[PATCH 5/5] watchdog: add GPIO watchdog driver

[Ahmad Fatoum]

This is a straight port from Linux v5.11.

Signed-off-by: Ahmad Fatoum <ahmad at a3f.at>
---
 drivers/watchdog/Kconfig    |   7 ++
 drivers/watchdog/Makefile   |   1 +
 drivers/watchdog/gpio_wdt.c | 142 ++++++++++++++++++++++++++++++++++++
 3 files changed, 150 insertions(+)
 create mode 100644 drivers/watchdog/gpio_wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 8750a97d8c50..fb4ea7ffac3c 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -117,6 +117,13 @@ config F71808E_WDT
 	  F71862FG, F71868, F71869, F71882FG, F71889FG, F81865 and F81866
 	  Super I/O controllers.
 
+config GPIO_WATCHDOG
+	tristate "Watchdog device controlled through GPIO-line"
+	depends on OF_GPIO
+	help
+	  If you say yes here you get support for watchdog device
+	  controlled through GPIO-line.
+
 config ITCO_WDT
 	bool "Intel TCO Timer/Watchdog"
 	depends on X86
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index b55c58cf3cb3..9edb73512903 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -17,3 +17,4 @@ obj-$(CONFIG_STM32_IWDG_WATCHDOG) += stm32_iwdg.o
 obj-$(CONFIG_STPMIC1_WATCHDOG) += stpmic1_wdt.o
 obj-$(CONFIG_F71808E_WDT) += f71808e_wdt.o
 obj-$(CONFIG_ITCO_WDT) += itco_wdt.o
+obj-$(CONFIG_GPIO_WATCHDOG)	+= gpio_wdt.o
diff --git a/drivers/watchdog/gpio_wdt.c b/drivers/watchdog/gpio_wdt.c
new file mode 100644
index 000000000000..4de49dcee38a
--- /dev/null
+++ b/drivers/watchdog/gpio_wdt.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for watchdog device controlled through GPIO-line
+ *
+ * Author: 2013, Alexander Shiyan <shc_work at mail.ru>
+ */
+
+#include <common.h>
+#include <driver.h>
+#include <watchdog.h>
+#include <superio.h>
+#include <gpiod.h>
+
+enum {
+	HW_ALGO_TOGGLE,
+	HW_ALGO_LEVEL,
+};
+
+struct gpio_wdt_priv {
+	int		gpio;
+	bool		state;
+	bool		started;
+	unsigned int	hw_algo;
+	struct watchdog	wdd;
+};
+
+static inline struct gpio_wdt_priv *to_gpio_wdt_priv(struct watchdog *wdd)
+{
+	return container_of(wdd, struct gpio_wdt_priv, wdd);
+}
+
+static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
+{
+	/* Eternal ping */
+	gpio_set_active(priv->gpio, 1);
+
+	/* Put GPIO back to tristate */
+	if (priv->hw_algo == HW_ALGO_TOGGLE)
+		gpio_direction_input(priv->gpio);
+
+	priv->started = false;
+}
+
+static void gpio_wdt_ping(struct gpio_wdt_priv *priv)
+{
+	switch (priv->hw_algo) {
+	case HW_ALGO_TOGGLE:
+		/* Toggle output pin */
+		priv->state = !priv->state;
+		gpio_set_active(priv->gpio, priv->state);
+		break;
+	case HW_ALGO_LEVEL:
+		/* Pulse */
+		gpio_set_active(priv->gpio, true);
+		udelay(1);
+		gpio_set_active(priv->gpio, false);
+		break;
+	}
+}
+
+static void gpio_wdt_start(struct gpio_wdt_priv *priv)
+{
+	priv->state = false;
+	gpio_direction_active(priv->gpio, priv->state);
+	priv->started = true;
+}
+
+static int gpio_wdt_set_timeout(struct watchdog *wdd, unsigned int new_timeout)
+{
+	struct gpio_wdt_priv *priv = to_gpio_wdt_priv(wdd);
+
+	if (!new_timeout) {
+		gpio_wdt_disable(priv);
+		return 0;
+	}
+
+	if (!priv->started)
+		gpio_wdt_start(priv);
+
+	gpio_wdt_ping(priv);
+	return 0;
+}
+
+static int gpio_wdt_probe(struct device_d *dev)
+{
+	struct device_node *np = dev->device_node;
+	struct gpio_wdt_priv *priv;
+	enum gpiod_flags gflags;
+	unsigned int hw_margin;
+	const char *algo;
+	int ret;
+
+	priv = xzalloc(sizeof(*priv));
+
+	ret = of_property_read_u32(np, "hw_margin_ms", &hw_margin);
+	if (ret)
+		return ret;
+
+	/* Autoping is fixed at one ping every 500 ms. Round it up to a second */
+	if (hw_margin < 1000)
+		return -EINVAL;
+
+	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->gpio = gpiod_get(dev, NULL, gflags);
+	if (priv->gpio < 0)
+		return priv->gpio;
+
+	priv->wdd.hwdev		= dev;
+	priv->wdd.timeout_max	= hw_margin / 1000;
+	priv->wdd.priority	= 129;
+	priv->wdd.set_timeout	= gpio_wdt_set_timeout;
+
+	return watchdog_register(&priv->wdd);
+}
+
+static const struct of_device_id gpio_wdt_dt_ids[] = {
+	{ .compatible = "linux,wdt-gpio", },
+	{ }
+};
+
+static struct driver_d gpio_wdt_driver = {
+	.name		= "gpio-wdt",
+	.of_compatible	= gpio_wdt_dt_ids,
+	.probe	= gpio_wdt_probe,
+};
+device_platform_driver(gpio_wdt_driver);
+
+MODULE_AUTHOR("Alexander Shiyan <shc_work at mail.ru>");
+MODULE_DESCRIPTION("GPIO Watchdog");
+MODULE_LICENSE("GPL");
-- 
2.30.0