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/*
* Multiplexed I2C bus driver.
*
* Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
* Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
* Copyright (c) 2009-2010 NSN GmbH & Co KG <michael.lawnick.ext@nsn.com>
*
* Simplifies access to complex multiplexed I2C bus topologies, by presenting
* each multiplexed bus segment as an additional I2C adapter.
* Supports multi-level mux'ing (mux behind a mux).
*
* Based on:
* i2c-virt.c from Kumar Gala <galak@kernel.crashing.org>
* i2c-virtual.c from Ken Harrenstien, Copyright (c) 2004 Google, Inc.
* i2c-virtual.c from Brian Kuschak <bkuschak@yahoo.com>
*
* This file is licensed under the terms of the GNU General Public
* License version 2. This program is licensed "as is" without any
* warranty of any kind, whether express or implied.
*/
#include <linux/acpi.h>
#include <linux/i2c.h>
#include <linux/i2c-mux.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/slab.h>
/* multiplexer per channel data */
struct i2c_mux_priv {
struct i2c_adapter adap;
struct i2c_algorithm algo;
struct i2c_mux_core *muxc;
u32 chan_id;
};
static int __i2c_mux_master_xfer(struct i2c_adapter *adap,
struct i2c_msg msgs[], int num)
{
struct i2c_mux_priv *priv = adap->algo_data;
struct i2c_mux_core *muxc = priv->muxc;
struct i2c_adapter *parent = muxc->parent;
int ret;
/* Switch to the right mux port and perform the transfer. */
ret = muxc->select(muxc, priv->chan_id);
if (ret >= 0)
ret = __i2c_transfer(parent, msgs, num);
if (muxc->deselect)
muxc->deselect(muxc, priv->chan_id);
return ret;
}
static int i2c_mux_master_xfer(struct i2c_adapter *adap,
struct i2c_msg msgs[], int num)
{
struct i2c_mux_priv *priv = adap->algo_data;
struct i2c_mux_core *muxc = priv->muxc;
struct i2c_adapter *parent = muxc->parent;
int ret;
/* Switch to the right mux port and perform the transfer. */
ret = muxc->select(muxc, priv->chan_id);
if (ret >= 0)
ret = i2c_transfer(parent, msgs, num);
if (muxc->deselect)
muxc->deselect(muxc, priv->chan_id);
return ret;
}
static int __i2c_mux_smbus_xfer(struct i2c_adapter *adap,
u16 addr, unsigned short flags,
char read_write, u8 command,
int size, union i2c_smbus_data *data)
{
struct i2c_mux_priv *priv = adap->algo_data;
struct i2c_mux_core *muxc = priv->muxc;
struct i2c_adapter *parent = muxc->parent;
int ret;
/* Select the right mux port and perform the transfer. */
ret = muxc->select(muxc, priv->chan_id);
if (ret >= 0)
ret = parent->algo->smbus_xfer(parent, addr, flags,
read_write, command, size, data);
if (muxc->deselect)
muxc->deselect(muxc, priv->chan_id);
return ret;
}
static int i2c_mux_smbus_xfer(struct i2c_adapter *adap,
u16 addr, unsigned short flags,
char read_write, u8 command,
int size, union i2c_smbus_data *data)
{
struct i2c_mux_priv *priv = adap->algo_data;
struct i2c_mux_core *muxc = priv->muxc;
struct i2c_adapter *parent = muxc->parent;
int ret;
/* Select the right mux port and perform the transfer. */
ret = muxc->select(muxc, priv->chan_id);
if (ret >= 0)
ret = i2c_smbus_xfer(parent, addr, flags,
read_write, command, size, data);
if (muxc->deselect)
muxc->deselect(muxc, priv->chan_id);
return ret;
}
/* Return the parent's functionality */
static u32 i2c_mux_functionality(struct i2c_adapter *adap)
{
struct i2c_mux_priv *priv = adap->algo_data;
struct i2c_adapter *parent = priv->muxc->parent;
return parent->algo->functionality(parent);
}
/* Return all parent classes, merged */
static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent)
{
unsigned int class = 0;
do {
class |= parent->class;
parent = i2c_parent_is_i2c_adapter(parent);
} while (parent);
return class;
}
static void i2c_mux_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
struct i2c_mux_priv *priv = adapter->algo_data;
struct i2c_adapter *parent = priv->muxc->parent;
rt_mutex_lock(&parent->mux_lock);
if (!(flags & I2C_LOCK_ROOT_ADAPTER))
return;
i2c_lock_bus(parent, flags);
}
static int i2c_mux_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
struct i2c_mux_priv *priv = adapter->algo_data;
struct i2c_adapter *parent = priv->muxc->parent;
if (!rt_mutex_trylock(&parent->mux_lock))
return 0; /* mux_lock not locked, failure */
if (!(flags & I2C_LOCK_ROOT_ADAPTER))
return 1; /* we only want mux_lock, success */
if (i2c_trylock_bus(parent, flags))
return 1; /* parent locked too, success */
rt_mutex_unlock(&parent->mux_lock);
return 0; /* parent not locked, failure */
}
static void i2c_mux_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
struct i2c_mux_priv *priv = adapter->algo_data;
struct i2c_adapter *parent = priv->muxc->parent;
if (flags & I2C_LOCK_ROOT_ADAPTER)
i2c_unlock_bus(parent, flags);
rt_mutex_unlock(&parent->mux_lock);
}
static void i2c_parent_lock_bus(struct i2c_adapter *adapter,
unsigned int flags)
{
struct i2c_mux_priv *priv = adapter->algo_data;
struct i2c_adapter *parent = priv->muxc->parent;
rt_mutex_lock(&parent->mux_lock);
i2c_lock_bus(parent, flags);
}
static int i2c_parent_trylock_bus(struct i2c_adapter *adapter,
unsigned int flags)
{
struct i2c_mux_priv *priv = adapter->algo_data;
struct i2c_adapter *parent = priv->muxc->parent;
if (!rt_mutex_trylock(&parent->mux_lock))
return 0; /* mux_lock not locked, failure */
if (i2c_trylock_bus(parent, flags))
return 1; /* parent locked too, success */
rt_mutex_unlock(&parent->mux_lock);
return 0; /* parent not locked, failure */
}
static void i2c_parent_unlock_bus(struct i2c_adapter *adapter,
unsigned int flags)
{
struct i2c_mux_priv *priv = adapter->algo_data;
struct i2c_adapter *parent = priv->muxc->parent;
i2c_unlock_bus(parent, flags);
rt_mutex_unlock(&parent->mux_lock);
}
struct i2c_adapter *i2c_root_adapter(struct device *dev)
{
struct device *i2c;
struct i2c_adapter *i2c_root;
/*
* Walk up the device tree to find an i2c adapter, indicating
* that this is an i2c client device. Check all ancestors to
* handle mfd devices etc.
*/
for (i2c = dev; i2c; i2c = i2c->parent) {
if (i2c->type == &i2c_adapter_type)
break;
}
if (!i2c)
return NULL;
/* Continue up the tree to find the root i2c adapter */
i2c_root = to_i2c_adapter(i2c);
while (i2c_parent_is_i2c_adapter(i2c_root))
i2c_root = i2c_parent_is_i2c_adapter(i2c_root);
return i2c_root;
}
EXPORT_SYMBOL_GPL(i2c_root_adapter);
struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
struct device *dev, int max_adapters,
int sizeof_priv, u32 flags,
int (*select)(struct i2c_mux_core *, u32),
int (*deselect)(struct i2c_mux_core *, u32))
{
struct i2c_mux_core *muxc;
muxc = devm_kzalloc(dev, sizeof(*muxc)
+ max_adapters * sizeof(muxc->adapter[0])
+ sizeof_priv, GFP_KERNEL);
if (!muxc)
return NULL;
if (sizeof_priv)
muxc->priv = &muxc->adapter[max_adapters];
muxc->parent = parent;
muxc->dev = dev;
if (flags & I2C_MUX_LOCKED)
muxc->mux_locked = true;
if (flags & I2C_MUX_ARBITRATOR)
muxc->arbitrator = true;
if (flags & I2C_MUX_GATE)
muxc->gate = true;
muxc->select = select;
muxc->deselect = deselect;
muxc->max_adapters = max_adapters;
return muxc;
}
EXPORT_SYMBOL_GPL(i2c_mux_alloc);
static const struct i2c_lock_operations i2c_mux_lock_ops = {
.lock_bus = i2c_mux_lock_bus,
.trylock_bus = i2c_mux_trylock_bus,
.unlock_bus = i2c_mux_unlock_bus,
};
static const struct i2c_lock_operations i2c_parent_lock_ops = {
.lock_bus = i2c_parent_lock_bus,
.trylock_bus = i2c_parent_trylock_bus,
.unlock_bus = i2c_parent_unlock_bus,
};
int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
u32 force_nr, u32 chan_id,
unsigned int class)
{
struct i2c_adapter *parent = muxc->parent;
struct i2c_mux_priv *priv;
char symlink_name[20];
int ret;
if (muxc->num_adapters >= muxc->max_adapters) {
dev_err(muxc->dev, "No room for more i2c-mux adapters\n");
return -EINVAL;
}
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
/* Set up private adapter data */
priv->muxc = muxc;
priv->chan_id = chan_id;
/* Need to do algo dynamically because we don't know ahead
* of time what sort of physical adapter we'll be dealing with.
*/
if (parent->algo->master_xfer) {
if (muxc->mux_locked)
priv->algo.master_xfer = i2c_mux_master_xfer;
else
priv->algo.master_xfer = __i2c_mux_master_xfer;
}
if (parent->algo->smbus_xfer) {
if (muxc->mux_locked)
priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
else
priv->algo.smbus_xfer = __i2c_mux_smbus_xfer;
}
priv->algo.functionality = i2c_mux_functionality;
/* Now fill out new adapter structure */
snprintf(priv->adap.name, sizeof(priv->adap.name),
"i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
priv->adap.owner = THIS_MODULE;
priv->adap.algo = &priv->algo;
priv->adap.algo_data = priv;
priv->adap.dev.parent = &parent->dev;
priv->adap.retries = parent->retries;
priv->adap.timeout = parent->timeout;
priv->adap.quirks = parent->quirks;
if (muxc->mux_locked)
priv->adap.lock_ops = &i2c_mux_lock_ops;
else
priv->adap.lock_ops = &i2c_parent_lock_ops;
/* Sanity check on class */
if (i2c_mux_parent_classes(parent) & class)
dev_err(&parent->dev,
"Segment %d behind mux can't share classes with ancestors\n",
chan_id);
else
priv->adap.class = class;
/*
* Try to populate the mux adapter's of_node, expands to
* nothing if !CONFIG_OF.
*/
if (muxc->dev->of_node) {
struct device_node *dev_node = muxc->dev->of_node;
struct device_node *mux_node, *child = NULL;
u32 reg;
if (muxc->arbitrator)
mux_node = of_get_child_by_name(dev_node, "i2c-arb");
else if (muxc->gate)
mux_node = of_get_child_by_name(dev_node, "i2c-gate");
else
mux_node = of_get_child_by_name(dev_node, "i2c-mux");
if (mux_node) {
/* A "reg" property indicates an old-style DT entry */
if (!of_property_read_u32(mux_node, "reg", &reg)) {
of_node_put(mux_node);
mux_node = NULL;
}
}
if (!mux_node)
mux_node = of_node_get(dev_node);
else if (muxc->arbitrator || muxc->gate)
child = of_node_get(mux_node);
if (!child) {
for_each_child_of_node(mux_node, child) {
ret = of_property_read_u32(child, "reg", &reg);
if (ret)
continue;
if (chan_id == reg)
break;
}
}
priv->adap.dev.of_node = child;
of_node_put(mux_node);
}
/*
* Associate the mux channel with an ACPI node.
*/
if (has_acpi_companion(muxc->dev))
acpi_preset_companion(&priv->adap.dev,
ACPI_COMPANION(muxc->dev),
chan_id);
if (force_nr) {
priv->adap.nr = force_nr;
ret = i2c_add_numbered_adapter(&priv->adap);
} else {
ret = i2c_add_adapter(&priv->adap);
}
if (ret < 0) {
dev_err(&parent->dev,
"failed to add mux-adapter (error=%d)\n",
ret);
kfree(priv);
return ret;
}
WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
"mux_device"),
"can't create symlink to mux device\n");
snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
symlink_name),
"can't create symlink for channel %u\n", chan_id);
dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
i2c_adapter_id(&priv->adap));
muxc->adapter[muxc->num_adapters++] = &priv->adap;
return 0;
}
EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);
void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
{
char symlink_name[20];
while (muxc->num_adapters) {
struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
struct i2c_mux_priv *priv = adap->algo_data;
muxc->adapter[muxc->num_adapters] = NULL;
snprintf(symlink_name, sizeof(symlink_name),
"channel-%u", priv->chan_id);
sysfs_remove_link(&muxc->dev->kobj, symlink_name);
sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
i2c_del_adapter(adap);
kfree(priv);
}
}
EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);
MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
MODULE_LICENSE("GPL v2");