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 	if (flags & I2C_MUX_LOCKED)
245 		muxc->mux_locked = true;
246 	if (flags & I2C_MUX_ARBITRATOR)
247 		muxc->arbitrator = true;
248 	if (flags & I2C_MUX_GATE)
249 		muxc->gate = true;
250 	muxc->select = select;
251 	muxc->deselect = deselect;
252 	muxc->max_adapters = max_adapters;
253 
254 	return muxc;
255 }
256 EXPORT_SYMBOL_GPL(i2c_mux_alloc);
257 
258 static const struct i2c_lock_operations i2c_mux_lock_ops = {
259 	.lock_bus =    i2c_mux_lock_bus,
260 	.trylock_bus = i2c_mux_trylock_bus,
261 	.unlock_bus =  i2c_mux_unlock_bus,
262 };
263 
264 static const struct i2c_lock_operations i2c_parent_lock_ops = {
265 	.lock_bus =    i2c_parent_lock_bus,
266 	.trylock_bus = i2c_parent_trylock_bus,
267 	.unlock_bus =  i2c_parent_unlock_bus,
268 };
269 
i2c_mux_add_adapter(struct i2c_mux_core * muxc,u32 force_nr,u32 chan_id)270 int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
271 			u32 force_nr, u32 chan_id)
272 {
273 	struct i2c_adapter *parent = muxc->parent;
274 	struct i2c_mux_priv *priv;
275 	char symlink_name[20];
276 	int ret;
277 
278 	if (muxc->num_adapters >= muxc->max_adapters) {
279 		dev_err(muxc->dev, "No room for more i2c-mux adapters\n");
280 		return -EINVAL;
281 	}
282 
283 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
284 	if (!priv)
285 		return -ENOMEM;
286 
287 	/* Set up private adapter data */
288 	priv->muxc = muxc;
289 	priv->chan_id = chan_id;
290 
291 	/* Need to do algo dynamically because we don't know ahead
292 	 * of time what sort of physical adapter we'll be dealing with.
293 	 */
294 	if (parent->algo->master_xfer) {
295 		if (muxc->mux_locked)
296 			priv->algo.master_xfer = i2c_mux_master_xfer;
297 		else
298 			priv->algo.master_xfer = __i2c_mux_master_xfer;
299 	}
300 	if (parent->algo->master_xfer_atomic)
301 		priv->algo.master_xfer_atomic = priv->algo.master_xfer;
302 
303 	if (parent->algo->smbus_xfer) {
304 		if (muxc->mux_locked)
305 			priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
306 		else
307 			priv->algo.smbus_xfer = __i2c_mux_smbus_xfer;
308 	}
309 	if (parent->algo->smbus_xfer_atomic)
310 		priv->algo.smbus_xfer_atomic = priv->algo.smbus_xfer;
311 
312 	priv->algo.functionality = i2c_mux_functionality;
313 
314 	/* Now fill out new adapter structure */
315 	snprintf(priv->adap.name, sizeof(priv->adap.name),
316 		 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
317 	priv->adap.owner = THIS_MODULE;
318 	priv->adap.algo = &priv->algo;
319 	priv->adap.algo_data = priv;
320 	priv->adap.dev.parent = &parent->dev;
321 	priv->adap.retries = parent->retries;
322 	priv->adap.timeout = parent->timeout;
323 	priv->adap.quirks = parent->quirks;
324 	if (muxc->mux_locked)
325 		priv->adap.lock_ops = &i2c_mux_lock_ops;
326 	else
327 		priv->adap.lock_ops = &i2c_parent_lock_ops;
328 
329 	/*
330 	 * Try to populate the mux adapter's of_node, expands to
331 	 * nothing if !CONFIG_OF.
332 	 */
333 	if (muxc->dev->of_node) {
334 		struct device_node *dev_node = muxc->dev->of_node;
335 		struct device_node *mux_node, *child = NULL;
336 		u32 reg;
337 
338 		if (muxc->arbitrator)
339 			mux_node = of_get_child_by_name(dev_node, "i2c-arb");
340 		else if (muxc->gate)
341 			mux_node = of_get_child_by_name(dev_node, "i2c-gate");
342 		else
343 			mux_node = of_get_child_by_name(dev_node, "i2c-mux");
344 
345 		if (mux_node) {
346 			/* A "reg" property indicates an old-style DT entry */
347 			if (!of_property_read_u32(mux_node, "reg", &reg)) {
348 				of_node_put(mux_node);
349 				mux_node = NULL;
350 			}
351 		}
352 
353 		if (!mux_node)
354 			mux_node = of_node_get(dev_node);
355 		else if (muxc->arbitrator || muxc->gate)
356 			child = of_node_get(mux_node);
357 
358 		if (!child) {
359 			for_each_child_of_node(mux_node, child) {
360 				ret = of_property_read_u32(child, "reg", &reg);
361 				if (ret)
362 					continue;
363 				if (chan_id == reg)
364 					break;
365 			}
366 		}
367 
368 		priv->adap.dev.of_node = child;
369 		of_node_put(mux_node);
370 	}
371 
372 	/*
373 	 * Associate the mux channel with an ACPI node.
374 	 */
375 	if (has_acpi_companion(muxc->dev))
376 		acpi_preset_companion(&priv->adap.dev,
377 				      ACPI_COMPANION(muxc->dev),
378 				      chan_id);
379 
380 	if (force_nr) {
381 		priv->adap.nr = force_nr;
382 		ret = i2c_add_numbered_adapter(&priv->adap);
383 		if (ret < 0) {
384 			dev_err(&parent->dev,
385 				"failed to add mux-adapter %u as bus %u (error=%d)\n",
386 				chan_id, force_nr, ret);
387 			goto err_free_priv;
388 		}
389 	} else {
390 		ret = i2c_add_adapter(&priv->adap);
391 		if (ret < 0) {
392 			dev_err(&parent->dev,
393 				"failed to add mux-adapter %u (error=%d)\n",
394 				chan_id, ret);
395 			goto err_free_priv;
396 		}
397 	}
398 
399 	WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
400 			       "mux_device"),
401 	     "can't create symlink to mux device\n");
402 
403 	snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
404 	WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
405 			       symlink_name),
406 	     "can't create symlink to channel %u\n", chan_id);
407 	dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
408 		 i2c_adapter_id(&priv->adap));
409 
410 	muxc->adapter[muxc->num_adapters++] = &priv->adap;
411 	return 0;
412 
413 err_free_priv:
414 	kfree(priv);
415 	return ret;
416 }
417 EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
418 
i2c_mux_del_adapters(struct i2c_mux_core * muxc)419 void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
420 {
421 	char symlink_name[20];
422 
423 	while (muxc->num_adapters) {
424 		struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
425 		struct i2c_mux_priv *priv = adap->algo_data;
426 		struct device_node *np = adap->dev.of_node;
427 
428 		muxc->adapter[muxc->num_adapters] = NULL;
429 
430 		snprintf(symlink_name, sizeof(symlink_name),
431 			 "channel-%u", priv->chan_id);
432 		sysfs_remove_link(&muxc->dev->kobj, symlink_name);
433 
434 		sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
435 		i2c_del_adapter(adap);
436 		of_node_put(np);
437 		kfree(priv);
438 	}
439 }
440 EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
441 
442 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
443 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
444 MODULE_LICENSE("GPL v2");
445