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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* GPIO latch driver
*
* Copyright (C) 2014 Gabor Juhos <juhosg@openwrt.org>
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
#include <linux/platform_device.h>
#include <linux/of_platform.h>
#include <linux/of_gpio.h>
#define GPIO_LATCH_DRIVER_NAME "gpio-latch"
#define GPIO_LATCH_LINES 9
struct gpio_latch_chip {
struct gpio_chip gc;
struct mutex mutex;
struct mutex latch_mutex;
bool latch_enabled;
int le_gpio;
bool le_active_low;
struct gpio_desc *gpios[GPIO_LATCH_LINES];
};
static inline struct gpio_latch_chip *to_gpio_latch_chip(struct gpio_chip *gc)
{
return container_of(gc, struct gpio_latch_chip, gc);
}
static void gpio_latch_lock(struct gpio_latch_chip *glc, bool enable)
{
mutex_lock(&glc->mutex);
if (enable)
glc->latch_enabled = true;
if (glc->latch_enabled)
mutex_lock(&glc->latch_mutex);
}
static void gpio_latch_unlock(struct gpio_latch_chip *glc, bool disable)
{
if (glc->latch_enabled)
mutex_unlock(&glc->latch_mutex);
if (disable)
glc->latch_enabled = true;
mutex_unlock(&glc->mutex);
}
static int
gpio_latch_get(struct gpio_chip *gc, unsigned offset)
{
struct gpio_latch_chip *glc = to_gpio_latch_chip(gc);
int ret;
gpio_latch_lock(glc, false);
ret = gpiod_get_value(glc->gpios[offset]);
gpio_latch_unlock(glc, false);
return ret;
}
static void
gpio_latch_set(struct gpio_chip *gc, unsigned offset, int value)
{
struct gpio_latch_chip *glc = to_gpio_latch_chip(gc);
bool enable_latch = false;
bool disable_latch = false;
if (offset == glc->le_gpio) {
enable_latch = value ^ glc->le_active_low;
disable_latch = !enable_latch;
}
gpio_latch_lock(glc, enable_latch);
gpiod_set_raw_value(glc->gpios[offset], value);
gpio_latch_unlock(glc, disable_latch);
}
static int
gpio_latch_direction_output(struct gpio_chip *gc, unsigned offset, int value)
{
struct gpio_latch_chip *glc = to_gpio_latch_chip(gc);
bool enable_latch = false;
bool disable_latch = false;
int ret;
if (offset == glc->le_gpio) {
enable_latch = value ^ glc->le_active_low;
disable_latch = !enable_latch;
}
gpio_latch_lock(glc, enable_latch);
ret = gpiod_direction_output_raw(glc->gpios[offset], value);
gpio_latch_unlock(glc, disable_latch);
return ret;
}
static int gpio_latch_probe(struct platform_device *pdev)
{
struct gpio_latch_chip *glc;
struct gpio_chip *gc;
struct device *dev = &pdev->dev;
struct device_node *of_node = dev->of_node;
int i, n;
glc = devm_kzalloc(dev, sizeof(*glc), GFP_KERNEL);
if (!glc)
return -ENOMEM;
mutex_init(&glc->mutex);
mutex_init(&glc->latch_mutex);
n = gpiod_count(dev, NULL);
if (n <= 0) {
dev_err(dev, "failed to get gpios: %d\n", n);
return n;
} else if (n != GPIO_LATCH_LINES) {
dev_err(dev, "expected %d gpios\n", GPIO_LATCH_LINES);
return -EINVAL;
}
for (i = 0; i < n; i++) {
glc->gpios[i] = devm_gpiod_get_index_optional(dev, NULL, i,
GPIOD_OUT_LOW);
if (IS_ERR(glc->gpios[i])) {
dev_err(dev, "failed to get gpio %d: %d\n", i,
PTR_ERR(glc->gpios[i]));
return PTR_ERR(glc->gpios[i]);
}
}
glc->le_gpio = 8;
glc->le_active_low = gpiod_is_active_low(glc->gpios[glc->le_gpio]);
if (!glc->gpios[glc->le_gpio]) {
dev_err(dev, "missing required latch-enable gpio %d\n",
glc->le_gpio);
return -EINVAL;
}
gc = &glc->gc;
gc->label = GPIO_LATCH_DRIVER_NAME;
gc->can_sleep = true;
gc->base = -1;
gc->ngpio = GPIO_LATCH_LINES;
gc->get = gpio_latch_get;
gc->set = gpio_latch_set;
gc->direction_output = gpio_latch_direction_output;
gc->of_node = of_node;
platform_set_drvdata(pdev, glc);
i = gpiochip_add(&glc->gc);
if (i) {
dev_err(dev, "gpiochip_add() failed: %d\n", i);
return i;
}
return 0;
}
static int gpio_latch_remove(struct platform_device *pdev)
{
struct gpio_latch_chip *glc = platform_get_drvdata(pdev);
gpiochip_remove(&glc->gc);
return 0;
}
static const struct of_device_id gpio_latch_match[] = {
{ .compatible = GPIO_LATCH_DRIVER_NAME },
{},
};
MODULE_DEVICE_TABLE(of, gpio_latch_match);
static struct platform_driver gpio_latch_driver = {
.probe = gpio_latch_probe,
.remove = gpio_latch_remove,
.driver = {
.name = GPIO_LATCH_DRIVER_NAME,
.owner = THIS_MODULE,
.of_match_table = gpio_latch_match,
},
};
module_platform_driver(gpio_latch_driver);
MODULE_DESCRIPTION("GPIO latch driver");
MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
MODULE_AUTHOR("Denis Kalashnikov <denis281089@gmail.com>");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:" GPIO_LATCH_DRIVER_NAME);
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