ACPI / watchdog: Add support for WDAT hardware watchdog

Starting from Intel Skylake the iTCO watchdog timer registers were moved to
reside in the same register space with SMBus host controller.  Not all
needed registers are available though and we need to unhide P2SB (Primary
to Sideband) device briefly to be able to read status of required NO_REBOOT
bit. The i2c-i801.c SMBus driver used to handle this and creation of the
iTCO watchdog platform device.

Windows, on the other hand, does not use the iTCO watchdog hardware
directly even if it is available. Instead it relies on ACPI Watchdog Action
Table (WDAT) table to describe the watchdog hardware to the OS. This table
contains necessary information about the the hardware and also set of
actions which are executed by a driver as needed.

This patch implements a new watchdog driver that takes advantage of the
ACPI WDAT table. We split the functionality into two parts: first part
enumerates the WDAT table and if found, populates resources and creates
platform device for the actual driver. The second part is the driver
itself.

The reason for the split is that this way we can make the driver itself to
be a module and loaded automatically if the WDAT table is found. Otherwise
the module is not loaded.
Signed-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/Kconfig

@@ -462,6 +462,9 @@ source "drivers/acpi/nfit/Kconfig"
 source "drivers/acpi/apei/Kconfig"
 source "drivers/acpi/dptf/Kconfig"
 
+config ACPI_WATCHDOG
+	bool
+
 config ACPI_EXTLOG
 	tristate "Extended Error Log support"
 	depends on X86_MCE && X86_LOCAL_APIC

drivers/acpi/Makefile

@@ -56,6 +56,7 @@ acpi-$(CONFIG_ACPI_NUMA)	+= numa.o
 acpi-$(CONFIG_ACPI_PROCFS_POWER) += cm_sbs.o
 acpi-y				+= acpi_lpat.o
 acpi-$(CONFIG_ACPI_GENERIC_GSI) += gsi.o
+acpi-$(CONFIG_ACPI_WATCHDOG)	+= acpi_watchdog.o
 
 # These are (potentially) separate modules
 

drivers/acpi/acpi_watchdog.c

+/*
+ * ACPI watchdog table parsing support.
+ *
+ * Copyright (C) 2016, Intel Corporation
+ * Author: Mika Westerberg <mika.westerberg@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#define pr_fmt(fmt) "ACPI: watchdog: " fmt
+
+#include <linux/acpi.h>
+#include <linux/ioport.h>
+#include <linux/platform_device.h>
+
+#include "internal.h"
+
+/**
+ * Returns true if this system should prefer ACPI based watchdog instead of
+ * the native one (which are typically the same hardware).
+ */
+bool acpi_has_watchdog(void)
+{
+	struct acpi_table_header hdr;
+
+	if (acpi_disabled)
+		return false;
+
+	return ACPI_SUCCESS(acpi_get_table_header(ACPI_SIG_WDAT, 0, &hdr));
+}
+EXPORT_SYMBOL_GPL(acpi_has_watchdog);
+
+void __init acpi_watchdog_init(void)
+{
+	const struct acpi_wdat_entry *entries;
+	const struct acpi_table_wdat *wdat;
+	struct list_head resource_list;
+	struct resource_entry *rentry;
+	struct platform_device *pdev;
+	struct resource *resources;
+	size_t nresources = 0;
+	acpi_status status;
+	int i;
+
+	status = acpi_get_table(ACPI_SIG_WDAT, 0,
+				(struct acpi_table_header **)&wdat);
+	if (ACPI_FAILURE(status)) {
+		/* It is fine if there is no WDAT */
+		return;
+	}
+
+	/* Watchdog disabled by BIOS */
+	if (!(wdat->flags & ACPI_WDAT_ENABLED))
+		return;
+
+	/* Skip legacy PCI WDT devices */
+	if (wdat->pci_segment != 0xff || wdat->pci_bus != 0xff ||
+	    wdat->pci_device != 0xff || wdat->pci_function != 0xff)
+		return;
+
+	INIT_LIST_HEAD(&resource_list);
+
+	entries = (struct acpi_wdat_entry *)(wdat + 1);
+	for (i = 0; i < wdat->entries; i++) {
+		const struct acpi_generic_address *gas;
+		struct resource_entry *rentry;
+		struct resource res;
+		bool found;
+
+		gas = &entries[i].register_region;
+
+		res.start = gas->address;
+		if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
+			res.flags = IORESOURCE_MEM;
+			res.end = res.start + ALIGN(gas->access_width, 4);
+		} else if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
+			res.flags = IORESOURCE_IO;
+			res.end = res.start + gas->access_width;
+		} else {
+			pr_warn("Unsupported address space: %u\n",
+				gas->space_id);
+			goto fail_free_resource_list;
+		}
+
+		found = false;
+		resource_list_for_each_entry(rentry, &resource_list) {
+			if (resource_contains(rentry->res, &res)) {
+				found = true;
+				break;
+			}
+		}
+
+		if (!found) {
+			rentry = resource_list_create_entry(NULL, 0);
+			if (!rentry)
+				goto fail_free_resource_list;
+
+			*rentry->res = res;
+			resource_list_add_tail(rentry, &resource_list);
+			nresources++;
+		}
+	}
+
+	resources = kcalloc(nresources, sizeof(*resources), GFP_KERNEL);
+	if (!resources)
+		goto fail_free_resource_list;
+
+	i = 0;
+	resource_list_for_each_entry(rentry, &resource_list)
+		resources[i++] = *rentry->res;
+
+	pdev = platform_device_register_simple("wdat_wdt", PLATFORM_DEVID_NONE,
+					       resources, nresources);
+	if (IS_ERR(pdev))
+		pr_err("Failed to create platform device\n");
+
+	kfree(resources);
+
+fail_free_resource_list:
+	resource_list_free(&resource_list);
+}

drivers/acpi/internal.h

@@ -225,4 +225,14 @@ static inline void suspend_nvs_restore(void) {}
 void acpi_init_properties(struct acpi_device *adev);
 void acpi_free_properties(struct acpi_device *adev);
 
+/*--------------------------------------------------------------------------
+				Watchdog
+  -------------------------------------------------------------------------- */
+
+#ifdef CONFIG_ACPI_WATCHDOG
+void acpi_watchdog_init(void);
+#else
+static inline void acpi_watchdog_init(void) {}
+#endif
+
 #endif /* _ACPI_INTERNAL_H_ */

drivers/acpi/scan.c

@@ -2002,6 +2002,7 @@ int __init acpi_scan_init(void)
 	acpi_pnp_init();
 	acpi_int340x_thermal_init();
 	acpi_amba_init();
+	acpi_watchdog_init();
 
 	acpi_scan_add_handler(&generic_device_handler);
 

drivers/watchdog/Kconfig

@@ -152,6 +152,19 @@ config TANGOX_WATCHDOG
 
 	  This driver can be built as a module. The module name is tangox_wdt.
 
+config WDAT_WDT
+	tristate "ACPI Watchdog Action Table (WDAT)"
+	depends on ACPI
+	select ACPI_WATCHDOG
+	help
+	  This driver adds support for systems with ACPI Watchdog Action
+	  Table (WDAT) table. Servers typically have this but it can be
+	  found on some desktop machines as well. This driver will take
+	  over the native iTCO watchdog driver found on many Intel CPUs.
+
+	  To compile this driver as module, choose M here: the module will
+	  be called wdat_wdt.
+
 config WM831X_WATCHDOG
 	tristate "WM831x watchdog"
 	depends on MFD_WM831X

drivers/watchdog/Makefile

@@ -202,6 +202,7 @@ obj-$(CONFIG_DA9062_WATCHDOG) += da9062_wdt.o
 obj-$(CONFIG_DA9063_WATCHDOG) += da9063_wdt.o
 obj-$(CONFIG_GPIO_WATCHDOG)	+= gpio_wdt.o
 obj-$(CONFIG_TANGOX_WATCHDOG) += tangox_wdt.o
+obj-$(CONFIG_WDAT_WDT) += wdat_wdt.o
 obj-$(CONFIG_WM831X_WATCHDOG) += wm831x_wdt.o
 obj-$(CONFIG_WM8350_WATCHDOG) += wm8350_wdt.o
 obj-$(CONFIG_MAX63XX_WATCHDOG) += max63xx_wdt.o

drivers/watchdog/wdat_wdt.c

+/*
+ * ACPI Hardware Watchdog (WDAT) driver.
+ *
+ * Copyright (C) 2016, Intel Corporation
+ * Author: Mika Westerberg <mika.westerberg@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/acpi.h>
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/watchdog.h>
+
+#define MAX_WDAT_ACTIONS ACPI_WDAT_ACTION_RESERVED
+
+/**
+ * struct wdat_instruction - Single ACPI WDAT instruction
+ * @entry: Copy of the ACPI table instruction
+ * @reg: Register the instruction is accessing
+ * @node: Next instruction in action sequence
+ */
+struct wdat_instruction {
+	struct acpi_wdat_entry entry;
+	void __iomem *reg;
+	struct list_head node;
+};
+
+/**
+ * struct wdat_wdt - ACPI WDAT watchdog device
+ * @pdev: Parent platform device
+ * @wdd: Watchdog core device
+ * @period: How long is one watchdog period in ms
+ * @stopped_in_sleep: Is this watchdog stopped by the firmware in S1-S5
+ * @stopped: Was the watchdog stopped by the driver in suspend
+ * @actions: An array of instruction lists indexed by an action number from
+ *           the WDAT table. There can be %NULL entries for not implemented
+ *           actions.
+ */
+struct wdat_wdt {
+	struct platform_device *pdev;
+	struct watchdog_device wdd;
+	unsigned int period;
+	bool stopped_in_sleep;
+	bool stopped;
+	struct list_head *instructions[MAX_WDAT_ACTIONS];
+};
+
+#define to_wdat_wdt(wdd) container_of(wdd, struct wdat_wdt, wdd)
+
+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 wdat_wdt_read(struct wdat_wdt *wdat,
+	 const struct wdat_instruction *instr, u32 *value)
+{
+	const struct acpi_generic_address *gas = &instr->entry.register_region;
+
+	switch (gas->access_width) {
+	case 1:
+		*value = ioread8(instr->reg);
+		break;
+	case 2:
+		*value = ioread16(instr->reg);
+		break;
+	case 3:
+		*value = ioread32(instr->reg);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	dev_dbg(&wdat->pdev->dev, "Read %#x from 0x%08llx\n", *value,
+		gas->address);
+
+	return 0;
+}
+
+static int wdat_wdt_write(struct wdat_wdt *wdat,
+	const struct wdat_instruction *instr, u32 value)
+{
+	const struct acpi_generic_address *gas = &instr->entry.register_region;
+
+	switch (gas->access_width) {
+	case 1:
+		iowrite8((u8)value, instr->reg);
+		break;
+	case 2:
+		iowrite16((u16)value, instr->reg);
+		break;
+	case 3:
+		iowrite32(value, instr->reg);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	dev_dbg(&wdat->pdev->dev, "Wrote %#x to 0x%08llx\n", value,
+		gas->address);
+
+	return 0;
+}
+
+static int wdat_wdt_run_action(struct wdat_wdt *wdat, unsigned int action,
+			       u32 param, u32 *retval)
+{
+	struct wdat_instruction *instr;
+
+	if (action >= ARRAY_SIZE(wdat->instructions))
+		return -EINVAL;
+
+	if (!wdat->instructions[action])
+		return -EOPNOTSUPP;
+
+	dev_dbg(&wdat->pdev->dev, "Running action %#x\n", action);
+
+	/* Run each instruction sequentially */
+	list_for_each_entry(instr, wdat->instructions[action], node) {
+		const struct acpi_wdat_entry *entry = &instr->entry;
+		const struct acpi_generic_address *gas;
+		u32 flags, value, mask, x, y;
+		bool preserve;
+		int ret;
+
+		gas = &entry->register_region;
+
+		preserve = entry->instruction & ACPI_WDAT_PRESERVE_REGISTER;
+		flags = entry->instruction & ~ACPI_WDAT_PRESERVE_REGISTER;
+		value = entry->value;
+		mask = entry->mask;
+
+		switch (flags) {
+		case ACPI_WDAT_READ_VALUE:
+			ret = wdat_wdt_read(wdat, instr, &x);
+			if (ret)
+				return ret;
+			x >>= gas->bit_offset;
+			x &= mask;
+			if (retval)
+				*retval = x == value;
+			break;
+
+		case ACPI_WDAT_READ_COUNTDOWN:
+			ret = wdat_wdt_read(wdat, instr, &x);
+			if (ret)
+				return ret;
+			x >>= gas->bit_offset;
+			x &= mask;
+			if (retval)
+				*retval = x;
+			break;
+
+		case ACPI_WDAT_WRITE_VALUE:
+			x = value & mask;
+			x <<= gas->bit_offset;
+			if (preserve) {
+				ret = wdat_wdt_read(wdat, instr, &y);
+				if (ret)
+					return ret;
+				y = y & ~(mask << gas->bit_offset);
+				x |= y;
+			}
+			ret = wdat_wdt_write(wdat, instr, x);
+			if (ret)
+				return ret;
+			break;
+
+		case ACPI_WDAT_WRITE_COUNTDOWN:
+			x = param;
+			x &= mask;
+			x <<= gas->bit_offset;
+			if (preserve) {
+				ret = wdat_wdt_read(wdat, instr, &y);
+				if (ret)
+					return ret;
+				y = y & ~(mask << gas->bit_offset);
+				x |= y;
+			}
+			ret = wdat_wdt_write(wdat, instr, x);
+			if (ret)
+				return ret;
+			break;
+
+		default:
+			dev_err(&wdat->pdev->dev, "Unknown instruction: %u\n",
+				flags);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+static int wdat_wdt_enable_reboot(struct wdat_wdt *wdat)
+{
+	int ret;
+
+	/*
+	 * WDAT specification says that the watchdog is required to reboot
+	 * the system when it fires. However, it also states that it is
+	 * recommeded to make it configurable through hardware register. We
+	 * enable reboot now if it is configrable, just in case.
+	 */
+	ret = wdat_wdt_run_action(wdat, ACPI_WDAT_SET_REBOOT, 0, 0);
+	if (ret && ret != -EOPNOTSUPP) {
+		dev_err(&wdat->pdev->dev,
+			"Failed to enable reboot when watchdog triggers\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static void wdat_wdt_boot_status(struct wdat_wdt *wdat)
+{
+	u32 boot_status = 0;
+	int ret;
+
+	ret = wdat_wdt_run_action(wdat, ACPI_WDAT_GET_STATUS, 0, &boot_status);
+	if (ret && ret != -EOPNOTSUPP) {
+		dev_err(&wdat->pdev->dev, "Failed to read boot status\n");
+		return;
+	}
+
+	if (boot_status)
+		wdat->wdd.bootstatus = WDIOF_CARDRESET;
+
+	/* Clear the boot status in case BIOS did not do it */
+	ret = wdat_wdt_run_action(wdat, ACPI_WDAT_SET_STATUS, 0, 0);
+	if (ret && ret != -EOPNOTSUPP)
+		dev_err(&wdat->pdev->dev, "Failed to clear boot status\n");
+}
+
+static void wdat_wdt_set_running(struct wdat_wdt *wdat)
+{
+	u32 running = 0;
+	int ret;
+
+	ret = wdat_wdt_run_action(wdat, ACPI_WDAT_GET_RUNNING_STATE, 0,
+				  &running);
+	if (ret && ret != -EOPNOTSUPP)
+		dev_err(&wdat->pdev->dev, "Failed to read running state\n");
+
+	if (running)
+		set_bit(WDOG_HW_RUNNING, &wdat->wdd.status);
+}
+
+static int wdat_wdt_start(struct watchdog_device *wdd)
+{
+	return wdat_wdt_run_action(to_wdat_wdt(wdd),
+				   ACPI_WDAT_SET_RUNNING_STATE, 0, NULL);
+}
+
+static int wdat_wdt_stop(struct watchdog_device *wdd)
+{
+	return wdat_wdt_run_action(to_wdat_wdt(wdd),
+				   ACPI_WDAT_SET_STOPPED_STATE, 0, NULL);
+}
+
+static int wdat_wdt_ping(struct watchdog_device *wdd)
+{
+	return wdat_wdt_run_action(to_wdat_wdt(wdd), ACPI_WDAT_RESET, 0, NULL);
+}
+
+static int wdat_wdt_set_timeout(struct watchdog_device *wdd,
+				unsigned int timeout)
+{
+	struct wdat_wdt *wdat = to_wdat_wdt(wdd);
+	unsigned int periods;
+	int ret;
+
+	periods = timeout * 1000 / wdat->period;
+	ret = wdat_wdt_run_action(wdat, ACPI_WDAT_SET_COUNTDOWN, periods, NULL);
+	if (!ret)
+		wdd->timeout = timeout;
+	return ret;
+}
+
+static unsigned int wdat_wdt_get_timeleft(struct watchdog_device *wdd)
+{
+	struct wdat_wdt *wdat = to_wdat_wdt(wdd);
+	u32 periods = 0;
+
+	wdat_wdt_run_action(wdat, ACPI_WDAT_GET_COUNTDOWN, 0, &periods);
+	return periods * wdat->period / 1000;
+}
+
+static const struct watchdog_info wdat_wdt_info = {
+	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+	.firmware_version = 0,
+	.identity = "wdat_wdt",
+};
+
+static const struct watchdog_ops wdat_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = wdat_wdt_start,
+	.stop = wdat_wdt_stop,
+	.ping = wdat_wdt_ping,
+	.set_timeout = wdat_wdt_set_timeout,
+	.get_timeleft = wdat_wdt_get_timeleft,
+};
+
+static int wdat_wdt_probe(struct platform_device *pdev)
+{
+	const struct acpi_wdat_entry *entries;
+	const struct acpi_table_wdat *tbl;
+	struct wdat_wdt *wdat;
+	struct resource *res;
+	void __iomem **regs;
+	acpi_status status;
+	int i, ret;
+
+	status = acpi_get_table(ACPI_SIG_WDAT, 0,
+				(struct acpi_table_header **)&tbl);
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+
+	wdat = devm_kzalloc(&pdev->dev, sizeof(*wdat), GFP_KERNEL);
+	if (!wdat)
+		return -ENOMEM;
+
+	regs = devm_kcalloc(&pdev->dev, pdev->num_resources, sizeof(*regs),
+			    GFP_KERNEL);
+	if (!regs)
+		return -ENOMEM;
+
+	/* WDAT specification wants to have >= 1ms period */
+	if (tbl->timer_period < 1)
+		return -EINVAL;
+	if (tbl->min_count > tbl->max_count)
+		return -EINVAL;
+
+	wdat->period = tbl->timer_period;
+	wdat->wdd.min_hw_heartbeat_ms = wdat->period * tbl->min_count;
+	wdat->wdd.max_hw_heartbeat_ms = wdat->period * tbl->max_count;
+	wdat->stopped_in_sleep = tbl->flags & ACPI_WDAT_STOPPED;
+	wdat->wdd.info = &wdat_wdt_info;
+	wdat->wdd.ops = &wdat_wdt_ops;
+	wdat->pdev = pdev;
+
+	/* Request and map all resources */
+	for (i = 0; i < pdev->num_resources; i++) {
+		void __iomem *reg;
+
+		res = &pdev->resource[i];
+		if (resource_type(res) == IORESOURCE_MEM) {
+			reg = devm_ioremap_resource(&pdev->dev, res);
+		} else if (resource_type(res) == IORESOURCE_IO) {
+			reg = devm_ioport_map(&pdev->dev, res->start, 1);
+		} else {
+			dev_err(&pdev->dev, "Unsupported resource\n");
+			return -EINVAL;
+		}
+
+		if (!reg)
+			return -ENOMEM;
+
+		regs[i] = reg;
+	}
+
+	entries = (struct acpi_wdat_entry *)(tbl + 1);
+	for (i = 0; i < tbl->entries; i++) {
+		const struct acpi_generic_address *gas;
+		struct wdat_instruction *instr;
+		struct list_head *instructions;
+		unsigned int action;
+		struct resource r;
+		int j;
+
+		action = entries[i].action;
+		if (action >= MAX_WDAT_ACTIONS) {
+			dev_dbg(&pdev->dev, "Skipping unknown action: %u\n",
+				action);
+			continue;
+		}
+
+		instr = devm_kzalloc(&pdev->dev, sizeof(*instr), GFP_KERNEL);
+		if (!instr)
+			return -ENOMEM;
+
+		INIT_LIST_HEAD(&instr->node);
+		instr->entry = entries[i];
+
+		gas = &entries[i].register_region;
+
+		memset(&r, 0, sizeof(r));
+		r.start = gas->address;
+		r.end = r.start + gas->access_width;
+		if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
+			r.flags = IORESOURCE_MEM;
+		} else if (gas->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
+			r.flags = IORESOURCE_IO;
+		} else {
+			dev_dbg(&pdev->dev, "Unsupported address space: %d\n",
+				gas->space_id);
+			continue;
+		}
+
+		/* Find the matching resource */
+		for (j = 0; j < pdev->num_resources; j++) {
+			res = &pdev->resource[j];
+			if (resource_contains(res, &r)) {
+				instr->reg = regs[j] + r.start - res->start;
+				break;
+			}
+		}
+
+		if (!instr->reg) {
+			dev_err(&pdev->dev, "I/O resource not found\n");
+			return -EINVAL;
+		}
+
+		instructions = wdat->instructions[action];
+		if (!instructions) {
+			instructions = devm_kzalloc(&pdev->dev,
+					sizeof(*instructions), GFP_KERNEL);
+			if (!instructions)
+				return -ENOMEM;
+
+			INIT_LIST_HEAD(instructions);
+			wdat->instructions[action] = instructions;
+		}
+
+		list_add_tail(&instr->node, instructions);
+	}
+
+	wdat_wdt_boot_status(wdat);
+	wdat_wdt_set_running(wdat);
+
+	ret = wdat_wdt_enable_reboot(wdat);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, wdat);
+
+	watchdog_set_nowayout(&wdat->wdd, nowayout);
+	return devm_watchdog_register_device(&pdev->dev, &wdat->wdd);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int wdat_wdt_suspend_noirq(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct wdat_wdt *wdat = platform_get_drvdata(pdev);
+	int ret;
+
+	if (!watchdog_active(&wdat->wdd))
+		return 0;
+
+	/*
+	 * We need to stop the watchdog if firmare is not doing it or if we
+	 * are going suspend to idle (where firmware is not involved). If
+	 * firmware is stopping the watchdog we kick it here one more time
+	 * to give it some time.
+	 */
+	wdat->stopped = false;
+	if (acpi_target_system_state() == ACPI_STATE_S0 ||
+	    !wdat->stopped_in_sleep) {
+		ret = wdat_wdt_stop(&wdat->wdd);
+		if (!ret)
+			wdat->stopped = true;
+	} else {
+		ret = wdat_wdt_ping(&wdat->wdd);
+	}
+
+	return ret;
+}
+
+static int wdat_wdt_resume_noirq(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct wdat_wdt *wdat = platform_get_drvdata(pdev);
+	int ret;
+
+	if (!watchdog_active(&wdat->wdd))
+		return 0;
+
+	if (!wdat->stopped) {
+		/*
+		 * Looks like the boot firmware reinitializes the watchdog
+		 * before it hands off to the OS on resume from sleep so we
+		 * stop and reprogram the watchdog here.
+		 */
+		ret = wdat_wdt_stop(&wdat->wdd);
+		if (ret)
+			return ret;
+
+		ret = wdat_wdt_set_timeout(&wdat->wdd, wdat->wdd.timeout);
+		if (ret)
+			return ret;
+
+		ret = wdat_wdt_enable_reboot(wdat);
+		if (ret)
+			return ret;
+	}
+
+	return wdat_wdt_start(&wdat->wdd);
+}
+#endif
+
+static const struct dev_pm_ops wdat_wdt_pm_ops = {
+	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(wdat_wdt_suspend_noirq,
+				      wdat_wdt_resume_noirq)
+};
+
+static struct platform_driver wdat_wdt_driver = {
+	.probe = wdat_wdt_probe,
+	.driver = {
+		.name = "wdat_wdt",
+		.pm = &wdat_wdt_pm_ops,
+	},
+};
+
+module_platform_driver(wdat_wdt_driver);
+
+MODULE_AUTHOR("Mika Westerberg <mika.westerberg@linux.intel.com>");
+MODULE_DESCRIPTION("ACPI Hardware Watchdog (WDAT) driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:wdat_wdt");

include/linux/acpi.h

@@ -1074,4 +1074,10 @@ void acpi_table_upgrade(void);
 static inline void acpi_table_upgrade(void) { }
 #endif
 
+#if defined(CONFIG_ACPI) && defined(CONFIG_ACPI_WATCHDOG)
+extern bool acpi_has_watchdog(void);
+#else
+static inline bool acpi_has_watchdog(void) { return false; }
+#endif
+
 #endif	/*_LINUX_ACPI_H*/