[AVR32] NMI debugging

Change the NMI handler to use the die notifier chain to signal anyone
who cares. Add a simple "nmi debugger" which hooks into this chain and
that may dump registers, task state, etc. when it happens.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>

arch/avr32/kernel/nmi_debug.c

@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2007 Atmel Corporation
+ *
+ * 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/delay.h>
+#include <linux/kdebug.h>
+#include <linux/notifier.h>
+#include <linux/sched.h>
+
+#include <asm/irq.h>
+
+enum nmi_action {
+	NMI_SHOW_STATE	= 1 << 0,
+	NMI_SHOW_REGS	= 1 << 1,
+	NMI_DIE		= 1 << 2,
+	NMI_DEBOUNCE	= 1 << 3,
+};
+
+static unsigned long nmi_actions;
+
+static int nmi_debug_notify(struct notifier_block *self,
+		unsigned long val, void *data)
+{
+	struct die_args *args = data;
+
+	if (likely(val != DIE_NMI))
+		return NOTIFY_DONE;
+
+	if (nmi_actions & NMI_SHOW_STATE)
+		show_state();
+	if (nmi_actions & NMI_SHOW_REGS)
+		show_regs(args->regs);
+	if (nmi_actions & NMI_DEBOUNCE)
+		mdelay(10);
+	if (nmi_actions & NMI_DIE)
+		return NOTIFY_BAD;
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block nmi_debug_nb = {
+	.notifier_call = nmi_debug_notify,
+};
+
+static int __init nmi_debug_setup(char *str)
+{
+	char *p, *sep;
+
+	register_die_notifier(&nmi_debug_nb);
+	if (nmi_enable()) {
+		printk(KERN_WARNING "Unable to enable NMI.\n");
+		return 0;
+	}
+
+	if (*str != '=')
+		return 0;
+
+	for (p = str + 1; *p; p = sep + 1) {
+		sep = strchr(p, ',');
+		if (sep)
+			*sep = 0;
+		if (strcmp(p, "state") == 0)
+			nmi_actions |= NMI_SHOW_STATE;
+		else if (strcmp(p, "regs") == 0)
+			nmi_actions |= NMI_SHOW_REGS;
+		else if (strcmp(p, "debounce") == 0)
+			nmi_actions |= NMI_DEBOUNCE;
+		else if (strcmp(p, "die") == 0)
+			nmi_actions |= NMI_DIE;
+		else
+			printk(KERN_WARNING "NMI: Unrecognized action `%s'\n",
+				p);
+		if (!sep)
+			break;
+	}
+
+	return 0;
+}
+__setup("nmi_debug", nmi_debug_setup);