From 1c23af90dc44d05bbb6a3b5246ab664b1f943943 Mon Sep 17 00:00:00 2001 From: Haavard Skinnemoen Date: Tue, 1 May 2007 23:26:34 +0200 Subject: i2c: Bitbanging I2C bus driver using the GPIO API This is a very simple bitbanging I2C bus driver utilizing the new arch-neutral GPIO API. Useful for chips that don't have a built-in I2C controller, additional I2C busses, or testing purposes. To use, include something similar to the following in the board-specific setup code: #include static struct i2c_gpio_platform_data i2c_gpio_data = { .sda_pin = GPIO_PIN_FOO, .scl_pin = GPIO_PIN_BAR, }; static struct platform_device i2c_gpio_device = { .name = "i2c-gpio", .id = 0, .dev = { .platform_data = &i2c_gpio_data, }, }; Register this platform_device, set up the I2C pins as GPIO if required and you're ready to go. This will use default values for udelay and timeout, and will work with GPIO hardware that does not support open drain mode, but allows sensing of the SDA and SCL lines even when they are being driven. Signed-off-by: Haavard Skinnemoen Signed-off-by: Jean Delvare --- drivers/i2c/busses/Kconfig | 8 ++ drivers/i2c/busses/Makefile | 1 + drivers/i2c/busses/i2c-gpio.c | 215 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 224 insertions(+) create mode 100644 drivers/i2c/busses/i2c-gpio.c (limited to 'drivers/i2c') diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig index 8ccf6e4e91d..33a8a67f161 100644 --- a/drivers/i2c/busses/Kconfig +++ b/drivers/i2c/busses/Kconfig @@ -117,6 +117,14 @@ config I2C_ELEKTOR This support is also available as a module. If so, the module will be called i2c-elektor. +config I2C_GPIO + tristate "GPIO-based bitbanging I2C" + depends on GENERIC_GPIO + select I2C_ALGOBIT + help + This is a very simple bitbanging I2C driver utilizing the + arch-neutral GPIO API to control the SCL and SDA lines. + config I2C_HYDRA tristate "CHRP Apple Hydra Mac I/O I2C interface" depends on PCI && PPC_CHRP && EXPERIMENTAL diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile index e51493cfbee..5689165f6d6 100644 --- a/drivers/i2c/busses/Makefile +++ b/drivers/i2c/busses/Makefile @@ -12,6 +12,7 @@ obj-$(CONFIG_I2C_AT91) += i2c-at91.o obj-$(CONFIG_I2C_AU1550) += i2c-au1550.o obj-$(CONFIG_I2C_BLACKFIN_TWI) += i2c-bfin-twi.o obj-$(CONFIG_I2C_ELEKTOR) += i2c-elektor.o +obj-$(CONFIG_I2C_GPIO) += i2c-gpio.o obj-$(CONFIG_I2C_HYDRA) += i2c-hydra.o obj-$(CONFIG_I2C_I801) += i2c-i801.o obj-$(CONFIG_I2C_I810) += i2c-i810.o diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c new file mode 100644 index 00000000000..a7dd54654a9 --- /dev/null +++ b/drivers/i2c/busses/i2c-gpio.c @@ -0,0 +1,215 @@ +/* + * Bitbanging I2C bus driver using the GPIO API + * + * Copyright (C) 2007 Atmel Corporation + * + * 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 +#include +#include +#include +#include +#include + +#include + +/* Toggle SDA by changing the direction of the pin */ +static void i2c_gpio_setsda_dir(void *data, int state) +{ + struct i2c_gpio_platform_data *pdata = data; + + if (state) + gpio_direction_input(pdata->sda_pin); + else + gpio_direction_output(pdata->sda_pin, 0); +} + +/* + * Toggle SDA by changing the output value of the pin. This is only + * valid for pins configured as open drain (i.e. setting the value + * high effectively turns off the output driver.) + */ +static void i2c_gpio_setsda_val(void *data, int state) +{ + struct i2c_gpio_platform_data *pdata = data; + + gpio_set_value(pdata->sda_pin, state); +} + +/* Toggle SCL by changing the direction of the pin. */ +static void i2c_gpio_setscl_dir(void *data, int state) +{ + struct i2c_gpio_platform_data *pdata = data; + + if (state) + gpio_direction_input(pdata->scl_pin); + else + gpio_direction_output(pdata->scl_pin, 0); +} + +/* + * Toggle SCL by changing the output value of the pin. This is used + * for pins that are configured as open drain and for output-only + * pins. The latter case will break the i2c protocol, but it will + * often work in practice. + */ +static void i2c_gpio_setscl_val(void *data, int state) +{ + struct i2c_gpio_platform_data *pdata = data; + + gpio_set_value(pdata->scl_pin, state); +} + +int i2c_gpio_getsda(void *data) +{ + struct i2c_gpio_platform_data *pdata = data; + + return gpio_get_value(pdata->sda_pin); +} + +int i2c_gpio_getscl(void *data) +{ + struct i2c_gpio_platform_data *pdata = data; + + return gpio_get_value(pdata->scl_pin); +} + +static int __init i2c_gpio_probe(struct platform_device *pdev) +{ + struct i2c_gpio_platform_data *pdata; + struct i2c_algo_bit_data *bit_data; + struct i2c_adapter *adap; + int ret; + + pdata = pdev->dev.platform_data; + if (!pdata) + return -ENXIO; + + ret = -ENOMEM; + adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL); + if (!adap) + goto err_alloc_adap; + bit_data = kzalloc(sizeof(struct i2c_algo_bit_data), GFP_KERNEL); + if (!bit_data) + goto err_alloc_bit_data; + + ret = gpio_request(pdata->sda_pin, "sda"); + if (ret) + goto err_request_sda; + ret = gpio_request(pdata->scl_pin, "scl"); + if (ret) + goto err_request_scl; + + if (pdata->sda_is_open_drain) { + gpio_direction_output(pdata->sda_pin, 1); + bit_data->setsda = i2c_gpio_setsda_val; + } else { + gpio_direction_input(pdata->sda_pin); + bit_data->setsda = i2c_gpio_setsda_dir; + } + + if (pdata->scl_is_open_drain || pdata->scl_is_output_only) { + gpio_direction_output(pdata->scl_pin, 1); + bit_data->setscl = i2c_gpio_setscl_val; + } else { + gpio_direction_input(pdata->scl_pin); + bit_data->setscl = i2c_gpio_setscl_dir; + } + + if (!pdata->scl_is_output_only) + bit_data->getscl = i2c_gpio_getscl; + bit_data->getsda = i2c_gpio_getsda; + + if (pdata->udelay) + bit_data->udelay = pdata->udelay; + else if (pdata->scl_is_output_only) + bit_data->udelay = 50; /* 10 kHz */ + else + bit_data->udelay = 5; /* 100 kHz */ + + if (pdata->timeout) + bit_data->timeout = pdata->timeout; + else + bit_data->timeout = HZ / 10; /* 100 ms */ + + bit_data->data = pdata; + + adap->owner = THIS_MODULE; + snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id); + adap->algo_data = bit_data; + adap->dev.parent = &pdev->dev; + + ret = i2c_bit_add_bus(adap); + if (ret) + goto err_add_bus; + + platform_set_drvdata(pdev, adap); + + dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n", + pdata->sda_pin, pdata->scl_pin, + pdata->scl_is_output_only + ? ", no clock stretching" : ""); + + return 0; + +err_add_bus: + gpio_free(pdata->scl_pin); +err_request_scl: + gpio_free(pdata->sda_pin); +err_request_sda: + kfree(bit_data); +err_alloc_bit_data: + kfree(adap); +err_alloc_adap: + return ret; +} + +static int __exit i2c_gpio_remove(struct platform_device *pdev) +{ + struct i2c_gpio_platform_data *pdata; + struct i2c_adapter *adap; + + adap = platform_get_drvdata(pdev); + pdata = pdev->dev.platform_data; + + i2c_del_adapter(adap); + gpio_free(pdata->scl_pin); + gpio_free(pdata->sda_pin); + kfree(adap->algo_data); + kfree(adap); + + return 0; +} + +static struct platform_driver i2c_gpio_driver = { + .driver = { + .name = "i2c-gpio", + .owner = THIS_MODULE, + }, + .remove = __exit_p(i2c_gpio_remove), +}; + +static int __init i2c_gpio_init(void) +{ + int ret; + + ret = platform_driver_probe(&i2c_gpio_driver, i2c_gpio_probe); + if (ret) + printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret); + + return ret; +} +module_init(i2c_gpio_init); + +static void __exit i2c_gpio_exit(void) +{ + platform_driver_unregister(&i2c_gpio_driver); +} +module_exit(i2c_gpio_exit); + +MODULE_AUTHOR("Haavard Skinnemoen "); +MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver"); +MODULE_LICENSE("GPL"); -- cgit v1.2.3