dev)
201 {
202 struct device *i2c;
203 struct i2c_adapter *i2c_root;
204
205 /*
206 * Walk up the device tree to find an i2c adapter, indicating
207 * that this is an i2c client device. Check all ancestors to
208 * handle mfd devices etc.
209 */
210 for (i2c = dev; i2c; i2c = i2c->parent) {
211 if (i2c->type == &i2c_adapter_type)
212 break;
213 }
214 if (!i2c)
215 return NULL;
216
217 /* Continue up the tree to find the root i2c adapter */
218 i2c_root = to_i2c_adapter(i2c);
219 while (i2c_parent_is_i2c_adapter(i2c_root))
220 i2c_root = i2c_parent_is_i2c_adapter(i2c_root);
221
222 return i2c_root;
223 }
224 EXPORT_SYMBOL_GPL(i2c_root_adapter);
225
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))226 struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
227 struct device *dev, int max_adapters,
228 int sizeof_priv, u32 flags,
229 int (*select)(struct i2c_mux_core *, u32),
230 int (*deselect)(struct i2c_mux_core *, u32))
231 {
232 struct i2c_mux_core *muxc;
233 size_t mux_size;
234
235 mux_size = struct_size(muxc, adapter, max_adapters);
236 muxc = devm_kzalloc(dev, size_add(mux_size, sizeof_priv), GFP_KERNEL);
237 if (!muxc)
238 return NULL;
239 if (sizeof_priv)
240 muxc->priv = &muxc->adapter[max_adapters];
241
242 muxc->parent = parent;
243 muxc->dev = dev;
244 muxc->mux_locked = !!(flags & I2C_MUX_LOCKED);
245 muxc->arbitrator = !!(flags & I2C_MUX_ARBITRATOR);
246 muxc->gate = !!(flags & I2C_MUX_GATE);
247 muxc->select = select;
248 muxc->deselect = deselect;
249 muxc->max_adapters = max_adapters;
250
251 return muxc;
252 }
253 EXPORT_SYMBOL_GPL(i2c_mux_alloc);
254
255 static const struct i2c_lock_operations i2c_mux_lock_ops = {
256 .lock_bus = i2c_mux_lock_bus,
257 .trylock_bus = i2c_mux_trylock_bus,
258 .unlock_bus = i2c_mux_unlock_bus,
259 };
260
261 static const struct i2c_lock_operations i2c_parent_lock_ops = {
262 .lock_bus = i2c_parent_lock_bus,
263 .trylock_bus = i2c_parent_trylock_bus,
264 .unlock_bus = i2c_parent_unlock_bus,
265 };
266
i2c_mux_add_adapter(struct i2c_mux_core * muxc,u32 force_nr,u32 chan_id)267 int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
268 u32 force_nr, u32 chan_id)
269 {
270 struct i2c_adapter *parent = muxc->parent;
271 struct i2c_mux_priv *priv;
272 char symlink_name[20];
273 int ret;
274
275 if (muxc->num_adapters >= muxc->max_adapters) {
276 dev_err(muxc->dev, "No room for more i2c-mux adapters\n");
277 return -EINVAL;
278 }
279
280 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
281 if (!priv)
282 return -ENOMEM;
283
284 /* Set up private adapter data */
285 priv->muxc = muxc;
286 priv->chan_id = chan_id;
287
288 /* Need to do algo dynamically because we don't know ahead
289 * of time what sort of physical adapter we'll be dealing with.
290 */
291 if (parent->algo->master_xfer) {
292 if (muxc->mux_locked)
293 priv->algo.xfer = i2c_mux_master_xfer;
294 else
295 priv->algo.xfer = __i2c_mux_master_xfer;
296 }
297 if (parent->algo->master_xfer_atomic)
298 priv->algo.xfer_atomic = priv->algo.master_xfer;
299
300 if (parent->algo->smbus_xfer) {
301 if (muxc->mux_locked)
302 priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
303 else
304 priv->algo.smbus_xfer = __i2c_mux_smbus_xfer;
305 }
306 if (parent->algo->smbus_xfer_atomic)
307 priv->algo.smbus_xfer_atomic = priv->algo.smbus_xfer;
308
309 priv->algo.functionality = i2c_mux_functionality;
310
311 /* Now fill out new adapter structure */
312 snprintf(priv->adap.name, sizeof(priv->adap.name),
313 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
314 priv->adap.owner = THIS_MODULE;
315 priv->adap.algo = &priv->algo;
316 priv->adap.algo_data = priv;
317 priv->adap.dev.parent = &parent->dev;
318 priv->adap.retries = parent->retries;
319 priv->adap.timeout = parent->timeout;
320 priv->adap.quirks = parent->quirks;
321 if (muxc->mux_locked)
322 priv->adap.lock_ops = &i2c_mux_lock_ops;
323 else
324 priv->adap.lock_ops = &i2c_parent_lock_ops;
325
326 /*
327 * Try to populate the mux adapter's of_node, expands to
328 * nothing if !CONFIG_OF.
329 */
330 if (muxc->dev->of_node) {
331 struct device_node *dev_node = muxc->dev->of_node;
332 struct device_node *mux_node, *child = NULL;
333 u32 reg;
334
335 if (muxc->arbitrator)
336 mux_node = of_get_child_by_name(dev_node, "i2c-arb");
337 else if (muxc->gate)
338 mux_node = of_get_child_by_name(dev_node, "i2c-gate");
339 else
340 mux_node = of_get_child_by_name(dev_node, "i2c-mux");
341
342 if (mux_node) {
343 /* A "reg" property indicates an old-style DT entry */
344 if (!of_property_read_u32(mux_node, "reg", ®)) {
345 of_node_put(mux_node);
346 mux_node = NULL;
347 }
348 }
349
350 if (!mux_node)
351 mux_node = of_node_get(dev_node);
352 else if (muxc->arbitrator || muxc->gate)
353 child = of_node_get(mux_node);
354
355 if (!child) {
356 for_each_child_of_node(mux_node, child) {
357 ret = of_property_read_u32(child, "reg", ®);
358 if (ret)
359 continue;
360 if (chan_id == reg)
361 break;
362 }
363 }
364
365 priv->adap.dev.of_node = child;
366 of_node_put(mux_node);
367 }
368
369 /*
370 * Associate the mux channel with an ACPI node.
371 */
372 if (has_acpi_companion(muxc->dev))
373 acpi_preset_companion(&priv->adap.dev,
374 ACPI_COMPANION(muxc->dev),
375 chan_id);
376
377 if (force_nr) {
378 priv->adap.nr = force_nr;
379 ret = i2c_add_numbered_adapter(&priv->adap);
380 if (ret < 0) {
381 dev_err(&parent->dev,
382 "failed to add mux-adapter %u as bus %u (error=%d)\n",
383 chan_id, force_nr, ret);
384 goto err_free_priv;
385 }
386 } else {
387 ret = i2c_add_adapter(&priv->adap);
388 if (ret < 0) {
389 dev_err(&parent->dev,
390 "failed to add mux-adapter %u (error=%d)\n",
391 chan_id, ret);
392 goto err_free_priv;
393 }
394 }
395
396 WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
397 "mux_device"),
398 "can't create symlink to mux device\n");
399
400 snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
401 WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
402 symlink_name),
403 "can't create symlink to channel %u\n", chan_id);
404 dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
405 i2c_adapter_id(&priv->adap));
406
407 muxc->adapter[muxc->num_adapters++] = &priv->adap;
408 return 0;
409
410 err_free_priv:
411 kfree(priv);
412 return ret;
413 }
414 EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
415
i2c_mux_del_adapters(struct i2c_mux_core * muxc)416 void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
417 {
418 char symlink_name[20];
419
420 while (muxc->num_adapters) {
421 struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
422 struct i2c_mux_priv *priv = adap->algo_data;
423 struct device_node *np = adap->dev.of_node;
424
425 muxc->adapter[muxc->num_adapters] = NULL;
426
427 snprintf(symlink_name, sizeof(symlink_name),
428 "channel-%u", priv->chan_id);
429 sysfs_remove_link(&muxc->dev->kobj, symlink_name);
430
431 sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
432 i2c_del_adapter(adap);
433 of_node_put(np);
434 kfree(priv);
435 }
436 }
437 EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
438
439 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
440 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
441 MODULE_LICENSE("GPL v2");
442