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