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: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

5 files changed, 138 insertions, 0 deletions

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 445ce28475b3..dcfa7e9e92f5 100644
--- a/drivers/acpi/Kconfig
+++ b/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
diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index 5ae9d85c5159..3a1fa8f03749 100644
--- a/drivers/acpi/Makefile
+++ b/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
 
diff --git a/drivers/acpi/acpi_watchdog.c b/drivers/acpi/acpi_watchdog.c
new file mode 100644
index 000000000000..13caebd679f5
--- /dev/null
+++ b/drivers/acpi/acpi_watchdog.c
@@ -0,0 +1,123 @@
+/*
+ * 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);
+}
diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 940218ff0193..fb9a7ad96756 100644
--- a/drivers/acpi/internal.h
+++ b/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_ */
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index e878fc799af7..3b85d87021da 100644
--- a/drivers/acpi/scan.c
+++ b/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);