watchdog: add watchdog pretimeout governor framework

The change adds a simple watchdog pretimeout framework infrastructure,
its purpose is to allow users to select a desired handling of watchdog
pretimeout events, which may be generated by some watchdog devices.

A user selects a default watchdog pretimeout governor during
compilation stage.

Watchdogs with WDIOF_PRETIMEOUT capability now have one more device
attribute in sysfs, pretimeout_governor attribute is intended to display
the selected watchdog pretimeout governor.

The framework has no impact at runtime on watchdog devices with no
WDIOF_PRETIMEOUT capability set.

Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

1 files changed, 131 insertions, 0 deletions

diff --git a/drivers/watchdog/watchdog_pretimeout.c b/drivers/watchdog/watchdog_pretimeout.c
new file mode 100644
index 000000000000..72612255fb55
--- /dev/null
+++ b/drivers/watchdog/watchdog_pretimeout.c
@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2015-2016 Mentor Graphics
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ */
+
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/watchdog.h>
+
+#include "watchdog_pretimeout.h"
+
+/* Default watchdog pretimeout governor */
+static struct watchdog_governor *default_gov;
+
+/* The spinlock protects default_gov, wdd->gov and pretimeout_list */
+static DEFINE_SPINLOCK(pretimeout_lock);
+
+/* List of watchdog devices, which can generate a pretimeout event */
+static LIST_HEAD(pretimeout_list);
+
+struct watchdog_pretimeout {
+	struct watchdog_device		*wdd;
+	struct list_head		entry;
+};
+
+int watchdog_pretimeout_governor_get(struct watchdog_device *wdd, char *buf)
+{
+	int count = 0;
+
+	spin_lock_irq(&pretimeout_lock);
+	if (wdd->gov)
+		count = sprintf(buf, "%s\n", wdd->gov->name);
+	spin_unlock_irq(&pretimeout_lock);
+
+	return count;
+}
+
+void watchdog_notify_pretimeout(struct watchdog_device *wdd)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&pretimeout_lock, flags);
+	if (!wdd->gov) {
+		spin_unlock_irqrestore(&pretimeout_lock, flags);
+		return;
+	}
+
+	wdd->gov->pretimeout(wdd);
+	spin_unlock_irqrestore(&pretimeout_lock, flags);
+}
+EXPORT_SYMBOL_GPL(watchdog_notify_pretimeout);
+
+int watchdog_register_governor(struct watchdog_governor *gov)
+{
+	struct watchdog_pretimeout *p;
+
+	if (!default_gov) {
+		spin_lock_irq(&pretimeout_lock);
+		default_gov = gov;
+
+		list_for_each_entry(p, &pretimeout_list, entry)
+			if (!p->wdd->gov)
+				p->wdd->gov = default_gov;
+		spin_unlock_irq(&pretimeout_lock);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(watchdog_register_governor);
+
+void watchdog_unregister_governor(struct watchdog_governor *gov)
+{
+	struct watchdog_pretimeout *p;
+
+	spin_lock_irq(&pretimeout_lock);
+	if (gov == default_gov)
+		default_gov = NULL;
+
+	list_for_each_entry(p, &pretimeout_list, entry)
+		if (p->wdd->gov == gov)
+			p->wdd->gov = default_gov;
+	spin_unlock_irq(&pretimeout_lock);
+}
+EXPORT_SYMBOL(watchdog_unregister_governor);
+
+int watchdog_register_pretimeout(struct watchdog_device *wdd)
+{
+	struct watchdog_pretimeout *p;
+
+	if (!(wdd->info->options & WDIOF_PRETIMEOUT))
+		return 0;
+
+	p = kzalloc(sizeof(*p), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+
+	spin_lock_irq(&pretimeout_lock);
+	list_add(&p->entry, &pretimeout_list);
+	p->wdd = wdd;
+	wdd->gov = default_gov;
+	spin_unlock_irq(&pretimeout_lock);
+
+	return 0;
+}
+
+void watchdog_unregister_pretimeout(struct watchdog_device *wdd)
+{
+	struct watchdog_pretimeout *p, *t;
+
+	if (!(wdd->info->options & WDIOF_PRETIMEOUT))
+		return;
+
+	spin_lock_irq(&pretimeout_lock);
+	wdd->gov = NULL;
+
+	list_for_each_entry_safe(p, t, &pretimeout_list, entry) {
+		if (p->wdd == wdd) {
+			list_del(&p->entry);
+			break;
+		}
+	}
+	spin_unlock_irq(&pretimeout_lock);
+
+	kfree(p);
+}