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 
247 	muxc = devm_kzalloc(dev, struct_size(muxc, adapter, max_adapters)
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 }
268 EXPORT_SYMBOL_GPL(i2c_mux_alloc);
269 
270 static 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 
276 static 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 
i2c_mux_add_adapter(struct i2c_mux_core * muxc,u32 force_nr,u32 chan_id,unsigned int class)282 int 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->master_xfer_atomic)
314 		priv->algo.master_xfer_atomic = priv->algo.master_xfer;
315 
316 	if (parent->algo->smbus_xfer) {
317 		if (muxc->mux_locked)
318 			priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
319 		else
320 			priv->algo.smbus_xfer = __i2c_mux_smbus_xfer;
321 	}
322 	if (parent->algo->smbus_xfer_atomic)
323 		priv->algo.smbus_xfer_atomic = priv->algo.smbus_xfer;
324 
325 	priv->algo.functionality = i2c_mux_functionality;
326 
327 	/* Now fill out new adapter structure */
328 	snprintf(priv->adap.name, sizeof(priv->adap.name),
329 		 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
330 	priv->adap.owner = THIS_MODULE;
331 	priv->adap.algo = &priv->algo;
332 	priv->adap.algo_data = priv;
333 	priv->adap.dev.parent = &parent->dev;
334 	priv->adap.retries = parent->retries;
335 	priv->adap.timeout = parent->timeout;
336 	priv->adap.quirks = parent->quirks;
337 	if (muxc->mux_locked)
338 		priv->adap.lock_ops = &i2c_mux_lock_ops;
339 	else
340 		priv->adap.lock_ops = &i2c_parent_lock_ops;
341 
342 	/* Sanity check on class */
343 	if (i2c_mux_parent_classes(parent) & class)
344 		dev_err(&parent->dev,
345 			"Segment %d behind mux can't share classes with ancestors\n",
346 			chan_id);
347 	else
348 		priv->adap.class = class;
349 
350 	/*
351 	 * Try to populate the mux adapter's of_node, expands to
352 	 * nothing if !CONFIG_OF.
353 	 */
354 	if (muxc->dev->of_node) {
355 		struct device_node *dev_node = muxc->dev->of_node;
356 		struct device_node *mux_node, *child = NULL;
357 		u32 reg;
358 
359 		if (muxc->arbitrator)
360 			mux_node = of_get_child_by_name(dev_node, "i2c-arb");
361 		else if (muxc->gate)
362 			mux_node = of_get_child_by_name(dev_node, "i2c-gate");
363 		else
364 			mux_node = of_get_child_by_name(dev_node, "i2c-mux");
365 
366 		if (mux_node) {
367 			/* A "reg" property indicates an old-style DT entry */
368 			if (!of_property_read_u32(mux_node, "reg", &reg)) {
369 				of_node_put(mux_node);
370 				mux_node = NULL;
371 			}
372 		}
373 
374 		if (!mux_node)
375 			mux_node = of_node_get(dev_node);
376 		else if (muxc->arbitrator || muxc->gate)
377 			child = of_node_get(mux_node);
378 
379 		if (!child) {
380 			for_each_child_of_node(mux_node, child) {
381 				ret = of_property_read_u32(child, "reg", &reg);
382 				if (ret)
383 					continue;
384 				if (chan_id == reg)
385 					break;
386 			}
387 		}
388 
389 		priv->adap.dev.of_node = child;
390 		of_node_put(mux_node);
391 	}
392 
393 	/*
394 	 * Associate the mux channel with an ACPI node.
395 	 */
396 	if (has_acpi_companion(muxc->dev))
397 		acpi_preset_companion(&priv->adap.dev,
398 				      ACPI_COMPANION(muxc->dev),
399 				      chan_id);
400 
401 	if (force_nr) {
402 		priv->adap.nr = force_nr;
403 		ret = i2c_add_numbered_adapter(&priv->adap);
404 		if (ret < 0) {
405 			dev_err(&parent->dev,
406 				"failed to add mux-adapter %u as bus %u (error=%d)\n",
407 				chan_id, force_nr, ret);
408 			goto err_free_priv;
409 		}
410 	} else {
411 		ret = i2c_add_adapter(&priv->adap);
412 		if (ret < 0) {
413 			dev_err(&parent->dev,
414 				"failed to add mux-adapter %u (error=%d)\n",
415 				chan_id, ret);
416 			goto err_free_priv;
417 		}
418 	}
419 
420 	WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
421 			       "mux_device"),
422 	     "can't create symlink to mux device\n");
423 
424 	snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
425 	WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
426 			       symlink_name),
427 	     "can't create symlink to channel %u\n", chan_id);
428 	dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
429 		 i2c_adapter_id(&priv->adap));
430 
431 	muxc->adapter[muxc->num_adapters++] = &priv->adap;
432 	return 0;
433 
434 err_free_priv:
435 	kfree(priv);
436 	return ret;
437 }
438 EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
439 
i2c_mux_del_adapters(struct i2c_mux_core * muxc)440 void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
441 {
442 	char symlink_name[20];
443 
444 	while (muxc->num_adapters) {
445 		struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
446 		struct i2c_mux_priv *priv = adap->algo_data;
447 		struct device_node *np = adap->dev.of_node;
448 
449 		muxc->adapter[muxc->num_adapters] = NULL;
450 
451 		snprintf(symlink_name, sizeof(symlink_name),
452 			 "channel-%u", priv->chan_id);
453 		sysfs_remove_link(&muxc->dev->kobj, symlink_name);
454 
455 		sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
456 		i2c_del_adapter(adap);
457 		of_node_put(np);
458 		kfree(priv);
459 	}
460 }
461 EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
462 
463 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
464 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
465 MODULE_LICENSE("GPL v2");
466