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