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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Driver for watchdog device controlled through GPIO-line
*
* Author: 2013, Alexander Shiyan <shc_work@mail.ru>
*/
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/gpio/consumer.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>
#define SOFT_TIMEOUT_MIN 1
#define SOFT_TIMEOUT_DEF 60
enum {
HW_ALGO_TOGGLE,
HW_ALGO_LEVEL,
};
struct gpio_wdt_priv {
struct gpio_desc *gpiod;
bool state;
bool always_running;
unsigned int hw_algo;
struct watchdog_device wdd;
};
static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
{
/* Eternal ping */
gpiod_set_value_cansleep(priv->gpiod, 1);
/* Put GPIO back to tristate */
if (priv->hw_algo == HW_ALGO_TOGGLE)
gpiod_direction_input(priv->gpiod);
}
static int gpio_wdt_ping(struct watchdog_device *wdd)
{
struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
switch (priv->hw_algo) {
case HW_ALGO_TOGGLE:
/* Toggle output pin */
priv->state = !priv->state;
gpiod_set_value_cansleep(priv->gpiod, priv->state);
break;
case HW_ALGO_LEVEL:
/* Pulse */
gpiod_set_value_cansleep(priv->gpiod, 1);
udelay(1);
gpiod_set_value_cansleep(priv->gpiod, 0);
break;
}
return 0;
}
static int gpio_wdt_start(struct watchdog_device *wdd)
{
struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
priv->state = 0;
gpiod_direction_output(priv->gpiod, priv->state);
set_bit(WDOG_HW_RUNNING, &wdd->status);
return gpio_wdt_ping(wdd);
}
static int gpio_wdt_stop(struct watchdog_device *wdd)
{
struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
if (!priv->always_running) {
gpio_wdt_disable(priv);
} else {
set_bit(WDOG_HW_RUNNING, &wdd->status);
}
return 0;
}
static const struct watchdog_info gpio_wdt_ident = {
.options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
WDIOF_SETTIMEOUT,
.identity = "GPIO Watchdog",
};
static const struct watchdog_ops gpio_wdt_ops = {
.owner = THIS_MODULE,
.start = gpio_wdt_start,
.stop = gpio_wdt_stop,
.ping = gpio_wdt_ping,
};
static int gpio_wdt_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct device_node *np = dev->of_node;
struct gpio_wdt_priv *priv;
enum gpiod_flags gflags;
unsigned int hw_margin;
const char *algo;
int ret;
priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
platform_set_drvdata(pdev, priv);
ret = of_property_read_string(np, "hw_algo", &algo);
if (ret)
return ret;
if (!strcmp(algo, "toggle")) {
priv->hw_algo = HW_ALGO_TOGGLE;
gflags = GPIOD_IN;
} else if (!strcmp(algo, "level")) {
priv->hw_algo = HW_ALGO_LEVEL;
gflags = GPIOD_OUT_LOW;
} else {
return -EINVAL;
}
priv->gpiod = devm_gpiod_get(dev, NULL, gflags);
if (IS_ERR(priv->gpiod))
return PTR_ERR(priv->gpiod);
ret = of_property_read_u32(np,
"hw_margin_ms", &hw_margin);
if (ret)
return ret;
/* Disallow values lower than 2 and higher than 65535 ms */
if (hw_margin < 2 || hw_margin > 65535)
return -EINVAL;
priv->always_running = of_property_read_bool(np,
"always-running");
watchdog_set_drvdata(&priv->wdd, priv);
priv->wdd.info = &gpio_wdt_ident;
priv->wdd.ops = &gpio_wdt_ops;
priv->wdd.min_timeout = SOFT_TIMEOUT_MIN;
priv->wdd.max_hw_heartbeat_ms = hw_margin;
priv->wdd.parent = dev;
priv->wdd.timeout = SOFT_TIMEOUT_DEF;
watchdog_init_timeout(&priv->wdd, 0, dev);
watchdog_stop_on_reboot(&priv->wdd);
if (priv->always_running)
gpio_wdt_start(&priv->wdd);
return devm_watchdog_register_device(dev, &priv->wdd);
}
static const struct of_device_id gpio_wdt_dt_ids[] = {
{ .compatible = "linux,wdt-gpio", },
{ }
};
MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
static struct platform_driver gpio_wdt_driver = {
.driver = {
.name = "gpio-wdt",
.of_match_table = gpio_wdt_dt_ids,
},
.probe = gpio_wdt_probe,
};
#ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL
static int __init gpio_wdt_init(void)
{
return platform_driver_register(&gpio_wdt_driver);
}
arch_initcall(gpio_wdt_init);
#else
module_platform_driver(gpio_wdt_driver);
#endif
MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
MODULE_DESCRIPTION("GPIO Watchdog");
MODULE_LICENSE("GPL");
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