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 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 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 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 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 */ 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 */ 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 } 142 143 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 } 153 154 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 } 168 169 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 } 178 179 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 } 188 189 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 } 202 203 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 } 212 213 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); 238 239 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 }; 281 282 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", ®)) { 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", ®); 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); 439 440 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