Add multiplexed bus core support. I2C multiplexer and switches like pca954x get instantiated as new adapters per output. Signed-off-by: Michael Lawnick <ml.lawnick@xxxxxx> --- Based on kernel 2.6.33 + [PATCH] i2c-core: Use per-adapter userspace device lists by Jean Delware <20100424201914.08b3f008@xxxxxxxxxxxxxxxx> <http://article.gmane.org/gmane.linux.drivers.i2c/5994/> drivers/i2c/Kconfig | 8 ++ drivers/i2c/Makefile | 1 + drivers/i2c/i2c-core.c | 93 ++++++++++++++++++++++-- drivers/i2c/i2c-dev.c | 46 ++++++++++++- drivers/i2c/i2c-mux.c | 184 +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/i2c-mux.h | 46 ++++++++++++ include/linux/i2c.h | 11 +++ 7 files changed, 381 insertions(+), 8 deletions(-) create mode 100755 drivers/i2c/i2c-mux.c create mode 100755 include/linux/i2c-mux.h diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig index 8d8a00e..2cd6d78 100755 --- a/drivers/i2c/Kconfig +++ b/drivers/i2c/Kconfig @@ -36,6 +36,14 @@ config I2C_COMPAT other user-space package which expects i2c adapters to be class devices. If you don't know, say Y. +config I2C_MUX + tristate "I2C bus multiplexing support" + depends on I2C + 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. + config I2C_CHARDEV tristate "I2C device interface" help diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile index ba26e6c..a488e8b 100755 --- a/drivers/i2c/Makefile +++ b/drivers/i2c/Makefile @@ -5,6 +5,7 @@ obj-$(CONFIG_I2C_BOARDINFO) += i2c-boardinfo.o obj-$(CONFIG_I2C) += i2c-core.o obj-$(CONFIG_I2C_CHARDEV) += i2c-dev.o +obj-$(CONFIG_I2C_MUX) += i2c-mux.o obj-y += busses/ chips/ algos/ ifeq ($(CONFIG_I2C_DEBUG_CORE),y) diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index fc93e28..682966a 100755 --- a/drivers/i2c/i2c-core.c +++ b/drivers/i2c/i2c-core.c @@ -20,7 +20,10 @@ /* With some changes from Kyösti Mälkki <kmalkki@xxxxxxxxx>. All SMBus-related things are written by Frodo Looijaard <frodol@xxxxxx> SMBus 2.0 support by Mark Studebaker <mdsxyz123@xxxxxxxxx> and - Jean Delvare <khali@xxxxxxxxxxxx> */ + Jean Delvare <khali@xxxxxxxxxxxx> + Mux support by Rodolfo Giometti <giometti@xxxxxxxxxxxx> and + Michael Lawnick <michael.lawnick.ext@xxxxxxx> */ + #include <linux/module.h> #include <linux/kernel.h> @@ -288,6 +291,12 @@ struct i2c_client *i2c_verify_client(struct device *dev) } EXPORT_SYMBOL(i2c_verify_client); +static int i2c_parent_is_i2c_adapter(const struct i2c_adapter *adapter) +{ + return adapter->dev.parent != NULL + && adapter->dev.parent->bus == &i2c_bus_type; +} + /** * i2c_new_device - instantiate an i2c device @@ -624,6 +633,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap) rt_mutex_init(&adap->bus_lock); INIT_LIST_HEAD(&adap->userspace_clients); + INIT_LIST_HEAD(&adap->mux_list_head); /* Set default timeout to 1 second if not already set */ if (adap->timeout == 0) @@ -949,9 +959,78 @@ static int __i2c_check_addr(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); + + 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_childs(struct i2c_adapter *adapter, int addr) +{ + int result = 0; + struct i2c_adapter *child, *next; + + list_for_each_entry_safe(child, next, &adapter->mux_list_head, + mux_list) { + result = device_for_each_child(&child->dev, &addr, + __i2c_check_addr); + if (result) + break; + result = i2c_check_mux_childs(child, addr); + } + return result; +} + static int i2c_check_addr(struct i2c_adapter *adapter, int addr) { - return device_for_each_child(&adapter->dev, &addr, __i2c_check_addr); + int result; + + result = i2c_check_mux_parents(adapter, addr); + + if (!result) + result = i2c_check_mux_childs(adapter, addr); + + return result; +} + +static void i2c_mux_tree_lock(struct i2c_adapter *adap) +{ + if (i2c_parent_is_i2c_adapter(adap)) + i2c_mux_tree_lock(to_i2c_adapter(adap->dev.parent)); + else + i2c_lock_adapter(adap); +} + +static int i2c_mux_tree_trylock(struct i2c_adapter *adap) +{ + int ret; + struct i2c_adapter *parent; + + if (i2c_parent_is_i2c_adapter(adap)) { + parent = to_i2c_adapter(adap->dev.parent); + ret = i2c_mux_tree_trylock(parent); + } else { + ret = i2c_trylock_adapter(adap); + } + + return ret; +} + +static void i2c_mux_tree_unlock(struct i2c_adapter *adap) +{ + if (i2c_parent_is_i2c_adapter(adap)) + i2c_mux_tree_unlock(to_i2c_adapter(adap->dev.parent)); + else + i2c_unlock_adapter(adap); } /** @@ -1104,12 +1183,12 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) #endif if (in_atomic() || irqs_disabled()) { - ret = rt_mutex_trylock(&adap->bus_lock); + ret = i2c_mux_tree_trylock(adap); if (!ret) /* I2C activity is ongoing. */ return -EAGAIN; } else { - rt_mutex_lock(&adap->bus_lock); + i2c_mux_tree_lock(adap); } /* Retry automatically on arbitration loss */ @@ -1121,7 +1200,7 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) if (time_after(jiffies, orig_jiffies + adap->timeout)) break; } - rt_mutex_unlock(&adap->bus_lock); + i2c_mux_tree_unlock(adap); return ret; } else { @@ -1857,7 +1936,7 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags, flags &= I2C_M_TEN | I2C_CLIENT_PEC; if (adapter->algo->smbus_xfer) { - rt_mutex_lock(&adapter->bus_lock); + i2c_mux_tree_lock(adapter); /* Retry automatically on arbitration loss */ orig_jiffies = jiffies; @@ -1871,7 +1950,7 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags, orig_jiffies + adapter->timeout)) break; } - rt_mutex_unlock(&adapter->bus_lock); + i2c_mux_tree_unlock(adapter); } else res = i2c_smbus_xfer_emulated(adapter,addr,flags,read_write, command, protocol, data); diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c index f4110aa..da5327f 100755 --- a/drivers/i2c/i2c-dev.c +++ b/drivers/i2c/i2c-dev.c @@ -193,12 +193,56 @@ static int i2cdev_check(struct device *dev, void *addrp) return dev->driver ? -EBUSY : 0; } +static int i2cdev_parent_is_i2c_adapter(const struct i2c_adapter *adapter) +{ + return adapter->dev.parent != NULL + && adapter->dev.parent->bus == &i2c_bus_type; +} + +/* 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 && i2cdev_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_childs(struct i2c_adapter *adapter, int addr) +{ + int result = 0; + struct i2c_adapter *child, *next; + + list_for_each_entry_safe(child, next, &adapter->mux_list_head, + mux_list) { + result = device_for_each_child(&child->dev, &addr, + i2cdev_check); + if (result) + break; + result = i2cdev_check_mux_childs(child, addr); + } + 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; + + result = i2cdev_check_mux_parents(adapter, addr); + + if (!result) + result = i2cdev_check_mux_childs(adapter, addr); + + 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 100755 index 0000000..f88d29a --- /dev/null +++ b/drivers/i2c/i2c-mux.c @@ -0,0 +1,184 @@ +/* + * Multiplexed I2C bus driver. + * + * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@xxxxxxxx> + * Copyright (c) 2008-2009 Eurotech S.p.A. <info@xxxxxxxxxxx> + * + * 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@xxxxxxxxxxxxxxxxxxx> + * i2c-virtual.c from Ken Harrenstien, Copyright (c) 2004 Google, Inc. + * i2c-virtual.c from Brian Kuschak <bkuschak@xxxxxxxxx> + * + * 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. + */ + +/* Adapted to kernel 2.6.33 by Michael Lawnick <michael.lawnick.ext@xxxxxxx> */ + +#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 *adap, void *mux_dev, u32 chan_id); + int (*deselect)(struct i2c_adapter *adap, void *mux_dev, u32 chan_id); +}; + +#define VIRT_TIMEOUT (HZ/2) +#define VIRT_RETRIES 3 + +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 for the virtual adapter */ +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; + } + + list_add_tail(&priv->adap.mux_list, &parent->mux_list_head); + + dev_info(&parent->dev, "i2c-mux-%d: Multiplexed I2C bus on " + "parent bus i2c-%d, chan_id %d\n", + i2c_adapter_id(&priv->adap), i2c_adapter_id(parent), chan_id); + + 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; + struct i2c_adapter *child, *next, *parent; + + if (adap->dev.parent != NULL + && adap->dev.parent->bus == &i2c_bus_type) { + parent = to_i2c_adapter(adap->dev.parent); + list_for_each_entry_safe(child, next, &parent->mux_list_head, + mux_list) { + if (child == adap) { + list_del(&child->mux_list); + break; + } + } + } + + 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@xxxxxxxx>"); +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 100755 index 0000000..0d5d6c8 --- /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@xxxxxxxx> + * Copyright (c) 2008-2009 Eurotech S.p.A. <info@xxxxxxxxxxx> + * Michael Lawnick <michael.lawnick.ext@xxxxxxx> + * + * 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 *adap, + 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_H */ diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 1fd7b12..898a8c1 100755 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -349,6 +349,8 @@ struct i2c_adapter { struct completion dev_released; struct list_head userspace_clients; + struct list_head mux_list_head; + struct list_head mux_list; }; #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev) @@ -380,6 +382,15 @@ static inline void i2c_unlock_adapter(struct i2c_adapter *adapter) rt_mutex_unlock(&adapter->bus_lock); } +/** + * i2c_trylock_adapter - Try to prevent access to an I2C bus segment + * @adapter: Target I2C bus segment + */ +static inline int i2c_trylock_adapter(struct i2c_adapter *adapter) +{ + return rt_mutex_trylock(&adapter->bus_lock); +} + /*flags for the client struct: */ #define I2C_CLIENT_PEC 0x04 /* Use Packet Error Checking */ #define I2C_CLIENT_TEN 0x10 /* we have a ten bit chip address */ -- 1.6.2.1
