aboutsummaryrefslogtreecommitdiff
path: root/drivers/i2c/muxes
diff options
context:
space:
mode:
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 /drivers/i2c/muxes
parentb18a5c80eb2e7e9c72d23f1960b09d78ddf7e5b0 (diff)
downloadlinux-linaro-stable-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>
Diffstat (limited to 'drivers/i2c/muxes')
-rw-r--r--drivers/i2c/muxes/Kconfig12
-rw-r--r--drivers/i2c/muxes/Makefile1
-rw-r--r--drivers/i2c/muxes/gpio-i2cmux.c184
3 files changed, 197 insertions, 0 deletions
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index 4d91d80bfd23..90b7a0163899 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 d743806d9b42..4640436ea61f 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 000000000000..7b6ce624cd6e
--- /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");