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/*
* 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/slab.h>
#include <linux/platform_device.h>
#include <linux/gpio/consumer.h>
#include <linux/of.h>
struct i2c_gpio_private_data {
struct gpio_desc *sda;
struct gpio_desc *scl;
struct i2c_adapter adap;
struct i2c_algo_bit_data bit_data;
struct i2c_gpio_platform_data pdata;
};
/*
* 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_private_data *priv = data;
gpiod_set_value(priv->sda, state);
}
/*
* 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_private_data *priv = data;
gpiod_set_value(priv->scl, state);
}
static int i2c_gpio_getsda(void *data)
{
struct i2c_gpio_private_data *priv = data;
return gpiod_get_value(priv->sda);
}
static int i2c_gpio_getscl(void *data)
{
struct i2c_gpio_private_data *priv = data;
return gpiod_get_value(priv->scl);
}
static void of_i2c_gpio_get_props(struct device_node *np,
struct i2c_gpio_platform_data *pdata)
{
u32 reg;
of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", &reg))
pdata->timeout = msecs_to_jiffies(reg);
pdata->sda_is_open_drain =
of_property_read_bool(np, "i2c-gpio,sda-open-drain");
pdata->scl_is_open_drain =
of_property_read_bool(np, "i2c-gpio,scl-open-drain");
pdata->scl_is_output_only =
of_property_read_bool(np, "i2c-gpio,scl-output-only");
}
static struct gpio_desc *i2c_gpio_get_desc(struct device *dev,
const char *con_id,
unsigned int index,
enum gpiod_flags gflags)
{
struct gpio_desc *retdesc;
int ret;
retdesc = devm_gpiod_get(dev, con_id, gflags);
if (!IS_ERR(retdesc)) {
dev_dbg(dev, "got GPIO from name %s\n", con_id);
return retdesc;
}
retdesc = devm_gpiod_get_index(dev, NULL, index, gflags);
if (!IS_ERR(retdesc)) {
dev_dbg(dev, "got GPIO from index %u\n", index);
return retdesc;
}
ret = PTR_ERR(retdesc);
/* FIXME: hack in the old code, is this really necessary? */
if (ret == -EINVAL)
retdesc = ERR_PTR(-EPROBE_DEFER);
/* This happens if the GPIO driver is not yet probed, let's defer */
if (ret == -ENOENT)
retdesc = ERR_PTR(-EPROBE_DEFER);
if (ret != -EPROBE_DEFER)
dev_err(dev, "error trying to get descriptor: %d\n", ret);
return retdesc;
}
static int i2c_gpio_probe(struct platform_device *pdev)
{
struct i2c_gpio_private_data *priv;
struct i2c_gpio_platform_data *pdata;
struct i2c_algo_bit_data *bit_data;
struct i2c_adapter *adap;
struct device *dev = &pdev->dev;
struct device_node *np = dev->of_node;
enum gpiod_flags gflags;
int ret;
priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
adap = &priv->adap;
bit_data = &priv->bit_data;
pdata = &priv->pdata;
if (np) {
of_i2c_gpio_get_props(np, pdata);
} else {
/*
* If all platform data settings are zero it is OK
* to not provide any platform data from the board.
*/
if (dev_get_platdata(dev))
memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata));
}
/*
* First get the GPIO pins; if it fails, we'll defer the probe.
* If the SDA line is marked from platform data or device tree as
* "open drain" it means something outside of our control is making
* this line being handled as open drain, and we should just handle
* it as any other output. Else we enforce open drain as this is
* required for an I2C bus.
*/
if (pdata->sda_is_open_drain)
gflags = GPIOD_OUT_HIGH;
else
gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
priv->sda = i2c_gpio_get_desc(dev, "sda", 0, gflags);
if (IS_ERR(priv->sda))
return PTR_ERR(priv->sda);
/*
* If the SCL line is marked from platform data or device tree as
* "open drain" it means something outside of our control is making
* this line being handled as open drain, and we should just handle
* it as any other output. Else we enforce open drain as this is
* required for an I2C bus.
*/
if (pdata->scl_is_open_drain)
gflags = GPIOD_OUT_LOW;
else
gflags = GPIOD_OUT_LOW_OPEN_DRAIN;
priv->scl = i2c_gpio_get_desc(dev, "scl", 1, gflags);
if (IS_ERR(priv->scl))
return PTR_ERR(priv->scl);
bit_data->setsda = i2c_gpio_setsda_val;
bit_data->setscl = i2c_gpio_setscl_val;
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 = priv;
adap->owner = THIS_MODULE;
if (np)
strlcpy(adap->name, dev_name(dev), sizeof(adap->name));
else
snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
adap->algo_data = bit_data;
adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
adap->dev.parent = dev;
adap->dev.of_node = np;
adap->nr = pdev->id;
ret = i2c_bit_add_numbered_bus(adap);
if (ret)
return ret;
platform_set_drvdata(pdev, priv);
/*
* FIXME: using global GPIO numbers is not helpful. If/when we
* get accessors to get the actual name of the GPIO line,
* from the descriptor, then provide that instead.
*/
dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n",
desc_to_gpio(priv->sda), desc_to_gpio(priv->scl),
pdata->scl_is_output_only
? ", no clock stretching" : "");
return 0;
}
static int i2c_gpio_remove(struct platform_device *pdev)
{
struct i2c_gpio_private_data *priv;
struct i2c_adapter *adap;
priv = platform_get_drvdata(pdev);
adap = &priv->adap;
i2c_del_adapter(adap);
return 0;
}
#if defined(CONFIG_OF)
static const struct of_device_id i2c_gpio_dt_ids[] = {
{ .compatible = "i2c-gpio", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
#endif
static struct platform_driver i2c_gpio_driver = {
.driver = {
.name = "i2c-gpio",
.of_match_table = of_match_ptr(i2c_gpio_dt_ids),
},
.probe = i2c_gpio_probe,
.remove = i2c_gpio_remove,
};
static int __init i2c_gpio_init(void)
{
int ret;
ret = platform_driver_register(&i2c_gpio_driver);
if (ret)
printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
return ret;
}
subsys_initcall(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 (Atmel)");
MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:i2c-gpio");