diff options
| -rw-r--r-- | Documentation/i2c/muxes/gpio-i2cmux | 65 | ||||
| -rw-r--r-- | MAINTAINERS | 8 | ||||
| -rw-r--r-- | drivers/i2c/muxes/Kconfig | 12 | ||||
| -rw-r--r-- | drivers/i2c/muxes/Makefile | 1 | ||||
| -rw-r--r-- | drivers/i2c/muxes/gpio-i2cmux.c | 184 | ||||
| -rw-r--r-- | include/linux/gpio-i2cmux.h | 38 |
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 0000000..811cd78 --- /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 23d0436..23a4765 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 4d91d80..90b7a01 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 d743806..4640436 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 0000000..7b6ce62 --- /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 0000000..4a333bb --- /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 */ |
