hwmon: (nct7904) Add watchdog function

Implement watchdog functionality for NCT7904.
Signed-off-by: Yuechao Zhao <yuechao.zhao@advantech.com.cn>
Link: https://lore.kernel.org/r/20200331052850.5419-1-yuechao.zhao@advantech.com.cn
[groeck: Squashed fixup patch]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/Kconfig

@@ -1340,10 +1340,12 @@ config SENSORS_NCT7802
 
 config SENSORS_NCT7904
 	tristate "Nuvoton NCT7904"
-	depends on I2C
+	depends on I2C && WATCHDOG
+	select WATCHDOG_CORE
 	help
 	  If you say yes here you get support for the Nuvoton NCT7904
-	  hardware monitoring chip, including manual fan speed control.
+	  hardware monitoring chip, including manual fan speed control
+	  and support for the integrated watchdog.
 
 	  This driver can also be built as a module. If so, the module
 	  will be called nct7904.

drivers/hwmon/nct7904.c

@@ -8,6 +8,9 @@
  * Copyright (c) 2019 Advantech
  * Author: Amy.Shih <amy.shih@advantech.com.tw>
  *
+ * Copyright (c) 2020 Advantech
+ * Author: Yuechao Zhao <yuechao.zhao@advantech.com.cn>
+ *
  * Supports the following chips:
  *
  * Chip        #vin  #fan  #pwm  #temp  #dts  chip ID
@@ -20,6 +23,7 @@
 #include <linux/i2c.h>
 #include <linux/mutex.h>
 #include <linux/hwmon.h>
+#include <linux/watchdog.h>
 
 #define VENDOR_ID_REG		0x7A	/* Any bank */
 #define NUVOTON_ID		0x50
@@ -88,18 +92,42 @@
 #define FANCTL1_FMR_REG		0x00	/* Bank 3; 1 reg per channel */
 #define FANCTL1_OUT_REG		0x10	/* Bank 3; 1 reg per channel */
 
+#define WDT_LOCK_REG		0xE0	/* W/O Lock Watchdog Register */
+#define WDT_EN_REG		0xE1	/* R/O Watchdog Enable Register */
+#define WDT_STS_REG		0xE2	/* R/O Watchdog Status Register */
+#define WDT_TIMER_REG		0xE3	/* R/W Watchdog Timer Register */
+#define WDT_SOFT_EN		0x55	/* Enable soft watchdog timer */
+#define WDT_SOFT_DIS		0xAA	/* Disable soft watchdog timer */
+
 #define VOLT_MONITOR_MODE	0x0
 #define THERMAL_DIODE_MODE	0x1
 #define THERMISTOR_MODE		0x3
 
 #define ENABLE_TSI	BIT(1)
 
+#define WATCHDOG_TIMEOUT	1	/* 1 minute default timeout */
+
+/*The timeout range is 1-255 minutes*/
+#define MIN_TIMEOUT		(1 * 60)
+#define MAX_TIMEOUT		(255 * 60)
+
+static int timeout = WATCHDOG_TIMEOUT;
+module_param(timeout, int, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in minutes. 1 <= timeout <= 255, default="
+			__MODULE_STRING(WATCHODOG_TIMEOUT) ".");
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started once started (default="
+			__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
 static const unsigned short normal_i2c[] = {
 	0x2d, 0x2e, I2C_CLIENT_END
 };
 
 struct nct7904_data {
 	struct i2c_client *client;
+	struct watchdog_device wdt;
 	struct mutex bank_lock;
 	int bank_sel;
 	u32 fanin_mask;
@@ -892,6 +920,95 @@ static const struct hwmon_chip_info nct7904_chip_info = {
 	.info = nct7904_info,
 };
 
+/*
+ * Watchdog Function
+ */
+static int nct7904_wdt_start(struct watchdog_device *wdt)
+{
+	struct nct7904_data *data = watchdog_get_drvdata(wdt);
+
+	/* Enable soft watchdog timer */
+	return nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_EN);
+}
+
+static int nct7904_wdt_stop(struct watchdog_device *wdt)
+{
+	struct nct7904_data *data = watchdog_get_drvdata(wdt);
+
+	return nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_DIS);
+}
+
+static int nct7904_wdt_set_timeout(struct watchdog_device *wdt,
+				   unsigned int timeout)
+{
+	struct nct7904_data *data = watchdog_get_drvdata(wdt);
+	/*
+	 * The NCT7904 is very special in watchdog function.
+	 * Its minimum unit is minutes. And wdt->timeout needs
+	 * to match the actual timeout selected. So, this needs
+	 * to be: wdt->timeout = timeout / 60 * 60.
+	 * For example, if the user configures a timeout of
+	 * 119 seconds, the actual timeout will be 60 seconds.
+	 * So, wdt->timeout must then be set to 60 seconds.
+	 */
+	wdt->timeout = timeout / 60 * 60;
+
+	return nct7904_write_reg(data, BANK_0, WDT_TIMER_REG,
+				 wdt->timeout / 60);
+}
+
+static int nct7904_wdt_ping(struct watchdog_device *wdt)
+{
+	/*
+	 * Note:
+	 * NCT7904 does not support refreshing WDT_TIMER_REG register when
+	 * the watchdog is active. Please disable watchdog before feeding
+	 * the watchdog and enable it again.
+	 */
+	struct nct7904_data *data = watchdog_get_drvdata(wdt);
+	int ret;
+
+	/* Disable soft watchdog timer */
+	ret = nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_DIS);
+	if (ret < 0)
+		return ret;
+
+	/* feed watchdog */
+	ret = nct7904_write_reg(data, BANK_0, WDT_TIMER_REG, wdt->timeout / 60);
+	if (ret < 0)
+		return ret;
+
+	/* Enable soft watchdog timer */
+	return nct7904_write_reg(data, BANK_0, WDT_LOCK_REG, WDT_SOFT_EN);
+}
+
+static unsigned int nct7904_wdt_get_timeleft(struct watchdog_device *wdt)
+{
+	struct nct7904_data *data = watchdog_get_drvdata(wdt);
+	int ret;
+
+	ret = nct7904_read_reg(data, BANK_0, WDT_TIMER_REG);
+	if (ret < 0)
+		return 0;
+
+	return ret * 60;
+}
+
+static const struct watchdog_info nct7904_wdt_info = {
+	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
+				WDIOF_MAGICCLOSE,
+	.identity	= "nct7904 watchdog",
+};
+
+static const struct watchdog_ops nct7904_wdt_ops = {
+	.owner		= THIS_MODULE,
+	.start		= nct7904_wdt_start,
+	.stop		= nct7904_wdt_stop,
+	.ping		= nct7904_wdt_ping,
+	.set_timeout	= nct7904_wdt_set_timeout,
+	.get_timeleft	= nct7904_wdt_get_timeleft,
+};
+
 static int nct7904_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
@@ -1022,7 +1139,26 @@ static int nct7904_probe(struct i2c_client *client,
 	hwmon_dev =
 		devm_hwmon_device_register_with_info(dev, client->name, data,
 						     &nct7904_chip_info, NULL);
-	return PTR_ERR_OR_ZERO(hwmon_dev);
+	ret = PTR_ERR_OR_ZERO(hwmon_dev);
+	if (ret)
+		return ret;
+
+	/* Watchdog initialization */
+	data->wdt.ops = &nct7904_wdt_ops;
+	data->wdt.info = &nct7904_wdt_info;
+
+	data->wdt.timeout = timeout * 60; /* in seconds */
+	data->wdt.min_timeout = MIN_TIMEOUT;
+	data->wdt.max_timeout = MAX_TIMEOUT;
+	data->wdt.parent = &client->dev;
+
+	watchdog_init_timeout(&data->wdt, timeout * 60, &client->dev);
+	watchdog_set_nowayout(&data->wdt, nowayout);
+	watchdog_set_drvdata(&data->wdt, data);
+
+	watchdog_stop_on_unregister(&data->wdt);
+
+	return devm_watchdog_register_device(dev, &data->wdt);
 }
 
 static const struct i2c_device_id nct7904_id[] = {