diff options
| -rw-r--r-- | drivers/i2c/busses/Kconfig | 8 | ||||
| -rw-r--r-- | drivers/i2c/busses/Makefile | 1 | ||||
| -rw-r--r-- | drivers/i2c/busses/i2c-gpio.c | 177 | ||||
| -rw-r--r-- | include/i2c/i2c-gpio.h | 38 |
4 files changed, 224 insertions, 0 deletions
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig index 3f998eafa5..17e33cb189 100644 --- a/drivers/i2c/busses/Kconfig +++ b/drivers/i2c/busses/Kconfig @@ -4,6 +4,14 @@ menu "I2C Hardware Bus support" +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_IMX bool "MPC85xx/i.MX I2C Master driver" depends on (ARCH_IMX && !ARCH_IMX1) || ARCH_MPC85XX diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile index e4c5125580..18c7c46ac5 100644 --- a/drivers/i2c/busses/Makefile +++ b/drivers/i2c/busses/Makefile @@ -1,2 +1,3 @@ +obj-$(CONFIG_I2C_GPIO) += i2c-gpio.o obj-$(CONFIG_I2C_IMX) += i2c-imx.o obj-$(CONFIG_I2C_OMAP) += i2c-omap.o diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c new file mode 100644 index 0000000000..98ce2d59ab --- /dev/null +++ b/drivers/i2c/busses/i2c-gpio.c @@ -0,0 +1,177 @@ +/* + * 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 <common.h> +#include <driver.h> +#include <i2c/i2c.h> +#include <i2c/i2c-algo-bit.h> +#include <i2c/i2c-gpio.h> +#include <init.h> +#include <gpio.h> + +struct i2c_gpio_private_data { + struct i2c_adapter adap; + struct i2c_algo_bit_data bit_data; + struct i2c_gpio_platform_data pdata; +}; + +/* 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); +} + +static int i2c_gpio_getsda(void *data) +{ + struct i2c_gpio_platform_data *pdata = data; + + return gpio_get_value(pdata->sda_pin); +} + +static int i2c_gpio_getscl(void *data) +{ + struct i2c_gpio_platform_data *pdata = data; + + return gpio_get_value(pdata->scl_pin); +} + +static int i2c_gpio_probe(struct device_d *dev) +{ + struct i2c_gpio_private_data *priv; + struct i2c_gpio_platform_data *pdata; + struct i2c_algo_bit_data *bit_data; + struct i2c_adapter *adap; + int ret; + + priv = xzalloc(sizeof(*priv)); + + adap = &priv->adap; + bit_data = &priv->bit_data; + pdata = &priv->pdata; + + if (!dev->platform_data) + return -ENXIO; + memcpy(pdata, dev->platform_data, sizeof(*pdata)); + + 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_ms) + bit_data->timeout_ms = pdata->timeout_ms; + else + bit_data->timeout_ms = 100; /* 100 ms */ + + bit_data->data = pdata; + + adap->algo_data = bit_data; + adap->dev.parent = dev; + + adap->nr = dev->id; + ret = i2c_bit_add_numbered_bus(adap); + if (ret) + goto err_add_bus; + + dev_info(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: + return ret; +} + +static struct driver_d i2c_gpio_driver = { + .name = "i2c-gpio", + .probe = i2c_gpio_probe, +}; + +static int __init i2c_gpio_init(void) +{ + return platform_driver_register(&i2c_gpio_driver); +} +device_initcall(i2c_gpio_init); diff --git a/include/i2c/i2c-gpio.h b/include/i2c/i2c-gpio.h new file mode 100644 index 0000000000..55feb82a90 --- /dev/null +++ b/include/i2c/i2c-gpio.h @@ -0,0 +1,38 @@ +/* + * i2c-gpio interface to platform code + * + * 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. + */ +#ifndef _LINUX_I2C_GPIO_H +#define _LINUX_I2C_GPIO_H + +/** + * struct i2c_gpio_platform_data - Platform-dependent data for i2c-gpio + * @sda_pin: GPIO pin ID to use for SDA + * @scl_pin: GPIO pin ID to use for SCL + * @udelay: signal toggle delay. SCL frequency is (500 / udelay) kHz + * @timeout_ms: clock stretching timeout in ms. If the slave keeps + * SCL low for longer than this, the transfer will time out. + * @sda_is_open_drain: SDA is configured as open drain, i.e. the pin + * isn't actively driven high when setting the output value high. + * gpio_get_value() must return the actual pin state even if the + * pin is configured as an output. + * @scl_is_open_drain: SCL is set up as open drain. Same requirements + * as for sda_is_open_drain apply. + * @scl_is_output_only: SCL output drivers cannot be turned off. + */ +struct i2c_gpio_platform_data { + unsigned int sda_pin; + unsigned int scl_pin; + int udelay; + int timeout_ms; + unsigned int sda_is_open_drain:1; + unsigned int scl_is_open_drain:1; + unsigned int scl_is_output_only:1; +}; + +#endif /* _LINUX_I2C_GPIO_H */ |