linux/drivers/i2c/i2c-mux.c
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   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 */
  31struct 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
  38static 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
  57static 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
  76static 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 = __i2c_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
  98static 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 */
 121static 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 */
 130static 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
 142static 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_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
 148        if (!(flags & I2C_LOCK_ROOT_ADAPTER))
 149                return;
 150        i2c_lock_bus(parent, flags);
 151}
 152
 153static 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
 168static 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
 178static 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_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
 185        i2c_lock_bus(parent, flags);
 186}
 187
 188static 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
 202static 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
 212struct 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}
 236EXPORT_SYMBOL_GPL(i2c_root_adapter);
 237
 238struct 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}
 268EXPORT_SYMBOL_GPL(i2c_mux_alloc);
 269
 270static 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
 276static 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
 282int 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                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
 428err_free_priv:
 429        kfree(priv);
 430        return ret;
 431}
 432EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
 433
 434void 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}
 455EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
 456
 457MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 458MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 459MODULE_LICENSE("GPL v2");
 460