drivers/i2c/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
  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", &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", &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         } else {
 399                 ret = i2c_add_adapter(&priv->adap);
 400         }
 401         if (ret < 0) {
 402                 dev_err(&parent->dev,
 403                         "failed to add mux-adapter (error=%d)\n",
 404                         ret);
 405                 kfree(priv);
 406                 return ret;
 407         }
 408
 409         WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
 410                                "mux_device"),
 411              "can't create symlink to mux device\n");
 412
 413         snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
 414         WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
 415                                symlink_name),
 416              "can't create symlink for channel %u\n", chan_id);
 417         dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
 418                  i2c_adapter_id(&priv->adap));
 419
 420         muxc->adapter[muxc->num_adapters++] = &priv->adap;
 421         return 0;
 422 }
 423 EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
 424
 425 void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
 426 {
 427         char symlink_name[20];
 428
 429         while (muxc->num_adapters) {
 430                 struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
 431                 struct i2c_mux_priv *priv = adap->algo_data;
 432
 433                 muxc->adapter[muxc->num_adapters] = NULL;
 434
 435                 snprintf(symlink_name, sizeof(symlink_name),
 436                          "channel-%u", priv->chan_id);
 437                 sysfs_remove_link(&muxc->dev->kobj, symlink_name);
 438
 439                 sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
 440                 i2c_del_adapter(adap);
 441                 kfree(priv);
 442         }
 443 }
 444 EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
 445
 446 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 447 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 448 MODULE_LICENSE("GPL v2");