blob: 3d69e0c1d09a936b0cdee2fd9ee0f50f0e1998f7 [file] [log] [blame]
/*
* Copyright (c) 2017 Linaro Ltd.
*
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @file
* @brief Driver for software driven I2C using GPIO lines
*
* This driver implements an I2C interface by driving two GPIO lines under
* software control. The GPIO pins used must be preconfigured to to a suitable
* state, i.e. the SDA pin as open-colector/open-drain with a pull-up resistor
* (possibly as an external component attached to the pin). When the SDA pin
* is read it must return the state of the physical hardware line, not just the
* last state written to it for output.
*
* The SCL pin should be configued in the same manner as SDA, or, if it is known
* that the hardware attached to pin doesn't attempt clock stretching, then the
* SCL pin may be a push/pull output.
*/
#include <device.h>
#include <errno.h>
#include <gpio.h>
#include <i2c.h>
#include <i2c_bitbang.h>
/* Driver config */
struct i2c_gpio_config {
char *gpio_name;
u8_t scl_pin;
u8_t sda_pin;
};
/* Driver instance data */
struct i2c_gpio_context {
struct i2c_bitbang bitbang; /* Bit-bang library data */
struct device *gpio; /* GPIO used for I2C lines */
u8_t scl_pin; /* Pin on gpio used for SCL line */
u8_t sda_pin; /* Pin on gpio used for SDA line */
};
static void i2c_gpio_set_scl(void *io_context, int state)
{
struct i2c_gpio_context *context = io_context;
gpio_pin_write(context->gpio, context->scl_pin, state);
}
static void i2c_gpio_set_sda(void *io_context, int state)
{
struct i2c_gpio_context *context = io_context;
gpio_pin_write(context->gpio, context->sda_pin, state);
}
static int i2c_gpio_get_sda(void *io_context)
{
struct i2c_gpio_context *context = io_context;
u32_t state = 1; /* Default high as that would be a NACK */
gpio_pin_read(context->gpio, context->sda_pin, &state);
return state;
}
static const struct i2c_bitbang_io io_fns = {
.set_scl = &i2c_gpio_set_scl,
.set_sda = &i2c_gpio_set_sda,
.get_sda = &i2c_gpio_get_sda,
};
static int i2c_gpio_configure(struct device *dev, u32_t dev_config)
{
struct i2c_gpio_context *context = dev->driver_data;
return i2c_bitbang_configure(&context->bitbang, dev_config);
}
static int i2c_gpio_transfer(struct device *dev, struct i2c_msg *msgs,
u8_t num_msgs, u16_t slave_address)
{
struct i2c_gpio_context *context = dev->driver_data;
return i2c_bitbang_transfer(&context->bitbang, msgs, num_msgs,
slave_address);
}
static struct i2c_driver_api api = {
.configure = i2c_gpio_configure,
.transfer = i2c_gpio_transfer,
};
static int i2c_gpio_init(struct device *dev)
{
struct i2c_gpio_context *context = dev->driver_data;
const struct i2c_gpio_config *config = dev->config->config_info;
context->gpio = device_get_binding(config->gpio_name);
if (!context->gpio) {
return -EINVAL;
}
context->sda_pin = config->sda_pin;
context->scl_pin = config->scl_pin;
i2c_bitbang_init(&context->bitbang, &io_fns, context);
/*
* Set driver_api at very end of init so if we return early with error
* then the device can't be found later by device_get_binding. This is
* important because driver framework ignores errors from init
* functions.
*/
dev->driver_api = &api;
return 0;
}
#define DEFINE_I2C_GPIO(_num) \
\
static struct i2c_gpio_context i2c_gpio_dev_data_##_num; \
\
static const struct i2c_gpio_config i2c_gpio_dev_cfg_##_num = { \
.gpio_name = CONFIG_I2C_GPIO_##_num##_GPIO, \
.scl_pin = CONFIG_I2C_GPIO_##_num##_SCL_PIN, \
.sda_pin = CONFIG_I2C_GPIO_##_num##_SDA_PIN, \
}; \
\
DEVICE_INIT(i2c_gpio_##_num, CONFIG_I2C_GPIO_##_num##_NAME, \
i2c_gpio_init, \
&i2c_gpio_dev_data_##_num, \
&i2c_gpio_dev_cfg_##_num, \
PRE_KERNEL_2, CONFIG_I2C_INIT_PRIORITY)
#ifdef CONFIG_I2C_GPIO_0
DEFINE_I2C_GPIO(0);
#endif
#ifdef CONFIG_I2C_GPIO_1
DEFINE_I2C_GPIO(1);
#endif
#ifdef CONFIG_I2C_GPIO_2
DEFINE_I2C_GPIO(2);
#endif
#ifdef CONFIG_I2C_GPIO_3
DEFINE_I2C_GPIO(3);
#endif