2 * Multiplexed I2C bus driver.
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>
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).
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>
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.
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>
28 #include <linux/slab.h>
30 /* multiplexer per channel data */
32 struct i2c_adapter adap;
33 struct i2c_algorithm algo;
34 struct i2c_mux_core *muxc;
38 static int __i2c_mux_master_xfer(struct i2c_adapter *adap,
39 struct i2c_msg msgs[], int num)
41 struct i2c_mux_priv *priv = adap->algo_data;
42 struct i2c_mux_core *muxc = priv->muxc;
43 struct i2c_adapter *parent = muxc->parent;
46 /* Switch to the right mux port and perform the transfer. */
48 ret = muxc->select(muxc, priv->chan_id);
50 ret = __i2c_transfer(parent, msgs, num);
52 muxc->deselect(muxc, priv->chan_id);
57 static int i2c_mux_master_xfer(struct i2c_adapter *adap,
58 struct i2c_msg msgs[], int num)
60 struct i2c_mux_priv *priv = adap->algo_data;
61 struct i2c_mux_core *muxc = priv->muxc;
62 struct i2c_adapter *parent = muxc->parent;
65 /* Switch to the right mux port and perform the transfer. */
67 ret = muxc->select(muxc, priv->chan_id);
69 ret = i2c_transfer(parent, msgs, num);
71 muxc->deselect(muxc, priv->chan_id);
76 static 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)
81 struct i2c_mux_priv *priv = adap->algo_data;
82 struct i2c_mux_core *muxc = priv->muxc;
83 struct i2c_adapter *parent = muxc->parent;
86 /* Select the right mux port and perform the transfer. */
88 ret = muxc->select(muxc, priv->chan_id);
90 ret = parent->algo->smbus_xfer(parent, addr, flags,
91 read_write, command, size, data);
93 muxc->deselect(muxc, priv->chan_id);
98 static 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)
103 struct i2c_mux_priv *priv = adap->algo_data;
104 struct i2c_mux_core *muxc = priv->muxc;
105 struct i2c_adapter *parent = muxc->parent;
108 /* Select the right mux port and perform the transfer. */
110 ret = muxc->select(muxc, priv->chan_id);
112 ret = i2c_smbus_xfer(parent, addr, flags,
113 read_write, command, size, data);
115 muxc->deselect(muxc, priv->chan_id);
120 /* Return the parent's functionality */
121 static u32 i2c_mux_functionality(struct i2c_adapter *adap)
123 struct i2c_mux_priv *priv = adap->algo_data;
124 struct i2c_adapter *parent = priv->muxc->parent;
126 return parent->algo->functionality(parent);
129 /* Return all parent classes, merged */
130 static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent)
132 unsigned int class = 0;
135 class |= parent->class;
136 parent = i2c_parent_is_i2c_adapter(parent);
142 static void i2c_mux_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
144 struct i2c_mux_priv *priv = adapter->algo_data;
145 struct i2c_adapter *parent = priv->muxc->parent;
147 rt_mutex_lock(&parent->mux_lock);
148 if (!(flags & I2C_LOCK_ROOT_ADAPTER))
150 i2c_lock_bus(parent, flags);
153 static int i2c_mux_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
155 struct i2c_mux_priv *priv = adapter->algo_data;
156 struct i2c_adapter *parent = priv->muxc->parent;
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 */
168 static void i2c_mux_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
170 struct i2c_mux_priv *priv = adapter->algo_data;
171 struct i2c_adapter *parent = priv->muxc->parent;
173 if (flags & I2C_LOCK_ROOT_ADAPTER)
174 i2c_unlock_bus(parent, flags);
175 rt_mutex_unlock(&parent->mux_lock);
178 static void i2c_parent_lock_bus(struct i2c_adapter *adapter,
181 struct i2c_mux_priv *priv = adapter->algo_data;
182 struct i2c_adapter *parent = priv->muxc->parent;
184 rt_mutex_lock(&parent->mux_lock);
185 i2c_lock_bus(parent, flags);
188 static int i2c_parent_trylock_bus(struct i2c_adapter *adapter,
191 struct i2c_mux_priv *priv = adapter->algo_data;
192 struct i2c_adapter *parent = priv->muxc->parent;
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 */
202 static void i2c_parent_unlock_bus(struct i2c_adapter *adapter,
205 struct i2c_mux_priv *priv = adapter->algo_data;
206 struct i2c_adapter *parent = priv->muxc->parent;
208 i2c_unlock_bus(parent, flags);
209 rt_mutex_unlock(&parent->mux_lock);
212 struct i2c_adapter *i2c_root_adapter(struct device *dev)
215 struct i2c_adapter *i2c_root;
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.
222 for (i2c = dev; i2c; i2c = i2c->parent) {
223 if (i2c->type == &i2c_adapter_type)
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);
236 EXPORT_SYMBOL_GPL(i2c_root_adapter);
238 struct 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))
244 struct i2c_mux_core *muxc;
246 muxc = devm_kzalloc(dev, sizeof(*muxc)
247 + max_adapters * sizeof(muxc->adapter[0])
248 + sizeof_priv, GFP_KERNEL);
252 muxc->priv = &muxc->adapter[max_adapters];
254 muxc->parent = parent;
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)
262 muxc->select = select;
263 muxc->deselect = deselect;
264 muxc->max_adapters = max_adapters;
268 EXPORT_SYMBOL_GPL(i2c_mux_alloc);
270 int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
271 u32 force_nr, u32 chan_id,
274 struct i2c_adapter *parent = muxc->parent;
275 struct i2c_mux_priv *priv;
276 char symlink_name[20];
279 if (muxc->num_adapters >= muxc->max_adapters) {
280 dev_err(muxc->dev, "No room for more i2c-mux adapters\n");
284 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
288 /* Set up private adapter data */
290 priv->chan_id = chan_id;
292 /* Need to do algo dynamically because we don't know ahead
293 * of time what sort of physical adapter we'll be dealing with.
295 if (parent->algo->master_xfer) {
296 if (muxc->mux_locked)
297 priv->algo.master_xfer = i2c_mux_master_xfer;
299 priv->algo.master_xfer = __i2c_mux_master_xfer;
301 if (parent->algo->smbus_xfer) {
302 if (muxc->mux_locked)
303 priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
305 priv->algo.smbus_xfer = __i2c_mux_smbus_xfer;
307 priv->algo.functionality = i2c_mux_functionality;
309 /* Now fill out new adapter structure */
310 snprintf(priv->adap.name, sizeof(priv->adap.name),
311 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
312 priv->adap.owner = THIS_MODULE;
313 priv->adap.algo = &priv->algo;
314 priv->adap.algo_data = priv;
315 priv->adap.dev.parent = &parent->dev;
316 priv->adap.retries = parent->retries;
317 priv->adap.timeout = parent->timeout;
318 priv->adap.quirks = parent->quirks;
319 if (muxc->mux_locked) {
320 priv->adap.lock_bus = i2c_mux_lock_bus;
321 priv->adap.trylock_bus = i2c_mux_trylock_bus;
322 priv->adap.unlock_bus = i2c_mux_unlock_bus;
324 priv->adap.lock_bus = i2c_parent_lock_bus;
325 priv->adap.trylock_bus = i2c_parent_trylock_bus;
326 priv->adap.unlock_bus = i2c_parent_unlock_bus;
329 /* Sanity check on class */
330 if (i2c_mux_parent_classes(parent) & class)
331 dev_err(&parent->dev,
332 "Segment %d behind mux can't share classes with ancestors\n",
335 priv->adap.class = class;
338 * Try to populate the mux adapter's of_node, expands to
339 * nothing if !CONFIG_OF.
341 if (muxc->dev->of_node) {
342 struct device_node *dev_node = muxc->dev->of_node;
343 struct device_node *mux_node, *child = NULL;
346 if (muxc->arbitrator)
347 mux_node = of_get_child_by_name(dev_node, "i2c-arb");
349 mux_node = of_get_child_by_name(dev_node, "i2c-gate");
351 mux_node = of_get_child_by_name(dev_node, "i2c-mux");
354 /* A "reg" property indicates an old-style DT entry */
355 if (!of_property_read_u32(mux_node, "reg", ®)) {
356 of_node_put(mux_node);
362 mux_node = of_node_get(dev_node);
363 else if (muxc->arbitrator || muxc->gate)
364 child = of_node_get(mux_node);
367 for_each_child_of_node(mux_node, child) {
368 ret = of_property_read_u32(child, "reg", ®);
376 priv->adap.dev.of_node = child;
377 of_node_put(mux_node);
381 * Associate the mux channel with an ACPI node.
383 if (has_acpi_companion(muxc->dev))
384 acpi_preset_companion(&priv->adap.dev,
385 ACPI_COMPANION(muxc->dev),
389 priv->adap.nr = force_nr;
390 ret = i2c_add_numbered_adapter(&priv->adap);
392 ret = i2c_add_adapter(&priv->adap);
395 dev_err(&parent->dev,
396 "failed to add mux-adapter (error=%d)\n",
402 WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
404 "can't create symlink to mux device\n");
406 snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
407 WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
409 "can't create symlink for channel %u\n", chan_id);
410 dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
411 i2c_adapter_id(&priv->adap));
413 muxc->adapter[muxc->num_adapters++] = &priv->adap;
416 EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
418 void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
420 char symlink_name[20];
422 while (muxc->num_adapters) {
423 struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
424 struct i2c_mux_priv *priv = adap->algo_data;
426 muxc->adapter[muxc->num_adapters] = NULL;
428 snprintf(symlink_name, sizeof(symlink_name),
429 "channel-%u", priv->chan_id);
430 sysfs_remove_link(&muxc->dev->kobj, symlink_name);
432 sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
433 i2c_del_adapter(adap);
437 EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
439 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
440 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
441 MODULE_LICENSE("GPL v2");