i2c-mux.c

  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 */
 32struct 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
 39static 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
 58static 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
 77static 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
 99static 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 */
122static 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
130static 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
141static 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
156static 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
166static 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
176static 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
190static 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
200struct 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}
224EXPORT_SYMBOL_GPL(i2c_root_adapter);
225
226struct 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}
253EXPORT_SYMBOL_GPL(i2c_mux_alloc);
254
255static 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
261static 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
267int 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", &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", &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
410err_free_priv:
411	kfree(priv);
412	return ret;
413}
414EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
415
416void 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}
437EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
438
439MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
440MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
441MODULE_LICENSE("GPL v2");