i2c: Multiplexed I2C bus core support

Add multiplexed bus core support. I2C multiplexer and switches
like pca954x get instantiated as new adapters per port.

Signed-off-by: Michael Lawnick <ml.lawnick@gmx.de>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

7 files changed, 327 insertions, 8 deletions

diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index d06083fdffbb..efb48ad1ba34 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -47,6 +47,17 @@ config I2C_CHARDEV
           This support is also available as a module.  If so, the module 
           will be called i2c-dev.
 
+config I2C_MUX
+        tristate "I2C bus multiplexing support"
+        depends on EXPERIMENTAL
+        help
+          Say Y here if you want the I2C core to support the ability to
+          handle multiplexed I2C bus topologies, by presenting each
+          multiplexed segment as a I2C adapter.
+
+          This support is also available as a module.  If so, the module
+          will be called i2c-mux.
+
 config I2C_HELPER_AUTO
         bool "Autoselect pertinent helper modules"
         default y
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index a7d9b4be9bb3..f363258daa3d 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_I2C_BOARDINFO)	+= i2c-boardinfo.o
 obj-$(CONFIG_I2C)               += i2c-core.o
 obj-$(CONFIG_I2C_SMBUS)         += i2c-smbus.o
 obj-$(CONFIG_I2C_CHARDEV)       += i2c-dev.o
+obj-$(CONFIG_I2C_MUX)           += i2c-mux.o
 obj-y                           += algos/ busses/
 
 ifeq ($(CONFIG_I2C_DEBUG_CORE),y)
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 97f96b66653c..6649176de940 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -20,7 +20,9 @@
 /* With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi>.
    All SMBus-related things are written by Frodo Looijaard <frodol@dds.nl>
    SMBus 2.0 support by Mark Studebaker <mdsxyz123@yahoo.com> and
-   Jean Delvare <khali@linux-fr.org> */
+   Jean Delvare <khali@linux-fr.org>
+   Mux support by Rodolfo Giometti <giometti@enneenne.com> and
+   Michael Lawnick <michael.lawnick.ext@nsn.com> */
 
 #include <linux/module.h>
 #include <linux/kernel.h>
@@ -423,10 +425,48 @@ static int __i2c_check_addr_busy(struct device *dev, void *addrp)
         return 0;
 }
 
+/* walk up mux tree */
+static int i2c_check_mux_parents(struct i2c_adapter *adapter, int addr)
+{
+        int result;
+
+        result = device_for_each_child(&adapter->dev, &addr,
+                                        __i2c_check_addr_busy);
+
+        if (!result && i2c_parent_is_i2c_adapter(adapter))
+                result = i2c_check_mux_parents(
+                                    to_i2c_adapter(adapter->dev.parent), addr);
+
+        return result;
+}
+
+/* recurse down mux tree */
+static int i2c_check_mux_children(struct device *dev, void *addrp)
+{
+        int result;
+
+        if (dev->type == &i2c_adapter_type)
+                result = device_for_each_child(dev, addrp,
+                                                i2c_check_mux_children);
+        else
+                result = __i2c_check_addr_busy(dev, addrp);
+
+        return result;
+}
+
 static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
 {
-        return device_for_each_child(&adapter->dev, &addr,
-                                     __i2c_check_addr_busy);
+        int result = 0;
+
+        if (i2c_parent_is_i2c_adapter(adapter))
+                result = i2c_check_mux_parents(
+                                    to_i2c_adapter(adapter->dev.parent), addr);
+
+        if (!result)
+                result = device_for_each_child(&adapter->dev, &addr,
+                                                i2c_check_mux_children);
+
+        return result;
 }
 
 /**
@@ -435,7 +475,10 @@ static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
  */
 void i2c_lock_adapter(struct i2c_adapter *adapter)
 {
-        rt_mutex_lock(&adapter->bus_lock);
+        if (i2c_parent_is_i2c_adapter(adapter))
+                i2c_lock_adapter(to_i2c_adapter(adapter->dev.parent));
+        else
+                rt_mutex_lock(&adapter->bus_lock);
 }
 EXPORT_SYMBOL_GPL(i2c_lock_adapter);
 
@@ -445,7 +488,10 @@ EXPORT_SYMBOL_GPL(i2c_lock_adapter);
  */
 static int i2c_trylock_adapter(struct i2c_adapter *adapter)
 {
-        return rt_mutex_trylock(&adapter->bus_lock);
+        if (i2c_parent_is_i2c_adapter(adapter))
+                return i2c_trylock_adapter(to_i2c_adapter(adapter->dev.parent));
+        else
+                return rt_mutex_trylock(&adapter->bus_lock);
 }
 
 /**
@@ -454,7 +500,10 @@ static int i2c_trylock_adapter(struct i2c_adapter *adapter)
  */
 void i2c_unlock_adapter(struct i2c_adapter *adapter)
 {
-        rt_mutex_unlock(&adapter->bus_lock);
+        if (i2c_parent_is_i2c_adapter(adapter))
+                i2c_unlock_adapter(to_i2c_adapter(adapter->dev.parent));
+        else
+                rt_mutex_unlock(&adapter->bus_lock);
 }
 EXPORT_SYMBOL_GPL(i2c_unlock_adapter);
 
@@ -743,10 +792,11 @@ static const struct attribute_group *i2c_adapter_attr_groups[] = {
         NULL
 };
 
-static struct device_type i2c_adapter_type = {
+struct device_type i2c_adapter_type = {
         .groups         = i2c_adapter_attr_groups,
         .release        = i2c_adapter_dev_release,
 };
+EXPORT_SYMBOL_GPL(i2c_adapter_type);
 
 #ifdef CONFIG_I2C_COMPAT
 static struct class_compat *i2c_adapter_compat_class;
diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index 0b0427f7d348..5f3a52d517c3 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -189,12 +189,50 @@ static int i2cdev_check(struct device *dev, void *addrp)
         return dev->driver ? -EBUSY : 0;
 }
 
+/* walk up mux tree */
+static int i2cdev_check_mux_parents(struct i2c_adapter *adapter, int addr)
+{
+        int result;
+
+        result = device_for_each_child(&adapter->dev, &addr, i2cdev_check);
+
+        if (!result && i2c_parent_is_i2c_adapter(adapter))
+                result = i2cdev_check_mux_parents(
+                                    to_i2c_adapter(adapter->dev.parent), addr);
+
+        return result;
+}
+
+/* recurse down mux tree */
+static int i2cdev_check_mux_children(struct device *dev, void *addrp)
+{
+        int result;
+
+        if (dev->type == &i2c_adapter_type)
+                result = device_for_each_child(dev, addrp,
+                                                i2cdev_check_mux_children);
+        else
+                result = i2cdev_check(dev, addrp);
+
+        return result;
+}
+
 /* This address checking function differs from the one in i2c-core
    in that it considers an address with a registered device, but no
    driver bound to it, as NOT busy. */
 static int i2cdev_check_addr(struct i2c_adapter *adapter, unsigned int addr)
 {
-        return device_for_each_child(&adapter->dev, &addr, i2cdev_check);
+        int result = 0;
+
+        if (i2c_parent_is_i2c_adapter(adapter))
+                result = i2cdev_check_mux_parents(
+                                    to_i2c_adapter(adapter->dev.parent), addr);
+
+        if (!result)
+                result = device_for_each_child(&adapter->dev, &addr,
+                                                i2cdev_check_mux_children);
+
+        return result;
 }
 
 static noinline int i2cdev_ioctl_rdrw(struct i2c_client *client,
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
new file mode 100644
index 000000000000..d32a4843fc3a
--- /dev/null
+++ b/drivers/i2c/i2c-mux.c
@@ -0,0 +1,165 @@
+/*
+ * 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/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+
+/* multiplexer per channel data */
+struct i2c_mux_priv {
+        struct i2c_adapter adap;
+        struct i2c_algorithm algo;
+
+        struct i2c_adapter *parent;
+        void *mux_dev;  /* the mux chip/device */
+        u32  chan_id;   /* the channel id */
+
+        int (*select)(struct i2c_adapter *, void *mux_dev, u32 chan_id);
+        int (*deselect)(struct i2c_adapter *, void *mux_dev, 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_adapter *parent = priv->parent;
+        int ret;
+
+        /* Switch to the right mux port and perform the transfer. */
+
+        ret = priv->select(parent, priv->mux_dev, priv->chan_id);
+        if (ret >= 0)
+                ret = parent->algo->master_xfer(parent, msgs, num);
+        if (priv->deselect)
+                priv->deselect(parent, priv->mux_dev, 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_adapter *parent = priv->parent;
+        int ret;
+
+        /* Select the right mux port and perform the transfer. */
+
+        ret = priv->select(parent, priv->mux_dev, priv->chan_id);
+        if (ret >= 0)
+                ret = parent->algo->smbus_xfer(parent, addr, flags,
+                                        read_write, command, size, data);
+        if (priv->deselect)
+                priv->deselect(parent, priv->mux_dev, 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->parent;
+
+        return parent->algo->functionality(parent);
+}
+
+struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
+                                void *mux_dev, u32 force_nr, u32 chan_id,
+                                int (*select) (struct i2c_adapter *,
+                                               void *, u32),
+                                int (*deselect) (struct i2c_adapter *,
+                                                 void *, u32))
+{
+        struct i2c_mux_priv *priv;
+        int ret;
+
+        priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
+        if (!priv)
+                return NULL;
+
+        /* Set up private adapter data */
+        priv->parent = parent;
+        priv->mux_dev = mux_dev;
+        priv->chan_id = chan_id;
+        priv->select = select;
+        priv->deselect = deselect;
+
+        /* 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)
+                priv->algo.master_xfer = i2c_mux_master_xfer;
+        if (parent->algo->smbus_xfer)
+                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.id = parent->id;
+        priv->adap.algo = &priv->algo;
+        priv->adap.algo_data = priv;
+        priv->adap.dev.parent = &parent->dev;
+
+        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 NULL;
+        }
+
+        dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
+                 i2c_adapter_id(&priv->adap));
+
+        return &priv->adap;
+}
+EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
+
+int i2c_del_mux_adapter(struct i2c_adapter *adap)
+{
+        struct i2c_mux_priv *priv = adap->algo_data;
+        int ret;
+
+        ret = i2c_del_adapter(adap);
+        if (ret < 0)
+                return ret;
+        kfree(priv);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
+MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/i2c-mux.h b/include/linux/i2c-mux.h
new file mode 100644
index 000000000000..34536effd652
--- /dev/null
+++ b/include/linux/i2c-mux.h
@@ -0,0 +1,46 @@
+/*
+ *
+ * i2c-mux.h - functions for the i2c-bus mux support
+ *
+ * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
+ * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
+ * Michael Lawnick <michael.lawnick.ext@nsn.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef _LINUX_I2C_MUX_H
+#define _LINUX_I2C_MUX_H
+
+#ifdef __KERNEL__
+
+/*
+ * Called to create a i2c bus on a multiplexed bus segment.
+ * The mux_dev and chan_id parameters are passed to the select
+ * and deselect callback functions to perform hardware-specific
+ * mux control.
+ */
+struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
+                                void *mux_dev, u32 force_nr, u32 chan_id,
+                                int (*select) (struct i2c_adapter *,
+                                               void *mux_dev, u32 chan_id),
+                                int (*deselect) (struct i2c_adapter *,
+                                                 void *mux_dev, u32 chan_id));
+
+int i2c_del_mux_adapter(struct i2c_adapter *adap);
+
+#endif /* __KERNEL__ */
+
+#endif /* _LINUX_I2C_MUX_H */
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 798bad8741e4..4bae0b72ed3c 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -37,6 +37,7 @@
 #include <linux/of.h>           /* for struct device_node */
 
 extern struct bus_type i2c_bus_type;
+extern struct device_type i2c_adapter_type;
 
 /* --- General options ------------------------------------------------ */
 
@@ -383,6 +384,13 @@ static inline void i2c_set_adapdata(struct i2c_adapter *dev, void *data)
         dev_set_drvdata(&dev->dev, data);
 }
 
+static inline int i2c_parent_is_i2c_adapter(const struct i2c_adapter *adapter)
+{
+        return adapter->dev.parent != NULL
+                && adapter->dev.parent->bus == &i2c_bus_type
+                && adapter->dev.parent->type == &i2c_adapter_type;
+}
+
 /* Adapter locking functions, exported for shared pin cases */
 void i2c_lock_adapter(struct i2c_adapter *);
 void i2c_unlock_adapter(struct i2c_adapter *);