watchdog: add in watchdog for nct6686

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 751458959411..64494f13e864 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -341,6 +341,17 @@  config RAVE_SP_WATCHDOG
 	help
 	  Support for the watchdog on RAVE SP device.
 
+config NCT6686_WDT
+	tristate "NCT6686 Watchdog Timer"
+	depends on I2C
+	select WATCHDOG_CORE
+	help
+	  Watchdog driver for the Nuvoton 6686 Watchdog
+	  Processor.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called nct6686_wdt.
+
 config MLX_WDT
 	tristate "Mellanox Watchdog"
 	depends on MELLANOX_PLATFORM || COMPILE_TEST
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 7eab9de311cb..6bcaedd5fc87 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -150,6 +150,7 @@  obj-$(CONFIG_INTEL_MEI_WDT) += mei_wdt.o
 obj-$(CONFIG_NI903X_WDT) += ni903x_wdt.o
 obj-$(CONFIG_NIC7018_WDT) += nic7018_wdt.o
 obj-$(CONFIG_MLX_WDT) += mlx_wdt.o
+obj-$(CONFIG_NCT6686_WDT) += nct6686_wdt.o
 obj-$(CONFIG_KEEMBAY_WATCHDOG) += keembay_wdt.o
 obj-$(CONFIG_SIEMENS_SIMATIC_IPC_WDT) += simatic-ipc-wdt.o
 
diff --git a/drivers/watchdog/nct6686_wdt.c b/drivers/watchdog/nct6686_wdt.c
new file mode 100644
index 000000000000..e2125f56faf5
--- /dev/null
+++ b/drivers/watchdog/nct6686_wdt.c
@@ -0,0 +1,492 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * NCT6686D Watchdog Driver
+ */
+
+#define dev_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/iommu.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+static bool force;
+module_param(force, bool, 0);
+MODULE_PARM_DESC(force, "Set to one to enable support for unknown vendors");
+
+#define DRVNAME "nct6686_wdt"
+
+/*
+ * Super-I/O constants and functions
+ */
+#define NCT6686_LD_HWM          0x0b
+#define SIO_REG_LDSEL           0x07    /* Logical device select */
+#define SIO_REG_DEVID           0x20    /* Device ID (2 bytes) */
+#define SIO_REG_ENABLE          0x30    /* Logical device enable */
+#define SIO_REG_ADDR            0x60    /* Logical device address (2 bytes) */
+
+#define SIO_NCT6686_ID          0xd440
+#define SIO_ID_MASK             0xFFF0
+
+#define WDT_CFG                 0x828    /* W/O Lock Watchdog Register */
+#define WDT_CNT                 0x829    /* R/W Watchdog Timer Register */
+#define WDT_STS                 0x82A    /* R/O Watchdog Status Register */
+#define WDT_STS_EVT_POS         (0)
+#define WDT_STS_EVT_MSK         (0x3 << WDT_STS_EVT_POS)
+#define WDT_SOFT_EN             0x87    /* Enable soft watchdog timer */
+#define WDT_SOFT_DIS            0xAA    /* Disable soft watchdog timer */
+
+#define WATCHDOG_TIMEOUT        60      /* 1 minute default timeout */
+
+/* The timeout range is 1-255 seconds */
+#define MIN_TIMEOUT             1
+#define MAX_TIMEOUT             255
+
+static int timeout;
+module_param(timeout, int, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds. 1 <= timeout <= 255, default="
+		 __MODULE_STRING(WATCHDOG_TIMEOUT) ".");
+
+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) ")");
+
+static int early_disable;
+module_param(early_disable, int, 0);
+MODULE_PARM_DESC(early_disable, "Disable watchdog at boot time (default=0)");
+
+#define NCT6686_PAGE_REG_OFFSET         0
+#define NCT6686_ADDR_REG_OFFSET         1
+#define NCT6686_DATA_REG_OFFSET         2
+
+struct watchdog_device wdt;
+
+struct nct6686_sio_data {
+	int sioreg;
+};
+
+struct nct6686_data {
+	int addr;                          /* IO base of EC space */
+	struct nct6686_sio_data sio_data;  /* SIO register */
+
+	struct watchdog_device wdt;
+	struct mutex update_lock; /* used to protect sensor updates */
+};
+
+static inline void
+superio_outb(int ioreg, int reg, int val)
+{
+	outb(reg, ioreg);
+	outb(val, ioreg + 1);
+}
+
+static inline int
+superio_inb(int ioreg, int reg)
+{
+	outb(reg, ioreg);
+	return inb(ioreg + 1);
+}
+
+static inline void
+superio_select(int ioreg, int ld)
+{
+	outb(SIO_REG_LDSEL, ioreg);
+	outb(ld, ioreg + 1);
+}
+
+static inline int
+superio_enter(int ioreg)
+{
+	/*
+	 * Try to reserve <ioreg> and <ioreg + 1> for exclusive access.
+	 */
+	if (!request_muxed_region(ioreg, 2, DRVNAME))
+		return -EBUSY;
+
+	outb(0x87, ioreg);
+	outb(0x87, ioreg);
+
+	return 0;
+}
+
+static inline void
+superio_exit(int ioreg)
+{
+	outb(0xaa, ioreg);
+	outb(0x02, ioreg);
+	outb(0x02, ioreg + 1);
+	release_region(ioreg, 2);
+}
+
+/*
+ * ISA constants
+ */
+
+#define IOREGION_ALIGNMENT      (~7)
+#define IOREGION_OFFSET         4       /* Use EC port 1 */
+#define IOREGION_LENGTH         4
+
+#define EC_PAGE_REG             0
+#define EC_INDEX_REG            1
+#define EC_DATA_REG             2
+#define EC_EVENT_REG            3
+
+static inline void nct6686_wdt_set_bank(int base_addr, u16 reg)
+{
+	outb_p(0xFF, base_addr + NCT6686_PAGE_REG_OFFSET);
+	outb_p(reg >> 8, base_addr + NCT6686_PAGE_REG_OFFSET);
+}
+
+/* Not strictly necessary, but play it safe for now */
+static inline void nct6686_wdt_reset_bank(int base_addr, u16 reg)
+{
+	if (reg & 0xff00)
+		outb_p(0xFF, base_addr + NCT6686_PAGE_REG_OFFSET);
+}
+
+static u8 nct6686_read(struct nct6686_data *data, u16 reg)
+{
+	u8 res;
+
+	nct6686_wdt_set_bank(data->addr, reg);
+	outb_p(reg & 0xff, data->addr + NCT6686_ADDR_REG_OFFSET);
+	res = inb_p(data->addr + NCT6686_DATA_REG_OFFSET);
+
+	nct6686_wdt_reset_bank(data->addr, reg);
+	return res;
+}
+
+static void nct6686_write(struct nct6686_data *data, u16 reg, u8 value)
+{
+	nct6686_wdt_set_bank(data->addr, reg);
+	outb_p(reg & 0xff, data->addr + NCT6686_ADDR_REG_OFFSET);
+	outb_p(value & 0xff, data->addr + NCT6686_DATA_REG_OFFSET);
+	nct6686_wdt_reset_bank(data->addr, reg);
+}
+
+/*
+ * Watchdog Functions
+ */
+static int nct6686_wdt_enable(struct watchdog_device *wdog, bool enable)
+{
+	struct nct6686_data *data = watchdog_get_drvdata(wdog);
+
+	u_char reg;
+
+	mutex_lock(&data->update_lock);
+	reg = nct6686_read(data, WDT_CFG);
+
+	if (enable) {
+		nct6686_write(data, WDT_CFG, reg | 0x3);
+		mutex_unlock(&data->update_lock);
+		return 0;
+	}
+
+	nct6686_write(data, WDT_CFG, reg & ~BIT(0));
+	mutex_unlock(&data->update_lock);
+
+	return 0;
+}
+
+static int nct6686_wdt_set_time(struct watchdog_device *wdog)
+{
+	struct nct6686_data *data = watchdog_get_drvdata(wdog);
+
+	mutex_lock(&data->update_lock);
+	nct6686_write(data, WDT_CNT, wdog->timeout);
+	mutex_unlock(&data->update_lock);
+
+	if (wdog->timeout) {
+		nct6686_wdt_enable(wdog, true);
+		return 0;
+	}
+
+	nct6686_wdt_enable(wdog, false);
+	return 0;
+}
+
+static int nct6686_wdt_start(struct watchdog_device *wdt)
+{
+	struct nct6686_data *data = watchdog_get_drvdata(wdt);
+	u_char reg;
+
+	nct6686_wdt_set_time(wdt);
+
+	/* Enable soft watchdog timer */
+	mutex_lock(&data->update_lock);
+	/* reset trigger status */
+	reg = nct6686_read(data, WDT_STS);
+	nct6686_write(data, WDT_STS, reg & ~WDT_STS_EVT_MSK);
+	mutex_unlock(&data->update_lock);
+	return 0;
+}
+
+static int nct6686_wdt_stop(struct watchdog_device *wdt)
+{
+	struct nct6686_data *data = watchdog_get_drvdata(wdt);
+
+	mutex_lock(&data->update_lock);
+	nct6686_write(data, WDT_CFG, WDT_SOFT_DIS);
+	mutex_unlock(&data->update_lock);
+	return 0;
+}
+
+static int nct6686_wdt_set_timeout(struct watchdog_device *wdt,
+				   unsigned int timeout)
+{
+	struct nct6686_data *data = watchdog_get_drvdata(wdt);
+
+	wdt->timeout = timeout;
+	mutex_lock(&data->update_lock);
+	nct6686_write(data, WDT_CNT, timeout);
+	mutex_unlock(&data->update_lock);
+	return 0;
+}
+
+static int nct6686_wdt_ping(struct watchdog_device *wdt)
+{
+	struct nct6686_data *data = watchdog_get_drvdata(wdt);
+	int timeout;
+
+	/*
+	 * Note:
+	 * NCT6686 does not support refreshing WDT_TIMER_REG register when
+	 * the watchdog is active. Please disable watchdog before feeding
+	 * the watchdog and enable it again.
+	 */
+	/* Disable soft watchdog timer */
+	nct6686_wdt_enable(wdt, false);
+
+	/* feed watchdog */
+	timeout = wdt->timeout;
+	mutex_lock(&data->update_lock);
+	nct6686_write(data, WDT_CNT, timeout);
+	mutex_unlock(&data->update_lock);
+
+	/* Enable soft watchdog timer */
+	nct6686_wdt_enable(wdt, true);
+	return 0;
+}
+
+static unsigned int nct6686_wdt_get_timeleft(struct watchdog_device *wdt)
+{
+	struct nct6686_data *data = watchdog_get_drvdata(wdt);
+	int ret;
+
+	mutex_lock(&data->update_lock);
+	ret = nct6686_read(data, WDT_CNT);
+	mutex_unlock(&data->update_lock);
+	if (ret < 0)
+		return 0;
+
+	return ret;
+}
+
+static const struct watchdog_info nct6686_wdt_info = {
+	.options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
+			  WDIOF_MAGICCLOSE,
+	.identity       = "nct6686 watchdog",
+};
+
+static const struct watchdog_ops nct6686_wdt_ops = {
+	.owner          = THIS_MODULE,
+	.start          = nct6686_wdt_start,
+	.stop           = nct6686_wdt_stop,
+	.ping           = nct6686_wdt_ping,
+	.set_timeout    = nct6686_wdt_set_timeout,
+	.get_timeleft   = nct6686_wdt_get_timeleft,
+};
+
+static int nct6686_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct watchdog_device *wdt;
+	struct resource *res;
+	struct nct6686_data *data;
+	struct nct6686_sio_data *sio_data = dev->platform_data;
+	int ret;
+	u_char reg;
+
+	dev_dbg(&pdev->dev, "Probe NCT6686 called\n");
+	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
+	if (!devm_request_region(dev, res->start, IOREGION_LENGTH, DRVNAME))
+		return -EBUSY;
+
+	data = devm_kzalloc(dev, sizeof(struct nct6686_data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->sio_data.sioreg = sio_data->sioreg;
+	data->addr = res->start;
+	mutex_init(&data->update_lock);
+	platform_set_drvdata(pdev, data);
+
+	/* Watchdog initialization */
+	data->wdt.ops = &nct6686_wdt_ops;
+	data->wdt.info = &nct6686_wdt_info;
+
+	data->wdt.timeout = WATCHDOG_TIMEOUT; /* Set default timeout */
+	data->wdt.min_timeout = MIN_TIMEOUT;
+	data->wdt.max_timeout = MAX_TIMEOUT;
+	data->wdt.parent = &pdev->dev;
+
+	watchdog_init_timeout(&data->wdt, timeout, &pdev->dev);
+	watchdog_set_nowayout(&data->wdt, nowayout);
+	watchdog_set_drvdata(&data->wdt, data);
+
+	/* reset trigger status */
+	reg = nct6686_read(data, WDT_STS);
+	nct6686_write(data, WDT_STS, reg & ~WDT_STS_EVT_MSK);
+
+	watchdog_stop_on_unregister(&data->wdt);
+
+	ret = devm_watchdog_register_device(dev, &data->wdt);
+
+	dev_dbg(&pdev->dev, "initialized. timeout=%d sec (nowayout=%d)\n",
+		wdt->timeout, nowayout);
+
+	return ret;
+}
+
+static struct platform_driver nct6686_driver = {
+	.driver = {
+		.name = DRVNAME,
+	},
+	.probe  = nct6686_probe,
+};
+
+static int __init nct6686_find(int sioaddr, u_long *base_phys)
+{
+	u16 val;
+	int err = 0;
+	u_long addr;
+
+	err = superio_enter(sioaddr);
+	if (err)
+		return err;
+
+	val = (superio_inb(sioaddr, SIO_REG_DEVID) << 8)
+	       | superio_inb(sioaddr, SIO_REG_DEVID + 1);
+
+	if ((val & SIO_ID_MASK) != SIO_NCT6686_ID)
+		goto fail;
+
+	/* We have a known chip, find the HWM I/O address */
+	superio_select(sioaddr, NCT6686_LD_HWM);
+	val = (superio_inb(sioaddr, SIO_REG_ADDR) << 8)
+	      | superio_inb(sioaddr, SIO_REG_ADDR + 1);
+	addr = val & IOREGION_ALIGNMENT;
+	if (addr == 0) {
+		pr_err("EC base I/O port unconfigured\n");
+		goto fail;
+	}
+
+	/* Activate logical device if needed */
+	val = superio_inb(sioaddr, SIO_REG_ENABLE);
+	if (!(val & 0x01)) {
+		pr_warn("Forcibly enabling EC access. Data may be unusable.\n");
+		superio_outb(sioaddr, SIO_REG_ENABLE, val | 0x01);
+	}
+
+	superio_exit(sioaddr);
+	*base_phys = addr;
+
+	return 0;
+
+fail:
+	superio_exit(sioaddr);
+	return -ENODEV;
+}
+
+static struct platform_device *pdev;
+
+static int __init nct6686_init(void)
+{
+	struct nct6686_sio_data sio_data;
+	int sioaddr[2] = { 0x2e, 0x4e };
+	struct resource res;
+	int err;
+	u_long addr;
+
+	/*
+	 * when Super-I/O functions move to a separate file, the Super-I/O
+	 * driver will probe 0x2e and 0x4e and auto-detect the presence of a
+	 * nct6686 hardware monitor, and call probe()
+	 */
+	err = nct6686_find(sioaddr[0], &addr);
+	if (err) {
+		err = nct6686_find(sioaddr[1], &addr);
+		if (err)
+			return -ENODEV;
+	}
+
+	pdev = platform_device_alloc(DRVNAME, addr);
+	if (!pdev) {
+		err = -ENOMEM;
+		goto exit_device_unregister;
+	}
+
+	err = platform_device_add_data(pdev, &sio_data,
+				       sizeof(struct nct6686_sio_data));
+	if (err)
+		goto exit_device_put;
+
+	memset(&res, 0, sizeof(res));
+	res.name = DRVNAME;
+	res.start = addr + IOREGION_OFFSET;
+	res.end = addr + IOREGION_OFFSET + IOREGION_LENGTH - 1;
+	res.flags = IORESOURCE_IO;
+
+	err = acpi_check_resource_conflict(&res);
+	if (err)
+		return err;
+
+	platform_driver_register(&nct6686_driver);
+
+	pdev = platform_device_alloc(DRVNAME, addr);
+	if (!pdev) {
+		err = -ENOMEM;
+		goto exit_device_unregister;
+	}
+	err = platform_device_add_data(pdev, &sio_data,
+				       sizeof(struct nct6686_sio_data));
+	if (err)
+		goto exit_device_put;
+
+	err = platform_device_add_resources(pdev, &res, 1);
+	if (err)
+		goto exit_device_put;
+
+	dev_info(&pdev->dev, "NCT6686 device found\n");
+	/* platform_device_add calls probe() */
+	err = platform_device_add(pdev);
+	if (err)
+		goto exit_device_put;
+
+	return 0;
+exit_device_put:
+	platform_device_put(pdev);
+	platform_device_unregister(pdev);
+exit_device_unregister:
+	platform_driver_unregister(&nct6686_driver);
+	return err;
+}
+
+static void __exit nct6686_exit(void)
+{
+	platform_device_unregister(pdev);
+	platform_driver_unregister(&nct6686_driver);
+}
+
+MODULE_AUTHOR("David Ober <dober@lenovo.com>");
+MODULE_DESCRIPTION("NCT6686D driver");
+MODULE_LICENSE("GPL");
+
+module_init(nct6686_init);
+module_exit(nct6686_exit);