i2c: Multiplexed I2C bus core support
Michael Lawnick [Wed, 11 Aug 2010 16:21:02 +0000 (18:21 +0200)]
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>

drivers/i2c/Kconfig
drivers/i2c/Makefile
drivers/i2c/i2c-core.c
drivers/i2c/i2c-dev.c
drivers/i2c/i2c-mux.c [new file with mode: 0644]
include/linux/i2c-mux.h [new file with mode: 0644]
include/linux/i2c.h

index d06083f..efb48ad 100644 (file)
@@ -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
index a7d9b4b..f363258 100644 (file)
@@ -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)
index 97f96b6..6649176 100644 (file)
@@ -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;
index 0b0427f..5f3a52d 100644 (file)
@@ -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 (file)
index 0000000..d32a484
--- /dev/null
@@ -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 (file)
index 0000000..34536ef
--- /dev/null
@@ -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 */
index 798bad8..4bae0b7 100644 (file)
@@ -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 *);