diff options
Diffstat (limited to 'drivers/i2c/busses/i2c-gpio.c')
| -rw-r--r-- | drivers/i2c/busses/i2c-gpio.c | 215 |
1 files changed, 215 insertions, 0 deletions
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 <linux/i2c.h> +#include <linux/i2c-algo-bit.h> +#include <linux/i2c-gpio.h> +#include <linux/init.h> +#include <linux/module.h> +#include <linux/platform_device.h> + +#include <asm/gpio.h> + +/* 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 <hskinnemoen@atmel.com>"); +MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver"); +MODULE_LICENSE("GPL"); |