drivers/i2c/i2c-mux.c

0001 /*
0002  * Multiplexed I2C bus driver.
0003  *
0004  * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
0005  * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
0006  * Copyright (c) 2009-2010 NSN GmbH & Co KG <michael.lawnick.ext@nsn.com>
0007  *
0008  * Simplifies access to complex multiplexed I2C bus topologies, by presenting
0009  * each multiplexed bus segment as an additional I2C adapter.
0010  * Supports multi-level mux'ing (mux behind a mux).
0011  *
0012  * Based on:
0013  *  i2c-virt.c from Kumar Gala <galak@kernel.crashing.org>
0014  *  i2c-virtual.c from Ken Harrenstien, Copyright (c) 2004 Google, Inc.
0015  *  i2c-virtual.c from Brian Kuschak <bkuschak@yahoo.com>
0016  *
0017  * This file is licensed under the terms of the GNU General Public
0018  * License version 2. This program is licensed "as is" without any
0019  * warranty of any kind, whether express or implied.
0020  */
0021
0022 #include <linux/acpi.h>
0023 #include <linux/i2c.h>
0024 #include <linux/i2c-mux.h>
0025 #include <linux/kernel.h>
0026 #include <linux/module.h>
0027 #include <linux/of.h>
0028 #include <linux/slab.h>
0029 #include <linux/sysfs.h>
0030
0031 /* multiplexer per channel data */
0032 struct i2c_mux_priv {
0033     struct i2c_adapter adap;
0034     struct i2c_algorithm algo;
0035     struct i2c_mux_core *muxc;
0036     u32 chan_id;
0037 };
0038
0039 static int __i2c_mux_master_xfer(struct i2c_adapter *adap,
0040                  struct i2c_msg msgs[], int num)
0041 {
0042     struct i2c_mux_priv *priv = adap->algo_data;
0043     struct i2c_mux_core *muxc = priv->muxc;
0044     struct i2c_adapter *parent = muxc->parent;
0045     int ret;
0046
0047     /* Switch to the right mux port and perform the transfer. */
0048
0049     ret = muxc->select(muxc, priv->chan_id);
0050     if (ret >= 0)
0051         ret = __i2c_transfer(parent, msgs, num);
0052     if (muxc->deselect)
0053         muxc->deselect(muxc, priv->chan_id);
0054
0055     return ret;
0056 }
0057
0058 static int i2c_mux_master_xfer(struct i2c_adapter *adap,
0059                    struct i2c_msg msgs[], int num)
0060 {
0061     struct i2c_mux_priv *priv = adap->algo_data;
0062     struct i2c_mux_core *muxc = priv->muxc;
0063     struct i2c_adapter *parent = muxc->parent;
0064     int ret;
0065
0066     /* Switch to the right mux port and perform the transfer. */
0067
0068     ret = muxc->select(muxc, priv->chan_id);
0069     if (ret >= 0)
0070         ret = i2c_transfer(parent, msgs, num);
0071     if (muxc->deselect)
0072         muxc->deselect(muxc, priv->chan_id);
0073
0074     return ret;
0075 }
0076
0077 static int __i2c_mux_smbus_xfer(struct i2c_adapter *adap,
0078                 u16 addr, unsigned short flags,
0079                 char read_write, u8 command,
0080                 int size, union i2c_smbus_data *data)
0081 {
0082     struct i2c_mux_priv *priv = adap->algo_data;
0083     struct i2c_mux_core *muxc = priv->muxc;
0084     struct i2c_adapter *parent = muxc->parent;
0085     int ret;
0086
0087     /* Select the right mux port and perform the transfer. */
0088
0089     ret = muxc->select(muxc, priv->chan_id);
0090     if (ret >= 0)
0091         ret = __i2c_smbus_xfer(parent, addr, flags,
0092                        read_write, command, size, data);
0093     if (muxc->deselect)
0094         muxc->deselect(muxc, priv->chan_id);
0095
0096     return ret;
0097 }
0098
0099 static int i2c_mux_smbus_xfer(struct i2c_adapter *adap,
0100                   u16 addr, unsigned short flags,
0101                   char read_write, u8 command,
0102                   int size, union i2c_smbus_data *data)
0103 {
0104     struct i2c_mux_priv *priv = adap->algo_data;
0105     struct i2c_mux_core *muxc = priv->muxc;
0106     struct i2c_adapter *parent = muxc->parent;
0107     int ret;
0108
0109     /* Select the right mux port and perform the transfer. */
0110
0111     ret = muxc->select(muxc, priv->chan_id);
0112     if (ret >= 0)
0113         ret = i2c_smbus_xfer(parent, addr, flags,
0114                      read_write, command, size, data);
0115     if (muxc->deselect)
0116         muxc->deselect(muxc, priv->chan_id);
0117
0118     return ret;
0119 }
0120
0121 /* Return the parent's functionality */
0122 static u32 i2c_mux_functionality(struct i2c_adapter *adap)
0123 {
0124     struct i2c_mux_priv *priv = adap->algo_data;
0125     struct i2c_adapter *parent = priv->muxc->parent;
0126
0127     return parent->algo->functionality(parent);
0128 }
0129
0130 /* Return all parent classes, merged */
0131 static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent)
0132 {
0133     unsigned int class = 0;
0134
0135     do {
0136         class |= parent->class;
0137         parent = i2c_parent_is_i2c_adapter(parent);
0138     } while (parent);
0139
0140     return class;
0141 }
0142
0143 static void i2c_mux_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
0144 {
0145     struct i2c_mux_priv *priv = adapter->algo_data;
0146     struct i2c_adapter *parent = priv->muxc->parent;
0147
0148     rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
0149     if (!(flags & I2C_LOCK_ROOT_ADAPTER))
0150         return;
0151     i2c_lock_bus(parent, flags);
0152 }
0153
0154 static int i2c_mux_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
0155 {
0156     struct i2c_mux_priv *priv = adapter->algo_data;
0157     struct i2c_adapter *parent = priv->muxc->parent;
0158
0159     if (!rt_mutex_trylock(&parent->mux_lock))
0160         return 0;   /* mux_lock not locked, failure */
0161     if (!(flags & I2C_LOCK_ROOT_ADAPTER))
0162         return 1;   /* we only want mux_lock, success */
0163     if (i2c_trylock_bus(parent, flags))
0164         return 1;   /* parent locked too, success */
0165     rt_mutex_unlock(&parent->mux_lock);
0166     return 0;       /* parent not locked, failure */
0167 }
0168
0169 static void i2c_mux_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
0170 {
0171     struct i2c_mux_priv *priv = adapter->algo_data;
0172     struct i2c_adapter *parent = priv->muxc->parent;
0173
0174     if (flags & I2C_LOCK_ROOT_ADAPTER)
0175         i2c_unlock_bus(parent, flags);
0176     rt_mutex_unlock(&parent->mux_lock);
0177 }
0178
0179 static void i2c_parent_lock_bus(struct i2c_adapter *adapter,
0180                 unsigned int flags)
0181 {
0182     struct i2c_mux_priv *priv = adapter->algo_data;
0183     struct i2c_adapter *parent = priv->muxc->parent;
0184
0185     rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
0186     i2c_lock_bus(parent, flags);
0187 }
0188
0189 static int i2c_parent_trylock_bus(struct i2c_adapter *adapter,
0190                   unsigned int flags)
0191 {
0192     struct i2c_mux_priv *priv = adapter->algo_data;
0193     struct i2c_adapter *parent = priv->muxc->parent;
0194
0195     if (!rt_mutex_trylock(&parent->mux_lock))
0196         return 0;   /* mux_lock not locked, failure */
0197     if (i2c_trylock_bus(parent, flags))
0198         return 1;   /* parent locked too, success */
0199     rt_mutex_unlock(&parent->mux_lock);
0200     return 0;       /* parent not locked, failure */
0201 }
0202
0203 static void i2c_parent_unlock_bus(struct i2c_adapter *adapter,
0204                   unsigned int flags)
0205 {
0206     struct i2c_mux_priv *priv = adapter->algo_data;
0207     struct i2c_adapter *parent = priv->muxc->parent;
0208
0209     i2c_unlock_bus(parent, flags);
0210     rt_mutex_unlock(&parent->mux_lock);
0211 }
0212
0213 struct i2c_adapter *i2c_root_adapter(struct device *dev)
0214 {
0215     struct device *i2c;
0216     struct i2c_adapter *i2c_root;
0217
0218     /*
0219      * Walk up the device tree to find an i2c adapter, indicating
0220      * that this is an i2c client device. Check all ancestors to
0221      * handle mfd devices etc.
0222      */
0223     for (i2c = dev; i2c; i2c = i2c->parent) {
0224         if (i2c->type == &i2c_adapter_type)
0225             break;
0226     }
0227     if (!i2c)
0228         return NULL;
0229
0230     /* Continue up the tree to find the root i2c adapter */
0231     i2c_root = to_i2c_adapter(i2c);
0232     while (i2c_parent_is_i2c_adapter(i2c_root))
0233         i2c_root = i2c_parent_is_i2c_adapter(i2c_root);
0234
0235     return i2c_root;
0236 }
0237 EXPORT_SYMBOL_GPL(i2c_root_adapter);
0238
0239 struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
0240                    struct device *dev, int max_adapters,
0241                    int sizeof_priv, u32 flags,
0242                    int (*select)(struct i2c_mux_core *, u32),
0243                    int (*deselect)(struct i2c_mux_core *, u32))
0244 {
0245     struct i2c_mux_core *muxc;
0246     size_t mux_size;
0247
0248     mux_size = struct_size(muxc, adapter, max_adapters);
0249     muxc = devm_kzalloc(dev, size_add(mux_size, sizeof_priv), GFP_KERNEL);
0250     if (!muxc)
0251         return NULL;
0252     if (sizeof_priv)
0253         muxc->priv = &muxc->adapter[max_adapters];
0254
0255     muxc->parent = parent;
0256     muxc->dev = dev;
0257     if (flags & I2C_MUX_LOCKED)
0258         muxc->mux_locked = true;
0259     if (flags & I2C_MUX_ARBITRATOR)
0260         muxc->arbitrator = true;
0261     if (flags & I2C_MUX_GATE)
0262         muxc->gate = true;
0263     muxc->select = select;
0264     muxc->deselect = deselect;
0265     muxc->max_adapters = max_adapters;
0266
0267     return muxc;
0268 }
0269 EXPORT_SYMBOL_GPL(i2c_mux_alloc);
0270
0271 static const struct i2c_lock_operations i2c_mux_lock_ops = {
0272     .lock_bus =    i2c_mux_lock_bus,
0273     .trylock_bus = i2c_mux_trylock_bus,
0274     .unlock_bus =  i2c_mux_unlock_bus,
0275 };
0276
0277 static const struct i2c_lock_operations i2c_parent_lock_ops = {
0278     .lock_bus =    i2c_parent_lock_bus,
0279     .trylock_bus = i2c_parent_trylock_bus,
0280     .unlock_bus =  i2c_parent_unlock_bus,
0281 };
0282
0283 int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
0284             u32 force_nr, u32 chan_id,
0285             unsigned int class)
0286 {
0287     struct i2c_adapter *parent = muxc->parent;
0288     struct i2c_mux_priv *priv;
0289     char symlink_name[20];
0290     int ret;
0291
0292     if (muxc->num_adapters >= muxc->max_adapters) {
0293         dev_err(muxc->dev, "No room for more i2c-mux adapters\n");
0294         return -EINVAL;
0295     }
0296
0297     priv = kzalloc(sizeof(*priv), GFP_KERNEL);
0298     if (!priv)
0299         return -ENOMEM;
0300
0301     /* Set up private adapter data */
0302     priv->muxc = muxc;
0303     priv->chan_id = chan_id;
0304
0305     /* Need to do algo dynamically because we don't know ahead
0306      * of time what sort of physical adapter we'll be dealing with.
0307      */
0308     if (parent->algo->master_xfer) {
0309         if (muxc->mux_locked)
0310             priv->algo.master_xfer = i2c_mux_master_xfer;
0311         else
0312             priv->algo.master_xfer = __i2c_mux_master_xfer;
0313     }
0314     if (parent->algo->master_xfer_atomic)
0315         priv->algo.master_xfer_atomic = priv->algo.master_xfer;
0316
0317     if (parent->algo->smbus_xfer) {
0318         if (muxc->mux_locked)
0319             priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
0320         else
0321             priv->algo.smbus_xfer = __i2c_mux_smbus_xfer;
0322     }
0323     if (parent->algo->smbus_xfer_atomic)
0324         priv->algo.smbus_xfer_atomic = priv->algo.smbus_xfer;
0325
0326     priv->algo.functionality = i2c_mux_functionality;
0327
0328     /* Now fill out new adapter structure */
0329     snprintf(priv->adap.name, sizeof(priv->adap.name),
0330          "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
0331     priv->adap.owner = THIS_MODULE;
0332     priv->adap.algo = &priv->algo;
0333     priv->adap.algo_data = priv;
0334     priv->adap.dev.parent = &parent->dev;
0335     priv->adap.retries = parent->retries;
0336     priv->adap.timeout = parent->timeout;
0337     priv->adap.quirks = parent->quirks;
0338     if (muxc->mux_locked)
0339         priv->adap.lock_ops = &i2c_mux_lock_ops;
0340     else
0341         priv->adap.lock_ops = &i2c_parent_lock_ops;
0342
0343     /* Sanity check on class */
0344     if (i2c_mux_parent_classes(parent) & class)
0345         dev_err(&parent->dev,
0346             "Segment %d behind mux can't share classes with ancestors\n",
0347             chan_id);
0348     else
0349         priv->adap.class = class;
0350
0351     /*
0352      * Try to populate the mux adapter's of_node, expands to
0353      * nothing if !CONFIG_OF.
0354      */
0355     if (muxc->dev->of_node) {
0356         struct device_node *dev_node = muxc->dev->of_node;
0357         struct device_node *mux_node, *child = NULL;
0358         u32 reg;
0359
0360         if (muxc->arbitrator)
0361             mux_node = of_get_child_by_name(dev_node, "i2c-arb");
0362         else if (muxc->gate)
0363             mux_node = of_get_child_by_name(dev_node, "i2c-gate");
0364         else
0365             mux_node = of_get_child_by_name(dev_node, "i2c-mux");
0366
0367         if (mux_node) {
0368             /* A "reg" property indicates an old-style DT entry */
0369             if (!of_property_read_u32(mux_node, "reg", &reg)) {
0370                 of_node_put(mux_node);
0371                 mux_node = NULL;
0372             }
0373         }
0374
0375         if (!mux_node)
0376             mux_node = of_node_get(dev_node);
0377         else if (muxc->arbitrator || muxc->gate)
0378             child = of_node_get(mux_node);
0379
0380         if (!child) {
0381             for_each_child_of_node(mux_node, child) {
0382                 ret = of_property_read_u32(child, "reg", &reg);
0383                 if (ret)
0384                     continue;
0385                 if (chan_id == reg)
0386                     break;
0387             }
0388         }
0389
0390         priv->adap.dev.of_node = child;
0391         of_node_put(mux_node);
0392     }
0393
0394     /*
0395      * Associate the mux channel with an ACPI node.
0396      */
0397     if (has_acpi_companion(muxc->dev))
0398         acpi_preset_companion(&priv->adap.dev,
0399                       ACPI_COMPANION(muxc->dev),
0400                       chan_id);
0401
0402     if (force_nr) {
0403         priv->adap.nr = force_nr;
0404         ret = i2c_add_numbered_adapter(&priv->adap);
0405         if (ret < 0) {
0406             dev_err(&parent->dev,
0407                 "failed to add mux-adapter %u as bus %u (error=%d)\n",
0408                 chan_id, force_nr, ret);
0409             goto err_free_priv;
0410         }
0411     } else {
0412         ret = i2c_add_adapter(&priv->adap);
0413         if (ret < 0) {
0414             dev_err(&parent->dev,
0415                 "failed to add mux-adapter %u (error=%d)\n",
0416                 chan_id, ret);
0417             goto err_free_priv;
0418         }
0419     }
0420
0421     WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
0422                    "mux_device"),
0423          "can't create symlink to mux device\n");
0424
0425     snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
0426     WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
0427                    symlink_name),
0428          "can't create symlink to channel %u\n", chan_id);
0429     dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
0430          i2c_adapter_id(&priv->adap));
0431
0432     muxc->adapter[muxc->num_adapters++] = &priv->adap;
0433     return 0;
0434
0435 err_free_priv:
0436     kfree(priv);
0437     return ret;
0438 }
0439 EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
0440
0441 void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
0442 {
0443     char symlink_name[20];
0444
0445     while (muxc->num_adapters) {
0446         struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
0447         struct i2c_mux_priv *priv = adap->algo_data;
0448         struct device_node *np = adap->dev.of_node;
0449
0450         muxc->adapter[muxc->num_adapters] = NULL;
0451
0452         snprintf(symlink_name, sizeof(symlink_name),
0453              "channel-%u", priv->chan_id);
0454         sysfs_remove_link(&muxc->dev->kobj, symlink_name);
0455
0456         sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
0457         i2c_del_adapter(adap);
0458         of_node_put(np);
0459         kfree(priv);
0460     }
0461 }
0462 EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
0463
0464 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
0465 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
0466 MODULE_LICENSE("GPL v2");