linux/drivers/watchdog/gpio_wdt.c

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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>
static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
"Watchdog cannot be stopped once started (default="
__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
#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);
watchdog: gpio_wdt: set WDOG_HW_RUNNING in gpio_wdt_stop The first patch above (https://patchwork.kernel.org/patch/9970181/) makes the oops go away, but it just papers over the problem. The real problem is that the watchdog core clears WDOG_HW_RUNNING in watchdog_stop, and the gpio driver fails to set it in its stop function when it doesn't actually stop it. This means that the core doesn't know that it now has responsibility for petting the device, in turn causing the device to reset the system (I hadn't noticed this because the board I'm working on has that reset logic disabled). How about this (other drivers may of course have the same problem, I haven't checked). One might say that ->stop should return an error when the device can't be stopped, but OTOH this brings parity between a device without a ->stop method and a GPIO wd that has always-running set. IOW, I think ->stop should only return an error when an actual attempt to stop the hardware failed. From: Rasmus Villemoes <rasmus.villemoes@prevas.dk> The watchdog framework clears WDOG_HW_RUNNING before calling ->stop. If the driver is unable to stop the device, it is supposed to set that bit again so that the watchdog core takes care of sending heart-beats while the device is not open from user-space. Update the gpio_wdt driver to honour that contract (and get rid of the redundant clearing of WDOG_HW_RUNNING). Fixes: 3c10bbde10 ("watchdog: core: Clear WDOG_HW_RUNNING before calling the stop function") Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
2017-11-09 16:39:55 +03:00
} 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_set_nowayout(&priv->wdd, nowayout);
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");