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 #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 static void i2c_mux_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
 131 {
 132         struct i2c_mux_priv *priv = adapter->algo_data;
 133         struct i2c_adapter *parent = priv->muxc->parent;
 134
 135         rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
 136         if (!(flags & I2C_LOCK_ROOT_ADAPTER))
 137                 return;
 138         i2c_lock_bus(parent, flags);
 139 }
 140
 141 static int i2c_mux_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
 142 {
 143         struct i2c_mux_priv *priv = adapter->algo_data;
 144         struct i2c_adapter *parent = priv->muxc->parent;
 145
 146         if (!rt_mutex_trylock(&parent->mux_lock))
 147                 return 0;       /* mux_lock not locked, failure */
 148         if (!(flags & I2C_LOCK_ROOT_ADAPTER))
 149                 return 1;       /* we only want mux_lock, success */
 150         if (i2c_trylock_bus(parent, flags))
 151                 return 1;       /* parent locked too, success */
 152         rt_mutex_unlock(&parent->mux_lock);
 153         return 0;               /* parent not locked, failure */
 154 }
 155
 156 static void i2c_mux_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
 157 {
 158         struct i2c_mux_priv *priv = adapter->algo_data;
 159         struct i2c_adapter *parent = priv->muxc->parent;
 160
 161         if (flags & I2C_LOCK_ROOT_ADAPTER)
 162                 i2c_unlock_bus(parent, flags);
 163         rt_mutex_unlock(&parent->mux_lock);
 164 }
 165
 166 static void i2c_parent_lock_bus(struct i2c_adapter *adapter,
 167                                 unsigned int flags)
 168 {
 169         struct i2c_mux_priv *priv = adapter->algo_data;
 170         struct i2c_adapter *parent = priv->muxc->parent;
 171
 172         rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
 173         i2c_lock_bus(parent, flags);
 174 }
 175
 176 static int i2c_parent_trylock_bus(struct i2c_adapter *adapter,
 177                                   unsigned int flags)
 178 {
 179         struct i2c_mux_priv *priv = adapter->algo_data;
 180         struct i2c_adapter *parent = priv->muxc->parent;
 181
 182         if (!rt_mutex_trylock(&parent->mux_lock))
 183                 return 0;       /* mux_lock not locked, failure */
 184         if (i2c_trylock_bus(parent, flags))
 185                 return 1;       /* parent locked too, success */
 186         rt_mutex_unlock(&parent->mux_lock);
 187         return 0;               /* parent not locked, failure */
 188 }
 189
 190 static void i2c_parent_unlock_bus(struct i2c_adapter *adapter,
 191                                   unsigned int flags)
 192 {
 193         struct i2c_mux_priv *priv = adapter->algo_data;
 194         struct i2c_adapter *parent = priv->muxc->parent;
 195
 196         i2c_unlock_bus(parent, flags);
 197         rt_mutex_unlock(&parent->mux_lock);
 198 }
 199
 200 struct i2c_adapter *i2c_root_adapter(struct device *dev)
 201 {
 202         struct device *i2c;
 203         struct i2c_adapter *i2c_root;
 204
 205         /*
 206          * Walk up the device tree to find an i2c adapter, indicating
 207          * that this is an i2c client device. Check all ancestors to
 208          * handle mfd devices etc.
 209          */
 210         for (i2c = dev; i2c; i2c = i2c->parent) {
 211                 if (i2c->type == &i2c_adapter_type)
 212                         break;
 213         }
 214         if (!i2c)
 215                 return NULL;
 216
 217         /* Continue up the tree to find the root i2c adapter */
 218         i2c_root = to_i2c_adapter(i2c);
 219         while (i2c_parent_is_i2c_adapter(i2c_root))
 220                 i2c_root = i2c_parent_is_i2c_adapter(i2c_root);
 221
 222         return i2c_root;
 223 }
 224 EXPORT_SYMBOL_GPL(i2c_root_adapter);
 225
 226 struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
 227                                    struct device *dev, int max_adapters,
 228                                    int sizeof_priv, u32 flags,
 229                                    int (*select)(struct i2c_mux_core *, u32),
 230                                    int (*deselect)(struct i2c_mux_core *, u32))
 231 {
 232         struct i2c_mux_core *muxc;
 233         size_t mux_size;
 234
 235         mux_size = struct_size(muxc, adapter, max_adapters);
 236         muxc = devm_kzalloc(dev, size_add(mux_size, sizeof_priv), GFP_KERNEL);
 237         if (!muxc)
 238                 return NULL;
 239         if (sizeof_priv)
 240                 muxc->priv = &muxc->adapter[max_adapters];
 241
 242         muxc->parent = parent;
 243         muxc->dev = dev;
 244         if (flags & I2C_MUX_LOCKED)
 245                 muxc->mux_locked = true;
 246         if (flags & I2C_MUX_ARBITRATOR)
 247                 muxc->arbitrator = true;
 248         if (flags & I2C_MUX_GATE)
 249                 muxc->gate = true;
 250         muxc->select = select;
 251         muxc->deselect = deselect;
 252         muxc->max_adapters = max_adapters;
 253
 254         return muxc;
 255 }
 256 EXPORT_SYMBOL_GPL(i2c_mux_alloc);
 257
 258 static const struct i2c_lock_operations i2c_mux_lock_ops = {
 259         .lock_bus =    i2c_mux_lock_bus,
 260         .trylock_bus = i2c_mux_trylock_bus,
 261         .unlock_bus =  i2c_mux_unlock_bus,
 262 };
 263
 264 static const struct i2c_lock_operations i2c_parent_lock_ops = {
 265         .lock_bus =    i2c_parent_lock_bus,
 266         .trylock_bus = i2c_parent_trylock_bus,
 267         .unlock_bus =  i2c_parent_unlock_bus,
 268 };
 269
 270 int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 271                         u32 force_nr, u32 chan_id)
 272 {
 273         struct i2c_adapter *parent = muxc->parent;
 274         struct i2c_mux_priv *priv;
 275         char symlink_name[20];
 276         int ret;
 277
 278         if (muxc->num_adapters >= muxc->max_adapters) {
 279                 dev_err(muxc->dev, "No room for more i2c-mux adapters\n");
 280                 return -EINVAL;
 281         }
 282
 283         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 284         if (!priv)
 285                 return -ENOMEM;
 286
 287         /* Set up private adapter data */
 288         priv->muxc = muxc;
 289         priv->chan_id = chan_id;
 290
 291         /* Need to do algo dynamically because we don't know ahead
 292          * of time what sort of physical adapter we'll be dealing with.
 293          */
 294         if (parent->algo->master_xfer) {
 295                 if (muxc->mux_locked)
 296                         priv->algo.master_xfer = i2c_mux_master_xfer;
 297                 else
 298                         priv->algo.master_xfer = __i2c_mux_master_xfer;
 299         }
 300         if (parent->algo->master_xfer_atomic)
 301                 priv->algo.master_xfer_atomic = priv->algo.master_xfer;
 302
 303         if (parent->algo->smbus_xfer) {
 304                 if (muxc->mux_locked)
 305                         priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
 306                 else
 307                         priv->algo.smbus_xfer = __i2c_mux_smbus_xfer;
 308         }
 309         if (parent->algo->smbus_xfer_atomic)
 310                 priv->algo.smbus_xfer_atomic = priv->algo.smbus_xfer;
 311
 312         priv->algo.functionality = i2c_mux_functionality;
 313
 314         /* Now fill out new adapter structure */
 315         snprintf(priv->adap.name, sizeof(priv->adap.name),
 316                  "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
 317         priv->adap.owner = THIS_MODULE;
 318         priv->adap.algo = &priv->algo;
 319         priv->adap.algo_data = priv;
 320         priv->adap.dev.parent = &parent->dev;
 321         priv->adap.retries = parent->retries;
 322         priv->adap.timeout = parent->timeout;
 323         priv->adap.quirks = parent->quirks;
 324         if (muxc->mux_locked)
 325                 priv->adap.lock_ops = &i2c_mux_lock_ops;
 326         else
 327                 priv->adap.lock_ops = &i2c_parent_lock_ops;
 328
 329         /*
 330          * Try to populate the mux adapter's of_node, expands to
 331          * nothing if !CONFIG_OF.
 332          */
 333         if (muxc->dev->of_node) {
 334                 struct device_node *dev_node = muxc->dev->of_node;
 335                 struct device_node *mux_node, *child = NULL;
 336                 u32 reg;
 337
 338                 if (muxc->arbitrator)
 339                         mux_node = of_get_child_by_name(dev_node, "i2c-arb");
 340                 else if (muxc->gate)
 341                         mux_node = of_get_child_by_name(dev_node, "i2c-gate");
 342                 else
 343                         mux_node = of_get_child_by_name(dev_node, "i2c-mux");
 344
 345                 if (mux_node) {
 346                         /* A "reg" property indicates an old-style DT entry */
 347                         if (!of_property_read_u32(mux_node, "reg", &reg)) {
 348                                 of_node_put(mux_node);
 349                                 mux_node = NULL;
 350                         }
 351                 }
 352
 353                 if (!mux_node)
 354                         mux_node = of_node_get(dev_node);
 355                 else if (muxc->arbitrator || muxc->gate)
 356                         child = of_node_get(mux_node);
 357
 358                 if (!child) {
 359                         for_each_child_of_node(mux_node, child) {
 360                                 ret = of_property_read_u32(child, "reg", &reg);
 361                                 if (ret)
 362                                         continue;
 363                                 if (chan_id == reg)
 364                                         break;
 365                         }
 366                 }
 367
 368                 priv->adap.dev.of_node = child;
 369                 of_node_put(mux_node);
 370         }
 371
 372         /*
 373          * Associate the mux channel with an ACPI node.
 374          */
 375         if (has_acpi_companion(muxc->dev))
 376                 acpi_preset_companion(&priv->adap.dev,
 377                                       ACPI_COMPANION(muxc->dev),
 378                                       chan_id);
 379
 380         if (force_nr) {
 381                 priv->adap.nr = force_nr;
 382                 ret = i2c_add_numbered_adapter(&priv->adap);
 383                 if (ret < 0) {
 384                         dev_err(&parent->dev,
 385                                 "failed to add mux-adapter %u as bus %u (error=%d)\n",
 386                                 chan_id, force_nr, ret);
 387                         goto err_free_priv;
 388                 }
 389         } else {
 390                 ret = i2c_add_adapter(&priv->adap);
 391                 if (ret < 0) {
 392                         dev_err(&parent->dev,
 393                                 "failed to add mux-adapter %u (error=%d)\n",
 394                                 chan_id, ret);
 395                         goto err_free_priv;
 396                 }
 397         }
 398
 399         WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
 400                                "mux_device"),
 401              "can't create symlink to mux device\n");
 402
 403         snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
 404         WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
 405                                symlink_name),
 406              "can't create symlink to channel %u\n", chan_id);
 407         dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
 408                  i2c_adapter_id(&priv->adap));
 409
 410         muxc->adapter[muxc->num_adapters++] = &priv->adap;
 411         return 0;
 412
 413 err_free_priv:
 414         kfree(priv);
 415         return ret;
 416 }
 417 EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
 418
 419 void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
 420 {
 421         char symlink_name[20];
 422
 423         while (muxc->num_adapters) {
 424                 struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
 425                 struct i2c_mux_priv *priv = adap->algo_data;
 426                 struct device_node *np = adap->dev.of_node;
 427
 428                 muxc->adapter[muxc->num_adapters] = NULL;
 429
 430                 snprintf(symlink_name, sizeof(symlink_name),
 431                          "channel-%u", priv->chan_id);
 432                 sysfs_remove_link(&muxc->dev->kobj, symlink_name);
 433
 434                 sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
 435                 i2c_del_adapter(adap);
 436                 of_node_put(np);
 437                 kfree(priv);
 438         }
 439 }
 440 EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
 441
 442 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 443 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 444 MODULE_LICENSE("GPL v2");