--- /dev/null
+/*
+ * 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");
projects / powerpc.git / blobdiff