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/*
* Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/
* Andrew F. Davis <afd@ti.com>
*
* 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.
*
* This program is distributed "as is" WITHOUT ANY WARRANTY of any
* kind, whether expressed or implied; without even the implied warranty
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License version 2 for more details.
*/
#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/spi/spi.h>
#define DEFAULT_NGPIO 8
/**
* struct pisosr_gpio - GPIO driver data
* @chip: GPIO controller chip
* @spi: SPI device pointer
* @buffer: Buffer for device reads
* @buffer_size: Size of buffer
* @load_gpio: GPIO pin used to load input into device
* @lock: Protects read sequences
*/
struct pisosr_gpio {
struct gpio_chip chip;
struct spi_device *spi;
u8 *buffer;
size_t buffer_size;
struct gpio_desc *load_gpio;
struct mutex lock;
};
static int pisosr_gpio_refresh(struct pisosr_gpio *gpio)
{
int ret;
mutex_lock(&gpio->lock);
if (gpio->load_gpio) {
gpiod_set_value_cansleep(gpio->load_gpio, 1);
udelay(1); /* registers load time (~10ns) */
gpiod_set_value_cansleep(gpio->load_gpio, 0);
udelay(1); /* registers recovery time (~5ns) */
}
ret = spi_read(gpio->spi, gpio->buffer, gpio->buffer_size);
mutex_unlock(&gpio->lock);
return ret;
}
static int pisosr_gpio_get_direction(struct gpio_chip *chip,
unsigned offset)
{
/* This device always input */
return 1;
}
static int pisosr_gpio_direction_input(struct gpio_chip *chip,
unsigned offset)
{
/* This device always input */
return 0;
}
static int pisosr_gpio_direction_output(struct gpio_chip *chip,
unsigned offset, int value)
{
/* This device is input only */
return -EINVAL;
}
static int pisosr_gpio_get(struct gpio_chip *chip, unsigned offset)
{
struct pisosr_gpio *gpio = gpiochip_get_data(chip);
/* Refresh may not always be needed */
pisosr_gpio_refresh(gpio);
return (gpio->buffer[offset / 8] >> (offset % 8)) & 0x1;
}
static const struct gpio_chip template_chip = {
.label = "pisosr-gpio",
.owner = THIS_MODULE,
.get_direction = pisosr_gpio_get_direction,
.direction_input = pisosr_gpio_direction_input,
.direction_output = pisosr_gpio_direction_output,
.get = pisosr_gpio_get,
.base = -1,
.ngpio = DEFAULT_NGPIO,
.can_sleep = true,
};
static int pisosr_gpio_probe(struct spi_device *spi)
{
struct device *dev = &spi->dev;
struct pisosr_gpio *gpio;
int ret;
gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL);
if (!gpio)
return -ENOMEM;
spi_set_drvdata(spi, gpio);
gpio->chip = template_chip;
gpio->chip.parent = dev;
of_property_read_u16(dev->of_node, "ngpios", &gpio->chip.ngpio);
gpio->spi = spi;
gpio->buffer_size = DIV_ROUND_UP(gpio->chip.ngpio, 8);
gpio->buffer = devm_kzalloc(dev, gpio->buffer_size, GFP_KERNEL);
if (!gpio->buffer)
return -ENOMEM;
gpio->load_gpio = devm_gpiod_get_optional(dev, "load", GPIOD_OUT_LOW);
if (IS_ERR(gpio->load_gpio)) {
ret = PTR_ERR(gpio->load_gpio);
if (ret != -EPROBE_DEFER)
dev_err(dev, "Unable to allocate load GPIO\n");
return ret;
}
mutex_init(&gpio->lock);
ret = gpiochip_add_data(&gpio->chip, gpio);
if (ret < 0) {
dev_err(dev, "Unable to register gpiochip\n");
return ret;
}
return 0;
}
static int pisosr_gpio_remove(struct spi_device *spi)
{
struct pisosr_gpio *gpio = spi_get_drvdata(spi);
gpiochip_remove(&gpio->chip);
mutex_destroy(&gpio->lock);
return 0;
}
static const struct spi_device_id pisosr_gpio_id_table[] = {
{ "pisosr-gpio", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table);
static const struct of_device_id pisosr_gpio_of_match_table[] = {
{ .compatible = "pisosr-gpio", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table);
static struct spi_driver pisosr_gpio_driver = {
.driver = {
.name = "pisosr-gpio",
.of_match_table = pisosr_gpio_of_match_table,
},
.probe = pisosr_gpio_probe,
.remove = pisosr_gpio_remove,
.id_table = pisosr_gpio_id_table,
};
module_spi_driver(pisosr_gpio_driver);
MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver");
MODULE_LICENSE("GPL v2");
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