mirror of https://gitee.com/openkylin/linux.git
216 lines
5.0 KiB
C
216 lines
5.0 KiB
C
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/*
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* Bitbanging I2C bus driver using the GPIO API
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*
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* Copyright (C) 2007 Atmel Corporation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/i2c.h>
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#include <linux/i2c-algo-bit.h>
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#include <linux/i2c-gpio.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/platform_device.h>
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#include <asm/gpio.h>
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/* Toggle SDA by changing the direction of the pin */
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static void i2c_gpio_setsda_dir(void *data, int state)
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{
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struct i2c_gpio_platform_data *pdata = data;
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if (state)
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gpio_direction_input(pdata->sda_pin);
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else
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gpio_direction_output(pdata->sda_pin, 0);
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}
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/*
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* Toggle SDA by changing the output value of the pin. This is only
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* valid for pins configured as open drain (i.e. setting the value
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* high effectively turns off the output driver.)
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*/
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static void i2c_gpio_setsda_val(void *data, int state)
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{
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struct i2c_gpio_platform_data *pdata = data;
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gpio_set_value(pdata->sda_pin, state);
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}
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/* Toggle SCL by changing the direction of the pin. */
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static void i2c_gpio_setscl_dir(void *data, int state)
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{
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struct i2c_gpio_platform_data *pdata = data;
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if (state)
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gpio_direction_input(pdata->scl_pin);
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else
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gpio_direction_output(pdata->scl_pin, 0);
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}
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/*
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* Toggle SCL by changing the output value of the pin. This is used
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* for pins that are configured as open drain and for output-only
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* pins. The latter case will break the i2c protocol, but it will
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* often work in practice.
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*/
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static void i2c_gpio_setscl_val(void *data, int state)
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{
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struct i2c_gpio_platform_data *pdata = data;
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gpio_set_value(pdata->scl_pin, state);
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}
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int i2c_gpio_getsda(void *data)
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{
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struct i2c_gpio_platform_data *pdata = data;
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return gpio_get_value(pdata->sda_pin);
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}
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int i2c_gpio_getscl(void *data)
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{
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struct i2c_gpio_platform_data *pdata = data;
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return gpio_get_value(pdata->scl_pin);
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}
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static int __init i2c_gpio_probe(struct platform_device *pdev)
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{
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struct i2c_gpio_platform_data *pdata;
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struct i2c_algo_bit_data *bit_data;
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struct i2c_adapter *adap;
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int ret;
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pdata = pdev->dev.platform_data;
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if (!pdata)
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return -ENXIO;
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ret = -ENOMEM;
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adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
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if (!adap)
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goto err_alloc_adap;
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bit_data = kzalloc(sizeof(struct i2c_algo_bit_data), GFP_KERNEL);
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if (!bit_data)
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goto err_alloc_bit_data;
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ret = gpio_request(pdata->sda_pin, "sda");
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if (ret)
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goto err_request_sda;
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ret = gpio_request(pdata->scl_pin, "scl");
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if (ret)
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goto err_request_scl;
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if (pdata->sda_is_open_drain) {
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gpio_direction_output(pdata->sda_pin, 1);
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bit_data->setsda = i2c_gpio_setsda_val;
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} else {
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gpio_direction_input(pdata->sda_pin);
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bit_data->setsda = i2c_gpio_setsda_dir;
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}
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if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
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gpio_direction_output(pdata->scl_pin, 1);
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bit_data->setscl = i2c_gpio_setscl_val;
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} else {
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gpio_direction_input(pdata->scl_pin);
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bit_data->setscl = i2c_gpio_setscl_dir;
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}
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if (!pdata->scl_is_output_only)
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bit_data->getscl = i2c_gpio_getscl;
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bit_data->getsda = i2c_gpio_getsda;
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if (pdata->udelay)
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bit_data->udelay = pdata->udelay;
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else if (pdata->scl_is_output_only)
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bit_data->udelay = 50; /* 10 kHz */
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else
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bit_data->udelay = 5; /* 100 kHz */
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if (pdata->timeout)
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bit_data->timeout = pdata->timeout;
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else
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bit_data->timeout = HZ / 10; /* 100 ms */
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bit_data->data = pdata;
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adap->owner = THIS_MODULE;
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snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
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adap->algo_data = bit_data;
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adap->dev.parent = &pdev->dev;
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ret = i2c_bit_add_bus(adap);
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if (ret)
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goto err_add_bus;
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platform_set_drvdata(pdev, adap);
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dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
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pdata->sda_pin, pdata->scl_pin,
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pdata->scl_is_output_only
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? ", no clock stretching" : "");
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return 0;
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err_add_bus:
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gpio_free(pdata->scl_pin);
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err_request_scl:
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gpio_free(pdata->sda_pin);
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err_request_sda:
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kfree(bit_data);
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err_alloc_bit_data:
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kfree(adap);
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err_alloc_adap:
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return ret;
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}
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static int __exit i2c_gpio_remove(struct platform_device *pdev)
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{
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struct i2c_gpio_platform_data *pdata;
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struct i2c_adapter *adap;
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adap = platform_get_drvdata(pdev);
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pdata = pdev->dev.platform_data;
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i2c_del_adapter(adap);
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gpio_free(pdata->scl_pin);
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gpio_free(pdata->sda_pin);
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kfree(adap->algo_data);
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kfree(adap);
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return 0;
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}
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static struct platform_driver i2c_gpio_driver = {
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.driver = {
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.name = "i2c-gpio",
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.owner = THIS_MODULE,
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},
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.remove = __exit_p(i2c_gpio_remove),
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};
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static int __init i2c_gpio_init(void)
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{
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int ret;
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ret = platform_driver_probe(&i2c_gpio_driver, i2c_gpio_probe);
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if (ret)
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printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
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return ret;
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}
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module_init(i2c_gpio_init);
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static void __exit i2c_gpio_exit(void)
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{
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platform_driver_unregister(&i2c_gpio_driver);
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}
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module_exit(i2c_gpio_exit);
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MODULE_AUTHOR("Haavard Skinnemoen <hskinnemoen@atmel.com>");
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MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
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MODULE_LICENSE("GPL");
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