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 30 /* multiplexer per channel data */ 31 struct i2c_mux_priv { 32 struct i2c_adapter adap; 33 struct i2c_algorithm algo; 34 struct i2c_mux_core *muxc; 35 u32 chan_id; 36 }; 37 38 static int __i2c_mux_master_xfer(struct i2c_adapter *adap, 39 struct i2c_msg msgs[], int num) 40 { 41 struct i2c_mux_priv *priv = adap->algo_data; 42 struct i2c_mux_core *muxc = priv->muxc; 43 struct i2c_adapter *parent = muxc->parent; 44 int ret; 45 46 /* Switch to the right mux port and perform the transfer. */ 47 48 ret = muxc->select(muxc, priv->chan_id); 49 if (ret >= 0) 50 ret = __i2c_transfer(parent, msgs, num); 51 if (muxc->deselect) 52 muxc->deselect(muxc, priv->chan_id); 53 54 return ret; 55 } 56 57 static int i2c_mux_master_xfer(struct i2c_adapter *adap, 58 struct i2c_msg msgs[], int num) 59 { 60 struct i2c_mux_priv *priv = adap->algo_data; 61 struct i2c_mux_core *muxc = priv->muxc; 62 struct i2c_adapter *parent = muxc->parent; 63 int ret; 64 65 /* Switch to the right mux port and perform the transfer. */ 66 67 ret = muxc->select(muxc, priv->chan_id); 68 if (ret >= 0) 69 ret = i2c_transfer(parent, msgs, num); 70 if (muxc->deselect) 71 muxc->deselect(muxc, priv->chan_id); 72 73 return ret; 74 } 75 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) 80 { 81 struct i2c_mux_priv *priv = adap->algo_data; 82 struct i2c_mux_core *muxc = priv->muxc; 83 struct i2c_adapter *parent = muxc->parent; 84 int ret; 85 86 /* Select the right mux port and perform the transfer. */ 87 88 ret = muxc->select(muxc, priv->chan_id); 89 if (ret >= 0) 90 ret = parent->algo->smbus_xfer(parent, addr, flags, 91 read_write, command, size, data); 92 if (muxc->deselect) 93 muxc->deselect(muxc, priv->chan_id); 94 95 return ret; 96 } 97 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) 102 { 103 struct i2c_mux_priv *priv = adap->algo_data; 104 struct i2c_mux_core *muxc = priv->muxc; 105 struct i2c_adapter *parent = muxc->parent; 106 int ret; 107 108 /* Select the right mux port and perform the transfer. */ 109 110 ret = muxc->select(muxc, priv->chan_id); 111 if (ret >= 0) 112 ret = i2c_smbus_xfer(parent, addr, flags, 113 read_write, command, size, data); 114 if (muxc->deselect) 115 muxc->deselect(muxc, priv->chan_id); 116 117 return ret; 118 } 119 120 /* Return the parent's functionality */ 121 static u32 i2c_mux_functionality(struct i2c_adapter *adap) 122 { 123 struct i2c_mux_priv *priv = adap->algo_data; 124 struct i2c_adapter *parent = priv->muxc->parent; 125 126 return parent->algo->functionality(parent); 127 } 128 129 /* Return all parent classes, merged */ 130 static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent) 131 { 132 unsigned int class = 0; 133 134 do { 135 class |= parent->class; 136 parent = i2c_parent_is_i2c_adapter(parent); 137 } while (parent); 138 139 return class; 140 } 141 142 static void i2c_mux_lock_bus(struct i2c_adapter *adapter, unsigned int flags) 143 { 144 struct i2c_mux_priv *priv = adapter->algo_data; 145 struct i2c_adapter *parent = priv->muxc->parent; 146 147 rt_mutex_lock(&parent->mux_lock); 148 if (!(flags & I2C_LOCK_ROOT_ADAPTER)) 149 return; 150 i2c_lock_bus(parent, flags); 151 } 152 153 static int i2c_mux_trylock_bus(struct i2c_adapter *adapter, unsigned int flags) 154 { 155 struct i2c_mux_priv *priv = adapter->algo_data; 156 struct i2c_adapter *parent = priv->muxc->parent; 157 158 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 */ 166 } 167 168 static void i2c_mux_unlock_bus(struct i2c_adapter *adapter, unsigned int flags) 169 { 170 struct i2c_mux_priv *priv = adapter->algo_data; 171 struct i2c_adapter *parent = priv->muxc->parent; 172 173 if (flags & I2C_LOCK_ROOT_ADAPTER) 174 i2c_unlock_bus(parent, flags); 175 rt_mutex_unlock(&parent->mux_lock); 176 } 177 178 static void i2c_parent_lock_bus(struct i2c_adapter *adapter, 179 unsigned int flags) 180 { 181 struct i2c_mux_priv *priv = adapter->algo_data; 182 struct i2c_adapter *parent = priv->muxc->parent; 183 184 rt_mutex_lock(&parent->mux_lock); 185 i2c_lock_bus(parent, flags); 186 } 187 188 static int i2c_parent_trylock_bus(struct i2c_adapter *adapter, 189 unsigned int flags) 190 { 191 struct i2c_mux_priv *priv = adapter->algo_data; 192 struct i2c_adapter *parent = priv->muxc->parent; 193 194 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 */ 200 } 201 202 static void i2c_parent_unlock_bus(struct i2c_adapter *adapter, 203 unsigned int flags) 204 { 205 struct i2c_mux_priv *priv = adapter->algo_data; 206 struct i2c_adapter *parent = priv->muxc->parent; 207 208 i2c_unlock_bus(parent, flags); 209 rt_mutex_unlock(&parent->mux_lock); 210 } 211 212 struct i2c_adapter *i2c_root_adapter(struct device *dev) 213 { 214 struct device *i2c; 215 struct i2c_adapter *i2c_root; 216 217 /* 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. 221 */ 222 for (i2c = dev; i2c; i2c = i2c->parent) { 223 if (i2c->type == &i2c_adapter_type) 224 break; 225 } 226 if (!i2c) 227 return NULL; 228 229 /* 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); 233 234 return i2c_root; 235 } 236 EXPORT_SYMBOL_GPL(i2c_root_adapter); 237 238 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)) 243 { 244 struct i2c_mux_core *muxc; 245 246 muxc = devm_kzalloc(dev, sizeof(*muxc) 247 + max_adapters * sizeof(muxc->adapter[0]) 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->smbus_xfer) { 314 if (muxc->mux_locked) 315 priv->algo.smbus_xfer = i2c_mux_smbus_xfer; 316 else 317 priv->algo.smbus_xfer = __i2c_mux_smbus_xfer; 318 } 319 priv->algo.functionality = i2c_mux_functionality; 320 321 /* Now fill out new adapter structure */ 322 snprintf(priv->adap.name, sizeof(priv->adap.name), 323 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id); 324 priv->adap.owner = THIS_MODULE; 325 priv->adap.algo = &priv->algo; 326 priv->adap.algo_data = priv; 327 priv->adap.dev.parent = &parent->dev; 328 priv->adap.retries = parent->retries; 329 priv->adap.timeout = parent->timeout; 330 priv->adap.quirks = parent->quirks; 331 if (muxc->mux_locked) 332 priv->adap.lock_ops = &i2c_mux_lock_ops; 333 else 334 priv->adap.lock_ops = &i2c_parent_lock_ops; 335 336 /* Sanity check on class */ 337 if (i2c_mux_parent_classes(parent) & class) 338 dev_err(&parent->dev, 339 "Segment %d behind mux can't share classes with ancestors\n", 340 chan_id); 341 else 342 priv->adap.class = class; 343 344 /* 345 * Try to populate the mux adapter's of_node, expands to 346 * nothing if !CONFIG_OF. 347 */ 348 if (muxc->dev->of_node) { 349 struct device_node *dev_node = muxc->dev->of_node; 350 struct device_node *mux_node, *child = NULL; 351 u32 reg; 352 353 if (muxc->arbitrator) 354 mux_node = of_get_child_by_name(dev_node, "i2c-arb"); 355 else if (muxc->gate) 356 mux_node = of_get_child_by_name(dev_node, "i2c-gate"); 357 else 358 mux_node = of_get_child_by_name(dev_node, "i2c-mux"); 359 360 if (mux_node) { 361 /* A "reg" property indicates an old-style DT entry */ 362 if (!of_property_read_u32(mux_node, "reg", ®)) { 363 of_node_put(mux_node); 364 mux_node = NULL; 365 } 366 } 367 368 if (!mux_node) 369 mux_node = of_node_get(dev_node); 370 else if (muxc->arbitrator || muxc->gate) 371 child = of_node_get(mux_node); 372 373 if (!child) { 374 for_each_child_of_node(mux_node, child) { 375 ret = of_property_read_u32(child, "reg", ®); 376 if (ret) 377 continue; 378 if (chan_id == reg) 379 break; 380 } 381 } 382 383 priv->adap.dev.of_node = child; 384 of_node_put(mux_node); 385 } 386 387 /* 388 * Associate the mux channel with an ACPI node. 389 */ 390 if (has_acpi_companion(muxc->dev)) 391 acpi_preset_companion(&priv->adap.dev, 392 ACPI_COMPANION(muxc->dev), 393 chan_id); 394 395 if (force_nr) { 396 priv->adap.nr = force_nr; 397 ret = i2c_add_numbered_adapter(&priv->adap); 398 if (ret < 0) { 399 dev_err(&parent->dev, 400 "failed to add mux-adapter %u as bus %u (error=%d)\n", 401 chan_id, force_nr, ret); 402 goto err_free_priv; 403 } 404 } else { 405 ret = i2c_add_adapter(&priv->adap); 406 if (ret < 0) { 407 dev_err(&parent->dev, 408 "failed to add mux-adapter %u (error=%d)\n", 409 chan_id, ret); 410 goto err_free_priv; 411 } 412 } 413 414 WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj, 415 "mux_device"), 416 "can't create symlink to mux device\n"); 417 418 snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id); 419 WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj, 420 symlink_name), 421 "can't create symlink to channel %u\n", chan_id); 422 dev_info(&parent->dev, "Added multiplexed i2c bus %d\n", 423 i2c_adapter_id(&priv->adap)); 424 425 muxc->adapter[muxc->num_adapters++] = &priv->adap; 426 return 0; 427 428 err_free_priv: 429 kfree(priv); 430 return ret; 431 } 432 EXPORT_SYMBOL_GPL(i2c_mux_add_adapter); 433 434 void i2c_mux_del_adapters(struct i2c_mux_core *muxc) 435 { 436 char symlink_name[20]; 437 438 while (muxc->num_adapters) { 439 struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters]; 440 struct i2c_mux_priv *priv = adap->algo_data; 441 struct device_node *np = adap->dev.of_node; 442 443 muxc->adapter[muxc->num_adapters] = NULL; 444 445 snprintf(symlink_name, sizeof(symlink_name), 446 "channel-%u", priv->chan_id); 447 sysfs_remove_link(&muxc->dev->kobj, symlink_name); 448 449 sysfs_remove_link(&priv->adap.dev.kobj, "mux_device"); 450 i2c_del_adapter(adap); 451 of_node_put(np); 452 kfree(priv); 453 } 454 } 455 EXPORT_SYMBOL_GPL(i2c_mux_del_adapters); 456 457 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>"); 458 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses"); 459 MODULE_LICENSE("GPL v2"); 460