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>
29 #include <linux/sysfs.h>
31 /* multiplexer per channel data */
33 struct i2c_adapter adap;
34 struct i2c_algorithm algo;
35 struct i2c_mux_core *muxc;
39 static int __i2c_mux_master_xfer(struct i2c_adapter *adap,
40 struct i2c_msg msgs[], int num)
42 struct i2c_mux_priv *priv = adap->algo_data;
43 struct i2c_mux_core *muxc = priv->muxc;
44 struct i2c_adapter *parent = muxc->parent;
47 /* Switch to the right mux port and perform the transfer. */
49 ret = muxc->select(muxc, priv->chan_id);
51 ret = __i2c_transfer(parent, msgs, num);
53 muxc->deselect(muxc, priv->chan_id);
58 static int i2c_mux_master_xfer(struct i2c_adapter *adap,
59 struct i2c_msg msgs[], int num)
61 struct i2c_mux_priv *priv = adap->algo_data;
62 struct i2c_mux_core *muxc = priv->muxc;
63 struct i2c_adapter *parent = muxc->parent;
66 /* Switch to the right mux port and perform the transfer. */
68 ret = muxc->select(muxc, priv->chan_id);
70 ret = i2c_transfer(parent, msgs, num);
72 muxc->deselect(muxc, priv->chan_id);
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)
82 struct i2c_mux_priv *priv = adap->algo_data;
83 struct i2c_mux_core *muxc = priv->muxc;
84 struct i2c_adapter *parent = muxc->parent;
87 /* Select the right mux port and perform the transfer. */
89 ret = muxc->select(muxc, priv->chan_id);
91 ret = __i2c_smbus_xfer(parent, addr, flags,
92 read_write, command, size, data);
94 muxc->deselect(muxc, priv->chan_id);
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)
104 struct i2c_mux_priv *priv = adap->algo_data;
105 struct i2c_mux_core *muxc = priv->muxc;
106 struct i2c_adapter *parent = muxc->parent;
109 /* Select the right mux port and perform the transfer. */
111 ret = muxc->select(muxc, priv->chan_id);
113 ret = i2c_smbus_xfer(parent, addr, flags,
114 read_write, command, size, data);
116 muxc->deselect(muxc, priv->chan_id);
121 /* Return the parent's functionality */
122 static u32 i2c_mux_functionality(struct i2c_adapter *adap)
124 struct i2c_mux_priv *priv = adap->algo_data;
125 struct i2c_adapter *parent = priv->muxc->parent;
127 return parent->algo->functionality(parent);
130 /* Return all parent classes, merged */
131 static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent)
133 unsigned int class = 0;
136 class |= parent->class;
137 parent = i2c_parent_is_i2c_adapter(parent);
143 static void i2c_mux_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
145 struct i2c_mux_priv *priv = adapter->algo_data;
146 struct i2c_adapter *parent = priv->muxc->parent;
148 rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
149 if (!(flags & I2C_LOCK_ROOT_ADAPTER))
151 i2c_lock_bus(parent, flags);
154 static int i2c_mux_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
156 struct i2c_mux_priv *priv = adapter->algo_data;
157 struct i2c_adapter *parent = priv->muxc->parent;
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 */
169 static void i2c_mux_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
171 struct i2c_mux_priv *priv = adapter->algo_data;
172 struct i2c_adapter *parent = priv->muxc->parent;
174 if (flags & I2C_LOCK_ROOT_ADAPTER)
175 i2c_unlock_bus(parent, flags);
176 rt_mutex_unlock(&parent->mux_lock);
179 static void i2c_parent_lock_bus(struct i2c_adapter *adapter,
182 struct i2c_mux_priv *priv = adapter->algo_data;
183 struct i2c_adapter *parent = priv->muxc->parent;
185 rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
186 i2c_lock_bus(parent, flags);
189 static int i2c_parent_trylock_bus(struct i2c_adapter *adapter,
192 struct i2c_mux_priv *priv = adapter->algo_data;
193 struct i2c_adapter *parent = priv->muxc->parent;
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 */
203 static void i2c_parent_unlock_bus(struct i2c_adapter *adapter,
206 struct i2c_mux_priv *priv = adapter->algo_data;
207 struct i2c_adapter *parent = priv->muxc->parent;
209 i2c_unlock_bus(parent, flags);
210 rt_mutex_unlock(&parent->mux_lock);
213 struct i2c_adapter *i2c_root_adapter(struct device *dev)
216 struct i2c_adapter *i2c_root;
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.
223 for (i2c = dev; i2c; i2c = i2c->parent) {
224 if (i2c->type == &i2c_adapter_type)
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);
237 EXPORT_SYMBOL_GPL(i2c_root_adapter);
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))
245 struct i2c_mux_core *muxc;
247 muxc = devm_kzalloc(dev, struct_size(muxc, adapter, max_adapters)
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 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,
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,
282 int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
283 u32 force_nr, u32 chan_id,
286 struct i2c_adapter *parent = muxc->parent;
287 struct i2c_mux_priv *priv;
288 char symlink_name[20];
291 if (muxc->num_adapters >= muxc->max_adapters) {
292 dev_err(muxc->dev, "No room for more i2c-mux adapters\n");
296 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
300 /* Set up private adapter data */
302 priv->chan_id = chan_id;
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.
307 if (parent->algo->master_xfer) {
308 if (muxc->mux_locked)
309 priv->algo.master_xfer = i2c_mux_master_xfer;
311 priv->algo.master_xfer = __i2c_mux_master_xfer;
313 if (parent->algo->master_xfer_atomic)
314 priv->algo.master_xfer_atomic = priv->algo.master_xfer;
316 if (parent->algo->smbus_xfer) {
317 if (muxc->mux_locked)
318 priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
320 priv->algo.smbus_xfer = __i2c_mux_smbus_xfer;
322 if (parent->algo->smbus_xfer_atomic)
323 priv->algo.smbus_xfer_atomic = priv->algo.smbus_xfer;
325 priv->algo.functionality = i2c_mux_functionality;
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;
340 priv->adap.lock_ops = &i2c_parent_lock_ops;
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",
348 priv->adap.class = class;
351 * Try to populate the mux adapter's of_node, expands to
352 * nothing if !CONFIG_OF.
354 if (muxc->dev->of_node) {
355 struct device_node *dev_node = muxc->dev->of_node;
356 struct device_node *mux_node, *child = NULL;
359 if (muxc->arbitrator)
360 mux_node = of_get_child_by_name(dev_node, "i2c-arb");
362 mux_node = of_get_child_by_name(dev_node, "i2c-gate");
364 mux_node = of_get_child_by_name(dev_node, "i2c-mux");
367 /* A "reg" property indicates an old-style DT entry */
368 if (!of_property_read_u32(mux_node, "reg", ®)) {
369 of_node_put(mux_node);
375 mux_node = of_node_get(dev_node);
376 else if (muxc->arbitrator || muxc->gate)
377 child = of_node_get(mux_node);
380 for_each_child_of_node(mux_node, child) {
381 ret = of_property_read_u32(child, "reg", ®);
389 priv->adap.dev.of_node = child;
390 of_node_put(mux_node);
394 * Associate the mux channel with an ACPI node.
396 if (has_acpi_companion(muxc->dev))
397 acpi_preset_companion(&priv->adap.dev,
398 ACPI_COMPANION(muxc->dev),
402 priv->adap.nr = force_nr;
403 ret = i2c_add_numbered_adapter(&priv->adap);
405 dev_err(&parent->dev,
406 "failed to add mux-adapter %u as bus %u (error=%d)\n",
407 chan_id, force_nr, ret);
411 ret = i2c_add_adapter(&priv->adap);
413 dev_err(&parent->dev,
414 "failed to add mux-adapter %u (error=%d)\n",
420 WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
422 "can't create symlink to mux device\n");
424 snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
425 WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
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));
431 muxc->adapter[muxc->num_adapters++] = &priv->adap;
438 EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
440 void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
442 char symlink_name[20];
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;
449 muxc->adapter[muxc->num_adapters] = NULL;
451 snprintf(symlink_name, sizeof(symlink_name),
452 "channel-%u", priv->chan_id);
453 sysfs_remove_link(&muxc->dev->kobj, symlink_name);
455 sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
456 i2c_del_adapter(adap);
461 EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
463 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
464 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
465 MODULE_LICENSE("GPL v2");