Commit 92ed1a76 authored by Peter Korsgaard's avatar Peter Korsgaard Committed by Jean Delvare

i2c: Add generic I2C multiplexer using GPIO API

Add an i2c mux driver providing access to i2c bus segments using a
hardware MUX sitting on a master bus and controlled through gpio pins.

E.G. something like:

  ----------              ----------  Bus segment 1   - - - - -
 |          | SCL/SDA    |          |-------------- |           |
 |          |------------|          |
 |          |            |          | Bus segment 2 |           |
 |  Linux   | GPIO 1..N  |   MUX    |---------------   Devices
 |          |------------|          |               |           |
 |          |            |          | Bus segment M
 |          |            |          |---------------|           |
  ----------              ----------                  - - - - -

SCL/SDA of the master I2C bus is multiplexed to bus segment 1..M
according to the settings of the GPIO pins 1..N.
Signed-off-by: default avatarPeter Korsgaard <peter.korsgaard@barco.com>
Signed-off-by: default avatarJean Delvare <khali@linux-fr.org>
parent b18a5c80
Kernel driver gpio-i2cmux
Author: Peter Korsgaard <peter.korsgaard@barco.com>
Description
-----------
gpio-i2cmux is an i2c mux driver providing access to I2C bus segments
from a master I2C bus and a hardware MUX controlled through GPIO pins.
E.G.:
---------- ---------- Bus segment 1 - - - - -
| | SCL/SDA | |-------------- | |
| |------------| |
| | | | Bus segment 2 | |
| Linux | GPIO 1..N | MUX |--------------- Devices
| |------------| | | |
| | | | Bus segment M
| | | |---------------| |
---------- ---------- - - - - -
SCL/SDA of the master I2C bus is multiplexed to bus segment 1..M
according to the settings of the GPIO pins 1..N.
Usage
-----
gpio-i2cmux uses the platform bus, so you need to provide a struct
platform_device with the platform_data pointing to a struct
gpio_i2cmux_platform_data with the I2C adapter number of the master
bus, the number of bus segments to create and the GPIO pins used
to control it. See include/linux/gpio-i2cmux.h for details.
E.G. something like this for a MUX providing 4 bus segments
controlled through 3 GPIO pins:
#include <linux/gpio-i2cmux.h>
#include <linux/platform_device.h>
static const unsigned myboard_gpiomux_gpios[] = {
AT91_PIN_PC26, AT91_PIN_PC25, AT91_PIN_PC24
};
static const unsigned myboard_gpiomux_values[] = {
0, 1, 2, 3
};
static struct gpio_i2cmux_platform_data myboard_i2cmux_data = {
.parent = 1,
.base_nr = 2, /* optional */
.values = myboard_gpiomux_values,
.n_values = ARRAY_SIZE(myboard_gpiomux_values),
.gpios = myboard_gpiomux_gpios,
.n_gpios = ARRAY_SIZE(myboard_gpiomux_gpios),
.idle = 4, /* optional */
};
static struct platform_device myboard_i2cmux = {
.name = "gpio-i2cmux",
.id = 0,
.dev = {
.platform_data = &myboard_i2cmux_data,
},
};
...@@ -2608,6 +2608,14 @@ S: Supported ...@@ -2608,6 +2608,14 @@ S: Supported
F: drivers/i2c/busses/i2c-gpio.c F: drivers/i2c/busses/i2c-gpio.c
F: include/linux/i2c-gpio.h F: include/linux/i2c-gpio.h
GENERIC GPIO I2C MULTIPLEXER DRIVER
M: Peter Korsgaard <peter.korsgaard@barco.com>
L: linux-i2c@vger.kernel.org
S: Supported
F: drivers/i2c/muxes/gpio-i2cmux.c
F: include/linux/gpio-i2cmux.h
F: Documentation/i2c/muxes/gpio-i2cmux
GENERIC HDLC (WAN) DRIVERS GENERIC HDLC (WAN) DRIVERS
M: Krzysztof Halasa <khc@pm.waw.pl> M: Krzysztof Halasa <khc@pm.waw.pl>
W: http://www.kernel.org/pub/linux/utils/net/hdlc/ W: http://www.kernel.org/pub/linux/utils/net/hdlc/
......
...@@ -5,6 +5,18 @@ ...@@ -5,6 +5,18 @@
menu "Multiplexer I2C Chip support" menu "Multiplexer I2C Chip support"
depends on I2C_MUX depends on I2C_MUX
config I2C_MUX_GPIO
tristate "GPIO-based I2C multiplexer"
depends on GENERIC_GPIO
help
If you say yes to this option, support will be included for a
GPIO based I2C multiplexer. This driver provides access to
I2C busses connected through a MUX, which is controlled
through GPIO pins.
This driver can also be built as a module. If so, the module
will be called gpio-i2cmux.
config I2C_MUX_PCA9541 config I2C_MUX_PCA9541
tristate "NXP PCA9541 I2C Master Selector" tristate "NXP PCA9541 I2C Master Selector"
depends on EXPERIMENTAL depends on EXPERIMENTAL
......
# #
# Makefile for multiplexer I2C chip drivers. # Makefile for multiplexer I2C chip drivers.
obj-$(CONFIG_I2C_MUX_GPIO) += gpio-i2cmux.o
obj-$(CONFIG_I2C_MUX_PCA9541) += pca9541.o obj-$(CONFIG_I2C_MUX_PCA9541) += pca9541.o
obj-$(CONFIG_I2C_MUX_PCA954x) += pca954x.o obj-$(CONFIG_I2C_MUX_PCA954x) += pca954x.o
......
/*
* I2C multiplexer using GPIO API
*
* Peter Korsgaard <peter.korsgaard@barco.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/i2c.h>
#include <linux/i2c-mux.h>
#include <linux/gpio-i2cmux.h>
#include <linux/platform_device.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/gpio.h>
struct gpiomux {
struct i2c_adapter *parent;
struct i2c_adapter **adap; /* child busses */
struct gpio_i2cmux_platform_data data;
};
static void gpiomux_set(const struct gpiomux *mux, unsigned val)
{
int i;
for (i = 0; i < mux->data.n_gpios; i++)
gpio_set_value(mux->data.gpios[i], val & (1 << i));
}
static int gpiomux_select(struct i2c_adapter *adap, void *data, u32 chan)
{
struct gpiomux *mux = data;
gpiomux_set(mux, mux->data.values[chan]);
return 0;
}
static int gpiomux_deselect(struct i2c_adapter *adap, void *data, u32 chan)
{
struct gpiomux *mux = data;
gpiomux_set(mux, mux->data.idle);
return 0;
}
static int __devinit gpiomux_probe(struct platform_device *pdev)
{
struct gpiomux *mux;
struct gpio_i2cmux_platform_data *pdata;
struct i2c_adapter *parent;
int (*deselect) (struct i2c_adapter *, void *, u32);
unsigned initial_state;
int i, ret;
pdata = pdev->dev.platform_data;
if (!pdata) {
dev_err(&pdev->dev, "Missing platform data\n");
return -ENODEV;
}
parent = i2c_get_adapter(pdata->parent);
if (!parent) {
dev_err(&pdev->dev, "Parent adapter (%d) not found\n",
pdata->parent);
return -ENODEV;
}
mux = kzalloc(sizeof(*mux), GFP_KERNEL);
if (!mux) {
ret = -ENOMEM;
goto alloc_failed;
}
mux->parent = parent;
mux->data = *pdata;
mux->adap = kzalloc(sizeof(struct i2c_adapter *) * pdata->n_values,
GFP_KERNEL);
if (!mux->adap) {
ret = -ENOMEM;
goto alloc_failed2;
}
if (pdata->idle != GPIO_I2CMUX_NO_IDLE) {
initial_state = pdata->idle;
deselect = gpiomux_deselect;
} else {
initial_state = pdata->values[0];
deselect = NULL;
}
for (i = 0; i < pdata->n_gpios; i++) {
ret = gpio_request(pdata->gpios[i], "gpio-i2cmux");
if (ret)
goto err_request_gpio;
gpio_direction_output(pdata->gpios[i],
initial_state & (1 << i));
}
for (i = 0; i < pdata->n_values; i++) {
u32 nr = pdata->base_nr ? (pdata->base_nr + i) : 0;
mux->adap[i] = i2c_add_mux_adapter(parent, mux, nr, i,
gpiomux_select, deselect);
if (!mux->adap[i]) {
ret = -ENODEV;
dev_err(&pdev->dev, "Failed to add adapter %d\n", i);
goto add_adapter_failed;
}
}
dev_info(&pdev->dev, "%d port mux on %s adapter\n",
pdata->n_values, parent->name);
platform_set_drvdata(pdev, mux);
return 0;
add_adapter_failed:
for (; i > 0; i--)
i2c_del_mux_adapter(mux->adap[i - 1]);
i = pdata->n_gpios;
err_request_gpio:
for (; i > 0; i--)
gpio_free(pdata->gpios[i - 1]);
kfree(mux->adap);
alloc_failed2:
kfree(mux);
alloc_failed:
i2c_put_adapter(parent);
return ret;
}
static int __devexit gpiomux_remove(struct platform_device *pdev)
{
struct gpiomux *mux = platform_get_drvdata(pdev);
int i;
for (i = 0; i < mux->data.n_values; i++)
i2c_del_mux_adapter(mux->adap[i]);
for (i = 0; i < mux->data.n_gpios; i++)
gpio_free(mux->data.gpios[i]);
platform_set_drvdata(pdev, NULL);
i2c_put_adapter(mux->parent);
kfree(mux->adap);
kfree(mux);
return 0;
}
static struct platform_driver gpiomux_driver = {
.probe = gpiomux_probe,
.remove = __devexit_p(gpiomux_remove),
.driver = {
.owner = THIS_MODULE,
.name = "gpio-i2cmux",
},
};
static int __init gpiomux_init(void)
{
return platform_driver_register(&gpiomux_driver);
}
static void __exit gpiomux_exit(void)
{
platform_driver_unregister(&gpiomux_driver);
}
module_init(gpiomux_init);
module_exit(gpiomux_exit);
MODULE_DESCRIPTION("GPIO-based I2C multiplexer driver");
MODULE_AUTHOR("Peter Korsgaard <peter.korsgaard@barco.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:gpio-i2cmux");
/*
* gpio-i2cmux interface to platform code
*
* Peter Korsgaard <peter.korsgaard@barco.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef _LINUX_GPIO_I2CMUX_H
#define _LINUX_GPIO_I2CMUX_H
/* MUX has no specific idle mode */
#define GPIO_I2CMUX_NO_IDLE ((unsigned)-1)
/**
* struct gpio_i2cmux_platform_data - Platform-dependent data for gpio-i2cmux
* @parent: Parent I2C bus adapter number
* @base_nr: Base I2C bus number to number adapters from or zero for dynamic
* @values: Array of bitmasks of GPIO settings (low/high) for each
* position
* @n_values: Number of multiplexer positions (busses to instantiate)
* @gpios: Array of GPIO numbers used to control MUX
* @n_gpios: Number of GPIOs used to control MUX
* @idle: Bitmask to write to MUX when idle or GPIO_I2CMUX_NO_IDLE if not used
*/
struct gpio_i2cmux_platform_data {
int parent;
int base_nr;
const unsigned *values;
int n_values;
const unsigned *gpios;
int n_gpios;
unsigned idle;
};
#endif /* _LINUX_GPIO_I2CMUX_H */
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