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authorPeter Korsgaard <peter.korsgaard@barco.com>2011-01-10 22:11:23 +0100
committerJean Delvare <khali@endymion.delvare>2011-01-10 22:11:23 +0100
commit92ed1a76ca31774eb27de14b2215841367c68056 (patch)
treef9becefa5dbcdaa8cfd65100e1735044cd3910d6
parentb18a5c80eb2e7e9c72d23f1960b09d78ddf7e5b0 (diff)
downloadlinux-2.6.38-lt-ux500-92ed1a76ca31774eb27de14b2215841367c68056.tar.gz
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: Peter Korsgaard <peter.korsgaard@barco.com> Signed-off-by: Jean Delvare <khali@linux-fr.org>
-rw-r--r--Documentation/i2c/muxes/gpio-i2cmux65
-rw-r--r--MAINTAINERS8
-rw-r--r--drivers/i2c/muxes/Kconfig12
-rw-r--r--drivers/i2c/muxes/Makefile1
-rw-r--r--drivers/i2c/muxes/gpio-i2cmux.c184
-rw-r--r--include/linux/gpio-i2cmux.h38
6 files changed, 308 insertions, 0 deletions
diff --git a/Documentation/i2c/muxes/gpio-i2cmux b/Documentation/i2c/muxes/gpio-i2cmux
new file mode 100644
index 00000000000..811cd78d4cd
--- /dev/null
+++ b/Documentation/i2c/muxes/gpio-i2cmux
@@ -0,0 +1,65 @@
+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,
+ },
+};
diff --git a/MAINTAINERS b/MAINTAINERS
index 23d04363a19..23a4765ab8d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2608,6 +2608,14 @@ S: Supported
F: drivers/i2c/busses/i2c-gpio.c
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
M: Krzysztof Halasa <khc@pm.waw.pl>
W: http://www.kernel.org/pub/linux/utils/net/hdlc/
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index 4d91d80bfd2..90b7a016389 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -5,6 +5,18 @@
menu "Multiplexer I2C Chip support"
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
tristate "NXP PCA9541 I2C Master Selector"
depends on EXPERIMENTAL
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index d743806d9b4..4640436ea61 100644
--- a/drivers/i2c/muxes/Makefile
+++ b/drivers/i2c/muxes/Makefile
@@ -1,6 +1,7 @@
#
# 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_PCA954x) += pca954x.o
diff --git a/drivers/i2c/muxes/gpio-i2cmux.c b/drivers/i2c/muxes/gpio-i2cmux.c
new file mode 100644
index 00000000000..7b6ce624cd6
--- /dev/null
+++ b/drivers/i2c/muxes/gpio-i2cmux.c
@@ -0,0 +1,184 @@
+/*
+ * 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");
diff --git a/include/linux/gpio-i2cmux.h b/include/linux/gpio-i2cmux.h
new file mode 100644
index 00000000000..4a333bb0bd0
--- /dev/null
+++ b/include/linux/gpio-i2cmux.h
@@ -0,0 +1,38 @@
+/*
+ * 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 */