watchdog: Add driver for Intel OC WDT

Add a driver for the Intel Over-Clocking Watchdog found in Intel
Platform Controller (PCH) chipsets. This watchdog is controlled
via a simple single-register interface and would otherwise be
standard except for the presence of a LOCK bit that can only be
set once per power cycle, needing extra handling around it.

Signed-off-by: Diogo Ivo <[email protected]>
Reviewed-by: Guenter Roeck <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Guenter Roeck <[email protected]>
Signed-off-by: Wim Van Sebroeck <[email protected]>

Author: diogo-ivo

drivers/watchdog/Kconfig

@@ -1372,6 +1372,17 @@ config INTEL_MID_WATCHDOG
 
 	  To compile this driver as a module, choose M here.
 
+config INTEL_OC_WATCHDOG
+	tristate "Intel OC Watchdog"
+	depends on (X86 || COMPILE_TEST) && ACPI && HAS_IOPORT
+	select WATCHDOG_CORE
+	help
+	  Hardware driver for Intel Over-Clocking watchdog present in
+	  Platform Controller Hub (PCH) chipsets.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called intel_oc_wdt.
+
 config ITCO_WDT
 	tristate "Intel TCO Timer/Watchdog"
 	depends on X86 && PCI

drivers/watchdog/Makefile

@@ -151,6 +151,7 @@ obj-$(CONFIG_W83977F_WDT) += w83977f_wdt.o
 obj-$(CONFIG_MACHZ_WDT) += machzwd.o
 obj-$(CONFIG_SBC_EPX_C3_WATCHDOG) += sbc_epx_c3.o
 obj-$(CONFIG_INTEL_MID_WATCHDOG) += intel-mid_wdt.o
+obj-$(CONFIG_INTEL_OC_WATCHDOG) += intel_oc_wdt.o
 obj-$(CONFIG_INTEL_MEI_WDT) += mei_wdt.o
 obj-$(CONFIG_NI903X_WDT) += ni903x_wdt.o
 obj-$(CONFIG_NIC7018_WDT) += nic7018_wdt.o

drivers/watchdog/intel_oc_wdt.c

@@ -0,0 +1,233 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Intel OC Watchdog driver
+ *
+ * Copyright (C) 2025, Siemens
+ * Author: Diogo Ivo <[email protected]>
+ */
+
+#define DRV_NAME	"intel_oc_wdt"
+
+#include <linux/acpi.h>
+#include <linux/bits.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+#define INTEL_OC_WDT_TOV		GENMASK(9, 0)
+#define INTEL_OC_WDT_MIN_TOV		1
+#define INTEL_OC_WDT_MAX_TOV		1024
+#define INTEL_OC_WDT_DEF_TOV		60
+
+/*
+ * One-time writable lock bit. If set forbids
+ * modification of itself, _TOV and _EN until
+ * next reboot.
+ */
+#define INTEL_OC_WDT_CTL_LCK		BIT(12)
+
+#define INTEL_OC_WDT_EN			BIT(14)
+#define INTEL_OC_WDT_NO_ICCSURV_STS	BIT(24)
+#define INTEL_OC_WDT_ICCSURV_STS	BIT(25)
+#define INTEL_OC_WDT_RLD		BIT(31)
+
+#define INTEL_OC_WDT_STS_BITS (INTEL_OC_WDT_NO_ICCSURV_STS | \
+			       INTEL_OC_WDT_ICCSURV_STS)
+
+#define INTEL_OC_WDT_CTRL_REG(wdt)	((wdt)->ctrl_res->start)
+
+struct intel_oc_wdt {
+	struct watchdog_device wdd;
+	struct resource *ctrl_res;
+	bool locked;
+};
+
+static int heartbeat;
+module_param(heartbeat, uint, 0);
+MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. (default="
+		 __MODULE_STRING(WDT_HEARTBEAT) ")");
+
+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 intel_oc_wdt_start(struct watchdog_device *wdd)
+{
+	struct intel_oc_wdt *oc_wdt = watchdog_get_drvdata(wdd);
+
+	if (oc_wdt->locked)
+		return 0;
+
+	outl(inl(INTEL_OC_WDT_CTRL_REG(oc_wdt)) | INTEL_OC_WDT_EN,
+	     INTEL_OC_WDT_CTRL_REG(oc_wdt));
+
+	return 0;
+}
+
+static int intel_oc_wdt_stop(struct watchdog_device *wdd)
+{
+	struct intel_oc_wdt *oc_wdt = watchdog_get_drvdata(wdd);
+
+	outl(inl(INTEL_OC_WDT_CTRL_REG(oc_wdt)) & ~INTEL_OC_WDT_EN,
+	     INTEL_OC_WDT_CTRL_REG(oc_wdt));
+
+	return 0;
+}
+
+static int intel_oc_wdt_ping(struct watchdog_device *wdd)
+{
+	struct intel_oc_wdt *oc_wdt = watchdog_get_drvdata(wdd);
+
+	outl(inl(INTEL_OC_WDT_CTRL_REG(oc_wdt)) | INTEL_OC_WDT_RLD,
+	     INTEL_OC_WDT_CTRL_REG(oc_wdt));
+
+	return 0;
+}
+
+static int intel_oc_wdt_set_timeout(struct watchdog_device *wdd,
+				    unsigned int t)
+{
+	struct intel_oc_wdt *oc_wdt = watchdog_get_drvdata(wdd);
+
+	outl((inl(INTEL_OC_WDT_CTRL_REG(oc_wdt)) & ~INTEL_OC_WDT_TOV) | (t - 1),
+	     INTEL_OC_WDT_CTRL_REG(oc_wdt));
+
+	wdd->timeout = t;
+
+	return 0;
+}
+
+static const struct watchdog_info intel_oc_wdt_info = {
+	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
+	.identity = DRV_NAME,
+};
+
+static const struct watchdog_ops intel_oc_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = intel_oc_wdt_start,
+	.stop = intel_oc_wdt_stop,
+	.ping = intel_oc_wdt_ping,
+	.set_timeout = intel_oc_wdt_set_timeout,
+};
+
+static int intel_oc_wdt_setup(struct intel_oc_wdt *oc_wdt)
+{
+	struct watchdog_info *info;
+	unsigned long val;
+
+	val = inl(INTEL_OC_WDT_CTRL_REG(oc_wdt));
+
+	if (val & INTEL_OC_WDT_STS_BITS)
+		oc_wdt->wdd.bootstatus |= WDIOF_CARDRESET;
+
+	oc_wdt->locked = !!(val & INTEL_OC_WDT_CTL_LCK);
+
+	if (val & INTEL_OC_WDT_EN) {
+		/*
+		 * No need to issue a ping here to "commit" the new timeout
+		 * value to hardware as the watchdog core schedules one
+		 * immediately when registering the watchdog.
+		 */
+		set_bit(WDOG_HW_RUNNING, &oc_wdt->wdd.status);
+
+		if (oc_wdt->locked) {
+			info = (struct watchdog_info *)&intel_oc_wdt_info;
+			/*
+			 * Set nowayout unconditionally as we cannot stop
+			 * the watchdog.
+			 */
+			nowayout = true;
+			/*
+			 * If we are locked read the current timeout value
+			 * and inform the core we can't change it.
+			 */
+			oc_wdt->wdd.timeout = (val & INTEL_OC_WDT_TOV) + 1;
+			info->options &= ~WDIOF_SETTIMEOUT;
+
+			dev_info(oc_wdt->wdd.parent,
+				 "Register access locked, heartbeat fixed at: %u s\n",
+				 oc_wdt->wdd.timeout);
+		}
+	} else if (oc_wdt->locked) {
+		/*
+		 * In case the watchdog is disabled and locked there
+		 * is nothing we can do with it so just fail probing.
+		 */
+		return -EACCES;
+	}
+
+	val &= ~INTEL_OC_WDT_TOV;
+	outl(val | (oc_wdt->wdd.timeout - 1), INTEL_OC_WDT_CTRL_REG(oc_wdt));
+
+	return 0;
+}
+
+static int intel_oc_wdt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct intel_oc_wdt *oc_wdt;
+	struct watchdog_device *wdd;
+	int ret;
+
+	oc_wdt = devm_kzalloc(&pdev->dev, sizeof(*oc_wdt), GFP_KERNEL);
+	if (!oc_wdt)
+		return -ENOMEM;
+
+	oc_wdt->ctrl_res = platform_get_resource(pdev, IORESOURCE_IO, 0);
+	if (!oc_wdt->ctrl_res) {
+		dev_err(&pdev->dev, "missing I/O resource\n");
+		return -ENODEV;
+	}
+
+	if (!devm_request_region(&pdev->dev, oc_wdt->ctrl_res->start,
+				 resource_size(oc_wdt->ctrl_res), pdev->name)) {
+		dev_err(dev, "resource %pR already in use, device disabled\n",
+			oc_wdt->ctrl_res);
+		return -EBUSY;
+	}
+
+	wdd = &oc_wdt->wdd;
+	wdd->min_timeout = INTEL_OC_WDT_MIN_TOV;
+	wdd->max_timeout = INTEL_OC_WDT_MAX_TOV;
+	wdd->timeout = INTEL_OC_WDT_DEF_TOV;
+	wdd->info = &intel_oc_wdt_info;
+	wdd->ops = &intel_oc_wdt_ops;
+	wdd->parent = dev;
+
+	watchdog_init_timeout(wdd, heartbeat, dev);
+
+	ret = intel_oc_wdt_setup(oc_wdt);
+	if (ret)
+		return ret;
+
+	watchdog_set_drvdata(wdd, oc_wdt);
+	watchdog_set_nowayout(wdd, nowayout);
+	watchdog_stop_on_reboot(wdd);
+	watchdog_stop_on_unregister(wdd);
+
+	return devm_watchdog_register_device(dev, wdd);
+}
+
+static const struct acpi_device_id intel_oc_wdt_match[] = {
+	{ "INT3F0D" },
+	{ "INTC1099" },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, intel_oc_wdt_match);
+
+static struct platform_driver intel_oc_wdt_platform_driver = {
+	.driver = {
+		.name = DRV_NAME,
+		.acpi_match_table = intel_oc_wdt_match,
+	},
+	.probe = intel_oc_wdt_probe,
+};
+
+module_platform_driver(intel_oc_wdt_platform_driver);
+
+MODULE_AUTHOR("Diogo Ivo <[email protected]>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Intel OC Watchdog driver");