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 (parent->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 (parent->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         muxc->select = select;
 259         muxc->deselect = deselect;
 260         muxc->max_adapters = max_adapters;
 261
 262         return muxc;
 263 }
 264 EXPORT_SYMBOL_GPL(i2c_mux_alloc);
 265
 266 int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 267                         u32 force_nr, u32 chan_id,
 268                         unsigned int class)
 269 {
 270         struct i2c_adapter *parent = muxc->parent;
 271         struct i2c_mux_priv *priv;
 272         char symlink_name[20];
 273         int ret;
 274
 275         if (muxc->num_adapters >= muxc->max_adapters) {
 276                 dev_err(muxc->dev, "No room for more i2c-mux adapters\n");
 277                 return -EINVAL;
 278         }
 279
 280         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 281         if (!priv)
 282                 return -ENOMEM;
 283
 284         /* Set up private adapter data */
 285         priv->muxc = muxc;
 286         priv->chan_id = chan_id;
 287
 288         /* Need to do algo dynamically because we don't know ahead
 289          * of time what sort of physical adapter we'll be dealing with.
 290          */
 291         if (parent->algo->master_xfer) {
 292                 if (muxc->mux_locked)
 293                         priv->algo.master_xfer = i2c_mux_master_xfer;
 294                 else
 295                         priv->algo.master_xfer = __i2c_mux_master_xfer;
 296         }
 297         if (parent->algo->smbus_xfer) {
 298                 if (muxc->mux_locked)
 299                         priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
 300                 else
 301                         priv->algo.smbus_xfer = __i2c_mux_smbus_xfer;
 302         }
 303         priv->algo.functionality = i2c_mux_functionality;
 304
 305         /* Now fill out new adapter structure */
 306         snprintf(priv->adap.name, sizeof(priv->adap.name),
 307                  "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
 308         priv->adap.owner = THIS_MODULE;
 309         priv->adap.algo = &priv->algo;
 310         priv->adap.algo_data = priv;
 311         priv->adap.dev.parent = &parent->dev;
 312         priv->adap.retries = parent->retries;
 313         priv->adap.timeout = parent->timeout;
 314         priv->adap.quirks = parent->quirks;
 315         if (muxc->mux_locked) {
 316                 priv->adap.lock_bus = i2c_mux_lock_bus;
 317                 priv->adap.trylock_bus = i2c_mux_trylock_bus;
 318                 priv->adap.unlock_bus = i2c_mux_unlock_bus;
 319         } else {
 320                 priv->adap.lock_bus = i2c_parent_lock_bus;
 321                 priv->adap.trylock_bus = i2c_parent_trylock_bus;
 322                 priv->adap.unlock_bus = i2c_parent_unlock_bus;
 323         }
 324
 325         /* Sanity check on class */
 326         if (i2c_mux_parent_classes(parent) & class)
 327                 dev_err(&parent->dev,
 328                         "Segment %d behind mux can't share classes with ancestors\n",
 329                         chan_id);
 330         else
 331                 priv->adap.class = class;
 332
 333         /*
 334          * Try to populate the mux adapter's of_node, expands to
 335          * nothing if !CONFIG_OF.
 336          */
 337         if (muxc->dev->of_node) {
 338                 struct device_node *child;
 339                 u32 reg;
 340
 341                 for_each_child_of_node(muxc->dev->of_node, child) {
 342                         ret = of_property_read_u32(child, "reg", &reg);
 343                         if (ret)
 344                                 continue;
 345                         if (chan_id == reg) {
 346                                 priv->adap.dev.of_node = child;
 347                                 break;
 348                         }
 349                 }
 350         }
 351
 352         /*
 353          * Associate the mux channel with an ACPI node.
 354          */
 355         if (has_acpi_companion(muxc->dev))
 356                 acpi_preset_companion(&priv->adap.dev,
 357                                       ACPI_COMPANION(muxc->dev),
 358                                       chan_id);
 359
 360         if (force_nr) {
 361                 priv->adap.nr = force_nr;
 362                 ret = i2c_add_numbered_adapter(&priv->adap);
 363         } else {
 364                 ret = i2c_add_adapter(&priv->adap);
 365         }
 366         if (ret < 0) {
 367                 dev_err(&parent->dev,
 368                         "failed to add mux-adapter (error=%d)\n",
 369                         ret);
 370                 kfree(priv);
 371                 return ret;
 372         }
 373
 374         WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
 375                                "mux_device"),
 376              "can't create symlink to mux device\n");
 377
 378         snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
 379         WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
 380                                symlink_name),
 381              "can't create symlink for channel %u\n", chan_id);
 382         dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
 383                  i2c_adapter_id(&priv->adap));
 384
 385         muxc->adapter[muxc->num_adapters++] = &priv->adap;
 386         return 0;
 387 }
 388 EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
 389
 390 void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
 391 {
 392         char symlink_name[20];
 393
 394         while (muxc->num_adapters) {
 395                 struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
 396                 struct i2c_mux_priv *priv = adap->algo_data;
 397
 398                 muxc->adapter[muxc->num_adapters] = NULL;
 399
 400                 snprintf(symlink_name, sizeof(symlink_name),
 401                          "channel-%u", priv->chan_id);
 402                 sysfs_remove_link(&muxc->dev->kobj, symlink_name);
 403
 404                 sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
 405                 i2c_del_adapter(adap);
 406                 kfree(priv);
 407         }
 408 }
 409 EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
 410
 411 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 412 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 413 MODULE_LICENSE("GPL v2");